United States Region VI EPA/906/R-98/002
Environmental Protection Ecosystems Protection Branch June 1998
Agency 6WQ-E
&EPA Galveston Bay 1993
Regional Environmental
Monitoring and Assessment
Program
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EPA/906/R-98/002
Regional Environmental Monitoring
And Assessment Program
Galveston Bay 1993
June 1998
By
Cynthia Gorham-Test
U.S. Environmental Protection Agency, Region 6
Ecosystems Protection Branch 6WQ-E
1445 Ross Avenue
Dallas, Texas 75202
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The R-EMAP Galveston Bay Study is a follow-up study of the EMAP-Estuaries: Louisiana
Province Studies. Several comparisons are made between data collected and analyzed in this
report and that of the following citation:
Macauley J.M., J.K. Summers, V.D. Engle, P.T. Heitmuller, and A.M. Adams. 1995.
Annual Statistical Summary: EMAP-Estuaries Louisianian Province - 1993. U.S.
Environmental Protection Agency, Offices of Research and Development, Environmental
Research Laboratory, Gulf Breeze, FL. EPA/620/R-96/003.
R-EMAP and EMAP data are available at http://www.epa.gov/emap
IV
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Acknowledgments
EPA Region 6, Water Quality Division
Jeff Catanzarita
Phil Crocker
Norm Dyer
Evan Hornig
Angel Kosfizer
James Stiebing
Kenneth Teague
U.S. EPA, ORD, Gulf Breeze Lab
Virginia Engle
Tom Heitmuller
John Macauley
Kevin Summers
U.S. EPA, ORD, EMAP
J^ick Linthurst
University of Mississippi
Carol Cleveland
Gary Gaston
Gulf Coast Research Group at USM IMS
Richard Heard
Tom Lytle
Ervin Otvos
Chet Rakocinski
William Walker
Texas A&M University, Geochemical and Environmental Research Group
Bob Pressley
Terry Wade
Texas Research and Analysis Corporation
Barbara Albrecht
Jerri Brecken-Folse
Texas Natural Resource Conservation Commission
George Guillen
Steve Twidwell
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Table of Contents
Acknowledgements v
List of Tables vii
List of Figures viii
List of Maps x
Executive Summary xii
Introduction 1
Methods 2
Results and Discussion 6
Benthic Distributions 6
Sediment Toxicity 13
Sediment Component Distributions 14
Abiotic Habitat Indicators 14
Heavy Metal Distributions 17
Butyltin Distributions 25
Pesticide Distributions 28
Polynuclear Aromatic Hydrocarbon Distributions 31
Fob/chlorinated Biphenyls 35
Sites Near Dredging Activities 36
Water Quality Measurements 36
Comparisons of Benthic Distributions with Sediment Chemistry 41
Conclusions 47
References 49
VI
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List of Tables
Table 1. Galveston Bay Benthic Community Values 12
Table 2. Benthic Community Structure Group Comparisons By Percent of Area or Sites 13
Table 3. Presence of Amphipods, Tubificids, Gastropods, and Polychaetes - Comparisons by
Percent of Area or Sites 13
Table 4. Sediment Component Distributions 17
Table 5. Acid Volatile Sulfides Distributions in Sediments 17
Table 6. Metal Concentration Ranges, and ERL, & ERM Exceedences in Sediments of
GalvestonBay & Marina Sites 20
Table 7. Galveston Bay Stations with Sediment Metal Concentrations Exceeding ERL or NOEL, and
Higher Aluminum and Silt Clay Content Values for Natural Deposition Rate Comparison 21
Table 8. Metal Concentrations Ranges, and NOEL & ERL Exceedences in Sediment of Galveston Bay
and its Associated Small Bay and Marina Sites 22
Table 9. Percent of Area with ERL Exceeded in Sediments of Galveston Bay (Represented by 29 Sites)
and the Louisianian Province 22
Table 10. Comparison of Heavy Metal Concentration with Regression Values for Metals in
Uncontaminated Sediments Using Aluminum Concentrations as a Standard 23
Table 11. Percent of Area or Sites with Sediment TBT Concentrations Greater than or
Equal to 1.0 ppb and 5.0 ppb 25
Table 12. GalvestonBay Sites withButyltin Concentrations Exceeding 1.0 ppb and 5.0 ppb 27
Table 13. Spearman Correlation Coefficients for Butyltin Compounds at Marina Sites 28
Table 14. Pesticide Concentration in Galveston Bay Sediments at 38 Sites 29
Table 15. Galveston Bay Stations with Sediment Pesticide and PAH Concentrations
Exceeding NOEL or ERL Values 30
Table 16. Percent of Area or Sites Exceeding Polynuclear Aromatic Hydrocarbon ERL Values 32
Table 17. Polynuclear Aromatic Hydrocarbon Concentrations in Galveston Bay Sediments 34
Table 18. Polychlorinated Biphenyl (PCB) Concentrations in Galveston Bay Sediments 35
Table 19. Galveston Bay Water Column Physical and Chemical Measurements 40
Table 20. Percent of Area or Sites Compared by Salinity Categories 41
Table 21. Degradation at Each Site Indicated by the Sediment Quality Triad Components 46
vii
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List of Figures
Figure 1. Abundance Categories Compared by Percent of Area or Sites 6
Figure 2. CDF of Benthic Abundance for Galveston Bay 6
Figure 3. Benthic Index Categories Compared by Percent of Area or Sites 7
Figure 4. CDF for Benthic Index Values for Galveston Bay 7
Figure 5. Species Richness Categories Compared by Percent of Area or Sites 9
Figure 6. CDF of Benthic Species Richness Numbers for GalvestonBay 9
Figure 7. Benthic Diversity Index Categories Compared by Percent of Area or Sites 9
Figure 8. CDF of Benthic Diversity in GalvestonBay 9
Figure 9. Percent of Area or Sites with an Absence of Amphipods, Tubificids, and Gastropods 10
Figure 10. CDF of Amphipod Abundance in Galveston Bay 10
Figure 11. CDF of Tubificid Abundance in Galveston Bay Sediments 10
Figure 12. CDF of Gastropod Abundance in Galveston Bay 10
Figure 13. CDF of Polychaete Abundance in Galveston Bay 10
Figure 14. Total Organic Carbon Distributions in the Sediments 14
Figure 15. CDF of Total Organic Carbon in Galveston Bay Sediments 14
Figure 16. Sediment Composition Compared by Percent of Area or Sites 14
Figure 17. CDF of Sediment Silt-Clay Distributions 14
Figure 18. Categories of Aluminum Cone, in Sediments Compared by Percent of Area or Sites 15
Figure 19. CDF of Aluminum Concentrations in Galveston Bay Sediments 15
Figure 20. CDF of Acid Volatile Suffides in Galveston Bay Sediments 15
Figure 21. ERL Exceedence for Five Metals 18
Figure 22. Comparison of Metal Concentration Classifications for Enrichment and Exceedence
for 38 Sites Sampled in the GalvestonBay Complex 18
* CDF is Cumulative Distribution Function.
CDF graphs represent data from the 29 randomly selected sites and depict 90% confidence intervals.
Vlll
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List of Figures (Continued)
Figure 23. Percent Area with TBT Concentrations in Sediment Greater than 1 ppb and 5 ppb 25
Figure 24. CDF of Tributyltin in Galveston Bay Sediments 25
Figure 25. Percent of Area or Sites withERL Exceedence of Pesticides 28
Figure 26. CDF of High Molecular PAHs in Galveston Bay Sediments 31
Figure 27. CDF of Low Molecular Weight PAHs in Galveston Bay Sediments 31
Figure 28. CDF of Bottom Water Temperature in Galveston Bay 36
Figure 29. CDF of Salinity in Surface Water in GalvestonBay 38
Figure 30. CDF of Salinity in Bottom Water in Galveston Bay 38
Figure 31. CDF of Salinity Stratification in Galveston Bay 38
Figure 32. Percent of Area with Bottom Salinity Within Category Ranges 38
Figure 33. CDF of Dissolved Oxygen in Surface Water in GalvestonBay 39
Figure 34. CDF of Dissolved Oxygen in Bottom Water in Galveston Bay 39
Figure 35. Degradation Status Categories Compared by Percent of Area or Sites 43
* CDF is Cumulative Distribution Function.
CDF graphs represent data from the 29 randomly selected sites and depict 90% confidence intervals.
IX
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List of Maps
Galveston Bay and Its Associated Small Bays and Marina Sites
Map la. R-EMAP Sampling Sites in the Galveston Bay Complex and the East Bay Bayou Area 3
Maplb. Texas Estuaries Sampled for in the 1993 R-EMAP Study 4
Map 2. Benthic Index Distributions 8
Map 3. Benthic Diversity Index Distributions 11
Map 4. Aluminum and Silt-Clay Distributions in Sediments Grouped Using Cluster Analysis 16
Map 5. Heavy Metal Distributions in Sediments Grouped Using Cluster Analysis 19
Map 6. Tributyltin Concentration Distributions in Sediments 26
Map 7. Polynuclear Aromatic Hydrocarbon Distributions in Sediments Using Cluster Analysis 33
Map 8. Surface Salinity (ppt) Gradient During R-EMAP Sampling 37
Map 9. Significant Environmental Factor Distributions Groupings Using
Principal Components Analysis 42
Map 10. Degradation Status at Each Site Using Sediment Quality Triad Components 44
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XI
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Executive Summary
The Regional Environmental Monitoring and
Assessment Program (R-EMAP) Study of
Galveston Bay, Texas addresses the ecological
health of this estuary by identifying benthic
community structure, measuring toxicity of
sediments, and measuring concentrations of
various pollutants in the sediments. The R-EMAP
Study of Galveston Bay was proposed after the
EPA's 1991 EMAP Study of the Louisianian
Province estuaries identified Galveston Bay as an
area of concern. The sampling design and
ecological indicators employed for the R-EMAP
Study of Galveston Bay are based on the EMAP
concept (a locally intensified EMAP sampling grid
was used), but they are limited to one sampling
event.
The purpose of this study was to characterize the
condition of Galveston Bay as a whole,
characterize conditions of four small bays in the
Galveston Bay Complex, and determine the
impacts of marinas.
For comparison of the main body of Galveston Bay
with other systems and the Louisianian Province as
a whole, twenty-nine randomly selected sites were
chosen to represent 1305 square kilometers of
surface area of Galveston Bay. Random sites are
located in Galveston Bay (GB), Trinity Bay (TB),
East Bay (EGB), and West Bay (WGB). In
addition, a random sample was taken for each of
four important small bays associated with
Galveston Bay: Clear Lake (CL), Dickenson Bay
(DKL), Moses Lake/Dollar Bay (MLDL), and
Offat's Bayou (OB). Also, five marina sites (MA)
were chosen to determine local marina influences
(see Map 1). This study does not include an
analysis of conditions in the upper Houston Ship
Channel, the Trinity River, or any other major
tributaries. The Louisianian
Province EMAP Study consisted of 96 sites which
represented 25,725 square kilometers of estuarine
area. The Louisianian Province
extends along the Gulf Coast from Anclote
Anchorage, Florida to the Rio Grande, Texas.
A comparison of the EMAP Study of the
Louisianian Province with the R-EMAP Study of
Galveston Bay did provide insight into the
differences between Galveston Bay and its Small
Bay & Marina Sites, and the entire Louisianian
Province. These comparisons revealed that the
EMAP results were useful as a screening tool to
determine which systems had toxic pollutants or
biological impairment and therefore, should be
studied in more detail.
The Sediment Quality Triad approach was used in
this study to differentiate between degraded sites
and undegraded sites. The Sediment Quality Triad
consists of three components: Benthic Community
Structure, Sediment Chemistry, and Sediment
Toxicity. For this study, a degraded site is defined
as a site which has at least two of the Sediment
Quality Triad Components indicating degradation.
Benthic Community Component
Several metrics were used to determine the benthic
community health. The Benthic Index (Engle and
Summers, in press), the Benthic Diversity Index
(the Shannon-Weiner Index), number of species
per site and abundance of amphipods at each site
proved useful in demonstrating that communities
living in contaminated sediments had a community
structure indicating poor conditions. The
proportions of the two indices and the number of
species in the Galveston Bay area were higher or
similar to the proportions reported for the
Louisianian Province in the 1993 EMAP Study. In
contrast, amphipod occurrence in Galveston Bay
sediments was significantly lower than in the entire
Louisianian Province sediments. Small Bay and
Marina Sites in Galveston Bay had no amphipods
present and had much lower index values relative
to Galveston Bay and the Louisianian Province
sites. A degraded Benthic Component was found at
7 of 29 sites in Galveston Bay, and 8 of 9 Small
Bay & Marina Sites (see Table 13).
Executive Summary - 1993 Galveston Bay R-EMAP Study
Page xii
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Sediment Toxicity Component
Ampelisca abdita (the tube dwelling amphipod),
and Mysldopsls bahia (a mysid shrimp) were used
as the lab organisms to test toxicity. Toxicity was
not seen when using mysid shrimp as a test
organism, but toxicity was reported when using
amphipods. Sites with toxic sediments included:
Offat's Bayou, Dickenson Lake, and West
Galveston Bay near Swan Lake (see Table 13).
Toxicity was present at 3.5% of Galveston Bay
area and 22% of Small Bay and Marina sites.
Toxicity could not be associated with any of the
measured parameters including presence or
absence of natural amphipod populations present at
each site. The only apparent similarity between
sites displaying toxicity is that all three sites are
located in the same general area of the bay.
Toxicity results revealed a low occurrence of acute
toxicity in Galveston Bay sediments.
Sediment Chemistry Component
Sediment contaminants analyzed included 44
individual Polynuclear Aromatic Hydrocarbons
(PAHs), High Molecular Weight PAHs and Low
Molecular Weight PAHs, 20 polychlorinated
biphenyl congeners, 24 pesticides (including DDT
and its derivatives), 15 heavy metals, and 3 forms
of butyltin. Sediment grain size, percent silt-clay
content, total organic carbon, and acid volatile
sulfides also were measured.
The contaminants were compared to established
criteria including NOEL, ERL, and ERM. The
range-low (ERL) criteria was established using the
lower 10th percentile of effects data for the metal or
chemical. Concentrations equal to or above the
ERL, but below the ERM, represent a possible-
effects range within which effects would
occasionally occur. The range-high (ERM) criteria
was established using the 50th percentile of the
effects data. The concentrations equal to or higher
than the ERM value represent a probable-effects
range within which effects would frequently occur
(Long, et al., 1995). The concentrations equal to
the NOEL value is the highest level at which
observed effects occur (MacDonald, 1992). In
addition, anthropogenic enrichment of metals was
measured. Enrichment was determined using
regression equations for each metal against
aluminum concentrations in the sediments.
In Galveston Bay, arsenic, copper, lead, nickel, and
zinc exceed the ERL but not the ERM criteria at
one or more sites sampled (Tables 2 & 3, Figure
21). NOEL values, but not ERL values, are
exceeded at one or more sites for arsenic,
chromium, lead, mercury, and zinc (Table 4). Sites
with the most metals contamination include Offat's
Bayou, Clear Lake, Moses Lake/Dollar Bay, and
two Marina sites (Table 2, Maps 5 and 6). All of
these sites are Small Bay and Marina sites, which
were chosen, not randomly selected, so they are not
included in comparisons of Galveston Bay with the
Louisianian Province 1993 EMAP sampling area.
However, several of the randomly sampled sites in
Galveston Bay did have exceedences for arsenic,
chromium, nickel, and zinc. Exceedences of
chromium, copper, lead, nickel, and zinc for each
site were almost always found at sites where the
above metal concentrations, when compared to
aluminum concentrations, indicated anthropogenic
inputs.
The Galveston Bay area (represented by the 29
randomly chosen sites) has high chromium and
nickel values distributed across a larger area than
would be expected when compared to the entire
Louisianian Province area. The percent of area
with exceeded values in Galveston Bay were
compared to the percent of area with exceeded
values in the entire Louisianian Province as
reported in Macauley, et al., 1995. Arsenic
distributions in Galveston Bay were lower than
expected when compared to the Louisianian
Province, while zinc distributions were similar.
Copper values above ERL values were found only
at marina sites and in Offat's Bayou, but not in the
randomly sampled area representing Galveston
Bay, nor in the entire Louisianian Province area.
Tributyltin (TBT) is toxic to marine animals and is
used in anti-fouling paint for boats, buoys, and
Executive Summary - 1993 Galveston Bay R-EMAP Study
Page xiii
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docks. TBT has been restricted for use in recent
years to only larger boats in an effort to reduce the
amount of TBT contamination in the marine
environment. Values exceeding 1.0 ppb in the
sediments are used as a screening criterion based
on studies by Laughlin, et al. (1984). TBT
concentrations are higher in Galveston Bay
sediments than expected with values greater than
1.0 ppb occurring in 52% of the area, compared to
31% of the total Louisianian Province area. A
significant relationship exists between butyltin
concentrations in the sediments and butyltin
concentrations in the water column.
Sites with high Dieldrin and Endrin concentrations
in the sediments are located in upper Galveston
Bay, Clear Lake and upper Trinity Bay.
For the Louisianian Province, Dieldrin and Endrin
were found to exceed the ERL guidelines at 57%
and 18%, respectively, of EMAP sites. Both
Dieldrin and Endrin concentration exceedance by
area are lower in Galveston Bay compared to the
Louisianian Province. Dieldrin and Endrin ERL
values were exceeded at 17% and 5% respectively
in Galveston Bay, and 33% and 0% for the Small
Bay and Marina sites. No other pesticides
(including DDT and its associated metabolites)
exceeded ERL values for either study.
Polynuclear Aromatic Hydrocarbons (PAHs) were
examined for exceedance of NOEL, ERL, and
ERM screening values. PAHs exceeding ERL
values in Galveston Bay include only C3-fluorene
at site TB5 in Trinity Bay where several active oil
wells are located. PAHs exceeding NOEL, but not
ERL, values in Galveston Bay include
Acenaphthylene and High Molecular Weight PAHs
only found at site TB5 in Trinity Bay.
Distributions of Low Molecular Weight PAHs and
High Molecular PAHs for Galveston Bay show
that three sites have PAHs that are considerably
higher than at the other sites in the Galveston Bay
area.
C3-fluorene exceeded ERL criteria in 3% of
Galveston Bay, which is similar to exceedences
found in the entire area of the Louisianian
Province. Also, the NOEL value for high
Molecular Weight PAHs was exceeded at site TB5.
In the Louisianian Province, only C3-fluorene ERL
values and High Molecular Weight PAHs ERL
values were exceeded.
Polychlorinated Biphenyl (PCB) concentrations in
Galveston Bay did not exceed the sediment quality
low-level ecological effects screening value of 22.7
ppb. In addition, only 1% of the Louisianian
Province area had exceedences of PCBs in the
sediments.
The major variables used to determine degraded
sediment chemistry in Galveston Bay included
metals, butyltins, PAHs, pesticides other than
DDTs, and silt-clay content. These variables were
compressed into one factor using Principal
Components Analysis (PCA). Sites with the
highest compressed significant environmental
factor values for sediment chemistry include
Offat's Bayou, Moses Lake/Dollar Bay, Clear
Lake, four of the Marina sites, and two sites near
large brine discharges in the Trinity Bay area (TB5
and GB6). Sites with the lowest significant
environmental PCA factor values include GB5 and
TB6 which are both areas with the highest
percentages of sediment grain sizes representing
sand. These sites could be areas of low deposition
and/or high scour.
Site Degradation
For this study, a degraded site is defined as a site
with at least two of the Sediment Quality Triad
Components indicating degradation. A marginal
site is defined as a site with a benthic index value
from 4.0 to 5.1 (which represents a marginal
benthic component) and with a degraded sediment
chemistry component. Degraded and healthy site
values were determined using Cluster Analysis.
Heavy metal concentrations greatly influenced the
determination of degraded sites for the Sediment
Chemistry Component of the Triad.
The most degraded areas in the Galveston Bay
Complex include seven Small Bay and Marina
Executive Summary - 1993 Galveston Bay R-EMAP Study
Page xiv
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sites and five randomly chosen sites in the open Upper Galveston Bay near Smith Point (GB7),
bay: Offat's Bayou (OB), Clear Lake (CL) and its Moses Lake/Dollar Bay (MLDL), Dickenson Lake
marina sites, Lafayette Landing and South Shore (DKL), mid-Trinity Bay (TBS) and Trinity Bay
(MAS and MA4), Upper Galveston Bay at the near the river mouth (TBS, TB9), and mid-East
Houston Yacht Club (MA2), Upper Galveston Bay Galveston Bay (EGB5).
near the upper Houston Ship Channel (GB1),
Executive Summary - 1993 Galveston Bay R-EMAP Study Page xv
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INTRODUCTION
The Regional Environmental Monitoring and
Assessment Program (R-EMAP) Study of Galveston
Bay, Texas, addresses the ecological health of this
estuary by identifying benthic community structure,
measuring toxicity of sediments, and measuring
concentrations of various pollutants in the sediments.
The study was proposed after the EPA=s 1991
EMAP Study of the Louisianian Province estuaries
identified Galveston Bay as an area of concern. The
sampling design and ecological indicators employed
are based on the EMAP concept (a locally intensified
EMAP sampling grid is used), but they are limited to
one sampling event. This study focuses on the main
body of Galveston Bay. In addition, four small bays
and five marinas located in the Galveston Bay
System were sampled. This study does not include
an analysis of the upper Houston Ship Channel, the
Trinity River, or any other major tributaries.
The purpose of this study was to characterize the
condition of the main body of Galveston Bay as a
whole, characterize conditions of the four small bays,
and determine the impacts of marinas.
The goals of this study were to:
• directly address the issues of toxic pollutants
and biological impairment in Texas coastal
waters,
• contribute data to characterize the extent and
severity of potential waterbody-specific
problems identified by the EMAP Study,
• provide management with the environmental
data needed for making decisions for
targeting toxic pollutants and specific
geographic areas, and
• link the EMAP Study (Macauley etal., 1993)
results with the 1993 R-EMAP Study results
for comparison. This comparison can be
used to evaluate the usefulness of coupling
EMAP as a screening tool with R-EMAP as
a follow-up tool and to test the utility of the
EMAP approach to address waterbody-
specific questions.
Galveston Bay is the most economically important
estuary on the Texas coast. It contains the State=s
largest seaport, houses the world=s largest industrial
complex, and produces the largest shellfish catch on
the Texas coast. It also contains sixty-three percent
of the boat slips in Texas. Galveston Bay is adjacent
to Houston, one of the most populated areas in
Texas. Thirty percent of the total U.S. petroleum
industry and nearly fifty percent of the total U.S.
chemical production is located adjacent to Galveston
Bay. From these and other sources, this estuary
receives more industrial and municipal effluent than
all the other Texas estuaries and their local
watersheds combined (GBNEP 44, 1994).
Significant improvements have been made in the
most polluted area of the bay system, the upper
Houston Ship Channel. In the early 1970's, the
Houston Ship Channel above Morgan=s Point was
listed by the U.S. EPA as one of the ten most
polluted bodies of water in the U.S. Starting in 1971,
increasingly stringent discharge goals were
established for point sources on the Houston Ship
Channel (GBNEP 44, 1994). In a 1980 report, the
EPA recognized the improvements made on the
Houston Ship Channel as Athe most notable
improvement, a truly remarkable feat® (GBNEP 44,
1994).
hi Galveston Bay, water and sediment quality
problems generally occur along the western shoreline
and western tributaries (including the Houston Ship
Channel), where anthropogenic activities are highest.
Water quality improvements in these areas over the
last 20 years have been attributed to improved
wastewater treatment and reduction by point source
dischargers (GBNEP 44, 1994). The Houston Ship
Channel and its tributaries are the receiving waters
for approximately 400 permitted industrial and
municipal discharges (TDWR, 1984). The Ship
Channel is still impacted by these discharges;
however, vast improvements have been made. A
majority of the remaining pollution problems to be
addressed involve nonpoint source pollution from
urban areas and industrial sites (Ward and
Armstrong, GBNEP 22, 1992).
Introduction - 1993 Galveston Bay R-EMAP Study
Page 1
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METHODS
Sampling Design
The Louisianian Province EMAP Study used 96 sites
which represented 25,725 square kilometers of
estuarine area. The Louisianian Province extends
along the Gulf Coast from Anclote Anchorage,
Florida, to the Rio Grande, Texas.
For comparison of Galveston Bay with other systems
and the Louisianian Province as a whole, twenty-nine
randomly selected sites were chosen to represent
1305 km2 of surface area in Galveston Bay. Random
sites are located in Galveston Bay (GB), Trinity Bay
(TB), East Bay (EGB), and West Bay (WGB). In
addition, a random sample was taken for each of four
important small bays associated with Galveston Bay:
Clear Lake (CL, 5.6 km2), Dickenson Bay (DKL,
11.0 km2), Moses Lake/Dollar Bay (MLDL, 7.7
km2), and Offat=s Bayou (OB, 2.6 km2). Also, five
marina sites (MA) were chosen to determine local
marina influences (see Map la). The tidal areas of
major tributaries, including the Houston Ship
Channel, were not sampled in this study.
The 1993 REMAP Study also includes six sites in
East Bay Bayou, ten sites in the Arroyo Colorado,
and three sites in the Rio Grande River (see Map Ib).
These three small systems will be addressed in a
separate report. Sites in East Bay Bayou (EBB 1-6)
are shown in Map la because of their proximity to
the Galveston Bay study area. East Bay Bayou,
Arroyo Colorado, and the Rio Grande sites were
selected by placing the first site at the mouth of the
system and placing each additional site 2.5 km2
upstream of the preceding site.
All samples were collected and analyzed using
EMAP Protocols (Summers and Macauley, 1993.
AStatistical Summary: EMAP - Estuaries Louisianian
Province - 1991", Appendix A). Samples for
analysis of benthic macroinvertebrate community
structure, sediment toxicity, and sediment chemistry
were collected for all 38 sites. Benthic
macroinvertebrate samples for measures of species
composition, abundance, and biomass were collected
at all sampling sites. Samples were collected with a
Young-modified Van Veen grab which samples a
surface area of 440 cm2. Three grabs were collected
at each site. A small core was taken from each grab,
and shipped on ice to the laboratory for sediment
characterization (grain size, silt-clay content, acid
volatile sulfides, and total organic carbon). The
remaining sample was sieved through a 0.5 mm
screen, with all organisms remaining on the sieve
identified and counted.
Sediment for the toxicity tests were collected using
the Young-modified Van Veen grab. Sediments
from the top 2 cm of 6 - 10 grabs were placed in a
mixing bowl, homogenized, placed in containers, and
stored on ice for transport. Sediment toxicity tests
were performed using the standard 10-day acute test
method and the tube-dwelling amphipod Ampeliscct
obdita. In addition, standard 4-day acute tests using
the mysid, Mysidopsis bahia, were conducted.
Sediment samples for contaminant analysis were
collected from a homogenate created during
sampling by combining the top 2 cm of sediment
from 6-10 sediment grabs. Sediments for organic
analysis were placed in clean glass jars with foil lid
liners, shipped on ice, and stored frozen in the
laboratory prior to analysis. Sediment for metals
analysis were placed in a plastic bag, shipped on ice,
and stored in the laboratory prior to analysis.
Sediment contaminants analyzed included 44
individual Polynuclear Aromatic Hydrocarbons
(PAHs), High Molecular Weight PAHs, and Low
Molecular Weight PAHs, 20 polychlorinated
biphenyl congeners, 24 pesticides (including DDT
and its metabolites), 15 heavy metals, and 3
butyltins.
Methods - 1993 Galveston BayR-EMAP Study
Page 2
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Map 1b. Texas Estuaries Sampled during the 1993 R-EMAP Study
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Rio Grande •% .
Miles
Methods - 1993 Galveston Bay R-EMAP Study Page 4
-------
Measurements of water column temperature, dissolved
oxygen, salinity, pH, water depth, and secchi depth
were taken at all sites. Water samples were collected
for mono-, di-, and tri- butyltin analysis at marina sites
only.
Samples offish tissue and fish community structure
were not collected for the Galveston Bay R-EMAP
Study.
Statistics
Variables that were not normally distributed and did not
have acceptable homogeneity of variances were log-
transformed to provide a normal distribution of the data.
Many, but not all log-transformed variable distributions,
were normal.
Spearman's Correlation Coefficients, Pearson's
Correlation Coefficients, Linear Regressions, and 95%
Confidence Intervals were determined using the
Windows Version of the Statistical Program for the
Social Sciences (SPSS). Cluster Analyses, Principal
Component Analyses (PCA), and Bartlett's Test for
Sphericity were determined using the Windows Version
of Statistical Applications for the Sciences (SAS). The
approach for the Sediment Quality Triad (SQT) data
analysis using PCA was adapted from Green and
Montagna (1996). Normally distributed data is
preferred when using PCA. Sediment chemistry
variables used in the principal components analysis
which were not normally distributed after log-
transformation included: aluminum, silt-clay content,
nickel, lead, and the three forms of butyltin. Major
variables in the sediment chemistry analysis had
communality values of 0.8 or greater. The first set of
factor scores were used to calculate the final Sediment
Chemistry Component values, which accounted for 66%
of the sediment chemistry variation and mainly
represented heavy metals and silt-clay content.
Methods - 1993 Galveston Bay R-EMAP Study Page 5
-------
RESULTS AND DISCUSSION
BENTHIC DISTRIBUTIONS: Biotic
Habitat Indicators for Sediments
Several metrics were used to determine the benthic
community health. Metrics calculated for each site
include: abundance of benthic organisms, abundance of
benthic organisms excluding polychaetes, the Benthic
Index (Engle and Summers, in press), the Benthic
Diversity Index (the Shannon-Weiner Index), number of
species (species richness), and abundance of
amphipods, gastropods, tubificids, and polychaetes.
Other metrics calculated for this study for each site but
not discussed in this report include: number of
polychaete species, polychaete/amphipod ratio, and
abundance of bivalves, decapods, and capitellids.
Abundance of Benthic Organisms
Abundance values represent the number of benthic
macroinvertebrates found per grab at each site. The
relative proportion of abundances of the 29 randomly
selected sites in Galveston Bay were similar to
abundances for the Louisianian Province. Selected
small bay and marina sites in Galveston Bay have much
lower relative abundances than the Galveston Bay and
Louisianian Province sites (Tables 1 & 2, Figures 1 &
2).
Seven percent of Galveston Bay area and 22% of small
bay/marina sites had abundances less than 10. Five
percent of Louisianian Province area had abundances
less than 10, indicating low benthic abundance.
Twenty-eight percent of Galveston Bay area and 22% of
small bay/marina sites had abundances from 10 to 25.
Fifteen percent of Louisianian Province area had
abundances from 10 and 25, indicating marginal benthic
abundance.
Abundances in Galveston Bay ranged from 1 to 217
mean number of organisms per site per grab. Higher
values generally contained large numbers of
polychaetes. Site MAS had low species richness,
Benthic Index, and diversity index values, but it had
137 polychaetes and only 4 other organisms!
Polychaetes can respond positively to high PAHs which
could complicate the response of the total benthic
abundance due to sediment contamination (Peterson et
al., 1996). Removal of polychaete numbers from the
total abundance clarified the relationship somewhat, but
not completely. Abundance without polychaetes ranged
from 0 to 81 mean number of organisms per site per
grab.
Figure 1. Benthic Abundance Categories Compared by Percent
of Area or Sites and 90% Confidence Intervals.
Small Bay & Galveston Bay Louisianian
Marina Sites Province
Figure 2. CDF of Benthic Abundance for Galveston Bay.
0 25 50 75 100 125 150 175 200 225
Benthic Abundance (per grab)
Benthic Index
Two sets of Benthic Index equations were developed for
the Louisianian Province estuaries by Engle and
Summers using EMAP data for the Louisianian
Province (Engle, et al., 1994). The second set of
equations was used for this study. The Benthic Index
was developed to provide environmental managers with
a simple tool to assess ecological conditions of benthic
macro-invertebrate communities. The Benthic Index
equation combines the Shannon-Wiener Diversity Index
(adjusted for salinity), tubificid oligochaete abundance,
percent capitellid polychaetes, percent bivalves, and
percent amphipods:
Methods - 1993 Galveston BayR-EMAP Study
Page 6
-------
Equation =
(1.5710 * Proportion of expected diversity) +
(-1.0335 * Mean abundance of tubificids) +
(-0.5607 * Percent capitellids) +
(-0.4470 * Percent bivalves) +
(0.5023 * Percent amphipods).
Benthic Index values less than 3.0 indicate a degraded
benthic community; values between 3.0 and 5.0 indicate
a marginal benthic community; and values greater than
5.0 indicate a healthy benthic community (Engle, pers
com.).
The Benthic Index value proportions for the 29
randomly selected sites in Galveston Bay are higher
than index values for the Louisianian Province. Small
Bay and Marina sites in Galveston Bay had much lower
index values relative to the Galveston Bay and
Louisianian Province sites (Tables 1 & 2, Figures 3 & 4,
Map 2).
Figure 3. Benthic Index Categories Compared by Percent of
Area or Sites and 90% Confidence Intervals.
Small Bay & Galveston Bay
Marina Sites
Figure 2. CDF of Benthic Abundance for Galveston Bay.
0 25 50 75 100 125 150 175 200
Benthic Abundance (per grab)
Fifty-two percent of the Galveston Bay area and 11% of
small bay/marina sites had a Benthic Index value
greater than 5.0, which indicated a healthy benthic
community structure. (The Galveston Bay data actually
has distinct separations points at 4.0 and 5.1.) Forty-
five percent of the Galveston Bay area had Benthic
Index values greater than 5.1. Forty percent of the
Louisianian Province area had Benthic Index values
greater than 5.0. Seventeen percent of the Galveston
Bay area and 78% of small bay/marina sites had
Benthic Index values less than 3.0, which indicated
stressed or degraded benthic communities. Twenty-
three percent of the Louisianian Province area had
Benthic Index values less than 3.0.
The Benthic Index proved useful in demonstrating that
communities living in contaminated sediments had a
community structure indicating poor conditions. A
significant negative relationship exists between
sediments contaminated with heavy metals and low
benthic index values (R = -0.62, F=0.00). These two
factors, metal concentrations and benthic values
indicate contamination. When comparing the benthic
index with PAHs, a significant relationship does not
exist (R = -0.37). Polychaetes responded positively or
indifferently to PAH enrichment at some sites which
could explain the non-significant value (Peterson et al.,
1996).
Species Richness
Benthic species richness is a measure of the number of
species found per grab at each site sampled. The
benthic species richness proportions for the area
represented by the 29 randomly selected sites in
Galveston Bay were similar to species proportions for
the Louisianian Province. Selected small bay and
marina sites in Galveston Bay had much lower species
richness overall than the Galveston Bay and Louisianian
Province sites. Sites with total number of benthic
species (mean species or species richness) less than or
equal to five included 3 Galveston Bay sites (GB 1,6,7),
and 6 small bay/marina sites (OB, CL, MA2,3,4,5)
(Table 1, Figures 5 & 6). Ten percent of Galveston Bay
sites and 67% of small bay/marina sites had less than or
equal to five species present. Fourteen percent of the
Louisianian Province area had less than or equal to five
species present. The poorest sites, with species richness
equal to 1 or 2 include: GB7 (1), MA3 (2), MA4 (1),
OB (1).
Methods - 1993 Galveston BayR-EMAP Study
Page 7
-------
CD
-------
Figure 5. Benthic Species Richness Categories Compared by
Percent of Area or Sites and 90% Confidence Intervals.
90 -
80 -
70 -
60 -
50 -
40 -
JO -
20 -
10 -
n -
^
Hh
T
— .
>
T -
I
n<=s
n>s
Small Bay & Galveston Bay Louisianian
Marina Sites Province
Figure 6. CDF of Benthic Species Richness for Galveston Bay.
0 10 20 30 40
Benthic Mean Species (per grab)
Benthic Diversity Index
(Shannon-Wiener Diversity Index)
The Shannon-Wiener Diversity Index is a measure of
both species richness and species evenness (which is
the distribution of individuals among species). The
Benthic Diversity Index refers to the measure of
benthic macroinvertebrates using the Shannon-
Wiener Index.
The Benthic Diversity Index proportions for the
Galveston Bay area were similar to the diversity
index proportions for the Louisianian Province.
However, the area with diversity index values greater
than 1.0 was only 17% for Galveston Bay compared
to approximately 30% for the Louisianian Province.
Selected small bay and marina sites in Galveston Bay
had much lower diversity values overall than the
Galveston Bay and Louisianian Province sites
(Tables 1 & 2, Figures 7 & 8, Map 3). In the present
study, Benthic Diversity Index values less than 0.4
indicate poor community structure; values between
0.4 and 0.7 indicate marginal community structure;
and values greater than 0.7 indicate a healthy benthic
community. The relationship between ten toxic
heavy metals and the diversity index was significant
(R = -0.61, F=0.00). The diversity index was not
closely associated with aluminum, silt-clay content,
or PAHs.
Figure 7. Benthic Diversity Index Categories Compared by
Percent of Area or Sites and 90% Confidence Intervals.
40 -
20 -
10 -
n -
r
I
1
1
1 i 1 i r~
rh
T
. ^
i
no.4
Small Bay & Galveston Bay Louisianian
Marina Sites
Province
Figure 8. CDF of Benthic Diversity in Galveston Bay.
0.50 1.00
Mean Shannon-Wiener Diversity Index
Abundances of Amphipods,
Tubificids, Gastropods, and
Polychaetes
Amphipods, tubificids, gastropods, and polychaetes
are key groups of organisms. Abundance
measurements of each provide a measure of benthic
community structure. Amphipod occurrence in
sediments of the area represented by the 29 randomly
selected sites in Galveston Bay and the small
bay/marina sites is significantly lower relative to the
Louisianian Province (Table 3). Amphipods were
found only at sites that had low metal concentrations,
low combined pollution concentrations, low
percentage of mud sediments, high benthic indices,
and high benthic diversities (Map 2 & 3).
Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 9
-------
Their presence was used in this study as an
indication of healthy benthic conditions (although
they were not found at every site with high index
values and low pollution values). Amphipod
distributions were not limited to high or low salinity
(Table 3, Figures 9 & 10). Amphipods were found at
six sites: WGB1 (3), TB6 (1), TB4 (8), GB5 (17),
GB11 (4), GB12 (8). Low occurrence of amphipods
in Galveston Bay could be due to degradation.
Tubificids are a group of oligochaete worms that are
considered opportunistic. Galveston Bay and the
small bay & marina sites have a lower relative
occurrence of tubificids than the Louisianian
Province (Table 3, Figures 9 & 11).
Gastropods did not occur as frequently in Galveston
Bay and its small bay & marina sites as in the
Louisianian Province (Table 3, Figures 9 & 12).
Polychaetes were the dominant benthic class found
in Galveston Bay sediment samples. Polychaete
presence in samples were similar for all Galveston
Bay sites and the Louisianian Province (Table 3).
Only one Galveston Bay site (GB7, in upper
Galveston Bay)(Figure 13), and only one small
bay/marina site (OB, Offat=s Bayou) did not have
polychaetes present. Very few sites in the
Louisianian Province area did not have polychaetes
present.
Figure 10. CDF of Amphipod Abundance in Galveston Bay.
40
30
20
10
0 5 10 15 20
Number of Amphipods (per grab)
Figure 11. CDF for Mean Tubificid Abundance in Galveston Bay
100 --
90 - - /
80 --/
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Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 11
-------
Table 1. Galveston Bay Benthic Community Values.
Station
GB1
GB2
GB3
GB4
GB5
GB6
GB7
GB8
GB9
GB10
GB11
GB12
TB1
TB2
TB3
TB4
TBS
TB6
TB7
TBS
TB9
TB10
EGB1
EGB2
EGB3
EGB4
EGB5
WGB1
WGB2
OB
MLDL
DKL
CL
MAI
MA2
MA3
MA4
MAS
Benthic Index
3.37
4.36
2.30
4.66
11.10
4.88
0.05
6.01
6.84
4.89
6.57
9.50
5.02
4.96
5.03
6.89
2.07
6.20
5.89
1.19
2.23
4.86
5.49
5.51
4.03
6.18
3.42
11.90
5.74
0.05
2.86
2.95
2.31
6.16
1.57
-0.34
0.05
3.00
Mean Diversity
0.50
0.62
0.74
0.79
0.90
0.64
0.00
0.87
1.03
0.84
1.02
0.81
0.73
0.72
0.91
1.05
0.72
0.78
0.80
0.60
0.84
0.81
0.85
0.82
0.74
0.90
0.61
1.34
0.92
0.00
0.53
0.57
0.28
0.75
0.47
0.05
0.00
0.27
Mean Abundance
13
19
23
36
48
7
2
48
61
50
170
124
20
18
25
119
113
16
62
96
155
40
42
42
23
33
35
217
86
1
26
47
10
14
42
137
2
49
Mean Species
4
6
6
8
14
5
1
14
20
13
27
27
8
8
10
17
15
7
11
9
17
10
13
11
10
11
7
52
19
1
6
8
3
7
5
2
1
4
* Benthic Index Range = -2.0 to +12.0. Shaded values indicate poor benthic community structure.
Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 12
-------
Table 2. Benthic Community Structure Group Comparisons by Percent of Area or Sites.
GB Small Bays /
Marinas
Galveston Bay
Louisiana Province
MEAN
ABUNDANCE
<10
22%
7%
5%
10-25
22%
28%
15%
>25
66%
65%
80%
BENTHIC
INDEX
<3
78%
17%
23%
3- 5
11%
31%
37%
>5
11%
52%
40%
BENTHIC
DIVERSITY INDEX
<0.2
33%
3%
3%
0.2-0.4
12%
3%
7%
>0.4
45%
94%
90%
MEAN
SPECIES
<=5
67%
10%
14%
>5
33%
90%
86%
Table 3. Presence of Amphipods, Tubificids, Gastropods, and Polychaetes
Comparisons by Percent of Area or Sites.
GB Small Bays/Marinas
Galveston Bay
Louisiana Province
AMPHIPODS
PRESENT
0%
20%
60%
TUBIFICIDS
PRESENT
11%
34%
60%
GASTROPODS
PRESENT
33%
55%
80%
POLYCHAETES
PRESENT
89%
96%
88%
TOXICITY
Ampelisca abdita (the tube dwelling amphipod), and
Mysidopsis bahia (a mysid shrimp) were used as the
lab organisms to test toxicity. Toxicity was not not
found at any site when using mysid shrimp as a test
organism, but toxicity was reported when using
amphipods. Sites with toxic sediments, based on
amphipod tests, included: Offat=s Bayou (OB) with
13% mortality, Dickinson Lake (DKL) with 13%
mortality, and West Galveston Bay near Swan Lake
(WGB1) with 14% mortality. Sites with sediments
not considered toxic had amphipod mortality values
of 3% to 8%. Only 3.5% of Galveston Bay sites and
22% of Small Bay and Marina sites had toxic
sediments. Toxicity could not be associated with any
of the parameters measured or with the presence or
absence of natural amphipod populations present at
each site. Site OB did not have any benthic
organisms present, and site DKL had low benthic
numbers and structure. In contrast, site WGB1 had
amphipods present in the sediments and high benthic
numbers and structure. The only apparent similarity
is that all three sites are located in the same general
location of the bay, although the general location
probably is not a factor in toxicity.
Sediment toxicity tests using amphipods results
indicated that acute toxicity due to contaminated
sediments occurred infrequently in sediments
sampled for Galveston Bay. Carr (1993) also
reported very low occurrence of amphipod toxicity in
Galveston Bay sediments. However, in contrast, he
reported that significant toxicity was observed at a
number of sites when sea urchin (Arbacia
punctulatd) fertilization and morphological
development assays were used.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 13
-------
SEDIMENT COMPONENT
DISTRIBUTIONS: Abiotic Habitat
Indicators for Sediments
Total Organic Carbon
Total Organic Carbon (TOC) in Galveston Bay
sediments ranged from 0.14% (at EGB5) to 2.43%
(at EGB1). Proportions of TOC concentrations in
sediments for the area represented by the 29
randomly selected sites in Galveston Bay were lower
overall than the entire Louisianian Province area.
Selected small bay and marina sites in Galveston Bay
have similar distributions of sediment TOC
concentrations as the Louisianian Province sites.
Galveston Bay area consists of 62% low sediment
organic content (<1% TOC), 34% slightly enriched
(1-2% TOC), and 3% highly enriched (>2% TOC).
Small Bay and Marina sites consist of 44% low
TOC concentrations, 44% slightly enriched, and 12%
highly enriched. The Louisianian Province area
consists of 49% low organic content, 37% slightly
enriched, and 14% highly enriched (Figures 14 &
15).
Sediment Composition (Silt-Clay
Content in Sediments)
Proportions of Silt-Clay in sediments for the area
represented by the 29 randomly selected sites in
Galveston Bay are higher than Silt-Clay contents in
sediments throughout the Louisianian Province
(Figures 16 & 17). The Galveston Bay area consists
of 48% mud, 45% muddy sand, and 7% sand. Small
Bay and Marina sites consists of 67% mud, and 33%
muddy sand. The Louisianian Province area consists
of 35% mud (>80%), 44% muddy sand, and 21%
sand (<20%).
Sediment texture is an important factor in
determining which benthic organisms will be found
in the estuarine environment. The texture of
sediment is defined by the percentage of silt, clay,
and sand in sediment. Higher Mean Amphipod
Abundance and higher Benthic Index values are
associated with lower Silt-Clay percentages in the
sediments with correlations of-0.57 and -0.67,
respectively.
Figure 14. Total Organic Carbon Distributions in the Sediments
and 90% Confidence Intervals
Figure 16. Sediment Composition Compared by Percent of
Area or Sites and 90% Confidence Intervals
Louisianian
Province
Figure 15. CDF of Total Organic Carbon in Galveston Bay
Sediments.
Figure 1 7. CDF of Percent of Silt-Clay in Galveston Bay
Sediments.
40 60
% Silt-Clay
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 14
-------
Aluminum in Sediments
Acid Volatile Sulfides
The earth=s crust is the source of most of the
aluminum found in sediments. Aluminum does
not have a significant anthropogenic source. For
the Texas estuaries sampled in 1993, aluminum
values covary with sediment texture and other
heavy metal concentrations in the sediments.
In Galveston Bay and the small bays and marina
areas sampled, a significant relationship exists
between percent aluminum distribution and the
percent silt-clay distribution (R = 0.84). A
significant relationship (R = -0.44) does not exist
between aluminum and the benthic index.
Aluminum concentrations in sediments at the
Small Bay and Marina sites were high, indicating
that all of these sites are in high depositional areas
with aluminum concentrations greater than 3.6%
(Table 4, Figures 18 & 19, Map 4).
Figure 1 8. Categories of Percent Aluminum in Sediments
Compared by Percent of Area or Sites and 90% Confidence
Intervals.
100
Acid Volatile Sulfides (AVS) are important in
controlling the bioavailability of metals under
anoxic conditions (DiToro, et al., 1991). In the
Louisianian Province sediments, the AVS
concentration ranged from 1-20 umoles.
Approximately 50% of the Louisianian Province
area has an AVS concentration in the sediments of
less than or equal to 1 umole/gram. Approximately
93% of the Louisianian Province estuarine area has
3 or less umoles/gram of AVS in the sediments.
The AVS concentration in Galveston Bay ranged
from 0.2 to 7.2 umoles/gram. Galveston Bay has
AVS sediment concentrations less than or equal to
1 umole at 66% of the area represented by the 29
randomly selected sites (Figure 20). Overall, the
Galveston Bay area has lower AVS concentrations
than the distribution throughout the Louisianian
Province. In the Galveston Bay, 93% of the area
had AVS concentrations less than 3 umoles/gram,
which is the same as the distribution for the
Louisianian Province.
AVS concentrations in the sediments of Small Bay
and Marina sites ranged from 1.2 to 10.0
umoles/gram. AVS concentrations are higher than
3 umoles/gram at 7 of 9 sites or 78% of sites.
GB Small Bay & Marina
Sites
Galveston Bay
Figure 19. CDF of Aluminum Concentration in Galveston Bay
Sediments.
2.0 4.0 6.0
Aluminum (%)
Figure 20. CDF of Acid Volatile Sulfides in Galveston Bay
Sediments.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 15
-------
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Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 16
-------
Table 4. Sediment Component Distributions.
System
GB Small Bays/Marinas
Galveston Bay
Louisiana Province
% SILT-CLAY
CONTENT
<20%
0
7
21
20-80
33
45
44
>80%
67
48
35
% ALUMINUM
<2.9
0
7
7
2.9-
3.6
0
24
7
3.6-
5.0
22
21
9
>5.0
78
48
9
% TOTAL ORGANIC
CARBON
2%
12
3
14
Table 5. Acid Volatile Sulfides Distributions in Sediments.
System
GB Small Bays/Marinas
Galveston Bay
Louisiana Province
ACID VOLATILE SULFIDES (UMOLES/GRAM)
<1
0
66
-50
Ito3
22
27
-43
>3
78
7
~7
Heavy Metal Distributions
Identifying Areas with Exceedences
and Contamination from
Anthropogenic Sources
Concentrations for fifteen heavy metals in sediments
of Galveston Bay were collected at 38 sites. Heavy
metals were compared to established criteria and
anthropogenic enrichment. The range-low (ERL)
criteria was established using the lower 10th
percentile of effects data for each metal or chemical.
Concentrations equal to or above the ERL, but
below the ERM, represent a possible-effects range
within which effects would occasionally occur. The
range-high (ERM) criteria was established using the
50th percentile of the effects data. The
concentrations equal to or higher than the ERM value
represent a probable-effects range within which
effects would frequently occur (Long, et al., 1995).
The concentrations equal to the NOEL value is the
highest level at which Ano observed effects® occur
(MacDonald, 1992). Anthropogenic enrichment was
determined using regression equations for each metal
against aluminum concentrations in the sediments.
Aluminum is used as a normalization factor because
it is an abundant and relatively uniform crustal
element, and it does not have a significant
anthropogenic source (Summers, et al., 1996). Two
sets of equations were used: 1) Hanson et al., 1993
and 2) Summers et al., 1996. Hanson=s equations
were developed from data collected along the
Atlantic and the Gulf of Mexico U.S. coasts.
Summers= equations were developed from data
collected during EMAP Studies for the Gulf of
Mexico U.S. coastal area only.
Metals of greatest concern for monitoring include
cadmium, chromium, mercury, lead, arsenic,
selenium, and antimony because they are highly toxic
to biota and they have few natural functions in biotic
processes (Kennish, 1992). Copper, nickel, silver,
tin, and zinc also are toxic to biota (Freedman, 1989).
These 12 metals (except selenium) have the criteria
threshold values, ERL, ERM, and NOEL, associated
with them.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 17
-------
Agriculture is an important source of arsenic, lead,
and copper pollution. Automobiles and boats are
major sources of lead pollution, and they are also a
source of cadmium, chromium, copper, nickel, and
zinc pollution. Sewage sludge is a source for several
heavy metal pollutants. Industry is a major source of
nickel, copper, zinc, lead, cadmium, and other metal
pollutants (Freedman, 1989).
Sources of metal contamination according to Cole et
al. (1984) include the following:
Arsenic - fossil fuel combustion and industrial
discharges.
Cadmium - corrosion of alloys and plated surfaces,
electroplating wastes, exterior paints and stains, and
industrial discharge.
Copper - corrosion of copper plumbing, anti-fouling
paint, and electroplating wastes.
Lead - leaded gasoline, batteries, and exterior paints
and stains.
Mercury - natural erosion and industrial discharges.
Zinc - tires, galvanized metal, and exterior paints and
stains.
In Galveston Bay, arsenic, copper, lead, nickel, and
zinc exceed the ERL but not the ERM criteria at one
or more sites sampled (Tables 6 & 7, Figure 21).
NOEL values, but not ERL values, are exceeded at
one or more sites for arsenic, chromium, lead,
mercury, and zinc (Table 8). Sites with the most
metals contamination include Offat=s Bayou (OB),
Clear Lake (CL), Moses Lake/Dollar Bay (MLDL),
and two Marina sites (Table 8, Maps 5 and 6). The
Small Bay and Marina sites were chosen, not
randomly selected, so they are not included in the
comparison of Galveston Bay with the entire
Louisianian Province 1993 EMAP sampling area.
The Galveston Bay area (represented by the 29
randomly chosen sites) has chromium and nickel
distributions that are higher than would be expected
when compared to the entire Louisianian Province
area (Table 9). However, chromium, lead, and nickel
are also highly correlated with aluminum, which
could indicate that these metals are in high
concentrations due to crustal abundance.
Heavy metal concentrations are often normalized to
aluminum concentrations to account for the metal
concentration expected based on crustal abundance
(Summers, et al., 1996). For this study, comparisons
focus on the second set of equations developed from
the 1993 EMAP data (Macauley et al., 1993).
According to these equations, most nickel
concentrations in the sediments are high due to
anthropogenic sources. In addition, chromium, lead,
mercury, silver, and zinc concentrations at several
sites are high due to anthropogenic sources.
Cadmium, arsenic, and copper concentrations are
higher than expected due to natural deposition at a
few sites (Table 10, Figure 22). Most sites with
metal concentrations exceeding ERL or NOEL
values are classified as having anthropogenic sources
for these metals.
Figure 21. NOEL Exceedence for Five Metals Compared by
Percent of Area or Sites and 90% Confidence Intervals
Small Bay & Marina Sites
Galveston Bay
Figure 22. Comparison of Metal Concentration Classifications
for Enrichment and Exceedance for 38 Sites in Galveston Bay
Complex.
As Cd Cr Cu Hg Ni Pb Zn
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 18
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Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 19
-------
Table 6. Metal Concentration (ppm) Ranges, and ERL & ERM
Exceeding in Sediments of Galveston Bay and Its Associated
Small Bay & Marina Sites.
METAL
Aluminum
Antimony
Arsenic
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Tin
Zinc
RANGE (PPM)
6510
0.03
1.62
0.1
6.6
2.3
2073
2.51
40.0
0.014
1.4
0.06
0.09
0.2
12.4
75700
0.86
11.09
0.78
75.5
57.8
40020
50.94
1194
0.096
33.8
0.69
0.35
3.4
216.6
ERL ERM
NA
2
8.2
1.2
51(81)
24 (34)
NA
46.7
NA
0.15
20.9
NA
3(1)
NA
150
NA
25
85 (70)
9.6
370
270
NA
218
NA
0.71
51.6
NA
3.7
NA
410
PERCENT EXCEEDED
ERL ERM
NA
0%
18% (18%)
0%
55% (0%)
16% (10%)
NA
3%
NA
0%
60%
NA
0%
NA
8%
NA
0%
0%
0%
0%
0%
NA
0%
NA
0%
0%
NA
0%
NA
0%
ERL and ERM exceeding values were taken from Long, et al. (1995).
ERL and ERM exceeding values in parentheses were taken from Long and Morgan (1990).
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 20
-------
Table 7. Galveston Bay Sites With a Summary of Sediment Metal Concentrations Exceeding
ERL or NOEL, and Higher Aluminum and Silt-Clay Content Values for Natural
Concentration Comparison.
Stations
GB1
GB2
GB3
GB4
GB5
GB6*
GB7*
GB8
GB9
GB10 *
GB11
GB12
TB1 *
TB2 *
TB3 *
TB4
TBS*
TB6
TB7
TBS*
TB9*
TB10
EGB1
EGB2 *
EGB3 *
EGB4 *
EGB5 *
WGB1
WGB2
OB *
MLDL*
DKL
CL *
MAI *
MA2 *
MA3 *
MA4 *
MAS
Aluminum
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Silt-Clay
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Arsenic
>
As
As
As>
As
As
As
As
As
Chromium
CrA >
CrA >
Cr >
CrA >
CrA >
CrA >
CrA
CrA
CrA
Cr
Cr
CrA
CrA
CrA >
Cr
CrA
CrA >
CrA
CrA >
Cr>
Cr
CrA >
CrA
CrA >
CrA >
CrA >
Cr
CrA
Cr
Copper
>
>
Cu>
>
Cu>
Cu>
Cu>
Cu>
Cu>
Lead
>
Pb >
Pb
Pb
Pb >
Pb
>
Pb >
Pb >
>
>
Pb >
Pb >
Pb >
Pb >
>
>
Pb >
Pb >
Pb >
Pb >
Pb >
Pb >
Mercury
>
>
>
>
>
>
>
>
>
Hg >
>
>
>
>
Nickel
Ni >
Ni >
>
>
Ni >
Ni >
>
Ni >
>
Ni
Ni >
Ni >
>
Ni >
>
Ni
Ni
>
Ni
Ni >
Ni >
Ni
Ni >
>
Ni >
Ni >
>
Ni
Ni >
Ni >
Ni >
Ni >
>
Zinc
Zn >
Zn >
>
>
>
Zn >
Zn >
>
Zn >
>
Zn
Zn
Zn
Zn >
Zn
Zn
Zn
Zn
Zn
Zn >
Zn >
>
Zn >
Zn >
>
Zn >
Zn >
Zn >
Zn >
Zn >
>
* Cluster analysis indicates highest heavy metal concentrations (for 15 metals measured).
Plain type - values exceed NOEL; Shading - values exceed ERL
> - higher than natural abundance; H - high Aluminum or % Silt-Clay values; CrA - exceeds old ERL value of 51.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 21
-------
Table 8. Metal Concentration Ranges, and NOEL & ERL
of Galveston Bay and Its Associated Small Bay
Exceeding in Sediments
& Marina Sites.
Galveston Bay Small Bays/Marinas
Percent Exceeded Percent Exceeded
Heavy Metals NOEL ERL NOEL ERL NOEL ERL
Arsenic
Chromium
Copper
Lead
Mercury
Nickel
Zinc
8
33
28
21
0.1
NA
68
8.2
51.0 (81.0)
24.0 (34.0)
46.7
0.15
20.9
150.0
17%
72%
0%
38%
0%
NA
55%
17%
52% (0%)
0%
0%
0%
55%
4%
33%
89%
67%
67%
11%
NA
78%
22%
78% ( 0%)
67% (44%)
11%
0%
78%
22%
ERL and ERM exceeding values were taken from Long, et al. (1995).
ERL and ERM exceeding values in parentheses were taken from Long and Morgan (1990).
Table 9. Percent of Area With ERL Exceeded in Sediments of Galveston Bay
(Represented by 29 Sites) and the Louisianian Province.
Metal
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Silver
Zinc
ERL
2.0
8.2
1.2
51.0(81.0)
24.0 (34.0)
46.7
0.15
20.9
3.0
150.0
Percent ERL Exceeded
in Galv. Bay Area
0%
17%
0%
52% (0%)
0%
0%
0%
55%
0%
4%
Percent ERL Exceeded
in Louisianian Province Area
0%
33%
1%
9%
0%
0%
3%
35%
0%
4%
ERL and ERM exceeding values were taken from Long, et al. (1995).
ERL and ERM exceeding values in parentheses were taken from Long and Morgan (1990).
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 22
-------
Table 10. Comparison of Heavy Metal Concentrations with Regression Values
for Metals in Uncontaminated Sediments using Aluminum
Concentrations as a Standard.
1) by Hanson, et al. 1993, and 2) from Summers et al., 1996 and
1993 EMAP Study.
Metals
Sites with Metal Concentrations Higher than Uncontaminated Sediments
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Silver
Zinc
1) none
2) *GB2,TB5
1) none
2) OB, MA4, MAS, MLDL, GB2*, TB7, TB8, TB9, TB10
1) *GB2
2) CL, OB, EGB3, EGB5, GB1, GB2*, GB3, GB4, GB6, GB7, MAI, MA2,
TB9,WGB1
1) CL, MAI, MA2, MA3, MA4, MLDL, OB
2) CL, MAI, MA2, MA3, MA4, MLDL, OB, GB2*, GB4
1) CL, OB
2) CL, OB, MLDL, EGB1, EGB2, EGB3, EGB4, EGB5, GB5*, GB6, MAI, MA2,
MA4, MAS, TB1, TB6, TB8, TB9, TB10, WGB1, WGB2
1) none
2) CL, OB, MLDL, GB1, GB2*, GB3, GB6, GB12, MAI, MA2, MA4, TB2,
TB5,WGB1,EGB2
1) *GB2, GB7,MA1
2) OB, MLDL, EGB1, EGB3, EGB4, GB1, GB2*, GB3, GB4, GB6, GB7, GB8,
GB10, GB12, MAI, MA2, MA3, MA4, MAS, TB2, TB3, TBS, TB6*,
WGB1,WGB2
1) CL, MA2, MA4, OB, MLDL
2) CL, OB, MLDL, MAI, MA2, MA3, MA4, MAS, GB1, GB2*, GB3, GB4,
GB5*, GB8, GB11, GB12, TB1, TB2, TB3, TB4, TBS, TB6*, TBS, TB9,
TB10,WGB1,WGB2
1) OB, CL, MAI, MA2, MA3, MA4, GB1, *GB2, GB6
2) CL, OB, MLDL, GB1, GB10, GB12, GB2*, GB3, GB4, GB6, GB7, GB8,
MAI, MA2, MA3, MA4, MAS, TBS, WGB1, WGB2
*GB2 has a low Aluminum value. GB5 and TB6 have very low Aluminum values.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 23
-------
Identifying Areas with High Metal
Concentrations in the Past and
Present
Several historic datasets from Galveston Bay (1950's
- 1980's) were analyzed by Ward and Armstrong
(GBNEP 22, 1992) with the following general
conclusions: 1) High concentrations of copper occur
in mid-Trinity Bay and mid-East Bay, while high
concentrations of lead and zinc occur in lower
Galveston Bay inside the inlet. 2) Metals are
elevated in general region of the lower bay and the
Houston Ship Channel and both sides of the Texas
City Dike. 3) They hypothesize that the principal
sources of metals in Galveston Bay are from the
Houston Ship Channel and Texas City areas, in turn
originating from runoff from highly industrialized
areas, waste discharges, and shipping activity.
Ward and Armstrong (GBNEP 22, 1992) reported
high copper sediment values in mid-Trinity Bay,
mid-East Bay and in lower Galveston Bay. The
Texas City Industrial Area is the likely source of the
copper contamination in lower Galveston Bay. In
addition, high copper values were reported near and
in Clear Lake area, which also are found in the
present study. The Bureau of Economic Geology
(BEG) Study (White et al., 1985) reported copper
concentrations exceeding the ERL screening value in
mid-Trinity Bay, western upper Galveston Bay,
Galveston Channel, Clear Lake, and Offat=s Bayou.
In the present study, copper concentrations exceed
ERL criteria and natural deposition values at six
Small Bay and Marina sites, including Clear Lake
and Offat=s Bayou (Tables 7 & 8). A recent study by
Guillien, et al. (1993) also reported high copper
concentrations at the same marina sites. When
comparing the results of the present and past studies,
copper contamination appears to have decreased in
the open areas of the Galveston Bay Complex. The
source of copper contamination could be anti-fouling
paint from boats or possibly urban nonpoint source
pollution.
Chromium values are high due to anthropogenic
sources at several sites throughout the Galveston Bay
Complex (Tables 7 & 8). Results from the Bureau
of Economic Geology Study also show chromium
concentrations higher than ERL in most of upper
Galveston Bay and Trinity Bay (except along bay
margins), the northern half and upper portion of East
Galveston Bay, in Galveston Channel, Clear Lake,
and Offat=s Bayou. The findings of the present study
are in agreement with the BEG=s reported locations
of high chromium contamination.
In the present study, higher lead concentrations
(above NOEL but not ERL values) are found on the
east side of Trinity Bay, East Bay and in the small
bays (OB, MLDL, & CL). Concentrations exceed
the ERL value in Offat=s Bayou only, and are near
exceedence in Clear Lake. Lead concentrations
appear to be lower in the present study compared to
results from the BEG study. In the BEG study, most
lead concentrations are lower than the ERL values.
A few isolated areas have values higher than the lead
ERL including 1) south of Morgan=s Point and east of
the Ship Channel (in the GB1 area), and 2) between
Eagle Point and Smith Point near the Ship Channel,
at the mouth of upper Galveston Bay.
Arsenic concentrations are highest at site TBS in
mid-Trinity Bay. Arsenic concentrations are above
the ERL value at six other sites but they are not
higher than expected based on normalization to
aluminum.
High Nickel and Zinc concentrations (higher than
ERL or NOEL) were reported by Ward and
Armstrong (GBNEP 22, 1992) at the same areas as in
the present study (Table 7). Also, nickel (above
ERL) and zinc (above NOEL) concentrations are
found at several sites throughout the bay. The BEG
Study results are in agreement with the present study
with nickel and zinc concentrations high throughout
the bay. Nickel concentrations were found to be
higher than the ERL in most of the open areas of
upper Galveston Bay and Trinity Bay, north and
upper East Bay, north of the Texas City Dike, Clear
Lake, and Galveston Channel. In the BEG Study
results, zinc concentrations are higher than the ERL
in Offat=s Bayou, Clear Lake, between Eagle Point
and Smith Point, Trinity Bay near Smith Point, and
Cedar Bayou Channel. Zinc concentrations are
higher than the NOEL but lower than the ERL in the
open area of Trinity Bay and upper portion of East
Bay, between Tiki Island and Offat=s Bayou in West
Bay, near Flamingo Isle in West Bay, and two
isolated areas of lower Galveston Bay.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 24
-------
Butyltin Compounds
Tributyltin (TBT) is toxic to marine animals and is
used in anti-fouling paint for boats. TBT has been
restricted for use in recent years to only larger boats
in an effort to reduce the amount of TBT
contamination in the marine environment. Values
exceeding 1.0 ppb in the sediments are used as a
screening criterion.
TBT values of 1 to 5 ppb occurred at 48% of
Galveston Bay sites, and 22% of Small Bay and
Marina sites. TBT values greater than 5 ppb occur at
3.4% of the Galveston Bay area (site GB1), and 67%
of Small Bay and Marina sites. Considerably higher
TBT values (13.3 ppb to 40.7 ppb) occurred at four
of five marina sites and in Offat=s Bayou (Tables 11
& 12, Map 7). Obviously, TBT concentrations in the
sediments were higher in areas of higher boat traffic.
Values were high in Offat=s Bayou due to the
restricted nature of this small bay.
TBT concentrations were higher in Galveston Bay
sediments than in Louisianian Province sediments
overall. Values greater than 1 ppb occurred in 52%
of the area, compared to 31% of the total Louisianian
Province area. Louisianian Province TBT values of
1-5 ppb were found in 24% of the total area and >5
ppb were found in 7% of the total area (Figures 23 &
24).
High Dibutyltin (DBT) values occurred at 38% of the
Galveston Bay area, and 89% of Small Bay and
Marina sites chosen. DBT values greater than 5 ppb
occurred at GB6, MA2, MA3, MA4.
Figure 24. CDF of Tributyltin in Galveston Bay Sediments.
High Monobutyltin (MET) values occurred at 34.5%
of the Galveston Bay area, and 89% of Small Bay
and Marina sites chosen. MET values greater than 5
ppb occurred at MAI and MA3.
Table 11. Percent of Area or Sites with
Sediment TBT Concentrations Greater than
or Equal to 1.0 ppb and 5.0 ppb.
System
Galveston Bay SB & MS
Galveston Bay
Louisianian Province
TBT> 1.0
78%
48%
31%
TBT > 5.0
67%
3%
7%
Figure 23. TBT Concentrations Exceeding 1.0 ppb and 5.0 ppb
Compared by Percent of Area or Sites and 90% Confidence
Intervals.
Louisianian
Province
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 25
-------
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Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 26
-------
Table 12. Galveston Bay Sites with Butyltin Concentrations Exceeding the
1.0 ppb Criteria.
Stations
GBl
GB2
GB3
GB4
GB5
GB6
GB7
GB8
GB9
GB10
GB11
GB12
TB1
TB2
TB3
TB4
TBS
TB6
TB7
TBS
TB9
TB10
EGB1
EGB2
EGB3
EGB4
EGB5
WGB1
WGB2
OB
MLDL
DKL
CL
MAI
MA2
MA3
MA4
MAS
TBT
6.3
2.2
3.6
2.4
2.5
3.0
2.3
3.8
3.0
2.3
0.9
1.5
1.0
1.8
0.9
2.5
17.7
1.7
1.2
8.5
19.4
13.3
40.7
24.5
DBT
4.0
1.8
2.2
1.6
12.5
2.5
1.0
1.1
1.3
1.4
0.95
1.8
4.5
2.5
2.3
3.3
4.0
5.0
10.3
11.2
MET
3.8
2.1
2.4
1.9
1.0
4.4
1.4
2.5
1.3
1.4
1.4
3.4
2.3
2.3
1.8
5.0
4.6
14.5
4.4
Total Butyltin
14.1
6.1
8.1
6.0
0.7
16.0
0.7
10.0
4.1
5.6
5.8
6.3
2.2
3.8
1.1
0.8
2.6
0.2
0.7
0.8
2.8
1.3
1.2
1.5
3.1
1.2
1.5
2.2
5.7
25.6
6.6
5.7
13.6
28.3
22.9
65.6
40.1
1.9
TBT, DBT, & MET Values less than 1.0 ppb not shown. All values shown for Total Butyltin.
All sites had detectable TBT, DBT, & MET concentrations.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 27
-------
Comparison of Butyltin Concentrations in the
Sediments and Water Column.
Water samples were collected at the Marina sites
only and analyzed for mono-, di-, and tri- butyltin.
A significant relationship was found between
butyltin concentrations in the sediments and butyltin
concentrations in the water column.
The butyltin concentrations in the sediment and the
butyltin concentrations in the water column were
found to be closely associated, which indicated that
the sediments may be a continuous source of butyltin
to the water column (Table 13).
Table 13. Spearman Correlation Coefficients for Butyltin Compounds
at Marina Sites.
TBT in Water
DBT in Water
MET in Water
TBT in Sediments
DBT in Sediments
TBT in Sediments
0.68*
0.62
0.60
—
—
DBT in Sediments
0.30
0.37
0.40
0.80*
—
MET in Sediments
0.98*
0.91*
0.89*
0.70*
0.30
'indicates significance at p<0.05.
Pesticides
DDT and its associated compounds individually
did not exceed the ERL values for Galveston Bay
and its associated small bay and marina areas.
DDE, ODD, and DDT ranged from non-detectable
to 0.9 ug/Kg for all 38 sites. However, Total DDT
concentrations exceeded ERL values in Offat=s
Bayou sediments.
Dieldrin and Endrin ERL values were exceeded
at 17% and 5% respectively, in Galveston Bay,
and 33% and 0% for both Galveston Bay and the
Small Bay and Marina sites (Tables 14 & 15,
Figure 25). Sites with high Dieldrin and Endrin
concentrations in the sediments are located in
upper Galveston Bay (GB1, GB2, GB3, GB4,
MA2), Clear Lake (CL, MA3, MA4), and upper
Trinity Bay (TBS, TB10). These distributions
appear to be related to the proximity of these sites
to the San Jacinto River, the Trinity River, and
Clear Creek. Low benthic values at these sites
could be related to the presence of Dieldrin and
Endrin in the sediments.
Dieldrin concentration distributions were much
lower in Galveston Bay than in the Louisianian
Province. Endrin concentration exceedence by
area were lower in Galveston Bay compared to the
Louisianian Province. For the Louisianian
Province, Dieldrin and Endrin both were found in
exceedence of the ERL guidelines at 57% and 18%
respectively, of EMAP sites (Table 14). No other
pesticides exceeded ERL values for both studies
(although, many pesticides do not have exceedence
criteria established).
Figure 25. Percent of Area or Sites with ERL Exceedence of
Pesticides and 90% Confidence Intervals.
100 -
90 -
80 -
70 -
60 -
50 -
40 -
30 -
20
10 -
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L
DDDE
• alpha-Chlordane
Dgamma-Chlordane
DDieldrin
• Endrin
1
•
Small Bay & Galveston Bay Louisianian
Marina Sites Province
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 28
-------
Table 14. Pesticide Concentrations in Galveston Bay Sediments at 38
Sites.
Pesticide
2,4 ODD
4,4 ODD
2,4 DDE
4,4 DDE
2,4 DDT
4,4 DDT
Total DDT
Aldrin
alpha-BHC
beta- BHC
delta-BHC
alpha-Chlordane
gamma-Chlordane
Dieldrin
Endrin
Hexachlorobenzene
Heptachlor
Heptachlor Epoxide
Mirex
cis-Nonachlor
trans-Nonachlor
Oxychlordane
Lindane
Range (ppb)
0
0
0
0
0
0
0.2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.2
0.6
0.1
0.9
0.1
0.4
2.0
0
0.6
0
0
0.4
0.3
0.2
0.1
0.9
0
0.7
0
0.6
0.4
0
0.4
ERL ERM
2.0
2.0
2.0
2.2
1.0
1.0
1.58
NA
NA
NA
NA
0.5
0.5
0.02
0.02
NA
NA
NA
NA
NA
NA
NA
NA
20
20
15
15
7
7
46.1
NA
NA
NA
NA
6
68
45
NA
NA
NA
NA
NA
NA
NA
NA
NA
Percent Exceeded
10% 50%
0
0
0
0
0
0
3(0)
NA
NA
NA
NA
0
0
21 (17)
7(5)
NA
NA
NA
NA
NA
NA
NA
NA
0
0
0
0
0
0
0
NA
NA
NA
NA
0
0
0
0
NA
NA
NA
NA
NA
NA
NA
NA
Values in parentheses represent percentage of the 29 randomly sampled sites with ERL exceedences.
ERL and ERM exceedence values from Long and Morgan (1990).
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 29
-------
Table 15. Galveston Bay Stations with Sediment Pesticide and PAH
Concentrations Exceeding NOEL or ERL Values.
Stations
GBl
GB2
GB3
GB4
GB5
GB6
GB7
GB8
GB9
GB10
GB11
GB12
TB1
TB2
TB3
TB4
TBS
TB6
TB7
TBS
TB9
TB10
EGB1
EGB2
EGB3
EGB4
EGB5
WGB1
WGB2
OB
MLDL
DKL
CL
MAI
MA2
MA3
MA4
MAS
Dieldrin
Dieldrin
Dieldrin
Dieldrin
Dieldrin
Dieldrin
Dieldrin
Dieldrin
Dieldrin
Endrin
Endrin
Endrin
PAHs
C3 Fluorene, *Acenapthene, *HM PAHs P
*Contaminant values exceed the NOEL values but not the ERL values.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 30
-------
Polynuclear Aromatic
Hydrocarbons (PAHs)
Forty-four PAHs were analyzed in sediment samples
taken at the 38 sites in Galveston Bay. PAHs were
examined for exceedence of NOEL, ERL, and ERM
criteria (Table 16). PAHs exceeding ERL values in
Galveston Bay included only C3-fluorene at site TBS
in Trinity Bay where several active oil wells are
located. PAHs exceeding NOEL, but not ERL values
in Galveston Bay included Acenaphthylene and High
Molecular Weight PAHs only found at site TBS in
Trinity Bay (Tables 16 & 17). Distributions of Low
Molecular Weight PAHs and High Molecular PAHs
for Galveston Bay showed that three randomly
chosen sites (TBS, WGB1, WGB2) have PAHs that
were considerably higher than at the other sites in the
Galveston Bay area (Figures 26 & 27, Map 7).
Figure 26. CDF of High Molecular Weight PAH's in
Galveston Bay Sediments.
200 400 600 800 1000 1200
High Molecular Weight PAHs (ppb)
ERL criteria for C3-fluorene were exceeded in 3% of
Galveston Bay (site TBS), which were similar to
exceedences found in the entire area of the
Louisianian Province. In the Louisianian Province,
C3-fluorene ERL values were exceeded at 5% of the
area, and High Molecular Weight PAHs ERL values
were exceeded at 1% of the area. These were the
only individual PAHs with ERL values exceeded in
the Louisianian Province.
Major sources of PAHs to Galveston Bay include
spilled or released petroleum products, and
combustion products found in urban runoff (GBNEP
44, 1994). Ward and Armstrong (GBNEP 36, 1993)
reported that 65.8% of the Oil & Grease loading to
Galveston Bay comes from non-point source
pollution, 31.1% comes from Municipal WWTP, and
3.1% comes from industry wastewater discharges.
PAH concentrations exceeding ERL and/or NOEL
criteria occurred only in mid-Trinity Bay (site TBS),
where several oil platforms are located (Map 7).
Ward and Armstrong (GBNEP 22, 1992) and Carr
(GBNEP 30, 1993) reported very high Oil & Grease
values in mid-Trinity Bay, where four large brine
discharges totaling 2,000 MG/yr are located in
Trinity Bay. Trinity Bay and Tabbs Bay (400
MG/yr) appear to receive the bulk of brine discharge
in the Galveston Bay Complex. Of the 51 brine
discharges in this system, 16 are located in Trinity
Bay and 10 are located in Tabbs Bay (Armstrong and
Ward, GBNEP 36, 1993).
Figure 27. CDF of Low Molecular Weight PAHs in
Galveston Bay Sediments.
50 100 150
Low Molecular Weight PAHs (ppb)
Ward and Armstrong (GBNEP 22, 1992) also report
high Oil & Grease values (although not as high as in
mid-Trinity Bay) in the Houston Ship Channel, in
and around the Clear Lake area, north of the Texas
City Dike, and in far West Bay. In the present study,
high PAH values (that do not exceed NOEL criteria)
also are found in Clear Lake, four of five Marina
sites, and Moses Lake/Dollar Bay. And, unlike the
GBNEP 22 Study, the present study also found high
PAHs in West Bay south of the Texas City Dike
which may be influenced by the petroleum industry
in Texas City . In contrast, two sites on the
Galveston Island shoreline that did not have PAHs
present in the sediments include Offat=s Bayou and
Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 31
-------
the Marina site (MAI) in Galveston Channel.
However, Qian et al. (1999) reported detecting
elevated PAH concentrations in samples collected
from these areas.
Cluster analysis results of PAH distributions are
shown on Map 7. High PAHs were found on the
western shoreline in Galveston Bay and near the
Galveston Island shoreline. These locations are near
areas of high human activity, such as urban areas,
industry, and shipping.
East Bay Bayou on the Intracoastal Waterway
(ICWW) was another area associated with Galveston
Bay that had PAH concentrations higher than ERL
values. (Map 7). Sediment concentrations in the
ICWW exceeded ERL criteria for C2 & C3 Fluorene
and C3 Phenanthrene. Nearby oil fields are a
possible continuous source of PAHs in this area.
The watershed in this area is sparsely populated with
very little human activity. The East Bay Bayou area
will be discussed in detail in a separate report.
Table 16. Percent of Area or Sites Exceeding Polynuclear Aromatic
Hydrocarbon ERL Values.
System
East Bay Bayou
Galveston Bay SB&MS
Galveston Bay
Louisianian Province
C2-Fluorene
50%
0%
0%
0%
C3-Fluorene
83%
0%
3%
5%
C3-Phenanthrene
33%
0%
0%
0%
Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 32
-------
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Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 33
-------
Table 17. Polynuclear Aromatic Hydrocarbon Concentrations in Galveston Bay
Sediments for 38 Sites.
PAH
Acenaphthene (L)
Acenaphthylene (L)
Anthracene (H)
Benzo(a)anthracene (H)
Benzo(a)pyrene (H)
Benzo(b)fluoranthene (H)
Benzo(e)pyrene (H)
Benzo(g,h,i)perylene (H)
Benzo(k)fluoranthene (H)
Biphenyl (L)
Chrysene (H)
Cl-chrysene (H)
C2-chrysene (H)
C3-chrysene (H)
C4-chrysene (H)
Dibenzo(a,h)anthracene (H)
Dibenzothio (H)
Cl-dibenzothio (H)
C2-dibenzothio (H)
C3-dibenzothio (H)
Fluoranthene (H)
Cl-fluoranthpyrene (H)
Fluorene (L)
Cl-fluorene (L)
C2-fluorene (L)
C3-fluorene (L)
Naphthalene (L)
Cl -naphthalene (L)
C2-naphthalene (L)
C 3 -naphthalene (L)
C4-naphthalene (L)
Perylene (H)
Phenanthrene (H)
Cl-phenanthrene (H)
C2-phenanthrene (H)
C3-phenanthrene (H)
C4-phenanthrene (H)
Pyrene (H)
(i)l,2,3-c,d-pyrene (H)
1-methylnaphthalene (L)
2-methylnaphthalene (L)
2,3,5-trimethylnaphthalene (L)
2,6-dimethylnaphthalene (L)
1-methylphenanthrene (H)
High Molecular Weight PAHs
Low Molecular Weight PAHs
Total PAHs
Range (ppb)
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.3
0.2
0.2
0.2
0
0
0
0
0.1
0
0
0
0
0.3
0
0.1
0
0
0
0.7
0.4
0
0
0
0.3
0.3
0
0
0
0
0.4
0.1
0.2
0.1
0.2
0.1
0.1
3.1
2.6
6.1
3.5
40.7
56.2
105
122
127.6
88.4
56.4
135.3
1.9
164.4
81.4
36.7
5.15
9.0
16.1
1.8
1.9
8.6
12.5
119.1
140.6
6.2
4.0
14.0
27.6
4.1
11.3
8.3
11.4
12.3
45.2
45.9
34.3
38.7
48.2
31.8
154.1
68.1
2.9
9.2
2.4
2.6
7.1
1201.7
173.7
1884.9
ERL
16.0
44.0
85.3
261
430
NA
430
NA
NA
NA
384
384
384
63.4
63.4
63.4
NA
NA
NA
NA
600
NA
19.0
19.0
19.0
19.0
160
160
160
160
160
NA
240
240
240
240
240
665
NA
NA
70.0
NA
NA
NA
1700
552
4022
ERM
500
640
1100
1600
1600
NA
1600
NA
NA
NA
2800
2800
2800
2800
2800
260
NA
NA
NA
NA
5100
NA
540
540
540
540
2100
2100
2100
2100
2100
NA
1500
1580
1580
1580
1580
2600
NA
NA
670
NA
NA
NA
9600
3160
44792
Percent Exceeded
10% 50%
0
0
0
0
0
NA
0
NA
NA
NA
0
0
0
0
0
0
NA
NA
NA
NA
0
NA
0
0
0
3
0
0
0
0
0
NA
0
0
0
0
0
0
NA
NA
0
NA
NA
NA
0
0
0
0
0
0
0
0
NA
0
NA
NA
NA
0
0
0
0
0
0
NA
NA
NA
NA
0
NA
0
0
0
0
0
0
0
0
0
NA
0
0
0
0
0
0
NA
NA
0
NA
NA
NA
0
0
0
Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 34
-------
The Louisianian Province Total PCBs range was 0.0
to 73.3 ppb, with less than 1% of the Louisianian
Province area having PCB levels exceeding the
criterion.
Polyclorinated Biphenyls
Total PCBs ranged from 0.0 to 6.1 ppb in Galveston
Bay and its associated Small Bay and Marina Sites.
None of the measured PCB concentrations exceeded
the criterion for low-level ecological effects which is
22.7 ppb. PCB congeners 128 and 138 were found
in greatest concentration among all PCB forms at 7.7
and 4.4 ppb, respectively (Table 18).
Table 18. Polychlorinated Biphenyl (PCB) Concentrations in
Galveston Bay Sediments.
PCB (Congener)
8 (CL2)
18 (CL3)
28 (CL3)
44 (CL3)
52 (CL4)
66 (CL4)
101 (CL5)
105 (CL5)
1 10/77 (CL5/4)
1 18/108/149 (CL5/5/6)
126 (CL5)
128 (CL6)
138 (CL6)
153 (CL6)
170 (CL7)
180 (CL7)
187/182/159 (CL7/7/6)
195 (CL8)
206 (CL9)
209 (CLIO)
TOTAL PCBs
Range (ppb)
0-1.0
0-0
0-0.6
0-0.2
0-0.5
0-0.7
0-0.6
0-0.4
0-0.7
0-0.8
0-0.7
0-7.7
0-4.4
0-1.7
0-4.1
0-0.5
0-1.5
0-0.1
0-0.2
0-0.5
0.0 - 8.2
Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 35
-------
Sites Near Dredging Activities.
A consistent pattern between dredging activities and
the Sediment Quality Triad Components did not
appear to exist when comparisons were made
throughout the bay. However, past dredging activity
was responsible for poor conditions in Offat=s Bayou,
and may have affected other sites individually rather
than affecting all sites in the same manner. High
cumulative 404-permitted dredged areas (>200
acres), which are distributed by GBNEP
hydrographic area, are located near sites DKL,
WGB2, and CL (GBNEP 28, 1993). Sites CL and
DKL have a degraded benthic community structure,
which may or may not be caused by dredging
activities. Note that these sites are chosen sites, not
randomly selected sites.
Randomly Sampled Sites with Dredging Activities:
1. GB8 and GB9 are located near the main
channel in lower Galveston Bay. Both sites
have healthy benthic community structure
and good sediment quality.
2. TB3 is located near the channel entering
Double Bayou. Site TB3 has a marginal
benthic community structure and degraded
sediment chemistry.
3. TBS is located on spoil areas of Anahuac
Channel in upper Trinity Bay. Site TBS has
both a degraded benthic community
structure and degraded sediment chemistry.
4. WGB2 is located on spoil areas of the
ICWW entering Galveston Channel. Site
WBG2 has a healthy benthic community
structure and good sediment chemistry.
Small Bay Sites with Dredging Activities:
1. Site CL is located on a spoil area in Clear
Lake. Site CL has both a degraded benthic
community structure and degraded sediment
chemistry.
2. Site OB is located in the dredged area of
Offat=s Bayou. Site OB is degraded for all
three Sediment Quality Triad Components.
3. Site DKL has a degraded benthic community
structure and toxic sediments.
All Marina Sites have been exposed to dredging
activities and do display poor benthic community
structure and/or degraded sediment chemistry. In
addition, they are poorly flushed areas.
Water Quality Measurements
Surface temperatures during R-EMAP sampling in
Galveston Bay ranged from 24.50 C to 30.45 C.
Bottom temperatures ranged from 24.6 C to 30.3 C
(Table 19, Figure 28). Bottom temperatures during
EMAP sampling in the Louisianian Province ranged
from 24 C to 34 C.
Figure 28. CDF of Bottom Water Temperature in Galveston
Bay.
100 •'
90 •'
80 •'
a 70 --
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III."'
ra
c
"a.
E
Q_
III
O)
C
0)
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Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 37
-------
Figure 29. CDF of Salinity in Surface Waters of Galveston Bay.
0.0 3.0 6.0 9.0 12.0 15.0 18.0 21.0 24.0 27.0
Salinity (ppt)
Figure 31. CDF of Salinity Stratification in Galveston Bay
Waters.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Difference between Bottom and Surface Water Salinity (ppt)
Salinity ranged from 11.3 ppt to 32.3 ppt in bottom
waters (Table 19, Figure 30). Significant water
column stratification was seen in upper Galveston
Bay and in Trinity Bay where freshwater inflows
enter the bay from the Houston Ship Channel, the
San Jacinto River and the Trinity River (Figure 31).
31% of the Galveston Bay area and 22% the Small
Bay and Marina sites had bottom water salinities
ranging from 11 ppt to 18 ppt. 69% of the Galveston
Bay area and 78% of Small Bay and Marina sites had
bottom water salinities greater than 18 ppt. None of
the Galveston Bay Complex sites had salinities less
than 11 ppt (Tables 19 & 20, Figure 32).
Figure 30. CDF of Salinity of Bottom Waters in Galveston Bay.
Figure 32. Bottom Water Salinity Compared by Percent of
Area or Sites and 90% Confidence Intervals.
0.0 3.0 6.0 9.0 12.0 15.0 18.0 21.0 24.0 27.0
Salinity (ppt)
In the Louisianian Province, 51% of estuarine area
had bottom water salinities greater than 18 ppt, and
26% of estuarine area had bottom water salinities
between 5 and 18 ppt. Galveston Bay had higher
salinities than those reported for the entire
Louisianian Province (Figure 32). These higher
salinities are not unexpected, because Texas estuaries
generally have lower freshwater inflow per unit area
than the remainder of the Louisianian Province.
Small Bay & Galveston Bay
Marina Sites
Dissolved Oxygen (DO) concentrations in the water
column of Galveston Bay are good, especially for
August when the warmer water temperatures lead to
lower dissolved oxygen levels in water. Surface
water dissolved oxygen concentrations ranged from
6.15 and 11.70 mg/1 in Galveston Bay (Figure 46),
and from 4.65 to 10.10 mg/1 at the Small Bay and
Marina sites. Bottom water Dissolved Oxygen
concentrations ranged from 6.00 to 9.40 mg/1 in
Galveston Bay (Figures 33 & 34), and from 3.70 to
10.20 mg/1 at the Small Bay and Marina sites.
Galveston Bay surface and bottom water DO
concentrations were above 5 mg/1 in 100% of the
area represented by the 29 randomly selected sites.
Surface water DO concentrations were similar for
Galveston Bay and the Louisianian Province.
Galveston Bay bottom water DO concentrations were
higher overall than DO concentrations throughout the
entire Louisianian Province. In the Louisianian
Province, 96% of the surface water and only 67% of
the bottom water area had DO concentrations greater
than 5 mg/1.
Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 38
-------
Sites with bottom water dissolved oxygen
concentrations lower than 5.0 mg/1 included Offat's
Bayou, Lafayette Landing Marina, and South Shore
Marina (sites OB, MA3, MA4). The effects of the
bathymetry and the high deposition rate at Offat's
Bayou, likely caused the bottom water concentrations
to be low at Offat's Bayou. Sites MA3 and MA4 are
both located in Clear Lake. The heavy use of these
marinas, and the constricted nature of the marinas, as
well as Clear Lake, could be the cause for these
lower bottom water concentrations. In contrast, the
dissolved oxygen measurements at the Clear Lake
site (CL) were high at 10.10 mg/1. These high DO
levels probably were caused by high photosynthetic
rates in the water column, which could be due to
high inputs of nutrients from the local watershed.
Surface and bottom water pH levels were within
acceptable ranges. Surface water pH levels ranged
from 7.25 to 8.45 for all 38 sites. Bottom water pH
levels ranged from 7.10 to 8.55 for all 38 sites.
Water clarity, measured as secchi depth, ranged from
0.5 m to 2.5 m. These values indicate that all 38
sites had measurements of acceptable water clarity.
Generally, water clarity is not a good indicator of
degradation for Texas estuaries, because these
systems are naturally turbid. High turbidity
predominates in Texas estuaries due to wind
suspending sediments from the shallow depths.
Figure 33. CDF of DO in Surface Waters of Galveston Bay.
10
90 -
80 -
70 -
60-
50 -
40-
30-
20 -
10 -
0
2.0 4.0 6.0 8.0 10.0 12.0 14.0
Dissolved Oxygen (mg/l)
Figure 34. CDF of DO in Bottom Waters of Galveston Bay.
100 -
90 -•
80 --
70 ~
60--
so -
4°
30 --
20
10 --
0 --
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
Dissolved Oxygen (mg/l)
Results and Discussion - 1993 Galveston BavR-EMAP Study
Page 39
-------
Table 19. Galveston Bay Water Column Physical and Chemical Measurements.
Dissolved Oxygen Salinity (ppt)
Station Surface Bottom Surface Bottom
GB1
GB2
GB3
GB4
GB5
GB6
GB7
GB8*
GB9*
GB10
GB11
GB12
TB1
TB2
TB3*
TB4
TBS
TB6
TB7*
TBS*
TB9
TB10
EGB1
EGB2
EGB3
EGB4
EGB5
WGB1
WGB2*
OB*
MLDL
DKL*
CL*
MAI
MA2
MA3
MA4
MAS
11.7
6.8
7.85
7.5
6.25
6.95
6.65
6.35
6.4
7.75
7.65
6.25
7.5
7.55
7.4
8.1
7.95
7.75
8.55
8.55
9.0
9.3
8.05
7.9
7.4
7.65
8.1
6.15
6.45
5.45
6.9
7.7
10.1
5.15
5.95
4.65
6.35
6.5
6.2
6.65
6.45
6.55
6.3
6.9
6.3
6.3
6.4
7.7
7.3
6.15
7.33
6.95
7.45
7.9
7.6
7.65
7.75
8.3
9.4
9.4
7.85
7.2
6.3
8.55
8.1
6.0
6.25
4.4
6.85
6.95
10.2
5.05
5.5
3.7
4.25
6.5
18.4
21.05
20.4
20.5
21.35
19.5
16.85
22.5
23.05
24.05
24.2
24.35
15.9
19.1
15.85
13.0
15.2
16.45
12.9
11.15
13.05
14.45
23.9
23.45
21.25
21.6
20.35
26.1
26.1
30.3
21.15
17.9
16.1
24.55
18.3
18.6
15.55
32.25
19.6
21.0
20.5
21.25
21.35
21.05
16.85
22.9
23.2
24.1
24.2
24.35
15.87
19.3
17.15
13.05
18.2
16.4
13.8
11.3
14.4
14.4
23.95
23.7
23.2
21.65
20.4
26.65
26.1
30.5
21.15
22.9
16.15
24.7
18.4
18.7
15.6
32.3
Temperature (C)
Surface Bottom
26.8
25.7
26.2
26.5
27.0
29.5
26.25
29.4
29.2
30.45
29.6
27.85
24.7
25.9
24.55
25.1
24.5
24.6
25.7
25.75
25.75
25.2
29.9
29.85
29.55
30.3
28.85
27.0
26.6
27.6
30.0
29.7
27.05
27.8
26.4
27.3
27.85
25.35
26.4
25.7
25.7
25.75
27.45
29.5
26.3
29.4
29.2
30.25
29.4
27.9
24.6
25.25
24.9
25.1
25.45
24.6
25.55
25.7
24.9
24.95
29.85
29.85
29.2
30.3
28.9
26.95
26.55
27.8
29.9
29.65
27.1
27.9
26.4
26.6
26.9
25.15
Secchi Depth
Depth (feet)
1.0
1.0
1.0
0.5
0.5
0.5
0.5
1.0
1.0
1.0
2.0
1.0
1.0
1.0
2.5
2.0
2.0
1.0
1.5
0.5
1.5
1.0
0.5
1.0
0.5
1.0
0.5
0.5
0.5
1.0
0.5
1.0
0.5
1.0
0.5
1.0
0.5
0.5
9.7
9.2
10.6
9.2
6.1
9.8
8.2
11.6
11.8
8.2
11.2
6.5
7.4
9.2
8.2
6.2
8.1
2.8
6.1
3.3
6.7
6.6
4.5
7.2
8.1
6.9
7.5
7.9
5.9
19.2
4.2
6.5
4.8
9.5
6.1
11.2
8.6
4.1
"Dredging activity at site or nearby.
Results and Discussion - 1993 Galveston BayR-EMAP Study
Page 40
-------
Table 20. Percent of Area or Sites Compared by Salinity Categories.
Bottom Water Salinity
>18ppt
11 to 18ppt
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Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 42
-------
The goal of the PCA analysis was to condense the
results and to statistically determine the
significance of the results of the Sediment Quality
Triad Approach, by compressing the sediment
variables of importance into one factor. PCA
determines the variables of importance for the
compressed factor and what weights should be
given to each variable in the equation that defines
the Sediment Chemistry Component. Variables of
importance include metals (aluminum, arsenic,
copper, chromium, iron, nickel, selenium, tin,
zinc), sediment grain size (percent of silt & clay),
Butyltins (mono-, di-, and tri-), PAHs (represented
by high molecular weight and low molecular
weight PAHs), and pesticides other than DDT and
DDT metabolites. The PCA analysis determined
that the Sediment Chemistry Component was
influenced most by the heavy metals listed above
and sediment grain size. Seven of eight of the
metals above were significantly correlated with the
deposition rate and sediment grain size. In the
final step, the Sediment Chemistry Component
(using the significant environmental factor values)
was compared with the Toxicity Component, and
the Benthic Component (the benthic index) using a
correlation matrix and Bartlett's Test of Sphericity
(as described by Green and Montagna, 1996).
Bartlett's Test of Sphericity indicates significance
(p = 0.005) when the correlation matrix of the
Benthic Index, Toxicity, and the compressed set of
significant environmental factors were compared.
A significant negative relationship exists between
the Benthic Index and Sediment Chemistry (R = -
0.63). The correlations involving the Toxicity
Factor reveal no relationship with Benthic or
Sediment Factors (with Benthic Index R = 0.05
and with sediment factors |R|= 0.03). As stated
earlier, toxicity was not found at most sites.
Despite the low occurrence of toxicity in
sediments, benthic distributions and sediment
chemistry support each other in defining degraded
sites (Table 21). For this study, a degraded site is
defined as a site with at least two of the Sediment
Quality Triad Components indicating degradation.
A marginal site is defined as a site with a benthic
index value from 4.0 to 5.1, which represents a
marginal benthic component, and a degraded
sediment chemistry component (Table 21, Map
10).
Figure 35. Degradation Status Compared by Percent of Area or
Sites and 90% Confidence Intervals.
1 00
90
£ 60 -
< 50 -
'o 40 -
= 30 -
I 2° "
°- 10 -
0
I
I
I
_u
I
DDegraded
• Marginal
DUndegraded
Twenty-one percent (21%) of the Galveston Bay
Area is degraded, 27% is marginal, 52% is
undegraded. 4% (Site GB3) of the undegraded
area in Galveston Bay has a poor benthic value but
a good sediment chemistry component value. 78%
of the Small Bay & Marina Sites are degraded. Of
the remaining two small bay and marina sites, one
has poor benthic values, and the other has poor
sediment chemistry values (Figure 35).
Comparisons of general degradation between
Galveston Bay and Louisianian Province could not
be made because some measurements of
degradation used in the 1993 EMAP Study were
not measured in the R-EMAP Study.
The most degraded areas in the Galveston Bay
Complex include:
1) Offat=s Bayou (OB),
2) Clear Lake (CL) and its marina sites, Lafayette
Landing and South Shore (MA3 and MA4),
3) Upper Galveston Bay in the Houston Yacht
Club Marina (MA2),
4) Upper Galveston Bay near the Upper Houston
Ship Channel (GB1),
5) Upper Galveston Bay near Smith Point (GB7),
6) Moses Lake/Dollar Bay (MLDL),
7) Dickinson Lake (DKL),
8) mid-Trinity Bay (TB5) and Trinity Bay near
the river mouth (TBS, TB9), and
9) mid-East Galveston Bay (EGB5).
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 43
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Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 44
-------
Carr (GBNEP 30, 1993) employed the Sediment
Quality Triad approach and used species richness
values of less than 10 to indicate stressed benthic
communities. He reported stressed communities in
Trinity Bay near the river mouth and mid-East
Galveston Bay, which is in agreement with the
present study. Carr also reported stressed conditions
in East Galveston Bay near Rollover Pass, which
could be associated with poor conditions found in the
1993 R-EMAP Study of East Bay Bayou (Map 10).
In addition, the GBNEP 30 Study (Carr, 1993)
reported stressed benthic communities, poor
sediment chemistry, and toxic sediments for sites in
the Houston Ship Channel.
The 1993 EMAP Study defines stressed benthic
communities as having Benthic Index values of 4.0
or less. In this study, cluster analysis of benthic
communities revealed five distinct groups. A
possible marginally stressed group falls in the lower
portion of the moderate category. These values
could indicate areas with marginal conditions when
coupled with the high Sediment Chemistry
Component values (marginal sites include: TB1,
TB2, GB2, GB6, GB10, and EGB3) (Table 21).
Other sites of interest, because of a marginal or
degraded Benthic Component but not a high
Sediment Chemistry Component, include sites TB3,
GB3, and GB4.
Results and Discussion - 1993 Galveston Bay R-EMAP Study Page 45
-------
Table 21. Degradation at Each Site Indicated by the Sediment Quality
Triad Components.
Station
GB1
GB2
GB3
GB4
GB5
GB6
GB7
GB8
GB9
GB10
GB11
GB12
TB1
TB2
TB3
TB4
TBS
TB6
TB7
TBS
TB9
TB10
EGB1
EGB2
EGB3
EGB4
EGB5
WGB1
WGB2
OB
MLDL
DKL
CL
MAI
MA2
MA3
MA4
MAS
Benthic Index
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sediment Chemistry
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sediment Toxicity
X
X
X
X = Values indicate degradation (Benthic Index Values less than 4.0),
x = Benthic Index Values between 4.0 and 5.1.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 46
-------
CONCLUSIONS
1. A comparison of the EMAP Study of the
Louisianian Province with the R-EMAP Study
of Galveston Bay did provide insight into the
differences between Galveston Bay and its
Small Bay & Marina Sites, and the entire
Louisianian Province. These comparisons
revealed that the EMAP results were useful as
a screening tool to determine which systems
had toxic pollutants or biological impairment
and, therefore, should be studied in more
detail.
2. The Benthic Index, Benthic Diversity Index,
number of species per site, and number of
Amphipods per site proved useful in
demonstrating that communities living in
contaminated sediments had a community
structure indicating poor conditions. The
proportions of the two indices and the number
of species in the Galveston Bay area were
similar to the proportions reported for the
Louisianian Province in the 1993 EMAP
Study. In contrast, amphipod occurrence in
Galveston Bay sediments was significantly
lower than in the entire Louisianian Province
sediments.
3. In Galveston Bay, arsenic, copper, chromium,
lead, nickel, and zinc exceed the ERL but not
the ERM sediment quality screening values at
one or more sites sampled. NOEL values, but
not ERL values, are exceeded at one or more
sites for arsenic, chromium, lead, mercury, and
zinc. Sites with the most metals contamination
include Offat=s Bayou (OB), Clear Lake (CL),
Moses Lake/Dollar Bay (MLDL), and two
Marina sites. All of these sites are Small Bay
and Marina sites, which were chosen, not
randomly selected, so they are not included in
comparisons of Galveston Bay with the
Louisianian Province 1993 EMAP sampling
area. However, several of the randomly
sampled sites in Galveston Bay did have
exceedences for arsenic, chromium, nickel,
zinc. Exceedences of chromium, copper, lead,
nickel, and zinc for each site were almost
always due to anthropogenic inputs and not
natural deposition rates.
4. The Galveston Bay area (represented by
randomly chosen sites) has chromium and
nickel values that are higher than would be
expected when compared to the entire
Louisianian Province area. Arsenic
distributions in Galveston Bay were lower than
expected when compared to the Louisianian
Province, while zinc distributions were
similar. Copper values above ERL values
were not found in the randomly sampled area
representing Galveston Bay, nor in the entire
Louisianian Province area.
5. TBT concentrations are higher in Galveston
Bay sediments than expected with values
greater than 1 ppb occurring in 52% of the
area, compared to 31% of the total Louisianian
Province area. A significant relationship
exists between butyltin concentrations in the
sediments and butyltin concentrations in the
water column in the marina sites.
6. Dieldrin concentration distributions are much
lower in Galveston Bay than in the
Louisianian Province. Endrin concentration
exceedence by area are lower in Galveston
Bay compared to the Louisianian Province.
Total DDT concentrations exceeded ERL
guidelines in Offat=s Bayou. No other
pesticides exceeded ERL values for both
studies.
7. C3-fluorene exceeded ERL criteria in 3% of
Galveston Bay (site TBS), which is similar to
exceedences found in the entire area of the
Louisianian Province. Also, the NOEL value
for high Molecular Weight PAHs was
exceeded at site TBS. In the Louisianian
Province, only C3-fluorene ERL values and
High Molecular Weight PAHs ERL values
were exceeded.
8. PCB concentrations in Galveston Bay did not
exceed sediment quality screening values.
Only 1% of the Louisianian Province area had
exceedences of PCBs in the sediments.
Results and Discussion - 1993 Galveston Bay R-EMAP Study
Page 47
-------
9. The major variables used to determine
degraded sediment chemistry in Galveston Bay
include metals, butyltins, PAHs, pesticides
other than DDTs, and silt-clay content. These
variables were compressed into one factor
using Principal Components Analysis.
Generally, sites with the highest significant
environmental PCA factor values and sites
with the most degradation were located near
the shoreline and near areas of high
anthropogenic activities.
10. Heavy metal concentrations greatly influenced
the determination of degraded sites.
11. Toxicity results reveal a low occurrence of
acute toxicity in Galveston Bay sediments.
12. The most degraded areas in the Galveston Bay
Complex include: Offat=s Bayou (OB), Clear
Lake (CL) and its marina sites, Lafayette
Landing and South Shore (MA3 and MA4),
Upper Galveston Bay at the Houston Yacht
Club (MA2), Upper Galveston Bay near the
upper Houston Ship Channel (GB1), Upper
Galveston Bay near Smith Point (GB7), Moses
Lake/Dollar Bay (MLDL), Dickenson Lake
(DKL), mid-Trinity Bay (TBS) and Trinity
Bay near the river mouth (TBS, TB9), and
mid-East Galveston Bay (EGB5).
Conclusions - 1993 Galveston Bay R-EMAP Study Page 48
-------
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