United States Region VI EPA/906/R-98/002
Environmental Protection Ecosystems Protection Branch June 1998
Agency 6WQ-E
v>EPA Galveston Bay 1993
Regional Environmental
Monitoring and Assessment
Program
Executive Summary
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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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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
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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
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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
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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),
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