DELAWARE
INLAND
BAYS
ESTUARY
PROGRAM
A Day in the Life of
Delaware's Forgotten Bay:
University of Delaware
Sea Grant College Program
A Scientific
Survey of Little
Assawoman
Production of this report was sponsored by the Inland Bays Estuary Program with
additional support from the University of Delaware Sea Grant College Program
DL 00049
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TABLE OF CONTENTS
Introduction by Kent S. Price i
Participants and Additional Authors ii
Geology, Geomorphology, Hydrology
Base-Flow Stream Discharge Measurements 1
by A. Scott Andres, Kathleen R. Butoryak, and Edmund M. Grace
Little Assawoman Bay Bottom Sediment Characteristics 3
by Evelyn M. Maurmeyer
Nutrients in Direct Groundwater Discharge to Little Assawoman Bay, Delaware 5
by Judith M. Denver and Deborah A. Bringman
Little Assawoman Bay Shoreline Characteristics 7
by Wendy Carey and Maria Sadler
Water Chemistry
Nutrient Survey of Little Assawoman Bay 9
by Susan Welch, Lisa Graziano, Bruce Overman, Til Pumell, and William Ullman
Light/Dark Bottle Studies and Light Extinction Measurements in Little Assawoman Bay 11
by John F. Davis
Distribution of Chlorophyll a, and Dissolved and Particulate Phosphate
in Little Assawoman Bay 13
by Lisa Graziano, Bruce Overman, and Richard Geider
A Hydrographic Survey of Little Assawoman Bay 15
by Greg Lambert
Biological Resources
The Benthos of Little Assawoman Bay 17
by Michael Bock, Susan Laessig, and Doug Miller
Little Assawoman Bay Seining Survey 19
by Kent S. Price and John Schneider
Juvenile Fish Survey 21
by Daniel Martin, T. Lankford, and Timothy Targett
Epibenthic Invertebrate Survey of Little Assawoman Bay 23
by Bennett Anderson
Preliminary Hard Clam and Macrobenthic Algae Survey of Little Assawoman Bay 25
by JeffTinsman
Human Usage
Assawoman Wildlife Area: A Description of Its History and Present Use 27
by Robert D. Gano, Jr.
Little Assawoman Bay Field Characterization of Recreational Use 29
by Jim Falk and Alan Graefe
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842R91O01
A Day in the Life of Delaware's Forgotten Bay:
A Scientific Survey of Little Assawoman Bay
12 June 1991
Scientific and Technical Advisory Committee
Inland Bays Estuary Program
c/o Department of Natural Resources and Environmental Control
P.O. Box 1401,89 Kings Highway
Dover, Delaware 19903
(302)739-4590
Edited by
William Ullman
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware 19958
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Rehoboth
Beach
Dewey
Beach
Georgetown
Herring
Rehoboth
Bay O
Indian
River
Bay
r Indian River
Millsboro
^->
24
Pepper Creek
i
Dagsboro
VW^NS!
26}— \ . Frankford
Bethany <
Beach
Ocean
View
South
Bethany
DELAWARE
Little
Assawoman
Bay
Dirickson
54
Selbyville
Fenwick
Island
MARYLAND
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INTRODUCTION
by Kent S. Price
In 1987, Governor Michael N. Castle nominated Delaware's Inland Bays—Rehoboth, Indian
River, and Little Assawoman bays—for inclusion in the National Estuary Program, which seeks to
protect, preserve, and restore key U.S. estuaries. One year later, the U.S. Environmental Protection
Agency accepted the Inland Bays into the program.
The Inland Bays Estuary Program is administered by staff within the Delaware Department of
Natural Resources and Environmental Control. It is, however, a multi-agency, multi-level program
effort The Department of Health and Social Services, Sussex County Council, and U.S. Environ-
mental Protection Agency, as well as the Department of Natural Resources and Environmental
Control are all represented on the Executive Council. Input from scientists and the many interested
and affected organizations and individuals is brought to the program through the Scientific and
Technical Advisory Committee (STAC) and the Citizens Advisory Committee (CAC).
The STAC of the Inland Bays is conducting a "characterization" of the bays that will consist
of assembling historic and present water quality and living resources data and men analyzing that
data to identify the most urgent environmental problems in these estuaries. Subcontractors have
been (or will be) selected to conduct the characterization and research involving (1) quantification
of groundwater nutrient contributions to the Inland Bays, (2) definition of hydrodynamic transport
processes influencing nutrient distribution within the Inland Bays, (3) quantification of ambient
levels of phosphorus and nitrogen and nutrient cycling in the Inland Bays, and (4) developing a
strategy for using living resources as an indicator of water quality in the Inland Bays.
The Inland Bay that essentially has been ignored in previous studies and thus suffers from a
notable lack of historic data is Little Assawoman Bay. To learn more about this scientifically
neglected member of the Inland Bays, the STAC, under the leadership of Dr. William Ullman as
principal scientist, designed a comprehensive, integrated set of field experiments and observations
that would allow for the establishment of a baseline of information facilitating the characterization
process. This study involved representatives of federal and state agencies, the university scientific
community, and individuals and firms from the private sector. In all likelihood, more data were
collected on Little Assawoman Bay during this single day than in all previous studies. The data
and the preliminary analyses contained in this report represent a snapshot in the life of Little
Assawoman Bay. Although few if any conclusions concerning long-term trends may be drawn
from this study, it does considerably strengthen our understanding of Little Assawoman Bay and
allow us to better compare conditions in this bay with those of Rehoboth and Indian River Bay,
which have been studied more intensely.
The STAC views this study as the first in a comprehensive series of studies to better under-
stand Delaware's Inland Bays.
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PARTICIPANTS
Bennett Anderson
Inland Bays Estuary Program
Delaware Department of Natural Resources
and Environmental Control
Dover, Delaware
A. Scon Andres
Delaware Geological Survey
Newark, Delaware
Michael Bock
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
William Brierly
Inland Bays Estuary Program
Department of Natural Resources
and Environmental Control
Dover, Delaware
Deborah Bringman
U.S. Geological Survey
Dover, Delaware
Kathleen R. Butoryak
Delaware Geological Survey
Newark, Delaware
Wendy Carey
Coastal & Estuarine Research, Inc.
Lewes, Delaware
John Davis
Watershed Assessment Branch
Department of Natural Resources
and Environmental Control
Dover, Delaware
Judy Denver
U.S. Geological Survey
Dover, Delaware
JimFalk
University of Delaware
Sea Grant Marine Advisory Service
Lewes, Delaware
Robert D. Gano, Jr.
Division of Fish and Wildlife
Department of Natural Resources
and Environmental Control
Dover, Delaware
Edmund M. Grace
Delaware Geological Survey
Newark, Delaware
AlanGraefe
Department of Recreation and
Leisure Studies
Pennsylvania State University
University Park, Pennsylvania
Lisa Graziano
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
Susan Laessig
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
Greg Lambert
U.S. Army Corps of Engineers
Philadelphia, Pennsylvania
ii
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T.Lankford
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
George Mangan
Citizens Monitoring Program
South Bethany, Delaware
Dan Martin
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
Evelyn M. Maurmeyer
Coastal & Estuarine Research, Inc.
Lewes, Delaware
Bruce Overman
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
Kent S. Price
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
mPurnell
Save Our Wetlands and Bays
Millsboro, Delaware
Kate Butoryak
Delaware Geological Survey
Newark, Delaware
Maria Sadler
Beach Preservation Section
Department of Natural Resources
and Environmental Control
Dover, Delaware
John Schneider
Inland Bays Estuary Program
Department of Natural Resources
and Environmental Control
Dover, Delaware
JeffTinsman
Division of Fish and Wildlife
Department of Natural Resources
and Environmental Control
Dover, Delaware
William Ullman
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
Susan Welch
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
Additional Authors
Doug Miller
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
Richard Geider
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
Timothy Target!
University of Delaware
Graduate College of Marine Studies
Lewes, Delaware
iii
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, LITTLE
ASSAWOMAN {
Middlesex
Beach -
South
Bethany
Public,
Beaches,
Fenwtek
Island
State
Park
Fenwtek
Island
Fenwtek island
Lighthouse
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BASE-FLOW STREAM DISCHARGE MEASUREMENTS
by A. Scott Andres, Kathleen R. Butoryak, and Edmund M. Grace
Stream discharge measurements under base-flow conditions were made on Bearhole Ditch at
Bunting, Beaver Dam Branch at Bayard, and Agricultural Ditch at Bayard. Samples for nutrient de-
termination were also collected at the same locations. Discharge was 1.63 cubic feet per second (cfs)
at Bearhole Ditch, 0.27 cfs at Beaver Dam Branch, and 0.35 cfs at Agricultural Ditch. Accuracy is
estimated to be in the range of +8-15%. The Bearhole Ditch site had been measured 14 times by the
U.S. Geological Survey (USGS) previous to this measurement The Beaver Dam Branch and Agri-
cultural Ditch sites had not been measured previously.
Given the lack of precipitation for about one month prior to the field day, the measurements
are representative of the low end of the range of discharges. For example, the recent Bearhole Ditch
measurement is similar to the June 23,1988, measured value of 1.23 cfs (Talley and Simmons, 1988),
which was also made after a similar period of dry weather. The range of 14 previous discharge
measurements of Bearhole Ditch is 0.18 cfs (Oct. 16,1987) to 7.71 cfs (Aug. 27,1969) (Talley
and Simmons, 1988).
Measurements of base flow are representative of the groundwater component of stream flow
for the drainage basin area upstream of the measurement point The flow in Bearhole Ditch repre-
sents a unit discharge of 0.25 cfs per square mile and in both Beaver Dam Branch and Agricultural
Ditch, 0.23 cfs per square mile. The similarity in unit discharges indicates that all of the drainage
basins have similar geologic, soils, and hydrologic characteristics.
The results of water sample analyses and loading rates for selected constituents are contained
in Table 1.
Discharge measurements were made using the current meter method described by Buchanan and
Somers (1969). Equipment and technical assistance were provided by Robert Simmons, USGS Water
Resources Division. The measurement sheets will be kept on file at the USGS office in Dover.
Stream
Bearhole Ditch
Agricultural Ditch
Beaver Dam Ditch
NO3-N
1.92/7.58
1.29/1.09
86/.561
NO2-N
.025/.1
.012/.01
.0157.01
NH4-N
.087.319
.0327.027
.2437.16
H4Si04
23790.5
23/19.7
25/16.5
Table 1. Results of chemical analyses and calculated loading rates given in mg/I
P04
.048/.192
.07/.06
.058/.038
andkg/d.
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References
Buchanan, T. J., and W. P. Somers. 1969. Discharge measurements at gaging stations. Techniques
of Water-Resources Investigations of the U.S. Geological Survey, Book 3, Chapter A8.
U.S. Geological Survey.
Talley, J. H., and R. H. Simmons. 1988. Inland Bays low-flow monitoring, July 1985-September
1988. Unpublished report prepared for Delaware Department of Natural Resources and
Environmental Control.
Explanation
V Observation Point
Drainage Basin Boundary
(approximate)
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LITTLE ASSAWOMAN BAY
BOTTOM SEDIMENT CHARACTERISTICS
by Evelyn M. Maurmeyer
Bottom sediment samples were collected from Little Assawoman Bay in June 1991 to charac-
terize the sediment distribution pattern within the bay. Samples were obtained from 35 stations
using a pole-mounted coring device which penetrated the upper 20 cm of the substrate. Sediments
were visually examined and classified on the basis of grain size. Water depths also were measured
at each station.
A map depicting bottom sediment characteristics of Little Assawoman Bay is shown in Figure 1.
Bottom sediments in the eastern portion of the bay generally consist of medium- to fine-grained
gray sand The deeper central portion of the bay is characterized by dark gray to black silty to
clayey sediments, which continue toward the western shore of the bay. Little Bay, an embayment
of the northern part of Little Assawoman Bay, shows a similar bottom sediment pattern, with sand
on the east, and silt/clay in the central and western sections. The Narrows, a channel connecting
Little Assawoman Bay with Little Bay, contains medium sand. Bottom sediments of the tidal
tributaries, Dirickson Creek and Miller Creek, consist of dark gray clay. Bottom sediments in
Assawoman Canal consist of sandy silty clay, and the artificial canals at South Bethany are
underlain by sand.
Bottom sediments in Little Assawoman Bay appear to correlate with water depth and distance
from the shoreline, and reflect present and past physical processes of sedimentation within the
various sections of the bay. Bottom sediments in the eastern section of the bay, located in
shallow water (<1 m), generally consist of well-sorted sand, characteristic of relict flood tidal
delta/overwash sediments derived from the adjacent coastal barrier. Sand content diminishes, and
silt/clay content increases in the deeper open waters of the central bay. Bottom sediments along the
western section of the bay reflect the low-energy estuarine conditions and also appear to correlate
with shoreline characteristics. Constricted channels, such as the Narrows, are underlain by sand
due to relatively high flow velocities. Low-energy natural tidal creeks are characterized by muddy
substrates, and bottom sediments of artificial waterways (Assawoman Canal and South Bethany
canals) exhibit the characteristics of the substrate into which these waterways were excavated.
Future work should involve a more extensive and detailed sampling grid, quantitative size
analysis of bottom sediment samples, and a coring study to document the vertical changes in
sedimentary sequences, in order to interpret the geological history of Little Assawoman Bay.
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South Bethany
000000000060
oojpoooooooooo
'OCTOOOOOOOOOOO
oooooooooooo
000000000000O
oooooooooo oo
ooooooo o
o „ vooooooo
S, sand; s, sandy
Z, silt; z. silly
C, day; c. clayey
M, mud; m, muddy
(from Folk. 1954)
Fenwick Island
CLAY
SILT
Figure 1. Bottom Sediment Characteristics, Little Assawoman Bay, Delaware.
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NUTRIENTS IN DIRECT GROUNDWATER DISCHARGE TO
LITTLE ASSAWOMAN BAY, DELAWARE
by Judith M. Denver and Deborah A. Bringman
The potential for significant contributions of nitrogen species and phosphorus to Little Assa-
woman Bay by direct groundwater discharge through bay-bottom sediments was indicated by a
limited survey conducted on June 12,1991, at three shoreline locations. The difference in hydraulic
head between groundwater and overlying surface water was measured, and samples of groundwater
were collected using a mini-piezometer (a small-diameter well point with a 3-centimeter-long screened
interval) connected to a peristaltic pump and a manometer.
Samples of water in bay-bottom sediments were collected about 1 meter offshore at depths
from 0.5 meters and 1.0 meters below the sediment-water interface. Measurements of salinity, pH,
and head difference were made on site, and nutrient analyses were performed in the laboratory (see
Table 1). Bottom sediments at Sites 1,2, and 3, where samples were collected, consisted of
permeable sand and gravel, whereas sediments at site 4, where samples could not be collected,
were predominantly fine-grained silt and clay (Figure 1).
Salinities in the groundwater (0.52-5.1 ppt) were significantly lower than those in the bay
water (14.0-27.0 ppt), indicating the presence of fresher groundwater beneath the saline water in
the bay. Hydraulic head differences indicated an upward head gradient at Site 1 and a downward
head gradient at Sites 2 and 3 (see table). The measurements were made close to high tide
(approximately 12:15 p.m. at the Narrows, according to Rob Gano, Delaware Department of
Natural Resources and Environmental Control, oral communication, July 22,1991). Because the
estimated tidal amplitude in the bay (15-33 cm) is greater than the downward hydraulic-head
differences measured, it is likely that groundwater at each site discharges to the bay during part of
each tidal cycle.
Most of the area around Little Assawoman Bay contains poorly drained soils and anoxic
groundwater. Therefore, the discharge of anoxic groundwater to the bay could be greater than the
discharge of oxic groundwater. Nitrogen speciation depends on redox conditions in the aquifer and
bay-bottom sediments. Anoxic conditions were indicated at Sites 1 and 2 by the relatively high
concentrations of ammonia, which is a reduced nitrogen species, compared to nitrate, which is an
oxidized-nitrogen species. In contrast, oxic conditions were indicated at Site 3 because of the rela-
tively high concentration of nitrate compared to ammonia (see table). Concentrations of phos- ,
phorus were higher in groundwater from the anoxic sites than in groundwater from the oxic site.
These results suggest mat groundwater sources of nitrogen species and phosphorus could be
important in the nutrient dynamics of Little Assawoman Bay and point out the need for additional
research in this area.
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Site
1
2
3
Time Ah Salinity Nitrate Ammonia Phosphate
(cm) (ppt) (n.M) (uM) (jjiM)
1000 +2.4 5.1 0.34 160.0 1.01
1100 -10.7 3.6 0 32.2 1.45
1200 -14.6 0.52 431.0 1.39 0.17
Table 1. Results of Groundwater Measurement and Sampling, 12 June 1991.
Ah - hydraulic head difference; + indicates groundwater head greater than surface-
water head; - indicates surface-water head greater than groundwater head; ppt = parts
per thousand; |xM = micromoles per liter, cm ^centimeter.
Silica
65.3
51.3
125.0
75°10'
75"05'
OCEAN CITY
Pop. 1493
1
Base from Delaware Department of Transportation
Sussex County highway map. 1:126.720
A^ Sampling site and site number
0 1 Z MILES
1 .'.<.'. I. I."I
1
2 KILOMETERS
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LITTLE ASSAWOMAN BAY SHORELINE CHARACTERISTICS
by Wendy Carey and Maria Sadler
A perimeter survey of Little Assawoman Bay was conducted in June 1991 to determine shore-
line characteristics. Field observations regarding shoreline type were made from a small boat and
recorded on a base map. Verification of field data was accomplished using a planimeter, USD A aerial
photographs (1"=660' scale), and National Wetlands Inventory maps.
Results from the on-site field inspection and qualitative analysis of aerial photos indicate that
the low-energy, transgressive shoreline of Little Assawoman Bay can be divided into three major
geomorphic types: (1) irregular marsh shoreline, (2) sandy pocket beaches, and (3) artificial stabili-
zation structures such as rubble and bulkheads. These comprise approximately 79%, 4%, and 17%
of the linear shoreline, respectively. The marsh shoreline along Little Assawoman Bay is character-
ized by broad emergent wetlands which have developed on topographically low areas along the
western shore and on relict flood tidal deltas/overwash fans in eastern sections. More narrow wet-
lands fringes are found along headlands such as Laws Point Typical wetlands vegetation includes
both low-marsh species, such as Spartina alterniflora, and high-marsh species, such as Spartina
patens, Distichlis spicata, Baccharis halimifolia, Ivafrutescens, and Phragmites austrails. The
bayward edge of the marsh appears to be erosional and is typified by a dense mat of sediment,
peat, and roots, usually in the form of an undercut and/or vertical scarp.
Sandy beaches comprise only 4% of the Little Assawoman Bay shoreline and are typically
narrow pocket beaches between crenulate marsh shoreline. Narrow, bluffed sandy beaches may be
found in areas where headlands intersect the bay, as in the vicinity of Strawberry Landing and
Drum Point Eroding pre-Holocene headlands such as Miller Neck and Dirickson Neck provide a
source of sandy material for the pocket beaches on the western bay shoreline. Pocket beaches along
the eastern side of Little Assawoman Bay are supplied by sand from the Atlantic coast, transported
across the narrow coastal barrier during storm and/or overwash episodes.
Approximately 17% of the Little Assawoman Bay shoreline consists of bulkheads and other
artificial stabilization structures. Many developments in the area include dead-end lagoon systems
with as many as 12 bulkheaded lagoons per developed area. A notable amount of rubble has been
dumped along a section of southern shoreline, from Drum Point to Point of Ridge. Continued
developmental pressure will likely result in additional man-made structures along the bay shoreline.
The geographic location of each of these three environments is dependent on geologic history,
coastal processes, and human developmental pressures. Future research should include analyses of
both long-term (sea-level rise) and short-term (wave, wind, storm) processes on shoreline evolution.
Additional data on natural processes and historical erosion rates would result in a comprehensive
determination of erosion-prone areas of the bay.
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Legend
| | Developed Areas
Undeveloped Land
Wetlands
[
Map of General Shoreline Characteristics, Little Assawoman Bay, Delaware.
Shorelines designated as "Developed Areas" are typically characterized by stabilization structures
such as rubble and bulkheads; "Wetlands" areas are dominated by Spartina altermflora and
Spartina patens tidal marshes; "Undeveloped Land" includes agricultural areas, forested uplands,
beaches, and associated back-barrier environments. Small pocket beaches along the Little Assa-
woman Bay shoreline are not depicted at this scale. (Map provided by Delaware Department of
Natural Resources and Environmental Control.)
10 1 2 3
Scale in Miles
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NUTRIENT SURVEY OF LITTLE ASSAWOMAN BAY
by Susan Welch, Lisa Graziano, Bruce Overman, Til Pumett, and William Ullman
Twenty-one surface water samples were collected from the "navigable" waters of Little Bay
and Little Assawoman Bay on June 12,1991. Temperature, salinity, acidity, and secchi disk depth
were determined. Water samples were collected, filtered, and stored for the subsequent deter-
mination of dissolved nitrate (NC>3~), nitrite (NO2~), ammonium (NH4+), phosphate (PO43'), and
silica (1148104). Samples were also collected for the determination of paniculate phosphorus and
chlorophyll a.
The results of this survey are displayed as property versus salinity plots in Figure 1. There was
very little variation in the salinity of Little Bay and Little Assawoman Bay waters. The total range
found was between 14 and 27 ppt The observed salinities are a reflection of the lack of rainfall and
therefore surface water runoff into the bays during the few weeks preceding sampling.
NC>3~ concentrations were highest in the more saline waters, those coming from Big Assa-
woman Bay having the highest concentration. This result is at odds with observations made in both
Indian River and Rehoboth bays, where the highest nitrogen concentrations are always found in the
freshest waters. It is not clear, on the basis of this single day of sampling, whether the Big
Assawoman Bay is a nitrogen source or sink for Little Assawoman Bay on an annual basis or
whether the low level of nitrogen is a characteristic of the Little Assawoman Bay lagoonal system.
Our studies of Indian River and Rehoboth bays indicate that the coastal ocean may be a nutrient
source during the summer when nutrients are otherwise depleted.
The concentrations of all nitrogen species were extremely low. NH4+ concentrations were
consistently below detection f 0.05 pM). The levels of DIN (= NO3- + NO2~ + NH4+) are as low
as the lowest levels we have previously measured elsewhere in the Inland Bays (central Rehoboth
Bay, 17 July 1990). They appear to reflect, as in the previous observations of the Rehoboth Bay
lagoon, the efficient utilization of nitrogen within the lagoon and die lack of significant external
fluxes to the bay during the summer. Based on our studies of Rehoboth Bay, we would conclude
that the present observations reflect an aspect of the seasonal cycle of nitrogen fluxes and
utilization and are not representative of the concentrations throughout the year.
The sample taken from upper Dirickson Creek (Sample 1) had anomalously high IfySK^, NO2~,
PO43", and chlorophyll a concentrations. The nutrient levels may have resulted from a recent resus-
pension of the bottom sediment (as by a boat) or an anomalous plume of water from a salt-marsh
creek. The high chlorophyll levels that co-occurred with these relatively high nutrient levels suggest
that where nutrients are more available, more primary production is possible. On die basis of this data
set alone, however, it is impossible to determine which nutrient or other factor limits productivity.
-------
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-------
LIGHT/DARK BOTTLE STUDIES AND LIGHT
EXTINCTION MEASUREMENTS IN LITTLE ASSAWOMAN BAY
by John F. Davis
Light- and daik bottle incubations of ambient water from Little Assawoman Bay were
conducted at Mulberry Landing pier on June 12,1991, to estimate gross photosynthesis rates and
respiration rates due to phytoplankton growth in the water column. The technical background,
procedures, and calculations are illustrated in Thomann and Mueller (pp. 284-291).
In conjunction with the light/dark bottle studies, the light extinction characteristics of the
water column were investigated by measuring the Photosynthetically Active Radiation (PAR) with
a submersible quantum meter (Licor) at several depths through the water column. Light extinction
coefficients were determined, as presented in Thomann and Mueller (pp. 420-422).
Four sets of light/dark bottles were incubated at 1 to 2 foot depths. Each bottle was incubated
for approximately two to three hours, spanning from 11:30 a.m. to 3:30 p.m. Net photosynthesis
rates ranged from 0.36 mg/l/hr to 0.55 mg/l/hr, with an average of 0.42 mg/l/hr. Gross photosyn-
thesis rates ranged from 0.29 mg/l/hr to 0.59 mg/l/hr, with an average of 0.42 mg/l/hr. Respiration
rates ranged from 0 mg/l/hr (undetectable) to 0.11 mg/l/hr, with an average of 0.03 mg/l/hr.
Calculations were conducted to extrapolate the measured photosynthesis and respiration rates
(as discussed above) to average daily rates and areal rates (expressed in terms of grams of DO per
square meter per day—gm/m2/day). The daily average gross photosynthesis rate was estimated as
5.4 mg/I/day, or 5.4 gm/m2/day assuming an average depth of 1.0 meter in the bay. The average
daily respiration rate was estimated as 1.8 mg/l/day, or 1.8 gm/m2/day assuming a depth of 1.0
meter. Based on these calculations, the P/R ratio was 3.0, which indicates that photosynthetic
production of dissolved oxygen outweighed the consumption of dissolved oxygen by algal
respiration on this day.
Light extinction coefficients ranged from 2.0 per meter (1/m) to 4.9 per meter, with an average
of 2.9 per meter. The depth of penetration of one percent of PAR ranged from 0.9 to 2.3 meters.
References
Thomann and Mueller. 1987. Principles of Surface Water Quality Modeling and Control.
New York: Harper and Row.
11
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Little Assawoman Bay Light-Dark Bottle Study
Bottle Number
Depth (ft)
Salinity (ppt)
Avg Temp ("Q
AVG PAR (iimol/mVsec)
Total Time (hr)
Initial DO (mg/I)
Final DO (mg/I)
Calculations
R(mg/I/hr)
P.. (mg/l/hr)
P, (mg/l/hr)
L-l
1
26
25.5
325
2
5.9
7
0.55
D-l
1
26
25.5
325
225
5.9
5.8
0.044
0.594
L-2
2
26
25.5
183
2J
5.9
6.8
036
D-2
2
26
25.5
183
2.83
5.9
5.6
0.106
0.466
L-3
1
263
26
303
2
62
7
0.4
D-3
1
263
26
303
225
62
63
-0.04
0356
L-4
1
263
26
303
is
62
7.1
036
D-4
1
263
26
303
2.75
62
6.4
•0.07
0287
Calculation of Daily Photosynthesis and Respiration Rates
Avg Max P, rate = 0.53 mg/l/hr
Avg Daily Rate (based on 16 hr photoperiod (Tp), and sin function):
P, - P»J2/3.1416)Tp P,= 5399 mg/l/day
Avg Daily Photosynthesis Based on avg depth « 1 meter (appro* 33ft):
P, » 5398 mg/Vd • 1 m » 5.4 gm/mVday
Avg Respiration Rate « .075 mg/l/hr = 1.80 mg/l/day » 1.8 gm/mVday assuming 1 meter depth
P/R ratio » 3.0
Light Extinction Measurements
Time
Depth (M)
0
0.01
02
03
0.4
0.6
0.7
1130
PAR
1500
330
150
83
64
12,00
PAR
1200
445
275
225
200
105
103
12.00
PAR
1200
445
355
260
200
115
99
13:00
PAR
1100
660
490
380
306
180
160
1330
PAR
1100
565
320
250
215
105
75
1430
PAR
608
210
116
67
49
27
Calculation of Extinction Coefficient (K.): I=Io(exp-K,*z)
Time
1130
4.9
0.9408
1200
22
2.095
12.00
2.1
1195
1300
2
2305
1330
1.6464
1430
33
1317
12
-------
DISTRIBUTION OF CHLOROPHYLL A,
DISSOLVED AND PARTICULATE PHOSPHATE
IN LITTLE ASSAWOMAN BAY
by Lisa Graziano, Bruce Overman, and Richard Geider
Samples were collected from 21 stations in Little Assawoman Bay on June 12,1991, for the
determination of chlorophyll a, and paniculate and dissolved phosphate concentrations. In the mid-
bay, dissolved phosphate concentrations were ^0.05 at all stations, while paniculate phosphate
levels were higher (20-30 pM). A slight positive co-variation was observed. Paniculate phosphate
also co-varied with chlorophyll at the mid-bay stations. Secchi disk measurements showed little
variation in water turbidity in the bay and no correlation with paniculate phosphate or chlorophyll a.
Dirickson Creek was sampled at the head, the mouth, and two points of intermediate salinity.
Paniculate phosphate, dissolved phosphate, and chlorophyll a concentrations increased with
increasing distance from the mouth of the creek and show a good apparent correlation with one
another. All three were associated with turbidity, as can be seen in the plots of chlorophyll a and
paniculate phosphate versus secchi disk depth. Dirickson Creek therefore appears to be a source of
fresh water and of dissolved inorganic phosphate.
Miller Creek, which discharges into Little Bay, was sampled at three stations along a slight
salinity gradient No change in chlorophyll a, paniculate phosphate, or dissolved phosphate with
salinity was observed in this creek. The minimum secchi disk depth was 0.4 meters, which is
greater than that observed at the end of Dirickson Creek. At the time of sampling, there appeared to
be no net inflow of freshwater from the creek.
Two samples were taken at the ends of the South Bethany Lagoons and indicate conditions
different from Dirickson Creek. The water was relatively clear and had only slightly elevated
paniculate and dissolved phosphate levels, but did have a high chlorophyll a concentration. This
particular area is deeper and less well-mixed by wind than Dirickson creek; paniculate phosphate
seemed to be associated with turbidity while chlorophyll a was not
Except for Dirickson Creek, Little Assawoman Bay was fairly uniform in regard to salinity,
chlorophyll a, and paniculate and dissolved phosphate concentrations. This is in contrast to Rehoboth
and Indian River bays, where there is greater freshwater input and a range of concentrations is ob-
served. For example, chlorophyll a concentration in Indian River Bay in June ranged from 0.33 p.g/L
to 96.8 iig/L, and salinity varied from near 0 to 25.0 ppt Another difference is the number of point
source inputs of phosphate. Several industries as well as sewage treatment plants are sources of
both nitrate and phosphate in the two larger bays. With the exception of Dirickson Creek, no major
point source of phosphate was apparent in Little Assawoman Bay.
13
-------
Table 1. Temperature, Salinity, and pH at 21 Stations in Little Assawoman Bay, 12 June 1991.
Station TcrnnfQ fiB
1 end of Diricbon Greek 248 14.8
2 mouth of trailer pule. Swan Key 243 19.1
3 end of Swtn Key- lagoon near booses 244 21.4
4 between Mulbeny Landing and Lam PnL 243 218
5 between Pnt Cedars 1st and Cooch Pat 243 23.6
6 East fork of 1\ibbs Cow 240 23.8
7 PI. of Cedars Isl-Barrier Island 243 23.2
8 bridge at Fenwick III 2O 249
9 Old Inlet and Drum Pot 242 24.6
10 by the tf in Assowoman on tbe map 246 234
11 off Pepper's Landing 23.9 23J
12 pffings at North end of bay 249 23.2
13 the Narrows 24.8 233
14 Reedy Point 2SJ) 224
15 Strawberry Point 25.5 21.8
16 off Long Point-Camp Btrnes 27.5 17.8
17 off Hone Point 274 193.
18 mouth of Canal 284 21.5
19off Canal Pond 26.4 215
20 end of lagoon off W. Canal 284 23.5
21 end of lagoon near road (Sth Bethany) 294 214
EH
7j63
7.81
7.43
750
7.99
7.93
7.97
843
840
7.99
842
7.96
840
7.92
7.93
742
7.74
7.87
7.88
848
7.93
30
Little Assawoman Bay
12 June 1991
Little Assawoman Bay
12 June 1991
I DirtdaonOMk
pouttiBithaiiy Lagoon |
10 15 20 25
Chlorophyll a (ug/L)
30
iro
(B *>
40
30
20
10
35
tothanyUgoont]
oos ai ai5 02 O2S 03 0.39 0.4 0.45
Dissolved Phosphate (uM)
Little Assawoman Bay
12 June 1991
20
*v
>. pouth Bethany Lagoon
/'
'"ST^ /
I S.»
• 1 *
X
'
i
OJ O3S 0.4 0.45 OJ OlSS O8
Sechhi Disk Depth (m)
Little Assawoman Bay
12 June 1991
'u — \
m \
™ \
u \
M \ J-1
«o y y»-
-, A A
** I
(south Mhany Lagoon J
/ \
r/ \
"
"O25 OJ O3S 0.4 0.48 0.5 Oii OJ
Sechhi Disk Depth (m)
14
-------
A HYDROGRAPHIC SURVEY OF LITTLE ASSAWOMAN BAY
by Greg Lambert
A hydrographic survey was performed on June 12,1991, along east-west transects across
Little Assawoman Bay. At specified stations, temperature, salinity, acidity (pH), and dissolved
oxygen concentration were determined. The locations of stations are given in Figure 1 and the
results of this survey are given in Table 1.
There is little variation in temperature, pH, and salinity across the bay, indicating that Little
Assawoman Bay should be described hydrographically as a lagoon rather that as a estuary. Lagoons
are characterized by little or no freshwater input. Although there is little evidence of seawater
dilution by fresh water at the time of sampling, it is possible that more estuarine conditions apply at
other times. In this case, the bay would more correctly be described as an estuarine lagoon.
A comparison of dissolved oxygen concentrations with turbidity as measured with a secchi
disk, indicates that the highest turbidity is associated with the highest oxygen concentrations (see
Figure 2). Since resuspension of bottom sediments often leads to a consumption of dissolved
oxygen, this result suggests that a large fraction of the turbidity in Little Assawoman Bay is due to
biologically active phytoplankton.
There is also a co-variance of dissolved oxygen concentration with the time of sampling. In the
course of the day, dissolved oxygen concentrations increased at the rate of 0.495 ± 0.095 mL/L/hr.
Assuming no exchange with the atmosphere over this time period and that the net rate of produc-
tion is constant over the whole bay depth and whole depth of light penetration (0.4 m secchi disk
depth) over an eight-hour daylight period, this is equivalent to a net rate of daylight productivity
of 0.78 ± 0.15 g C/m2/day. Due to the assumptions made, this is a minimum estimate of the net
primary production in Little Assawoman Bay.
South Bethany
Figure 1. Locations for
Hydrographic Survey,
Little Assawoman Bay, Delaware.
Fenwick Island
-------
Hydrographic surveys are needed at other times of the year to determine the correct
hydrographic classification of Little Assawoman Bay and to correctly determine the average
net primary productivity of the bay.
Table 1. Hydrographic Survey Results, Little Assawoman Bay, 12 June 1991.
Station
Al
A3
A3
Bl
B2
B3
B4
85
Cl
C2
C3
C4
C5
DO
Dl
D2
03
D4
OS
El
E2
E3
Fl
Cl
G2
HI
H2
H3
H4
11
Jl
J2
Kl
K2
Temperature
ra
24.1
24.2
24.3
24.3
24.3
24.3
24.2
23.8
24.2
24.3
24.5
24.5
24.7
26.2
24.8
25.1
25.0
24.9
24.9
24.8
25.0
25.2
25.1
25.4
25.5
25.4
25.1
25.8
26.1
25.8
26.8
26.1
26.9
25.8
pH
7.9
7.9
8.0
7.9
7.9
8.0
8.0
6.0
8.1
8.1
8.0
8.0
8.1
8.2
8.0
8.0
8.0
8.0
8.0
8.1
8.1
8.1
8.1
8.1
8.1
8.0
8.0
8.0
8.0
8.0
8.2
8.0
8.2
8.0
Dissolved
Oxygen
(mL/U
6.2
6.3
6.3
6.0
6.3
6.7
6.8
7.1
7.7
7.4
6.7
7.4
7.5
9.0
6.9
6.2
5.8
6.3
8.6
8.7
7.4
7.4
7.8
8.1
8.0
7.6
7.7
7.5
7.4
7.3
10.0
8.0
10.3
8.0
Salinity
(%o)
25.5
25.7
25.4
24.7
24.6
25.2
25.3
25.6
24.5
24.5
24.4
24.1
24.5
23.2
24.7
23.7
23.6
24.3
24.5 ;
24.6
24.0
23.8
24.0
24.3
24.3
23.6 :
23.4
23.4
22.5
23.9
24.1
24.0
24.1
24.1
0
10
8
5.5
0
•
• .
I Miller Creek]
^ ^s. • .
•
" •
•
• . •
l •
•
9 1 1.1 1.2 1.3 1.4 1.5
1.6 1.7 U
Secchi Disk Depth (ft)
9,
6
•
f
,_
• f
m •
•• •• '
••• • ••
•
9 10
11 12 13
Tune (hours)
14 15
Figure 2. Dissolved Oxygen Concentrations As Compared with lurbidity,
Little Assawoman Bay, 12 June 1991.
16
-------
THE BENTHOS OF LITTLE ASSAWOMAN BAY
by Michael Bock, Susan Laessig, and Doug Miller
The benthos of Little Assawoman Bay and Little Bay were sampled using a benthic grab
sampler. The grab sampler was lowered to the bottom and a4cmx6cmx4cm deep sample was
taken. Two grabs were taken at each station. In total, 14 stations were sampled. The samples were
field-sieved in 1 mm sieves and preserved in formaldehyde. The specimens were identified in the
laboratory using Wading and Maurer's Guide to the Macroscopic Estuarine and Marine
Invertebrates of the Delaware Bay Region (1973).
The samples revealed that the species abundances in the two bays were relatively low. The
dominant taxa was polychaetes (Phylum Annelida), with the most abundant species being the
bamboo worm, Cfymenella lorquata. This organism was found in most habitats occurring in the
bay. The only non-polychaete groups were Nematoda and Rhynchoceala. Small arthropods were
conspicuous by their absence; no arthropods were found in any of the grabs. No live mollusks
were found, but a small number of empty shells were found.
There was also a spatial trend within the bays. In the upper bays, nearest to the points of
freshwater input, very few specimens were found. In these areas, the sediment was a fine clay.
In the mid-bay region, diversity was relatively high, generally the highest in the bay. Here the
sediment was a fine sand. In the fore-bay region, closest to Fenwick Island, diversity was moderate.
Here the sediment was a medium sand. The exception to this trend was the Assawoman Canal. In
the canal, the diversity was high, whereas in Little Bay, proper diversity was low. This could be
due to the flow of water through the canal.
The patterns of species abundance could be caused by the physical nature of the bay. Little
Assawoman Bay is very shallow; its depth rarely exceeds 2 meters. In addition, it has no direct
connection to the ocean, and so the water chemistry of the bay should be closely coupled to run-
off. This would create a highly variable and stressful environment. In addition, the opportunities
for external recruitment would be low. Only those species capable of withstanding these variations
would survive, and the introduction of new species would be limited. These variations would be
more pronounced in the upper bay region and thus account for the low species abundance in
these areas.
In order to truly assess the state of the benthic ecosystem in Little Assawoman Bay, we must
collect more data. It is important to verify the observed spatial trends and to measure seasonal
trends. It is also important to determine the underlying reasons for the observed trend in species
abundance. The hypotheses put forth above should be expanded and tested.
17
-------
Station 1: 38°29.1'N 75°05.55'W, Dirickson Creek, Time 0905 EOT, 2 grabs, 6ft, fine clay, no organisms
Station 2: 38°28.77'N 75°04.57'W, Peppers Landing, Time 0930 EOT, 2 grabs, 6.5ft, fine clay, no organisms
Station 3: 38°28.35'N 75°04.35'W, Point of Cedars Island, Time 0935 EOT, 2 grabs, 4 ft, medium sand
Organisms: Unidentified polychaete A (Hereafter denoted UNK A) 1*
Station 4: 38°27.80'N 75°03.65'W, Drum Point, Time 0955 EOT, 2 grabs, 5.5 ft, fine sand
Organisms: Polychaete Onuphidae Diopatra cuprea 1
Polychaete Chaetopteridae Spiochaetopterus oculatus 2
Polychaete Maldanidae Ctymenella torquata 12
UNK A 5
Station 5: 38°28.23'N 75°03.23'W, Fenwick Island St. Pk., Time 1010 EOT, 2 grabs, 2 ft, medium sand
Organisms: Polychaete Maldanidae Ctymenella torquata 1
Station 6: 38°28.45'N 75°03.58'W, Fenwick Island State Park, Time 1035 EOT, 2 grabs, 6 ft, fine clay
Organisms: Polychaete Maldanidae Ctymenella torquata 5
Station 7: 38°28.84'N 75°04.05'W, Bennett Point, Time 1055 EOT, 2 grabs, 5.5 ft, fine sand
Organisms: Polychaete Maldanidae Ctymenella torquata 14
UNK A 5
Station 8: 38°30.31'N 75°03.90'W, Little Bay, Time 1115 EOT, 2 grabs, 3 ft, clay
Organisms: Polychaete Maldanidae Ctymenella torquata 3
Station 9: 38°30.43'N 75°03.94'W, Assawoman Canal, Time 1125 EOT, 2 grabs, 4 ft, med-fine sand
Organisms: small nematodes (3mm) 2
Polychaete Onuphidae Diopatra cuprea 1
Polychaete Nephyidae Nephtys bucera 2
UNK A 1
Station 10: 38°30.18'N 75°04.66IW, Strawberry Landing, Time 1135 EOT, 2 grabs, 4 ft, fine mud, no
organisms
Station 11: 38'29.29'N 75°04.27'W, off Tonys Pond, Time 1205 EOT, 2 grabs, 5 ft, clay
Organisms: Rhynchoceala Tubulanus pellucidus 1
Polychaete Maldanidae Ctymenella torquata 2
Station 12: 38°28.86'N 75°03.55'W, Daisy Marsh, Time 1215 EOT, 2 grabs, 4.5 ft, medium sand
Organisms: Polychaete Nereidae Nereis succinae 1
Polychaete Maldanidae Ctymenella torquata 32
UNK A 1
Station 13: 38°28.79'N 75°04.14'W, Cherrybush Island, Time 1240 EOT, 2 grabs, 6 ft, fine mud
Organisms: Polychaete Maldanidae Ctymenella torquata 3
Station 14: 38°28.96'N 75°04.80'W, Mulberry Landing, Time 1250 EOT, 2 grabs, 5 ft, fine mud, no organisms
*To convert from the number of organisms found per station to abundances in individuals per m2
multiply by 208.
18
-------
LITTLE ASSAWOMAN BAY SEINING SURVEY
by Kent S. Price and John Schneider
On June 12,1991, we undertook a survey at five collecting sites in Little Assawoman Bay
using a 10-meter-long x 1.2-meter-deep hand seine with a chain lead line and a 1.2 x 1.2-meter
pocket The seine was constructed of 1/4" stretched delta nylon mesh and was hauled approxi-
mately 30-35 meters in one tow at each station.
Little Assawoman Bay appears to be a thriving nursery for the blue crab (Callinectes sapidus),
the spot (Leiostomus xanthurus), and the summer flounder (Paralichthys dentatus)—three impor-
tant commercial and recreational species (Table 1).
Some stations differed in their species composition as was to be expected Muddy areas tend
to support the mummichog (F. heteroclitus) and the glass shrimp (Palaemonetes sp.) while the
striped killifish (F. majalis) tends toward sandy bottoms, and the striped mullet (Mugil cephalus)
was found only in a blind canal (Tables 1 and 2).
The composition of the fish fauna is quite similar to that demonstrated in studies conducted by
Derickson and Price (Trans. Amer. Fish Sec. 1973, #3) in Indian River and Rehoboth bays 20 years
ago with these exceptions. Only a dozen species were collected today compared to over 40 in the
original study. This result is most likely due to sampling frequency in that 20 monthly collections
from 18 stations in Indian River and Rehoboth bays from June 1968 to April 1970 yielded 41,286
fishes representing 46 species.
In the original study, the following five species, listed in order of abundance, comprised
89% of the catch: Fundulus majalis, Menidia menidia, Fundulus heteroclitus, Pseudopleuronectes
americanus (winter flounder), and Anchoa mitchilti (bay anchovy). The latter two species are con-
spicuously absent from today's survey but the spot seems to be more abundant than before. The
winter flounder seems to have suffered a long-term climate-related decline. However, the winter
flounder was captured at two of six deep-water locations sampled with a beam trawl on June 12,
1991, mostly in the sandy area of the lower bay (T. Lankford, personal communication). The bay
anchovy represented only 4.35% of the total catch in die original survey and may be rare enough to
have been missed by our gear. The fish fauna in Little Assawoman Bay appears to be as healthy as in
either of the other two bays based on the Derickson and Price (1973) study. More current data is
needed in all three bays to verify that assumption.
The relative abundance of blue crabs and forage species suggests that Little Assawoman Bay
is in a reasonably healthy state. This conclusion, however, is based only on this cursory study. More
sampling is needed to verify this conclusion.
19
-------
TABLE 1: (Strawberry (Sassafras (Bayview) (Sail Boat (Blind Canal)
Landing) Landing) Rental)
Species £ MSfmnrt £ MSfmirO £ MSfmnrt £ MSCmrn) £ MSfmnri
Callinectes saoidus 46 50.9 32 32.6 139 47.7 28 33.7 41 385
Blue Crab
Fundulus heteroclitus 170 75.0 93 65.8 36 69.7 21 66.0
Mummicbog
Fundulus maialis 14 102.1 4 95.0 14 102.1
Striped kfllifisb
Leiostomus xanthunis 60 56.1 8 505 9 65.0 35 725 6 73.8
Spot
Menidia menidia 626 33.8 463 45.0 138 923 80 625 80 46.8
Atlantic sflversides
Palaemontes so 20 10.1 22 11.4 5 10. 187 10.6
Glass shrimp
Tn'nectes maculatus 1 61.0
Hogchoker
Stroncvlura marina 1 105.0 1 43.0 3 82.0
Atlantic needlefish
Paralichthves dentatus 1 82.0 11 90.0 4 71.0 1 96.0
Summer flounder
Gobiosoma bosci 1 55.0
Goby
Svnodus foetens 1 43.0
Lizard •**"
Cvprinodon variegatus 1 52.0
Sheephead minnow
Sohoeroides pachveaster 1 32.0 1 34.0
Blunthead puffer
Muril cephalus 82 63.0
Striped mullet
MS = Mean Size; Total Length for fish; carapace width for crabs.
TABLE 2:
Station # and Location H,O Depth Secchi Depth Salinity H2O Temp Air Temp
Time (Bottom Type) (on) (cm) C/J (°Q (°Q
1 Strawberry Landing 20-40
(0930) (Sandy Mud)
2 Sassafras Landing 20-45
(1005) (Muddy Sand)
3 Bayview Park at Andrew Street 40-60
(1050) (Sand and eroded marsh mud)
4 Sail Boat Rental off Rt 1 South 20-55
(1140) (Sandy)
5 Corner Of Dagsboro St and 30-70
(1245) Shultz in Blind Canal
(Muddy Sand)
45
45
48
50
58
26
25
27
30
29
25.0
25.0
245
26.0
26.0
27.0
27.0
29.0
295
295
20
-------
JUVENILE FISH SURVEY
by Daniel Martin, T. Lankford, and Timothy Target!
Shallow bays and estuaries are important nursery grounds for juvenile fishes; roughly three-
quarters of western Atlantic marine fishes of commercial and sport value spend some part of their
lives in these habitats. Our survey of Little Assawoman Bay was designed to determine what role,
if any, the bay plays in the life cycle of marine fishes.
Juvenile ichthyofauna were sampled in the deeper reaches of Little Assawoman Bay
using a new (to us) beam trawl. The trawl is designed around a modified epibenthic sled frame,
1 m wide x 0.2 m high at the mouth, to which the sides and upper edge of a net (1-cm stretch mesh)
are attached. The lower lip of the net is recessed 1 meter in a V shape, and lead-lined. Ideally,
benthic organisms are disturbed by the lead line, but retained by the side and top net panels.
The fish and crab catches from six tows are given by station in Table 1, and the corres-
ponding transects are shown in Figure 1. Physical data collected at the beginning of each trawl
are given separately in Table 2.
Although only a meager 'snap-shot' of the demersal ichthyofauna was taken, Little Assa-
woman Bay does indeed appear to function as a nursery ground for juvenile fishes in much
the same manner as its larger sister bays. Our data are not quantitative, however, as sampling
efficiency probably varied due to variable towing speeds within and between trawls (i.e., ad-
justments were made as we became familiar with the new gear).
Table 1. Species Collected, Trawling Survey. Little Assawoman Bay,
Station
No.
1
2
3
4
5
6
Species Present
(fish and blue crab)
CoIUnectes sapidus
Letostomusxanthurus
Letostomus xanthurus
Calltnectes saptdus
—
Calltnectes sapldus
Psuedapleuranectes
amertcanus
ParaUchthys dentatus
Calltnectes saptdus
Pseudaplewunectes
amertcanus
ParaUchthys dentatus
Letostomus xanthurus
Trtnectss maculatus
Micropoganias unrfi/fnfns
Calllnectes sapldus
No. of Each
Species
1
1
3
4
—
2
4
2
16
2
4
5
1
1
187
Standard Lengths (mm)
(CW = carapace width, mm)
41
96.37.28
—
(CWapprox. 30-60)
59.55.55.54
71.67
(CWapprox. 30-60)
61.56
79.73.72.65
96.94.90.39.38
102
82
(CWapprox. 3O-150)
21
-------
Table 2. Trawling Survey Transects.
Sta.
No.
1
2
3
4
5
6
Trawl Start
&End
1015:00
1018:30
1058:00
1103:00
1142:00
1145:30
1221:00
1229:00
1303:00
1315:00
1329:00
1341:00
Air
(*q
23
23.5
26
26
24.5
mm
H/>
(•q
24
23
24
24
25
aj
Water
Depth (m)
0.6
1.0
1.2
1.4
U
fm
Sal.
(PPO
25
26
26
27
29
_
Secchi
Depth (m)
0.6
0.6
0.6
0.6
0.6
_
Notes on bottom
type, etc.
fine sand, many
polychaetes
fine sand bottom
stabilized by
worm tubes
day with some
silt
muddy sand
fine sand with
some mud
„ ,
Figure 1. Trawling Locations, Little Assawoman Bay, 12 June 1991.
South Bethany
Fenwick Island
22
-------
EPIBENTfflC INVERTEBRATE SURVEY OF LITTLE ASSAWOMAN BAY
by Bennett Anderson
There is little information concerning the distribution of non-commercial benthic invertebrates
in the Little Assawoman Bay system. The success of recruitment, survival, and reproduction of
benthic invertebrates is dependent on a wide range of environmental parameters. As such, the
distribution of benthic invertebrates is of particular value in the characterization of stressed coastal
marine environments.
Five samples of benthic fauna were collected from the deepest areas of Little Assawoman Bay
(Figure 1). A 1-meter beam trawl was towed for approximately 10 minutes at each site. The beam
trawl is designed to collect epibenthic species and infauna living within 2 cm of the sediment water
interface. Only individuals greater than 1 cm in size are quantitatively retained in the trawl A 225 cm2
box core was used to sample burrowing infauna at one station.
Two species dominate the epibenthic community in Little Assawoman Bay: the blue crab
(Callinectes sapidus) and the glassy bubble shell gastropod (Haminoea solitaria). The numbers
found at each station are given in Table 1. The blue crab population density appeared to be highest
in the deepest waters of the bay, which are also those where the sediment is coarsest (> 90% sand).
The glassy bubble shell gastropod was found primarily in the eastern zone of Little Assawoman
Bay and was most abundant in muddy and silty sandy sediments.
The blue crab is an important commercial and recreational species in Delaware and elsewhere
along the eastern coast of the United States. At the time of sampling, a large number of crab pots
were deployed in Little Assawoman Bay, and crabbers were abundant at Mulberry Landing. Appar-
ently, the local human population is aware of the crab population.
Haminoea solitaria is a small tectibranch snail. Its shell is thin and fragile and may range in
color from bluish white to brownish. It is a common species in muddy bays and well-sheltered
areas along the East Coast of die United States south of Cape Cod. It has no commercial value.
No epibenthic algae were recovered with the beam trawl during this survey. This result was
unexpected as epibenthic algae are abundant in many regions of Indian River and Rehoboth bays
throughout the year. The difference may be due to die very high turbidity (secchi disk depth «£ 0.6m)
in Little Assawoman Bay as compared to the other bays.
One small box core was recovered from the muddy sediments of Station 3, Dirickson Creek.
Although the organisms in this sample were neither identified nor counted, it appears that there is a
dense and diverse infaunal community dominated by bivalves and polychaetes in the muddy areas
of Little Assawoman Bay. These results must be confirmed with further sampling.
23
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South Bethany
Figure 1. Invertebrate Survey Stations,
Little Assawoman Bay, 12 June 1991.
Fenwick Island
Callinectes
sapidus
Haminoea
solitaria
Station 1
Not
found
Not
found
Station 2
3
Not
found
Station 3
1
28
Station 4
187
17
Station 5
16
Too
Numerous
To Count
Table 1. Dominant Benthic Species, Little Assawoman Bay.
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PRELIMINARY HARD CLAM AND MACROBENTHIC ALGAE SURVEY
OF LITTLE ASSAWOMAN BAY
byJeffTinsman
An important hand clam (Mercenaria mercenaria) resource has existed in Indian River and
Rehoboth bays since the stabilization of Indian River Inlet This resource is the basis of both an active
commercial and recreational fishery in the Inland Bays. Surveys of hard clam distributions in Indian
River and Rehoboth bays were conducted by Humphries and Daiber (1967), Cole and Spence (1977),
and the EPA (1987). These surveys provide a useful data set on the basis of which the status and
trends of the hard clam population can be determined. Despite occasional reports of isolated hard
clam populations in Little Assawoman Bay, no systematic survey has ever been conducted.
A preliminary assessment of hard clam densities was undertaken on June 12,1991. A total of
13 stations (Figure 1) were sampled using a commercial bull rake at most stations. At the shallow
stations (2,4, and 11), a recreational clam rake was used. Although the purpose of the survey was
to determine hard clam populations, the sampling gear also is appropriate for making a qualitative
assessment of macrobenthic algae. Macrobenthic algae are common in parts of Rehoboth Bay.
No live mollusks were collected during this sampling effort although old clam shells, soft
clam shells, and oyster shells were recovered at some stations. At the time of sampling, the salinity
exceeded 20 ppt—the minimum salinity needed to support a successful hard clam population—
everywhere in Little Assawoman Bay. Based on previous surveys and anecdotal evidence, these high
salinities are anomalous. During periods of high freshwater runoff, the average salinity in Little
Assawoman Bay may drop substantially below that needed to sustain the hard clam. Salinities less
than 20 ppt may be sustained for extended periods of time.
No macrobenthic algae were collected at any site in the Bay. This result was a major surprise
since, at this time of year, the sea lettuce, Ulva, would be commonly found in many areas of Indian
River and Rehoboth bays. More extensive sampling over the whole seasonal cycle will be
necessary to explain the absence of macrobenthic algae in Little Assawoman Bay.
References
Cole, R. W., and L. Spence. 1977. Hard clam survey of Indian River and Rehoboth Bays.
Dover Delaware Department of Natural Resources and Environmental Control.
U.S. Environmental Protection Agency, Annapolis Office. 1987. Hard clam survey of Indian River
Bay, Delaware.
Humphries, E., and F. C. Daiber. 1967. Shellfish survey of Indian River Bay and Rehoboth Bay,
Delaware. Technical Report Narragansett, Rhode Island: Northeast Maine Health Sciences
Laboratory, Public Health Service.
25
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Fenwick
Island
Figure 1. Hard Clam and Macrobenthic Algae Survey Locations, Little Assawoman Bay.
26
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ASS AWOMAN WILDLIFE AREA:
A DESCRIPTION OF ITS HISTORY AND PRESENT USE
by Robert D. Gano, Jr.
Little Assawoman Bay and its tributaries, Miller and Dirickson creeks, have relatively less
shoreline development and more public land than the other Inland Bays. At least 50% of the surface
area of Miller Neck, the peninsula between Miller and Dirickson Creeks, consists of Assawoman
Wildlife Area (AWA). Fenwick Island State Park shares jurisdiction of lands on the barrier island
(east of Route 1). A brief description of AWA and the management program may help characterize
public land use within the Little Assawoman Bay watershed.
The AWA was established from farms lost during the Great Depression. The U.S. Department of
Agriculture and the Forest Service took title to the eight farms (35-303 acres) from 1936-1942. The
Delaware Board of Fish and Game Commissioners agreed to a 99-year lease in 1943 to manage the
area for the "purpose of wildlife, recreation, and forest management" Camp Barnes was established
as a youth summer camp in 1949 by the Delaware Association of Police Chiefs. In 1954, the land was
sold to the State of Delaware. Pavilions built at Strawberry and Mulberry Landing in 1935-36 were
included in the sale.
The AWA is comprised of three disjunct, but contiguous parcels of land—Miller Neck (1335.5
acres), Muddy Neck (284 acres), and the Beach (75.8 acres). The AWA is 49% forested (828 acres)
with a sweet gum (Liquidambar styracifluaj-loblotiy pine (Pinus taeda) association. Six slightly
brackish (0-24 ppt salinity) impoundments totaling 264 acres account for 16% of the area. Salt
marsh (primarily Spartina patens and Distichlis spicata) comprises 20% of the acreage (332 acres).
Agricultural fields used as wildlife food and cover plots account for 85 acres (5%).
Numerous (15) ephemeral ponds (in varied degrees of wetness) (35 acres-2%) contain rare and
endangered plant species. The discovery of a seasonally flooded woodland pond or Delmarva Bay
containing at least nine rare plant species, including three federal candidates for endangered species
listing, prompted the purchase of an additional 227 acres in July 1989. Other rare plant species have
subsequently been discovered on other parts of the area.
The wildlife area is managed primarily for waterfowl, white-tailed deer, northern bobwhites,
and mourning doves. Free public hunting from 16 waterfowl blinds and 40 deer stands is provided
under a special permit hunt The fishing areas (Mulberry, Strawberry, and Sassafras landings) receive
heavy use (no utilization data available) for crabbing, boating, and picnicking. Reptiles and amphibians
receive special protection particularly within the freshwater ponds containing rare plant species and the
freshwater impoundments. A mammal on the state endangered list, the Delmarva fox squirrel (Sciurus
cinereus nigra), was reintroduced in 1984 with a release of 13 individuals. Surveys indicate some
reproductive success, but population status is uncertain. Squirrel hunting has been closed since 1984.
27
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The impoundments are managed to improve migratory and wintering waterfowl habitat and to
enhance water bird feeding habitat With the installation of two wells and pumps with a total capacity
of 390 gallons per minute in 1990, the two largest impoundments are actively managed for waterfowl
food and cover—salt-marsh bulrush (Scirpus robustus), dwarf spike rush (Eleocharis parvula), and
Walter's millet (Echinochha walterii). A third of the wildlife area is set aside as refuge where no
human activity is permitted.
Fields of corn, dwarf sorghum, soybean, and clover are planted within the refuge for waterfowl.
Outside the refuge is a mixture of soybean, buckwheat, German millet, and sorghum in small plots.
Larger fields managed for mourning dove hunting are planted in sunflower, com, and winter wheat.
All fields are limed and fertilized in accordance with a soil sample recommendation from the Uni-
versity of Delaware, although since die crops are not harvested, yearly fertilizer inputs are minimal.
A wildlife management plan describing the area, the fauna, and management techniques is
available from the Wildlife Section of the Delaware Division of Fish and Wildlife, Delaware
Department of Natural Resources and Environmental Control.
28
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LITTLE ASSAWOMAN BAY
FIELD CHARACTERIZATION OF RECREATIONAL USE
by Jim Folk and Alan Graefe
We traveled around the perimeter of Little Assawoman Bay to inspect recreational facilities and
uses. There is intense residential development in the South Bethany area and in Fenwick Island. Resi-
dential canal developments are evident in both locations. There is light tourism development (com-
mercial/retail trade) in the South Bethany area and heavier tourism development on Fenwick Island.
There was very little recreational activity observed on the bay during the morning hours. Two
or three small outboards were observed, as well as two pontoon boats passing the Route 54 bridge
between 11:30 a.m. and noon. We also noticed some crabbing activity from the bay shoreline (five
people) and three boats fishing near the Route 54 bridge at 12:20 p.m. Additional boating activity
started to pick up around 1:00 p.m.
A major part of characterizing recreational uses included counting boats at docks in canal de-
velopments on the bay (see map for site locations). We observed that a majority of docks in the
canals were unoccupied and many boats were not yet in the water (but they were on-site on trailers).
Bill Hamilton of the B-R Bait and Tackle Shop (York Beach Mall-South Bethany) stated that
75% of bay use is crabbing; there are no clams in the bay; that many boats never leave their docks;
and fishing is poor in this area. Better fishing is found farther south.
We stopped at the Fenwick Island State Park concession stand that rents sailboats, jet skis, and
sailboards. No boats had been rented by 10:45 a.m. when we arrived. The attendants told us,
however, that it had been very busy the previous day.
We talked with Brelle Beaston at Beaston's Marina in Bay View Park (South Bethany). It is a
small marina with 20 slips. There were six pontoon boats, two sailboats, and four powerboats in
the water. She confirmed that most of the activity in the bay is recreational crabbing, with some
water sports (jet skiing and wind surfing), but not much fishing.
We counted the boats at the 142nd Street Marina. There were 23 boats in the water. Eleven of
the boats were pontoon boats and there were 11 empty slips. We also talked to the attendant in
charge of rental boats at the facility. They had 16 to 20 boats available for rent (six pontoon boats
and five jet skis). Customers who rent pontoon boats are directed to proceed south from the marina
to Maryland waters. Jet-ski customers must use the marked course in Little Assawoman Bay
immediately north of the Route 54 bridge. The attendant commented mat many boats come from
Little Assawoman Bay and go under the Route 54 bridge every day heading to Maryland waters
for fishing.
We counted 17 boats at Shark's Cove Marina (nine pontoon boats) and 13 empty slips. The
marina attendant indicated there were still slips available in the marina. He noted that this vacancy
may be due to the poor economy. There were 26 more boat slips at a nearby townhouse complex.
29
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We visited Treasure Beach RV Resort There are over 1,000 sites. There were no counts avail-
able, but an attendant reported that campers at most of the waterfront sites do have boats. We esti-
mated there were 250 boats in this RV complex. We visited Magnolia Shores and Bulls Landing
(residential developments up Dirickson Creek, near the Route 54 bridge). We observed a few boats
docked at private homes. At our final stop, we observed two people crabbing at Sassafras Landing
in the Assawoman Wildlife Refuge at 2:00 p.m.
In summary, we conclude, based on this one-day field observation, that recreational impacts on
Little Assawoman Bay are minimal. The primary water-quality impacts in the bay are probably asso-
ciated with residential development, in particular, the canal developments in South Bethany and Fen-
wick Island. There appear to be no major water-use conflicts among or between recreational users.
There also do not appear to be any serious environmental impacts caused by recreational users.
Cam! Development
South Bethany
173 boats (ES pontoor
South Bethany
Canal Development
Bay View Pa*
27 boats (13 pontoon)
Swan Keys/Shady Park
150 boats (75 pontoon)
Ftnwick Island State Park
Sailing, Jet Sid, Windsurfing Rentals
fanwk* Man4
smcn
tO boats (SO pontoon)
30
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Scientific and Technical
Advisory Committee
Scott Andres
Delaware Geological Survey
John F. Davis
Division of Water Resources
Judith Denver
United States Geological Survey
Sam Eaton
Department of Natural Resources
and Environmental Control
James M. Falk
Sea Grant College Program
University of Delaware
Alan J. Farling
Division of Water Resources
John Forren
United States Environmental
Protection Agency, Region III
John L. Gallagher
College of Marine Studies
University of Delaware
Rob Gano
Division of Fish and Wildlife
Jeff Gebert
Philadelphia District
United States Army Corps of
Engineers
Richard J. Geider
College of Marine Studies
University of Delaware
Timothy Goodger
National Oceanographic and
Atmospheric Administration
Lyle Jones
Division of Water Resources
Robert Jublc
Delmarva Power and Light
Glenn Klnser
United States Fish and Wildlife
Service
Chris Kraft
Department of Geology/Marine
Studies, University of Delaware
David Krantz
College of Marine Studies
University of Delaware
Greg Lambert
Philadelphia District
United States Army Corps of
Engineers
Charles Lesser
Division of Fish and Wildlife
Susan Lussler
United States Environmental
Protection Agency, Region III
Evelyn Maurmeyer
Coastal and Estuarine Research,
Incorporated
John Maxted
Division of Water Resources
Rick McCorkle
United States Fish and Wildlife
Service
Douglas C. Miller
College of Marine Studies
University of Delaware
William F. Moyer
Division of Water Resources
Paul M. Petrlchenko
Soil Conservation Service
United States Department of
Agriculture
Jack Pingree
Division of Public Health
Anthony P. Pratt
Division of Soil and Water
Conservation
Kent S. Price
College of Marine Studies
University of Delaware
Til Purnell
Liaison, Citizens Advisory Committee
Jim F. Sadowski
Delmarva Power and Light
Paul T. Sandridge
Biology Department
Delaware State College
Sybil Seltzlnger
The Academy of Natural Sciences
Denise Sellskar
College of Marine Studies
University of Delaware
Tracy Skrabal
Division of Water Resources
James Smullen
Roy F. Weston, Incorporated
Leanne Stahl
United States Environmental
Protection Agency, Headquarters
David J. Stout
United States Fish and Wildlife
Service
Timothy E. Targett
College of Marine Studies
University of Delaware
Jeff Tlnsman
Division of Fish and Wildlife
Rick Trultt
Inland Bays Estuary Program
William Ullman
College of Marine Studies
University of Delaware
Keith D. Watson
Philadelphia District
United States Army Corps of
Engineers
Warren Watts
Delamarva Power and Light
Thomas H. Williams
University of Delaware
Cooperative Extension Service
Kuo-Chuln Wong
College of Marine Studies
University of Delaware
Hank Zygmunt
United States Environmental
Protection Agency, Region III
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DELAWARE
INLAND BAYS
ESTUARY PROGRAM
COMMITT
EXECUTIVE COUNCIL
Directs all program activities
• Ensures funding
• Delaware, Sussex County,
and EPA represented
IMPLEMENTATION COMMITTEE
• Operates program
• Local, state, and federal
agencies represented
SCIENTIFIC & TECHNICAL
ADVISORY COMMITTEE
• Reviews and recommends
research and projects
• Ensures scientific input
to management decisions
• Comprised of public and private
technical and scientific experts
CITIZENS ADVISORY
COMMITTEE
Provides program and
policy advice
Oversees public
participation and educatio
Comprised of a diversit
of citizen interests
This publication Is primed
on racydad paper.
This project has been funded by the State of Delaware and by Cooperative Agreement No. CE003473-90-0
between the U.S. Environmental Protection Agency and the State of Delaware.
DOC. NO. 40-08/92/01/02
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