Creek Component

No benthic data are available from Swanson Creek. Therefore, we propose to
collect samples at Swanson Creek and compare these samples to a nearby undisturbed or
minimally disturbed creek (e.g., Hunting Creek or Indian Creek). These samples will be
paired in the sense that the near-field (Swanson Creek) and far-field (Hunting/Indian
Creek) sites will be sampled simultaneously. We estimate that a minimum of 10 samples
collected at each of these two creeks will be necessary to make valid statistical inferences
related to impacts from the oil spill.

Field and Laboratory Procedures

Whenever possible, we will sample from vessels positioned in the area to conduct
LTB sampling, thus saving time and minimizing additional field sampling costs. River
and creek samples will be collected with the same gear used for historical samples so that
the data are comparable. We will process the samples using the same procedures used for
LTB analyses. Grab samples will be sieved through a 0.5-mm mesh screen, and the
organisms retained on the screen will be preserved in a 10% formalin solution and
stained. In the laboratory, organisms will be counted, identified, and their biomass
measured. All sorting and identification will be done in-house to minimize costs.

We will record water depth, salinity, temperature, dissolved oxygen, particle size
distribution (percent sand and silt-clay) and total organic carbon at every sampling site.
Environmental factors will be used as covariats in the analysis of data. Sediment samples
for analysis of PAH concentration will also be taken at each sampling site and will be
archived for chemical analysis if desired.

Data Analysis

Data from the river component will be analyzed using the BACI design outlined
above. In addition, summer data will be analyzed in the context of measures of benthic
community health using the B-IBI index. If sediment chemistry data are available, we
will look at variation in hydrocarbon concentrations that might explain differences in
abundance or biomass. The proposed design will allow us to determine if significant
differences exist within the benthic data. These data can be analyzed to determine the
relationship, if any, between PAH contamination and benthic condition. If such a
relationship is assessed (i.e., if the trustees determine that PAH assessment is necessary)
and a relationship can be elucidated, the trustees will be able to utilize these data to
evaluate the areal extent of the impact to the benthos. The statistical design of this study
will not produce a stand-alone assessment of areal impacts to benthos, but can be used in
accordance with other evaluations of the extent of PAH or oil impacts to determine the
areal extent of impact to the benthos. Deliverables will include a short report presenting
results and supporting data analyses.


AMENDMENT TO JUNE 15 PROPOSAL
As per trustees’ request
October 19, 2000

The creek component of the oil impact benthic assessment is modified as follows.
The September field effort (summer) will be increased to 20 samples in Swanson Creek
(10 more than originally proposed), 10 samples in Indian Creek, and 10 samples in Trent
Hall Creek. Indian Creek and Trent Hall Creek are new additions to the sampling design.
Sampling effort in Hunting Creek and the Patuxent River near Chalk Point will remain as
originally proposed, i.e., 10 samples will be collected in each of Hunting Creek and the
main Patuxent River near Chalk Point.

Swanson Creek will be divided into an upper and a lower stratum (separated at the
spit). Ten sites will be randomly allocated to each of the two strata. Within the upper
stratum we will revisit two of the three sites sampled in the spring and pick a new fresh
set of eight random sites. Within the lower stratum, we will revisit five of the sites
sampled in the spring and pick a new fresh set of five random sites. The sites to be
revisited in the lower stratum will be selected at random. The sites to be revisited in the
upper stratum are fixed because only three sites were sampled during the spring sampling
effort and one of them is excluded from the selection process because it was associated
with marsh vegetation. We believe that the presence of vegetation confounds the
interpretation of oil impacts. To avoid the marsh fringe, extra sites will be randomly
selected prior to sampling. The Field Crew Chief will then eliminate in the field any site
that has vegetation and move to the next available site in each stratum (in the order
determined by the random process). Samples from sites that are revisited will provide
estimates of seasonal variability. Seasonal differences at the impacted location (Swanson
Creek) will be compared with seasonal differences at the control location (Hunting
Creek). The additional summer sites will provide increased spatial coverage.

As with Swanson Creek, five of the Hunting Creek spring sites will be revisited in
summer, and these sites will be supplemented by a new fresh set of five additional
random sites. The marsh fringe will be avoided as explained above.

Sampling sites at Indian Creek and Trent Hall Creek will be selected within upper
strata that exclude the mouth of the creek. The marsh fringe will also be avoided.

The ten sampling sites in the main Patuxent River near Chalk Point will be
supplemented by LTB sites sampled in 2000 as part of the LTB program. Twenty-five
LTB sites are established annually throughout the Patuxent River to provide summer
areal estimates of benthic community condition. As with the spring sampling, the ten
summer sites proposed in the present study will be located in the vicinity of Chalk Point,
defined as the portion of the mainstem of the Patuxent River between the Highway 231
bridge at Benedict and the Holland Cliff region upstream. The ten summer sites in the
main Patuxent were previously sampled in 1998 or 1999 as part of LTB, so the present
effort will consist of revisiting these sites, as discussed in the original proposal. LTB


juveniles are the most sensitive stages of the life history of most species, and therefore,
the coincidence of recruitment peaks with the oil spill may have devastating effects on the
benthos. If a reduction or elimination of the benthos occurs, this may initially represent a
significant reduction of food for demersal fishes. It is important therefore that we follow
the recovery of the benthic community. This recovery may be hampered by additional
stresses from near bottom summer low dissolved oxygen concentrations or high water
temperatures. Sampling near the end of the summer season (early to mid September) will
allow us to determine the cumulative effects of these stresses. Where no previous data
are available (creek and beach/marsh components), we will assess the magnitude of the
impact through comparison of sites near and distant from the spill source. This assumes
that the baseline conditions between the near and distant areas studied are the same and
that the only difference between them is proximity to the spill.

METHODS
River Component

Our approach will be based on the Before-After-Control-Impact design (BACT)
(Stewart-Oaten et al. 1986, Underwood 1991) with modifications if necessary to take
advantage of the large data set collected by the LTB program and available for this study:
several dates (up to five years for random locations and up to 17 years for a fixed location
at Chalk Point) before the perturbation at the impact site in the Patuxent River and at
control sites in nearby rivers (for example, the Potomac and Rappahannock). The BACI
design allows for natural differences between Control and Impact locations, and for
changes from Before to the After period that influence the sites in a similar way. The
approach will be to test whether the mean Impact-Control difference has changed Before
and After the oil spill. We will use the data collected by LTB in spring (one fixed
location) and summer 2000 (one fixed and several random locations). However, these
data will need to be supplemented by additional data collected at the random sites
sampled by LTB in previous years. Only by comparing data from the same sites before
and after the impact can we assess changes to benthic populations that may be related to
the oil spill.

In addition to the fixed site at Chalk Point, LTB sampled 13 sites in spring 1990-
1993 as part of a historical random sampling design. We will revisit these sites and
collect one sample per site. The BACI design can be applied to the fixed site and the
summer random sites because we have the pre-spill and the post-spill condition at both
the impacted area and controls elsewhere in Chesapeake Bay. The 13 spring sites,
however, will not have comparable post-spill data outside the Patuxent River, and thus
the design will be modified. Additionally, summer data can be analyzed in the context of
measures of benthic community health using the B-IBI index. The B-IBI takes into
account the natural range of variability within reference areas in Chesapeake Bay, and
therefore it provides its own measure of stress without the necessity of a control.


REFERENCES

Agard, J.B. R., J. Gobin, and R.M. Warwick. 1993. Analysis of marine macrobenthic
community structure in relation to pollution, natural oil seepage and seasonal
disturbance in a tropical environment (Trinidad, West Indies). Mar. Ecol. Prog.
Ser. 92:233-243.

Clarke, K.R. 1993. Non-parametric multivariate analysis of changes in community
structure. Aust. J. Ecol. 18:117-143.

Dauer, D.M. 1993. Biological criteria, environmental health and estuarine macrobenthic
community structure. Mar. Pollut. Bull. 26:249-257.

Diaz, R.J. and L.C. Schaffner. 1990. The functional role of estuarine benthos. Pages 25-
56. In: M. Haire and E. C. Chrome (eds.), Perspectives on the Chesapeake Bay,
Chapter 2. Chesapeake Research Consortium, Gloucester Point, VA.

Frithsen, J. 1989. The benthic communities within Narragansett Bay. An assessment for
the Narragansett Bay Project by the Marine Ecosystems Research Laboratory,
Graduate School of Oceanography, University of Rhode Island, Narragansett, RI.

Gray, J.S. 1979. Pollution-induced changes in populations. Phil. Trans. R. Soc. Lond. B.
286:545-561.

Gray, J.S., K.R. Clarke, R.M. Warwick, and G. Hobbs. 1990. Detection of initial effects
of pollution on marine benthos: An example from the Ekofisk and Eldfisk
oilfields, North Sea. Mar. Ecol. Prog. Ser. 66:285-299.

Holland, A.F., N.K. Mountford, M.H. Hiegel, K.R. Kaumeyer, and J.A. Mihursky. 1980.
The influence of predation on infaunal abundance in upper Chesapeake Bay.
Mar. Biol. 57:221-235.

Holland, A.F., A.T. Shaughnessy, L.C. Scott, V.A. Dickens, J. Gerritsen, and J.A.
Ranasinghe. 1989. Long-term benthic monitoring and assessment program for
the Maryland portion of Chesapeake Bay: Interpretive report. Prepared for the
Maryland Department of Natural Resources by Versar, Inc., Columbia, MD.
CBRM-LTB/EST-2.

Homer, M., P.W. Jones, R. Bradford, J.M. Scolville, D. Morck, N. Kaumeyer, L.
Hoddaway, and D. Elam. 1980. Demersal fish food habits studies near Chalk
Point Power Plant, Patuxent Estuary, Maryland, 1978-1979. Prepared for the
Maryland Department of Natural Resources, Power Plant Siting Program, by the
University of Maryland, Center for Environmental and Estuarine Studies,
Chesapeake Biological Laboratory, Solomons, MD. UMCEES-80-32-CBL.


Patuxent River Oil Spill

Proposal to Assess Oil Spill Impacts on Benthic
Invertebrates

Prepared For

Maryland Department of Natural Resources
Power Plant Research Program
Tawes State Office Building
Annapolis Maryland

Prepared by
Versar, Inc.

9200 Rumsey Road
Columbia, Maryland

June 15, 2000


Homer, M. and W.R. Boynton. 1978. Stomach analysis of fish collected in the Calvert
Cliffs region, Chesapeake Bay-1977. Prepared for the Maryland Department of
Natural Resources, Power Plant Siting Program, by the University of Maryland,
Center for Environmental and Estuarine Studies, Chesapeake Biological
Laboratory, Solomons, MD. UMCEES 78-154-CBL.

McGuinness, K.A. 1990. Effects of oil spills on macroinvertebrates of saltmarshes and
mangrove forests in Botany Bay, New South Wales, Australia. J. Exp. Mar. Biol.
Ecol. 142:121-136.

Pearson, T.H. and R. Rosenberg. 1978. Macrobenthic succession in relation to organic
enrichment and pollution of the marine environment. Oceanogr. Mar. Biol. Ann.
Rev. 16:229-311.

Samiullah, Y. 1985. Biological effects of marine oil pollution. Oil and Petrochemical
Pollution 2:235-264.

Stewart-Oaten, A., W.W. Murdoch, and K.R. Parker. 1986. Environmental impact
assessment: “Pseudoreplication” in time”. Ecology 67:929-940.

Underwood, A.J. 1991. Beyond BACI: Experimental designs for detecting human
environmental impacts on temporal variations in natural populations. Aust. J.
Mar. Freshwater Res. 42:569-587.

Virnstein, R.W. 1977. The importance of predation of crabs and fishes on benthic
infauna in Chesapeake Bay. Ecology 58:1199-1217.

Warwick, R.M. 1986. A new method for detecting pollution effects on marine
macrobenthic communities. Mar. Biol. 92:557-562.

Weisberg, S.B., J.A. Ranasinghe, D.M. Dauer, L.C. Schaffner, R.J. Diaz, and J.B.
Frithsen. 1997. An estuarine benthic index of biotic integrity (B-IBI) for
Chesapeake Bay. Estuaries 20:149-158.

Wilson, J.G. and D.W. Jeffrey. 1994. Benthic biological pollution indices in estuaries.
Pages 311-327. In: J.M. Kramer (ed.), Biomonitoring of Coastal Waters and
Estuaries. CRC Press, Boca Raton, Florida.


INTRODUCTION

The state of Maryland has maintained an ecological monitoring program for
Chesapeake Bay since 1984. The program includes a number of fixed and randomly
selected sites in the Patuxent River. Many of the historical stations are located in the area
affected by the recent oil spill. Benthic macro-invertebrates have been included in the
Chesapeake Bay monitoring program because they are reliable and sensitive indicators of
habitat quality in aquatic environments. Most benthic organisms have limited mobility
and cannot avoid changes in environment conditions (Gray 1979). Benthos live in
bottom sediments, where exposure to contaminants and low dissolved oxygen is highest.
Benthic assemblages include diverse taxa representing a variety of physiological
tolerances to environmental conditions. Benthic assemblages, therefore, respond to
changes in environmental conditions, both natural and anthropogenic, in a variety of ways
and are sensitive indicators and integrators of environmental change (Pearson and
Rosenberg 1978, Warwick 1986, Dauer 1993, Wilson and Jeffrey 1994).

Benthic organisms are also important secondary producers, providing key linkages
between primary producers and higher trophic levels (Virnstein 1977, Holland et al. 1980,
1989, Diaz and Schaffner 1990). Benthic invertebrates are among the most important
components of estuarine ecosystems and may represent the largest standing stock of
organic carbon in estuaries (Frithsen 1989). Many benthic organisms, such as oysters and
clams, are economically important. Others, such as polychaete worms and crustaceans,
significantly contribute to the diets of economically important bottom-feeding juvenile
and adult fish such as spot and croaker (Homer and Boynton 1978, Homer at al. 1980)

Recent efforts by Maryland DNR have created a benthic index of biotic integrity
(B-IBJ) to help interpret these data (Weisberg et al. 1997). The B-IBI is an index that
varies from 1 to 5 and is based on a number of summer time benthic invertebrate
attributes such number of pollution tolerant species, number of opportunistic species,
total numbers, total biomass, among others. The B-IBI is based on a set of benthic
attributes that describe expected characteristics of benthic assemblages at site having
environmental stress. B-IBI scores near 1 indicate sites where environmental stress has
occurred, while sites with B-IBI scores near five indicate that the benthic community is
healthy. DNR has been monitoring the benthic communities around Chalk Point for the
last twenty years and the B-IBI has improved into the “good range” as a result of cleanup
efforts and reductions in nutrient inputs. The long-term benthic database provides a
unique opportunity to evaluate the effects of the oil spill on the ecological condition of
Patuxent River benthic communities.


PROPOSED WORK

We propose to initiate an assessment to determine if the oil spill has impacted the
benthic communities in Swanson Creek and the Patuxent River near Chalk Point. Benthic
sampling around the area affected by the oil spill will be conducted in spring and summer
2000. The summer assessment will be conducted in conjunction with the next scheduled
sampling event of the Maryland DNR Chesapeake Bay Benthic Monitoring Program
(LTB), and will use common locations and platforms for the collection of data whenever
possible. LTB has accumulated an extensive data base of benthic and water quality data
in the region and these existing data will be used as much as possible. The integration of
this study with on-going LTB efforts will result in a robust and scientifically-defensible
impact assessment and will minimize the large costs typically associated with benthic
sampling and processing. Furthermore, sample processing and organism identification
will be done in-house, eliminating the need for subcontracts and substantially reducing
the overall cost of the study.

The assessment will consist of river and creek subtidal benthic assessments. The
river component will consist of revisiting sites in the mainstem of the Patuxent River that
have been previously sampled as part of LTB. The creek component will allocate random
samples to Swanson Creek in the immediate vicinity of the spill, and to another creek that
has no impact or has been minimally impacted by the spill (to be determined with the
guidance of trustees from existing data).

RATIONALE

The effects of oil spills on benthic organisms vary as a function of the severity and
spatial extent of the event. The effects of oil spills and chronic hydrocarbon inputs on
benthic organisms have been widely documented (e.g., Samiullah 1985, Gray et al. 1990,
McGuinness 1990, Agard et al. 1993, Clarke 1993). Large hydrocarbon concentrations in
sediment are toxic to many organisms and may cause widespread mortality. However, in
systems that experience aperiodic disturbances such as those related to high summer
temperatures and low dissolved oxygen, sensitive species are usually eliminated. This
brings structural and organizational changes to the community and leads to pollution
resistant communities. It is therefore critical to examine the condition of the benthic
community before the oil spill in order to determine whether the impacted system differs
significantly from what it would have been in the absence of the impact. It might be that
the mortality resulting from the sediment toxicity after the oil spill is within the range of
variability expected of communities associated with multiple environmental stresses. Use
of the historical LTB database will therefore be very valuable to determining the status of
benthic communities in the Patuxent River prior to the impact from the oil spill.

LTB has collected samples at fixed and random locations within the Patuxent
River in the vicinity of Chalk Point both in the spring and summer seasons. Sampling in
the spring (mid May to early June) will be important because the timing of a disturbance
relative to the recruitment of species to the benthos is critical to survivorship. Larvae and