Oil Uptake and Contamination of Estuarine Food Webs
Investigators:
Brian Fry (PI), Department of Oceanography and Coastal Sciences, Louisiana State University,
Baton Rouge LA 70803; tel. 225 578 9403, fax -6326; bfry@lsu.edu
Don Baltz (co-PI), Department of Oceanography and Coastal Sciences, Louisiana State
University, Baton Rouge LA 70803; tel. 225 578 6512, fax - 6513; dbaltz@lsu.edu
A. Existing Project and a Shifting Focus
Fry has had phase I money from NGI/GRI to work on water quality issues in Barataria
Bay and Breton Sound, testing for low dissolved oxygen (DO) due to increased respiration by
microbes using the Macondo 252 oil. This work focused on direct respiration measurements in
Breton Sound and long-term decomposition experiments in Barataria Bay, extending a preexisting sampling programs through the summer and fall of 2010. This continuation enabled
comparisons of 2010 “+oil” conditions to pre-spill 2009 conditions.
Respiration samples have been collected and are being analyzed, but lab results for 2010
are not yet complete for reporting. To help assay oil incorporation into bay food webs, barnacle
samples also were collected in both estuaries at the end of summer 2010. Those samples have
been prepared and sent to New Zealand for 14C analysis via accelerator mass spectrometry, with
oil incorporation expected to be traced as low 14C activity due to the ancient age of oil. The 14C
results should be ready in December 2010 and unfortunately are not ready at this time (late
October 2010).
During the course of this field work for the phase I NGI/GRI project, Fry visited both
Barataria Bay and Breton Sound in late summer 2010, attended LSU seminars about the oil spill
and talked to local citizens about oil spread and impacts. The impression gained was that oil
effects were patchy, especially where slicks of oil stranded on marshes, and that many estuarine
areas seem little affected. However, longer-term effects could not be ruled out, and for this
reason the focus of the effort is proposed here to shift from water quality respiration work to
fisheries food webs where longer-term, low-level effects may still be detected in 2011. Even
though we are shifting focus somewhat, the following proposal is a continuation in that we will
especially use the barnacle data from phase I as an initial indicator where oil impacts occurred in
Barataria and Breton Sound and how strongly oil entered estuarine food webs of these areas.
Objectives. We propose using a combination of fisheries community analysis and
isotope descriptors of food webs to test perturbations of estuarine fisheries communities related
to the Macondo 252 oil spill. We will work in three estuarine systems to test for long-term
effects close to and far away from oil-impacted marshes, addressing the larger temporal and
spatial scales of the Phase II research question, “Did the Macondo 252 Oil Spill result in large
scale perturbation of the NGoM ecosystem structure or function?”. We seek to identify
changes in the following 3-step field program.
1. Locating Impact Areas. Existing oil spill maps and preliminary observations will
locate areas with stranded oil in Barataria Bay and Breton Sound, known Louisiana
estuarine impact areas nearest the Macondo 252 site and areas where oil came ashore.
Reconnaissance also will focus on locating unimpacted nearby reference areas. The
reference areas will be in Timbalier Bay that is adjacent to Barataria Bay to the west.
Some preliminary trawling will be done in all these areas to ensure that a
representative fisheries fauna is present, and two types of stations will be located in
each bay, nearshore (<100m from marsh) and offshore (>2 km from marsh) stations.
This results in 6 study locations (6 locations = 3 bays x 2 stations/bay) with
subsequent trawl work focused on triplicate trawls in each location. Sixteen foot otter
trawls will be used in this work to enable comparisons to extensive collections with
this gear by the Louisiana Department of Wildlife and Fisheries (LADWF). These
LADWF collections have been made over many (10+) years and give a reasonable
pre-spill baseline for species composition and abundance in estuarine food webs.
Also, some drop sampling will be conducted near marsh edges for comparison with
previous quantitative work that focused on oil contamination issues (Roth et al.
2009).
2. Sample collection. Samples will be collected in May and August 2011, with the May
samples representing spring and overwinter conditions, and the August samples
reflecting summer conditions when food web turnover is most rapid due to high
temperature. Fish and common invertebrates collected in trawls will be placed on ice
in the field and subsequently frozen for later work in the laboratory. Some animals
from oiled and non-oiled marsh surfaces will be collected as respective “dirty” and
“clean” reference end members for later isotope determinations.
3. Community Composition and Isotope Descriptors of Food Webs. Fish and
invertebrates will be identified to species, and community composition compared to
previous pre-spill collections to detect changes that might be due to oil incorporation
into estuarine food webs. Stable CNS isotopes will be determined for abundant
species to construct food web diagrams of basal food resources used (C and S
isotopes) and trophic levels present (N isotopes). Some samples will be analyzed for
14
C to detect oil incorporation into food webs, with low 14C values indicative of oil
use by microbes at the base of food webs. Where this low 14C oil signal is present
and indicates oil entry into the metabolic food web, animal samples also will be
analyzed directly for oil compounds such as PAHs to test for oil residues in tissues.
Isotopes will be used to assess residency and transience of fauna, with residents
expected to have a tight clustering of isotopes that is close to those of stationary filter
feeders (barnacles, oysters) from the same locations. Food webs and residents most
impacted by oil should have low 13C, low 14C and moderate-to-high 15N due to
microbial links and processing of oil (Spies and Desmarais 1983, Coffin et al. 1997,
Slater et al. 2005, Pearson 2008). Community-level species abundance and
distribution will be compared between areas with and without isotope indicators of
oil contamination to test for overall large-scale effects of the Macondo 252 oil spill
on estuarine fisheries communities and food webs.
4. Summary objectives. The proposed work encompasses three estuaries
with a long-term test of food web changes that would constitute “large-scale
perturbations” in estuarine systems. These systems are close to the spill site and the
most likely to show direct and indirect use of oil in fish food webs. These studies
may complement ongoing NGI estuarine work at several sites, and could be
potentially expanded to cover sites in several states. The work is largely
2
Observational. We will be using the phase I data as background for this continuation
request, and especially the 14C work with barnacles done in phase I should help us
identify locations where oil spill effects are likely strongest in food webs of Barataria
Bay and Breton Sound.
B. Methods
Methods follow established procedures currently in use in the Baltz and Fry laboratories.
Baltz and students have many years of experience collecting fish and analyzing community
structure with multivariate techniques (e.g. Granados and Baltz 2008, Roth et al. 2009). Fry
similarly is experienced with isotope measurement and interpretation, and has published several
papers about isotopes in fish and shrimp of the Louisiana coastal zone (Fry 1983, Wells et al.
2008, Fry 2008). The work with 14C is new to Louisiana but has been used effectively as an oil
tracers in several other coastal systems, and Fry has spent a recent sabbatical visiting a
radiocarbon AMS lab and becoming familiar with this technology.
Literature Cited
Coffin, R.B., L.A. Cifuentes, and P.H. Pritchard. 1997. Assimilation of oil-derived carbon and
remedial nitrogen applications by intertidal food chains on a contaminated beach in Prince
William Sound, Alaska. Marine Environmental Research 44: 27-39.
Fry, B. 1983. Fish and shrimp migrations in the northern Gulf of Mexico analyzed using stable
C, N, and S isotope ratios. Fishery Bulletin 81:789-801.
Fry, B. 2008. Importance of open bays as nurseries for Louisiana brown shrimp. Estuaries and
Coasts 31:776-789.
Granados-Dieseldorff, P. and D.M. Baltz. 2008. Habitat use by nekton along a stream-order
gradient in a Louisiana estuary. Estuaries and Coasts 31:572-583.
Pearson, A., K.S. Kraunz, A.L. Sessions, A.E. Dekas, W.D. Leavitt and K.J. Edwards. 2008.
Quantifying microbial utilization of petroleum hydrocarbons in salt marsh sediments by
using the 13C content of bacterial rRNA. Applied and Environmental Microbiology 74:11571166.
Roth, A. F. and D. M. Baltz. 2009. Short-term effects of an oil spill on marsh-edge fishes and
decapod crustaceans. Estuaries and Coasts 32:565-572.
Slater, G.F., H.K. White, T.I. Eglinton and C.M. Reddy. 2005. Determination of microbial
carbon sources in petroleum contaminated sediments using molecular 14C analysis.
Environmental Science and Technology 39:2552-2558.
Spies, R.B. and D.J. DesMarais. 1983. Natural isotope study of trophic enrichment of marine
benthic communities by petroleum seepage. Marine Biology 73:67-71.
Wells, R.J.D., J.H. Cowan Jr., and B. Fry. 2008. Feeding ecology of red snapper, Lutjanus
campechanus, in the northern Gulf of Mexico. Marine Ecology Progress Series 361:213-225.
3
C. Costs.
Budget Period: 1 year, January 01 –December 31, 2011. We have estimated a preliminary
budget of about 150k as follows:
Requested
Funds
A. Salaries and Wages
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
B. Subtotal Salaries and Wages
C. Fringe Benefits
@
Total Salaries, Wages and
D. Fringe
E. Travel
F. Supplies
G. Operating Services
H. Professional Services
1. Subcontracts
2. Consultants
Fry
Baltz
1 month
1 month
Other Investigators (list on justification)
Postdoctoral Associates
Other
Professionals
12 months RA
Graduate Assistants
Student
Workers
6 months
35.0%
$0
$0
$0
$31,410
$0
$4,000
$54,869
$17,804
$5,000
$5,000
$1,000
$0
$0
Radiocarbon and
Chemical Analyses
3. Other Services
I. Other Charges
J. Equipment
K. Total Direct Costs
L. Facilities & Administrative Costs
@ 47.0%
M. Total Project Costs
$9,639
$9,820
$18,000
$0
$101,673
*Base for request
= $101,673
4
$47,786
$149,460
Budget Justification. One month of summer salary is requested for each PI. PIs will run the
project with assistance from 2 RAs and 2 student workers. This personnel will work together to
collect and analyze the samples, compare results to pre-spill conditions and prepare reports and
publications. Travel and operating funds are requested to cover collections and presentations at
meetings. Supplies are requested for isotope determinations and for nets used in collections.
Natural abundance radiocarbon analyses needed to pinpoint oil contributions but these analyses
are expensive (about $600/sample done at specialized labs with accelerator mass spectrometers),
as are analyses of oil contaminants such as PAHs. Funds are requested for up to 30 radiocarbon
+ oil contaminant analyses.
5