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Response of Coastal Fishes to the Gulf of Mexico Oil Disaster


Abstract and Figures

The ecosystem-level impacts of the Deepwater Horizon disaster have been largely unpredictable due to the unique setting and magnitude of this spill. We used a five-year (2006-2010) data set within the oil-affected region to explore acute consequences for early-stage survival of fish species inhabiting seagrass nursery habitat. Although many of these species spawned during spring-summer, and produced larvae vulnerable to oil-polluted water, overall and species-by-species catch rates were high in 2010 after the spill (1,989±220 fishes km-towed(-1) [μ ± 1SE]) relative to the previous four years (1,080±43 fishes km-towed(-1)). Also, several exploited species were characterized by notably higher juvenile catch rates during 2010 following large-scale fisheries closures in the northern Gulf, although overall statistical results for the effects of fishery closures on assemblage-wide CPUE data were ambiguous. We conclude that immediate, catastrophic losses of 2010 cohorts were largely avoided, and that no shifts in species composition occurred following the spill. The potential long-term impacts facing fishes as a result of chronic exposure and delayed, indirect effects now require attention.
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Response of Coastal Fishes to the Gulf of Mexico Oil
F. Joel Fodrie
*, Kenneth L. Heck Jr.
1 Institute of Marine Sciences and Department of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, United States of America,
2 Dauphin Island Sea Lab and Department of Marine Sciences, University of South Alabama, Dauphin Island, Alabama, United States of America
The ecosystem-level impacts of the Deepwater Horizon disaster have been largely unpredictable due to the unique setting
and magnitude of this spill. We used a five-year (2006–2010) data set within the oil-affected region to explore acute
consequences for early-stage survival of fish species inhabiting seagrass nursery habitat. Although many of these species
spawned during spring-summer, and produced larvae vulnerable to oil-polluted water, overall and species-by-species catch
rates were high in 2010 after the spill (1,9896220 fishes km-towed
[m 6 1SE]) relative to the previous four years
(1,080643 fishes km-towed
). Also, several exploited species were characterized by notably higher juvenile catch rates
during 2010 following large-scale fisheries closures in the northern Gulf, although overall statistical results for the effects of
fishery closures on assemblage-wide CPUE data were ambiguous. We conclude that immediate, catastrophic losses of 2010
cohorts were largely avoided, and that no shifts in species composition occurred following the spill. The potential long-term
impacts facing fishes as a result of chronic exposure and delayed, indirect effects now require attention.
Citation: Fodrie FJ, Heck KL Jr (2011) Response of Coastal Fishes to the Gulf of Mexico Oil Disaster. PLoS ONE 6(7): e21609. doi:10.1371/journal.pone.0021609
Editor: Steven J. Bograd, National Oceanic and Atmospheric Administration/National Marine Fisheries Service/Southwest Fisheries Science Center, United States
of America
Received March 7, 2011; Accepted June 2, 2011; Published July 6, 2011
Copyright: ß 2011 Fodrie, Heck. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The authors acknowledge support from the National Marine Fisheries Service, National Oceanic and Atmospheric Administration Marine Fisheries
Initiative and Northern Gulf Institute. The funders had no role in study design, data collection and analyses, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: jfodrie
Prevailing models of ecological impacts resulting from oil
pollution are being revised after the April 2010 release of ,4.4
million barrels [1] of oil into the northern Gulf of Mexico (GOM).
In part, this is a legacy of the Exxon Valdez accident as a
watershed environmental catastrophe, and the extensive research
on acute and chronic impacts of the resulting inshore oil pollution
[2]. Unlike the 0.25–0.5 million barrels released by the Valdez [2],
however, the Deepwater Horizon (DH) disaster hemorrhaged oil
into the open ocean at 1500 m depth over a protracted 84-day
period [1]. As a critical step toward new model development
applicable for detecting impacts of the DH spill, rigorous
observational data at organismal through community levels are
needed to guide ecosystem-based toxicology.
We have already learned that a significant fraction of the oil
released into the GOM from the Macondo well did not rise to the
surface, and this has implications for the ecosystem-level responses
we should anticipate. Rather, oil was emulsified at the well head
due to turbulent mixing, reduced buoyancy at depth, and addition
of Corexit 9500 dispersant. Subsequently, mid-water hydrocarbon
plumes [3] have been observed with stimulation of petroleum-
degrading bacteria [4]. With this now understood, we revisit some
early concerns regarding impacts for nearshore fisheries [5].
During the DH spill, near-surface waters lacked any reliable
refuge from oil pollution, as slicks/sheens occurred at the
immediate surface and oil was emulsified throughout the water
column. For many fishes, including commercially valuable
snappers (Lutjanidae) and groupers (Serranidae), spawning occurs
during the spring or summer (table S1), and eggs, larvae and post-
larvae would have relied upon near-surface waters overlaying the
continental shelf during the DH spill [6–7]. Furthermore, eggs/
larvae and oil can be transported by the same hydrodynamic and
atmospheric processes, enhancing the probability of oil encounters
for many species. Because the population ecology of marine
species with bipartite life histories is disproportionately affected by
the health and survival of early life stages [8], understanding how
eggs, larvae and newly-settled juveniles coped with the DH spill is
essential for quantifying ecosystem responses.
We hypothesized that the strength of juvenile cohorts spawned
on the northern GOM continental shelf during May–September
2010 in the northern GOM would be negatively affected by egg/
larval-oil interactions. Oiled seawater contains toxic compounds
such as polycyclic aromatic hydrocarbons (PAHs) which, even
after weathering, can result in genetic damage, physical deformi-
ties and altered developmental timing for fish eggs/larvae [9–10].
These effects may be induced at very low (,1 ppb PAHs) levels of
exposure when persistent over days to weeks [11–12] - timescales
relevant for larval development and descriptive of the DH spill.
Additionally, emulsified oil droplets could mechanically damage
the feeding and breathing apparatus of relatively fragile larvae and
further decrease individual fitness. Unfortunately, observing egg/
larval mortality, growth or migration in situ is an enduring
challenge for biological oceanographers, as eggs/larvae are simply
too dilute and experience relatively high instantaneous mortality,
even in undisturbed systems [13].
In the absence of direct observations on eggs and larvae,
juvenile abundance data provide valuable indices of the acute,
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population-level responses of young fishes to the spill. Although
indirect evidence [14], early juvenile abundances are the
integrated products of early life-history processes such as
fertilization, larval growth/mortality, and settlement [6–8].
Therefore, effects of oil pollution on early life stages should be
detectable in time series data as shifts in the abundance of recently
settled juvenile fishes. We tested these predictions using 2006–
2010 survey data collected from the Chandeleur Islands, LA, to
Saint Joseph Bay, FL (Fig. 1), representing most of the nearshore
region directly impacted by oil. In contrast to the difficulties of
surveying marine larvae, quantitative measures of juvenile
abundances are tractable due to the tendency of settled fish to
aggregate in specialized nursery habitats [15]. In the northern
GOM, many fish species, such as those in the drum (Sciaenidae),
snapper and grouper families have juveniles that are routinely
collected from shallow-water seagrass meadows they use as
primary nurseries [16].
Our dataset consisted of 853 individual trawl samples taken
between July 15 and October 31 of 2006–2010 within seagrass
meadows of the northern GOM (tables S2, S3). We collected
167,740 individual fishes representing 86 taxa, and examined
catch-per-unit-effort (CPUE) data for all species pooled together,
as well as separately for each of the 20 most abundant species. We
also tested for post-spill community-level shifts in seagrass-
associated fish assemblages using multivariate analyses [17]. We
recognized that not all species were at equal risk for oil exposure
due to variation in spawning timing and larval distributions (tables
S1, S4). Furthermore, some species may have experienced release
from fishing pressure due to large-scale fishery closures [18] during
the spill (table S5), perhaps enhancing their larval production
during the summer spawning season. Therefore, we also
considered how these factors affected species-specific CPUEs
during 2010. In all analyses, comparisons among years were
considered as a proxy for the effects of oil disturbance (2006–2009
as undisturbed, 2010 as disturbed).
Within the oil-affected GOM, a five-year survey of seagrass-
associated fish communities did not indicate reductions in juvenile
abundances following the spill. Rather, of the twenty most
commonly collected fish species, twelve were characterized by
statistically higher catch rates in 2010 relative to 2006–20009
(a = 0.05; Table 1). Among the remaining eight taxa, pre- and
post-spill catch rates were statistically indistinguishable. Across our
entire study region, CPUE increased from 1,080643 fishes km-
(m 6 1SE) during 2006–2009 to 1,9896220 fishes km-
in 2010. When resolved among four geographical areas
(Chandeleur Islands, Gulf Islands, Grand Bay, Florida Bays;
Fig. 1), overall catch rates of juvenile fishes, as well as CPUE of the
most abundant species, pinfish (Lagodon rhomboides), were consis-
tently higher during 2010 than in 2008 or 2009, and in some areas
were higher in 2010 than all previous years (Fig. 2A–B; fig. S1, S2,
S3; table S6).
The species composition of juvenile fish assemblages was
unaltered in each sampling area during the months following the
DH disaster (Fig. 3). Prior to the spill, similarities among individual
trawl samples (SIMPER) ranged from 50.3% at the Chandeleur
Islands to 52.9% within Florida Bays (table S7). By comparison,
similarity percentages between pre- (2006–2009) and post-spill
Figure 1. Sampling region and study sites. Map of juvenile fish sampling stations, divided among four survey areas: Chandeleur Islands (blue
circles), Gulf Islands (green circles), Grand Bay (orange circles) and Florida Bays (red circles). 1. Chandeleur Is., LA; 2. Ship Is., MS; 3. Horn Is., MS; 4. Petit
Bois Is., MS; 5. Dauphin Is., AL; 6. Grand Bature Shoal, AL; 7. Point Aux Pines, AL, 8. Big Lagoon, FL; 9. Pensacola Bay, FL; 10. Choctawhatchee Bay, FL;
11. St. Andrew Sound, FL; 12. St. Joseph Bay, FL. The spread of surface oil during the 84-day spill is also shown (brown shading). Image at lower right
shows juvenile gray snapper (L. griseus), spotted seatrout (C. nebulosus) and pipefish (Syngnathus spp.).
Response of Fishes to GOM Oil Spill
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(2010) samples were correspondingly high, ranging from 43.4%
within Grand Bay to 50.8% at the Chandeleur Islands.
Furthermore, pinfish, silver perch (Bairdiella chyrsoura), mojarras
(Eucinostomus spp.), pigfish (Orthopristis chrysoptera) and spotted
seatrout (Cynoscion nebulosus) drove similarity patterns both before
and after the spill (table S7). Species richness (S, up 15%,
p,0.001), diversity (ES
, up 11%, p = 0.006; H9, up 18%,
p,0.001) and evenness (J9, up 11%, p = 0.003) among trawl
samples were all slightly elevated during 2010 relative to 2006–
2009 averages (table S8; fig. S4), indicating that high CPUEs in
2010 were broad based.
When averaged across species, there was little statistical
evidence that either exposure risk or release from fishing pressure
significantly affected CPUEs during 2010. When comparing 2010
CPUE data against pre-spill catch rates, we did observe that fishes
characterized by moderate (spring spawning, nearshore larvae) or
high risk (spring-summer spawning, larvae distributed across the
continental shelf) exhibited decreases in CPUE following the spill
at the Chandeleur Islands and Grand Bay (Fig. 4A). However, no
statistically significant differences were found as a function of egg/
larval risk (F
= 1.4 10, p = 0.242) or sampling areas (F
= 0.999 ,
p = 0.440; table S9). Similarly, release from fishing pressure on
spawning fishes could be implicated, although not proven, as a
determinant of post-spill CPUEs. Along the Chandeleur and Gulf
Islands, increases in catch rates during 2010 relative to 2006–2009
were 800% and 950% higher, respectively (Fig. 4B), for species
identified in state and federal management plans than for species not
harvested by fishermen (table S5). No similar patterns were recorded
within Grand Bay or Florida Bays, however, and effects of fishing
pressure (F
=1.510, p = 0.223) and area (F
p = 0.225) on CPUE responses were not significant.
Collectively, no significant, acute impacts on the strength of
juvenile cohorts within seagrass habitats were detected following
the DH disaster. This was true for all species examined, bolstering
our confidence in the conclusion that ecosystem-level injuries were
not severe for this community of fishes. Unfortunately, our
assessment cannot be compared to the most analogous spill, the
IXTOC 1 blowout [5], due to a paucity of formal scientific
investigation following that accident (The 1979 IXTOC I blowout
at 3600 m depth, 80-km north of the Yucata´n Peninsula, was a
,3.5-million-barrel spill.). The most parsimonious explanation for
our data is that these fishes were resilient to the spill, possibly due
to the retention of a large proportion of spilled oil at depth. As
such, these data add to a developing literature [3–4] in which the
acute impacts of the spill may be concentrated in the deep ocean
rather than shallow-water, coastal ecosystems that were the focus
of early concern [5]. For instance, gray snapper (Lutjanus griseus)
larvae were abundant in surface waters (0–25-m deep) over the
continental shelf from July through September [19], and were
among the most likely individuals to have contacted oil-polluted
water. Still, catch rates of gray snapper juveniles following the spill
Table 1. Relative frequencies and CPUE data for abundant fishes collected during sampling in seagrass meadows of the northern
Scientific name
Cumlative %
(df = 851) Trend
Risk of oil
Potential release
from fishing
Lagodon rhomboides 60.22 644.86 1379.32 ,0.001
Moderate-Low No
Eucinostomus spp. 72.67 119.94 60.21 0.086 NC Low Potential Bycatch
Bairdiella chrysoura 82.66 123.10 163.77 0.117 NC Moderate-Low No
Orthopristis chrysoptera 89.90 80.31 118.73 0.007
Moderate Potential Bycatch
Lutjanus griseus 91.64 23.63 43.02 0.003
High Yes
Stephanolepis hispidus 93.29 11.95 70.61 ,0.001
High No
Lutjanus synagris 94.68 14.79 19.18 0.171 NC High Yes
Cynoscion nebulosus 95.74 13.41 36.51 ,0.001
Low Yes
Syngnathus spp. 96.63 11.57 20.05 0.057 NC Moderate-Low No
Chilomycterus schoepfi 97.46 7.37 18.56 ,0.001
Unknown No
Leiostomus xanthurus 97.78 4.63 2.56 0.533 NC Moderate-Low Potential Bycatch
Opsanus beta 98.04 2.73 6.63 ,0.001
Low No
Arius felis 98.29 2.62 10.14 0.021
Low Potential Bycatch
Nicholsina usta 98.52 2.11 6.86 0.003
Unknown No
Sphoeroides spp. 98.70 2.26 2.24 0.974 NC Low No
Blenniidae 98.86 2.06 5.27 0.002
Low No
Mycteroperca microlepis 99.01 1.96 1.75 0.773 NC High Yes
Paralichthys spp. 99.16 1.97 2.90 0.133 NC Moderate Yes/ Potential
Archosargus probatocephalus 99.31 1.58 5.95 ,0.001
Unknown Yes
Lactophrys quadricorn is 99.43 1.47 3.22 0.036
Unknown No
Trend symbols indicate no change (NC) or statistically significant increase (q) in catch rates during 2010 relative to 2006–2009. Risk of oil encounters determined by
spawning season and across-shelf larval distribution for each species. Potential release from fishing pressure guided by state and federal management plans, as well as
shrimp-trawl bycatch data (SI).
Response of Fishes to GOM Oil Spill
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were high relative to the four previous years (up 82%, Fig. 2C;
area * pre/post spill context interaction p,0.001, table S6).
When averaged across species - and in some cases across species
with vastly different life histories - there were no statistically
significant differences in the response of fished or unfished species
to the spill (or their responses to subsequent management actions;
i.e., fishery closures). Still, there were notable patterns suggesting
that certain species may have been released from harvest pressure
during 2010, subsequently enhancing spawning activity and post-
spill cohort sizes despite any potentially negative oil impacts. For
example, spotted seatrout spawn during summer [20], but many
mature individuals are typically removed by recreational fishers
before reproducing. Following the fishery closures in 2010, we
recorded order-of-magnitude higher juvenile abundances of
spotted seatrout at the Chandeleur and Gulf Islands, as well as
elevated catch rates throughout our survey region (Fig. 2D; area,
pre/post spill context and 2-way interaction p,0.001, table S6).
Consistent with the patterns observed in the species-by-species
catch data and analyses of ‘risk’’ or ‘fishing’’ effects, there were no
significant post-spill shifts in community composition and
structure, nor were there changes in any of several biodiversity
measures. While natural recruitment variability can make it
difficult to detect population-level impacts for any one species
following large-scale disturbance [14], our whole-community
analyses and results are likely robust against these concerns.
Several other factors could have contributed to the high catch
rates of seagrass-associated fishes in 2010 despite large-scale oil
pollution. For instance, fishes may be uniquely buffered against oil
pollution due to their mobility or foraging ecology [21–22]. Also,
the major predators of fish eggs/larvae (e.g., gelatinous zooplank-
ton) may have been impacted by the spill, thereby reducing
natural mortality rates for coastal fishes [23]. Regardless of the
mechanism(s) involved, thus far the potential for 2010 cohorts to
support regional fisheries over the next several years has persisted
despite the spill. This information is critical for projecting the
mode and tempo of ecological and economic recovery in the oil-
affected GOM, as well as guiding future conservation/restoration
activities to mitigate oil-spill injuries.
While these data provide reason for early optimism, attention
should now turn to possible chronic effects of oil exposure on fishes
as well as delayed indirect effects cascading through the post-spill
GOM. Fish may suffer growth, survival or reproductive penalties
years after exposure to oil [24], or experience altered migratory
behaviors [25]. Oil sequestered in sediments may also affect
species laying benthic eggs for several years [26]. More broadly,
ecosystems experiencing large-scale disturbance can carry or build
Figure 2. Catch rates of juvenile fishes, 2006–2010. Catch rates among years and sampling areas (Chandeleur Islands, Gulf Islands, Grand Bay
and Florida Bays) for: (A) all fishes pooled; (B) pinfish (L. rhomboides), (C) gray snapper (L. griseus), and (D) spotted seatrout (C. nebulosus). CPUE data in
panels B–D are presented on a log scale, and all data are shown as means of trawl samples (m + 1SE).
Response of Fishes to GOM Oil Spill
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instabilities over protracted periods that can eventually result in
delayed collapses of fisheries stocks [27].
Improved threat assessment for energy exploration [28] and
process-oriented studies of ecosystem responses will be long-term
initiatives resulting from the DH spill. In the short term, however,
observational data collected over relevant spatial and temporal
scales are invaluable for guiding and evaluating targeted studies of
oil toxicology [29]. For fish species experiencing multiple stressors
such as habitat degradation [30] harvest pressure [31], climate
change [16], and now oil pollution, rigorous baseline survey data
and new syntheses are needed to enact effective ecosystem-based
Materials and Methods
We analyzed changes in northern Gulf of Mexico (GOM)
seagrass-associated fish communities during the last 5 years by
comparing survey data obtained either prior to (2006–2009) or
immediately following the Deepwater Horizon disaster (2010).
The survey region extended approximately 340 km along the
coastline, including a significant portion of the inshore area most
affected by oil (Fig. 1.). Each year, we made repeated sampling
trips to 12 sites, extending from the Chandeleur Islands, LA, to St.
Joseph Bay, FL (29.68–30.72uN, 85.30–89.10uW). Sampling
occurred within mixed seagrass meadows that serve as primary
nursery habitat for many juvenile fishes that have recently settled
from the water column following a 5–45 day larval period [6,16].
Our samples were collected from seagrass mosaics that included
turtle grass (Thalassia testudinum), shoal grass (Halodule wrightii),
widgeon grass (Ruppia maritima), and manatee grass (Syringodium
filiforme), along with scattered unvegetated patches (table S3).
During each year, trawls were conducted from July 15 through
October 31 in order to record the abundances and composition of
fishes during the period when seagrass meadows are utilized as
primary nurseries by recently settled juveniles (refer to table S1 for
reproductive seasons of common fishes). Fishes were collected
using a 5-m otter trawl (2.0-cm body mesh; 0.6-cm bag mesh;
0.360.7-m doors) with conventional 4-seam balloon design
including float and lead lines but without tickler chains. Trawls
consisted of 3.960.1 (m 6 1SE) minute tows behind small (,7m)
research vessels traveling at 3.3+0.1 kilometers hour
. Overall,
853 samples were taken (table S2), and the trawl covered a linear
distance of 184.7 kilometers during our sampling. These trawls
occurred in depths of 0.5–2.5-m, and were conducted during
daylight hours. During our surveys, species were enumerated in
the field unless species-level identifications were not easily made.
Unidentified specimens were transported to the lab where
meristics were used by at least two different technicians to identify
each individual. In cases in which species could not be identified,
specimens were classified to the lowest taxonomic level possible.
Typically, fishes were 20–100 mm long (standard length),
indicative of recently-spawned juveniles. However, we did not
record individual sizes for all species, and, for pipefishes (Syngnathus
Figure 3. Community composition of seagrass-associated fish communities, 2006–2010. Multi-dimensional scaling plots for seagrass-
associated fish communities prior to (2006–2009; colored symbols) and following (2010; black circles) the DH spill. Data for (A) Chandeleur Islands, (B)
Gulf Islands, (C) Grand Bay and (D) Florida Bays are presented separately. Each datum represents a single trawl sample.
Response of Fishes to GOM Oil Spill
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spp.) and hard-headed catfish (Arius felis), we did observe that a
small proportion of our catch included reproductive adults. For
four species: gray snapper (50.560.8 mm [m 6 SE]), lane snapper
(Lutjanus synagris; 55.760.7 mm), spotted seatrout (60.861.1 mm)
and gag grouper (Mycteroperca microlepis; 157.563.2 mm); we did
record the sizes of all individuals throughout our surveys. Based on
our own otolith analyses (Fodrie unpublished) and published
reports of first-year growth among these four species (age-1 sizes:
gray snapper ,109 mm; lane snapper ,140 mm; spotted seatrout
,127 mm; gag grouper .198 mm), we calculated that .96% of
individuals were captured in the same year as they were spawned
(including 2010).
Once enumerated, fishes were entered in to an Excel database,
and abundance data were converted into catch-per-unit-effort
(CPUE) data based on the linear distance over with each trawl
occurred. All statistical analyses were applied to these CPUE data.
Our complete CPUE dataset is included as a separate appendix in
our supporting information (dataset S1). This study was carried
out in strict accordance with the recommendations in the Guide
for the Care and Use of Laboratory Animals of the National
Institutes of Health. Our sampling protocol was approved by the
Committee on the Ethics of Animal Experiments of the University
of North Carolina at Chapel Hill (Permit Number: 10-114.0).
Statistical analyses
We investigated differences in the catch rates of seagrass-
associated fishes (all species pooled as well as the 20 most abundant
species individually) by unpaired t-tests comparing pre- (2006–2010)
and post-spill (2010) data (Table 1), as well as 2-way ANOVAs in
which sampling area (Chandeleur Islands, Gulf Islands, Grand Bay,
Florida Bays) and context (pre- versus post-spill) were fixed factors
(table S6). Regions were defined by basic geomorphology and
location, local water clarity, local salinity, and local seagrass
composition [32]. Because variances were stable among groups,
no data transformations were required prior to analyses.
We analyzed similarities and differences in fish communities
among years (2006–2009 versus 2010) within each sampling area
(each area considered separately) using non-metric multidimen-
sional scaling (MDS), based on Bray-Curtis similarity indices
among all individual trawl samples (4
root-transformed data).
Pairwise comparisons between trawl samples across years were
conducted with analysis of similarity (ANOSIM) and similarity (or
dissimilarity) percentages (SIMPER) using PRIMER 5.2.2 soft-
ware (PRIMER-E Ltd; [33]).
We also examined patterns of species diversity among regions
and years by computing the following measures for each trawl
sample: S, number of species collected; ES
, species richness
rarefied to 20 individuals; H9, Shannon-Weiner diversity index
); and J9, Pielou’s evenness measure (PRIMER 5.2.2 software).
We investigated differences in community diversity via 2-way
ANOVAs in which sampling area (Chandeleur Islands, Gulf
Islands, Grand Bay, Florida Bays) and context (pre- versus post-
spill) were fixed factors. Because variances were stable among
groups, no data transformations were required prior to analyses.
Figure 4. Larval risk and fishery closure impacts. Effects of (A) egg/larval vulnerability and (B) harvest pressure on the responses of fishes to the
DH spill. Response of individual species calculated as the ratio of 2010 versus 2006–2009 CPUE data. Data are presented on a log scale as group
means (m + 1SE), with ratios .1 indicating that 2010 catch rates were elevated relative to 2006–2010 data.
Response of Fishes to GOM Oil Spill
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These approaches are proscribed in earlier syntheses for
detecting environmental impacts [17]. Critiques of employing
parametric testing to detect ecosystem injury exist due to
interannual variability and reduced statistical power [14], although
those concerns have focused on analyses involving single species.
We determined the relative probability for oil-larvae encounters
(‘risk’) for the twenty most commonly captured fishes, and used
these data to explore how individual species responded differently to
large-scale oil pollution in the northern GOM. Information on the
seasonal timing of spawning and distribution of larvae from shore to
the outer margin of the continental shelf was collected from the
literature (tables S1 and S4), and used to define 4 levels of risk (in
addition to an ‘unknown’ [n = 4] category containing species for
which no data were available). ‘Low’ risk species (n = 6) included
those in which larvae remained inside estuaries, either in the
plankton or as benthic egg masses, regardless of spawning season.
‘Moderate-Low’ risk species (n = 4) were defined by having either 1)
larvae distributed in estuaries as well as across the continental shelf,
or 2) larvae distributed across the continental shelf, but not likely
during the spill period (i.e., April–September). Only two ‘Moderate’
risk species were identified: pigfish (Orthopristis chrysoptera) spawn
throughout summer, and have larvae distributed within nearshore
waters; while flounder (Paralichthys spp.) have larvae distributed
across the continental shelf, with a protracted spawning that extends
into April or May (i.e., some overlap with the oil spill). ‘High’ risk
species (n = 4) spawn offshore and have larvae distributed across the
continental shelf. Furthermore, spawning data indicates that these
species would have produced larvae sometime during the DH spill
(April–Sept in our classification scheme). Based on these risk guilds,
we examined the response of fishes to the spill by calculating the
ratio of 2010 CPUE data (averaged) to 2006–2009 CPUE data
(averaged) for each species. Following these calculations, ratios .1
indicate that average 2010 catch rates were higher than during the
previous 4 years, while ratios ,1 indicate that average 2010 catch
rates were lower than during the previous 4 years. Using each
species as a replicate measure, we used ‘risk’ and region
(Chandeleur Islands, Gulf Islands, Grand Bay, Florida Bays) as
fixed factors in a 2-way ANOVA that compared 2010 CPUE:
2006–2009 CPUE trends. Because variances were stable among
groups, no data transformations were required prior to analyses.
Similarly, we determined whether species were likely to have
experienced significant release from harvest pressure following
large-scale closures in the northern GOM, and examined how this
may have affected CPUE data in 2010. For each of the twenty
most commonly caught fish, we designated species as ‘fished’ if
they were included in any state or federal management plan as of
Dec 31, 2010 (table S5), or identified as ,1% (by biomass) of
bycatch in shrimp trawl fisheries within the northern GOM (table
S5). As before, we examined the response of fishes to the spill by
calculating the ratio of 2010 CPUE data (averaged) to 2006–2009
CPUE data (averaged) for each species. Using each species as a
replicate measure, we used ‘fishing pressure’ (with fished species
including species that are targeted or captured as incidental
bycatch at significant levels) and region (Chandeleur Islands, Gulf
Islands, Grand Bay, Florida Bays) as fixed factors in a 2-way
ANOVA that compared 2010 CPUE: 2006–2009 CPUE trends.
Because variances were stable among groups, no data transfor-
mations were required prior to analyses.
All univariate tests were conducted using StatView 5.0.1 software
(SAS Institute Inc.). Because each statistical analysis applied to
separate and easily distinguishable hypotheses, we made no
corrections to experiment-wise alpha for any of the univariate (total
fishes CPUE, individual fishes CPUE, risk guilds, harvest guilds,
diversity) or multivariate (ANOSIM) tests we conducted [34].
Supporting Information
Figure S1 Catch rates of all fishes, pooled together, among
sampling areas prior to (2006–2009) and following (2010) the
Deepwater Horizon disaster.
Figure S2 Catch rates of individual species, among sampling
areas prior to (2006–2009) and following (2010) the Deepwater
Horizon disaster. Data are presented for the 20 most abundant
Figure S3 Catch rates among sampling areas and years for the
20 most abundant species collected during trawl surveys.
Figure S4 Diversity measures for seagrass-associated fish
communities within sampling areas affected by the Deepwater
Horizon disaster.
Table S1 Summary table for CPUE data (fish kilometer-
) of fishes prior to (2006–2009) and following (2010) the
DH disaster.
Table S2 Distribution of trawl samples among sampling areas
(Chandeleur Islands, Gulf Islands, Grand Bay, Florida Bays) and
years (2006–2010).
Table S3 Quantitative description of seagrass habitats sampled
throughout the northern Gulf of Mexico during 2006–2010.
Table S4 Information used to determine the likelihood of larvae
contacting oiled water during the summer of 2010.
Table S5 Summary table for the management status of the 20
most abundant fishes collected during our survey program.
Table S6 Summary table of the effects of sampling area and
year (context: pre- versus post-spill) on the catch rates of the 20
most abundant fishes collected during surveys in northern Gulf of
Mexico seagrass meadows.
Table S7 Comparisons of community structure between catch
data prior to (2006–2009) or immediately following (2010) the
Deepwater Horizon disaster (ANOSIM and SIMPER).
Table S8 Summary table of the effects of sampling area and
year (context: pre- versus post-spill) on the diversity (S, ES
and J9) of trawl samples collected within northern Gulf of Mexico
seagrass meadows.
Table S9 Summary table of the effects of sampling area, larval
risk and harvest pressure on the change in catch rates of individual
species for pre- (2006–2009) and post-spill (2010) data.
Dataset S1 Complete CPUE data obtained for 2006–2009 trawl
surveys within seagrass meadows of the northern Gulf of Mexico.
Response of Fishes to GOM Oil Spill
PLoS ONE | 7 July 2011 | Volume 6 | Issue 7 | e21609
We are extremely grateful to the students and technicians who aided in the
field, especially C. Baillie, M. Brodeur, J. Myers, O. Rhoades and S.
Williams. B. Raines supplied the image of juvenile fishes in Fig. 1.
Constructive comments and support were provided by S. Powers, C.
Peterson, J. Kenworthy, and 2 anonymous reviewers.
Author Contributions
Conceived and designed the experiments: FJF KLH. Performed the
experiments: FJF KLH. Analyzed the data: FJF. Wrote the paper: FJF
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Response of Fishes to GOM Oil Spill
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... In addition to these spill-response patterns observed among marsh-associated nekton, similar patterns of stability in fish populations and communities have emerged post DWH in diverse northern Gulf settings such as seagrass-associated fishes (Fodrie and Heck, 2011), estuarine fishes throughout Mississippi Sound (Schaefer et al., 2016), and within the coastal population of Gulf menhaden, Brevoortia patronus, a key forage fish (Short et al., 2017). ...
... Several factors may help reconcile why these individual-level damages do not appear to manifest as losses at the population or community level for marshassociated nekton. In addition to the fishery closures in 2010 that potentially reduced adult mortality and increased recruitment of summer/fall spawning species (Fodrie and Heck, 2011), many fishes, crabs, and shrimps may have relied on their mobility to detect and then evade oiling (Martin, 2017). In many estuaries, the distribution of oil was highly patchy and could have allowed for avoid-Eight-year study quantifies how oiling is a continuing stressor on the marsh ecosystem. ...
Full-text available
Previous oil spills provide clear evidence that ecosystem restoration efforts are challenging, and recovery can take decades. Similar to the Ixtoc-I well blowout in 1979, the Deepwater Horizon (DWH) oil spill was enormous both in volume of oil spilled and duration, resulting in environmental impacts from the deep ocean to the Gulf of Mexico coastline. Data collected during the National Resource Damage Assessment showed significant damage to coastal areas (especially marshes), marine organisms, and deep-sea habitat. Previous spills have shown that disparate regions recover at different rates, with especially long-term effects in salt marshes and deep-sea habitat. Environmental recovery and restoration in the northern Gulf of Mexico are dependent upon fundamental knowledge of ecosystem processes in the region. Post-DWH research data provide a starting point for better understanding baselines and ecosystem processes. It is imperative to use the best science available to fully understand DWH environmental impacts and determine the appropriate means to ameliorate those impacts through restoration. Filling data gaps will be necessary to make better restoration decisions, and establishing new baselines will require long-term studies. Future research, especially via NOAA’s RESTORE Science Program and its state-based Centers of Excellence, should provide a path to understanding the potential for restoration and recovery of this vital marine ecosystem.
... Responses in fishery sectors appear to have been underpinned by relative population-level stability among harvested taxa in the aftermath of the DwH oiling disaster. This stability among fishery species has been corroborated by several nearshore fishery-independent surveys following this unparalleled perturbation among both finfishes (Fodrie and Heck 2011, Able et al. 2015, Schaefer et al. 2016, Martin et al. 2020) and decapod crustaceans (Moody et al. 2013, Van der Ham and de Mutsert 2014, Grey et al. 2015. Multiple species of sciaenids, lutjanids, serranids, and penaeids comprise these outcomes, despite known harms for individuals exposed to oil among nekton (reviewed in Fodrie et al. 2014). ...
... Similarly, food-safety fishery closures (Ylitalo et al. 2012) contributed toward seasonal (May-October) reductions in 2010 fishing mortality. These changes in summer-fall harvest pressure likely had positive effects on the reproductive output and subsequent abundances of fishes and shellfishes throughout 2010-2017 (Fodrie and Heck 2011). We do note, however, that overall GOM harvests in 2010 were remarkably high given the broad closures following the spill. ...
Full-text available
The 2010 Deepwater Horizon (DwH) disaster challenged the integrity of the Gulf of Mexico (GOM) large‐marine ecosystem at unprecedented scales, prompting concerns of devastating injury for GOM fisheries in the post‐spill decade. Following the catastrophe, projected economic losses for regional commercial, recreational, and mariculture sectors for the decade after oiling were US$3.7–8.7 billion overall, owing to the vulnerability of economically prized, primarily nearshore taxa that support fishing communities. State and federal fisheries data during 2000–2017 indicated that GOM fishery sectors appeared to serve as remarkable anchors of resilience following the largest accidental marine oil spill in human history. Evidence of post‐disaster impacts on fisheries economies was negligible. Rather, GOM commercial sales during 2010–2017 were US$0.8–1.5 billion above forecasts derived using pre‐spill (2000–2009) trajectories, while pre‐ and post‐spill recreational fishery trends did not differ appreciably. No post‐spill shifts in target species or effort distribution across states were apparent to explain these findings. Unraveling the mechanisms for this unforeseen stability represents an important avenue for understanding the vulnerability or resilience of human–natural systems to future disturbances. Following DwH, the causes for fishery responses are likely multifaceted and complex (including exogenous economic forces that typically affect fisheries‐dependent data), but appear partially explained by the relative ecological stability of coastal fishery assemblages despite widespread oiling, which has been corroborated by multiple fishery‐independent surveys across the northern GOM. Additionally, we hypothesize that damage payments to fishermen led to acquisition or retooling of commercial fisheries infrastructure, and subsequent rises in harvest effort. Combined, these social–ecological dynamics likely aided recovery of stressed coastal GOM communities in the years after DwH, although increased fishing pressure in the post‐spill era may have consequences for future GOM ecosystem structure, function, and resilience.
... In the northern Gulf of Mexico, community stability has been widely documented after the drilling rig Deepwater Horizon (DWH) exploded in 2010 (Fodrie and Heck 2011;Moody et al. 2013;Able et al. 2015;Schaefer et al. 2016;Martin et al. 2020). This disaster discharged~3.19 million barrels (~0.5 million m 3 ) of crude oil over 180,000 km 2 . ...
... At the closure, approximately 88,500 km 2 were closed to fishing of all kinds, accounting for 35% of all federal waters in the northern Gulf of Mexico and 40% of state waters in Alabama (Upton 2011). After initial impacts of the spill, marine communities in the northern Gulf showed little subsequent disruptions of species' abundance, composition, or size (Rozas et al. 2000;Fodrie and Heck 2011;Moody et al. 2013;Able et al. 2014;Van Der Ham and De Mutsert 2014;Schaefer et al. 2016;Martin et al. 2020). Roth and Baltz (2009) noted similar community stability following a smaller oil spill in Barataria Bay, Louisiana, in 2005 (~600 barrels). ...
Full-text available
A primary aspect of applied marine ecology assesses how food webs change in response to ecosystem disturbances. In 2010, the drilling rig Deepwater Horizon (DWH) discharged~3.19 million barrels of crude oil into the northern Gulf of Mexico. The spill, followed by widespread dispersant application to enhance oil degradation , represented a significant anthropogenic disturbance in the region. We created network models of four multi-year periods, to represent the acute and chronic food web responses to the DWH spill. Using ecological network analysis (ENA) and information theory, we compared multiple food web metrics among these periods in the context of food web resilience theory. This analysis was conducted at three levels of hierarchical organization: whole ecosystem, nekton community, and individual nekton taxa. We analyzed how individual taxa contribute to resilience of the food web with a novel informational index: Redundancy/Ascendency. Apparent responses to the disturbance differed across hierarchical levels. Some metrics dependent on biomass change and flow distribution temporarily increased during the years immediately following the discharge and subsequently returned to pre-DWH levels. Metrics of energy flow linked to primary production rose in the last two periods, perhaps reflecting eutrophication. Other metrics changed little or had no obviously explainable patterns. Overall , our results indicate the nektonic food web in this region is flexible to disturbance and likely has redundant energy pathways explaining the reported ecosystem resilience to the DWH spill. We show that an ENA, when applied to multiple levels of ecosystem hierarchy, may aid understanding of marine food web resilience.
... Since the spill there have been several studies to identify the potential residual effects of the DWH oil and it's PAH effects on fish species, both from initial exposure and chronic exposure (Beyer et al., 2016;Fodrie and Heck, 2011;Mendelssohn et al., 2012;Szedlmayer and Mudrak, 2014;Whitehead et al., 2012). Sub-lethal DWH oil concentrations were reported to cause changes in genome expression and tissue morphology impairment in gulf killifish (Fundulus grandis; Whitehead et al., 2012). ...
... Based on the chemical make-up of the DWH oil, immunotoxicity effects could include increased parasitism and reduced disease resistance, which could affect population reproduction (Barron, 2012). However, there has yet to be any detected year-class failures or recruitment failures associated with the DWH spill (Beyer et al., 2016;Fodrie and Heck, 2011;Szedlmayer and Mudrak, 2014). ...
Age, growth, mortality, and polycyclic aromatic hydrocarbons (PAHs) in roughtongue bass (Pronotogrammus martinicensis) were examined in the northern Gulf of Mexico following the 2010 Deepwater Horizon oil spill. Fish (N = 1090) were collected from September 2014 to July 2015 from the Alabama Alps (54 km from the spill site) and Roughtongue Reef (111 km from the spill site). Sites were dominated by the 2010 year-class. Growth rates were significantly lower for fish from Alabama Alps compared to Roughtongue Reef (p < 0.001) and likely linked to proximity of the Mississippi River discharge. Mean total PAH ± SD was 50 ± 52.6 and ranged from 0 to 220 ppb. These PAH levels were below a 300-ppb minimum effect level and not significantly different between sites. The dominant 2010 year-class, low PAH levels, and similar growth rates to pre-spill measures indicated that the Deepwater Horizon oil spill had little effect on roughtongue bass.
... The National Research Council (NRC, 2013) assessed oil spill impacts on the provisioning ecosystem service of seafood and fish-based products, as well as the cultural services provided through recreational fishing (among other case studies). Results suggested that, while fishery closures may have decreased landings in the immediate aftermath of the spill (McCrea-Strub et al., 2011;NRC, 2013), increased catch rates were later observed for a large group of regularly harvested species (Fodrie and Heck, 2011;NRC, 2013). However, impacts from the spill to fishery harvest may take years or even decades to materialize, particularly regarding cascading effects through marine food chains (NRC, 2013). ...
Full-text available
The Deepwater Horizon (DWH) oil spill is the only declared Spill of National Significance in US history, and it significantly impacted the health of people and communities in the Gulf of Mexico region. These impacts amplified adverse effects of prior disasters and may compound those of future traumas. Studies, both to date and ongoing, show some negative mental and physical health outcomes associated with DWH in some spill workers, as well as some coastal residents in all Gulf States. The spill was also associated with negative effects in the living resources, tourism, and recreation sectors, at least in the short term. Compared with others, people dependent on these sectors reported more health and financial concerns. Consumer concerns about the safety and marketability of seafood persisted well after data demonstrated very low risk. Parents were concerned about possible exposures of children as they played on beaches, but this risk was found to be minor. Spill-related stress was an overarching factor associated with adverse health outcomes, and some residents reported greater stress from navigating the legal and claims processes following the spill than from the spill itself. Research revealed a serious lack of baseline health, environmental, and socioeconomic data against which to compare spill effects. This finding highlighted the need for ongoing observing systems to monitor health and socioeconomic parameters and establish continuous baselines of such information.
... Our productivity estimates imply that Gulf menhaden were vulnerable to stress by inadequate food availability in 2011 and 2012. The demand that increased Gulf menhaden production placed on the food supply was likely augmented by production associated with the recruitment increases of other forage fishes in 2010 [39,40] that feed at similar trophic levels. Spatial variation in Gulf menhaden recruitment in 2010 [6] implies that this increased demand was most acute in Barataria Bay and vicinity west of the Mississippi River, such that food demand from Gulf menhaden may have accounted for more than half the available supply there. ...
Full-text available
Unprecedented recruitment of Gulf menhaden (Brevoortia patronus) followed the 2010 Deepwater Horizon blowout (DWH). The foregone consumption of Gulf menhaden, after their many predator species were killed by oiling, increased competition among menhaden for food, resulting in poor physiological conditions and low lipid content during 2011 and 2012. Menhaden sampled for length and weight measurements, beginning in 2011, exhibited the poorest condition around Barataria Bay, west of the Mississippi River, where recruitment of the 2010 year class was highest. Trophodynamic comparisons indicate that ~20% of net primary production flowed through Gulf menhaden prior to the DWH, increasing to ~38% in 2011 and ~27% in 2012, confirming the dominant role of Gulf menhaden in their food web. Hyperabundant Gulf menhaden likely suppressed populations of their zooplankton prey, suggesting a trophic cascade triggered by increased menhaden recruitment. Additionally, low-lipid menhaden likely became “junk food” for predators, further propagating adverse effects. We posit that food web analyses based on inappropriate spatial scales for dominant species, or solely on biomass, provide insufficient indication of the ecosystem consequences of oiling injury. Including such cascading and associated indirect effects in damage assessment models will enhance the ability to anticipate and estimate ecosystem damage from, and provide recovery guidance for, major oil spills.
Full-text available
Abstract The 2019 oil spill was the biggest in Brazilian history. Oil was found along more than 3,000 km of the Brazilian coastline, mainly in the Northeast, in more than 1,000 localities. This article analyzes the disaster’s damage using a sample of interviewers who were impacted - fishers, tourism and beach hawkers - distributed along 40 of the affected municipalities in the Northeast Region of Brazil. The socio-economic indicators obtained by the research show that the impacts were not homogeneous between the segments and cities researched. Localities specialized in tourism and with a workforce relatively more specialized in fishing were the most affected. Accordingly, the populations of fishers and beach hawkers suffered the most severe impacts in terms of income reduction and the sale of products. These agents report a negative impact of the disaster on their work activities of 73% (fishers) and 65% (beach vendors), while the lodging and food sectors reported losses in about 38% of the cases. The interviewees’ health indicators demonstrated that the volunteers at the oil spill clean- up suffered damage due to the exposure experienced, evidencing the public health emergency dimension of the disaster.
Large-scale wetland reforestation and hydrologic restoration projects have been implemented worldwide though few have been well studied or monitored following restoration. Many are located in the United States where laws require restoration to compensate for the loss of aquatic and wetland resources. Many projects are in coastal areas or deltas where the rate of wetland loss is great and where water and sediment are available to restore hydrology and build (wet)lands. Seven examples are presented: saline tidal marshes (2), inland freshwater marshes (2), delta wetlands (2), and mangrove reforestation (1). Techniques range from large-scale plantings to river diversions, and nearly all require reintroduction of hydrology. Large restoration projects often involve rewetting with river water (marshes of Mesopotamia (Iraq) and Yellow River Delta (China)), and/or sediment (Louisiana, United States). Perhaps the largest wetland restoration project in the world, the Florida Everglades, is a restoration in progress that may not be completed for another 60 years.
Full-text available
Estuarine and coastal geomorphology, biogeochemistry, water quality, and coastal food webs in river-dominated shelves of the Gulf of Mexico (GoM) are modulated by transport processes associated with river inputs, winds, waves, tides, and deepocean/continental shelf interactions. For instance, transport processes control the fate of river-borne sediments, which in turn affect coastal land loss. Similarly, transport of freshwater, nutrients, and carbon control the dynamics of eutrophication, hypoxia, harmful algal blooms, and coastal acidification. Further, freshwater inflow transports pesticides, herbicides, heavy metals, and oil into receiving estuaries and coastal systems. Lastly, transport processes along the continuum from the rivers and estuaries to coastal and shelf areas and adjacent open ocean (abbreviated herein as “river-estuary-shelf-ocean”) regulate the movements of organisms, including the spatial distributions of individuals and the exchange of genetic information between distinct subpopulations. The Gulf of Mexico Research Initiative (GoMRI) provided unprecedented opportunities to study transport processes along the river-estuary-shelf-ocean continuum in the GoM. The understanding of transport at multiple spatial and temporal scales in this topographically and dynamically complex marginal sea was improved, allowing for more accurate forecasting of the fate of oil and other constituents. For this review, we focus on five specific transport themes: (i) wetland, estuary, and shelf exchanges; (ii) river-estuary coupling; (iii) nearshore and inlet processes; (iv) open ocean transport processes; and (v) river-induced fronts and cross-basin transport. We then discuss the relevancy of GoMRI findings on the transport processes for ecological connectivity and oil transport and fate. We also examine the implications of new findings for informing the response to future oil spills, and the management of coastal resources and ecosystems. Lastly, we summarize the research gaps identified in the many studies and offer recommendations for continuing the momentum of the research provided by the GoMRI effort. A number of uncertainties were identified that occurred in multiple settings. These include the quantification of sediment, carbon, dissolved gasses and nutrient fluxes during storms, consistent specification of the various external forcings used in analyses, methods for smooth integration of multiscale advection mechanisms across different flow regimes, dynamic coupling of the atmosphere with sub-mesoscale and mesoscale phenomena, and methods for simulating finer-scale dynamics over long time periods. Addressing these uncertainties would allow the scientific community to be better prepared to predict the fate of hydrocarbons and their impacts to the coastal ocean, rivers, and marshes in the event of another spill in the GoM.
Full-text available
After the explosion and subsequent sinking of the Deepwater Horizon (DWH) on 22 April 2010, an estimated 780,000 m3 of Sweet Louisiana Crude (SLC) and 205,000 mT of methane were released into the northern Gulf of Mexico over an 85 d period. A great deal of controversy ensued regarding the application of unprecedented volumes of chemical dispersants both at the surface and at depth. One of the consequences of dispersing such large volumes of oil into the water column was the difficulty of tracking its fate over distance and through the food web. Most of the attention to date has been on large underwater plumes of oil, and scant evidence exists for subsea oil in warm (>25 °C), shallow shelf waters due to rapid weathering and utilization by prokaryotes. A large pool of isotopically depleted carbon from released oil and methane is presumably available to zooplankton and zooplankton-eating fish and invertebrates via prokaryotic consumers. Thus, carbon isotopic depletion extending into marine zooplankton grazers, a pathway mediated by the microbial food web, is a good proxy for food web modification by the spill. We employed delta13C as a tracer of oil-derived carbon incorporation into the lower marine food web across the middle and inner continental shelf. During June-August 2010, we followed two particle size classes: the nominally 1 mum - 0.2 mm ``small suspended particulate'' and the >0.2-2 mm ``mesozooplankton'' fractions, with the former considered likely food particle size for the latter. A clear pattern of delta13C depletion occurring in each fraction at middle and inner shelf stations was consistent with two sequential northward pulses of surface oil slicks from DWH. Relative to early June, an isotopic shift of -1 to -3 0/00 (toward weathered and fresh oil, -27.23 ± 0.03 0/00 and -27.34 ± 0.34 0/00, respectively) occurred during the peak of areal coverage of oil over the sites in late June 2010. Recovery of this depletion was 2-4 wks. A third pulse of residual oil occurred in late July, and depleted delta13C was observed in mid-August at the furthest offshore stations. Depletion and recovery cycles on the order of a few weeks are consistent with published warm water petroleum hydrocarbon decay time-scales. Carbon isotopic depletion in both surface and bottom samples suggests trophic transfer of oil carbon into the planktonic food web. A similar response found in benthic communities around natural seeps suggests that carbon isotopic shifts in the plankton fractions are likely due to the duration and magnitude of depleted carbon released into the system. These data provide strong evidence that labile fractions of the oil extended throughout the shallow water column during northward slick transport and that this carbon was processed at least two trophic levels beyond prokaryotic hydrocarbon consumers.
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Despite the ecological and economic importance of western Atlantic Ocean lutjanid species, little is known about their larval stage. Pelagic larval distribution, abundance, growth, mortality, and spawning patterns of 6 western Atlantic snapper species were examined from ichthyoplankton samples collected monthly over 2 yr along a transect spanning the east-west axis of the Straits of Florida (SOF). Successful spawning occurred primarily from July to September when water temperatures were warmest and larvae were most abundant in the upper 50 m towards the east or west sides of the SOF. Species-specific variability in spatiotemporal larval patterns tracked adult life history characters. Larvae of species associated with shallow coral reefs were spawned in the waning half of the lunar cycle (third quarter to new moon), were most abundant in the 0 to 25 m depth range, and where cross-SOF distributions were not uniform, were distributed mainly towards the eastern SOF. Larvae of deeper-dwelling species exhibited lower mortality and no lunar pattern in spawning (Etelis oculatus only), were distributed deeper in the water column and occurred progressively deeper with ontogeny, and where cross-SOF distributions were not uniform, were most abundant in the western SOF. Despite species-specific variability in spatial distributions and equivalent east-west mortality rates, at least one measure of larval growth in 4 of 6 species of snapper revealed significantly faster growth in the western versus the eastern SOF, which may be related to higher prey availability in the west. Results of this study provide insight into the pelagic phase of 6 important snapper species, with implications for understanding adult populations.
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We report delayed effects on the growth and marine survival of pink salmon Oncorhynchus gorbuscha, which were exposed to oil as embryos under conditions similar to those observed after the 'Exxon Valdez' oil spill. Pink salmon eggs were incubated in water that became contaminated with polynuclear aromatic hydrocarbons (PAHs) after percolating through gravel coated with weathered oil. Weathering ensured that the PAH composition of the water was dominated by alkyl-substituted naphthalenes and larger compounds. Most survivors of the exposures appeared healthy, and were released to the marine environment with coded-wire tags. Their survival was evaluated when they returned at maturity 2 yr later. Other survivors, also healthy in appearance, were retained in net pens to measure delayed effects on growth during the early juvenile stage. Pink salmon exposed to an initial concentration of total PAH equal to 5.4 ppb experienced a 15 % decrease in marine survival compared to unexposed salmon. A delayed effect on growth was measured in juvenile salmon that survived embryonic exposure to doses as low as 18 ppb PAH. Reductions in juvenile growth could account for the reduced marine survival observed in the released fish. The demonstration of delayed effects on growth and survival support claims of delayed effects in pink salmon after the 'Exxon Valdez' oil spill, and indicate the potential for population-level effects resulting from embryonic exposure to oil.
The life cycles of fishes are complex and varied, and knowledge of the early life stages is important for understanding the biology, ecology, and evolution of fishes. In Early Life History of Marine Fishes, Bruce S. Miller and Arthur W. Kendall Jr., bring together in a single reference much of the research available and its application to fishery science-knowledge increasingly important because for most fishes, adult populations are determined at the earliest stages of life. Clear and well written, this book offers expert guidance on how to collect and analyze larval fish data and on how this information is interpreted by applied fish biologists and fisheries managers.