Assessing the Impacts of the Deepwater Horizon Oil Spill:

The National Status and Trends Program Response 

A Summary Report of Coastal Contamination

Dennis Apeti, David Whitall, Gunnar Lauenstein, Teresa McTigue, Kimani Kimbrough, 

Annie Jacob, and Andrew Mason

March 2013

National Centers for Coastal Ocean Science (NCCOS)

NOAA Technical Memorandum NOS NCCOS 167
Mention of trade names or commercial products does not constitute endorsement or recommendation for their use by the United 

States government.

This report should be cited as: Apeti, D., D. Whitall, G. Lauenstein, T. McTigue, K. Kimbrough, A. Jacob, and A. Mason. 2013. 

Assessing the Impacts of the Deepwater Horizon Oil Spill: The National Status and Trends Program Response. A Summary 

Report of Coastal Contamination. NOAA Technical Memorandum NOS NCCOS 167. National Centers for Coastal Ocean 

Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA). Silver Spring, MD.
Assessing the Impacts of the Deepwater Horizon Oil Spill:

The National Status and Trends Program Response 

A Summary Report of Coastal Contamination

United States Department 

of Commerce

Rebecca Blank

Acting Secretary

National Oceanic and 

Atmospheric Administration

Kathy Sullivan

Acting Administrator

National Ocean Service

Holly Bamford

Administrator

National Centers for

Coastal Ocean Science

Mary C. Erickson

Acting Director

Center for Coastal Monitoring and Assessment (CCMA)

Coastal Oceanographic Assessment of Status and Trends (COAST) Branch

1305 East-West Highway

Silver Spring, MD 20910

Dennis Apeti, David Whitall, Gunnar Lauenstein, Teresa McTigue, Kimani Kimbrough, 

Annie Jacob, and Andrew Mason

March 2013

National Centers for Coastal Ocean Science (NCCOS)

NOAA Technical Memorandum NOS NCCOS 167
Executive Summary

NOAA’s National Status and Trends Program (NS&T) collected oyster tissue and sediments for quantification 

of polycyclic aromatic hydrocarbons (PAHs) and petroleum associated metals before and after the landfall of oil 

from the Deepwater Horizon incident of 2010. These new pre- and post- landfall measurements were put into 

a historical context by comparing them to data collected in the region over three decades during Mussel Watch 

monitoring. 

Overall, the levels of PAHs in both sediment and oysters both pre- and post-landfall were within the range of 

historically observed values for the Gulf of Mexico. Some specific sites did have elevated PAH levels. While those 

locations generally correspond to areas in which oil reached coastal areas, it cannot be conclusively stated that 

the contamination is due to oiling from the Deepwater Horizon incident at these sites due to the survey nature 

of these sampling efforts. Instead, our data indicate locations along the coast where intensive investigation of 

hydrocarbon contamination should be undertaken. 

Post-spill concentrations of oil-related trace metals (V, Hg, Ni) were generally within historically observed 

ranges for a given site, however, nickel and vanadium were elevated at some sites including areas in Mississippi 

Sound and Galveston, Terrebonne, Mobile, Pensacola, and Apalachicola Bays. No oyster tissue metal body burden 

exceeded any of the United States Food and Drug Administration’s (FDA) shellfish permissible action levels for 

human consumption.

1
Introduction

The Deepwater Horizon incident of April 2010 caused an estimated 4.93 million barrels of crude oil to be spilled 

into the northern Gulf of Mexico over a span of three months (National Commission on BP DWH, 2011). Oil spills 

can have acute and chronic deleterious effects on biota and the environment as a result of chemical contamination. 

Major classes of oil-related compounds that can pose risks to biota are PAHs and heavy metals. Many PAHs are 

toxic and/or carcinogenic to humans and wildlife (Eisler, 1987; ATSDR, 1995 and 2009). Toxic metals such arsenic, 

cadmium, chromium, iron, manganese, mercury, and selenium are also present in crude oil in trace amounts 

(Nadkarni, 1991). However, the most prevalent oil-related metals are vanadium, nickel, and mercury, which can 

cause ecosystem damage at high concentrations (Nadkarni, 1991; Osuji and Achugasim, 2010).

Since 1986, the National Centers for Coastal Ocean Science (NCCOS) Mussel Watch Program (MWP) has 

monitored the concentration and distribution of more than 400 contaminants in U.S. waters. These contaminants 

include but are not limited to metals, legacy organics, PAHs, and selected contaminants of emerging concern. 

Over 300 sites are monitored nationwide, with bivalves collected biennially and sediment collected on a decadal 

frequency (Kimbrough et al., 2008). To assess the potential impacts of the Deepwater Horizon oil spill on the 

coastal zone of the Gulf of Mexico, NCCOS collected and analyzed sediment and oyster samples at long-term 

MWP monitoring sites, both before and after the spilled oil made landfall. The MWP has previously used its 

long-term monitoring data as a baseline to assess environmental changes in the aftermath of other catastrophic 

environmental disasters including Hurricanes Katrina and Rita, the attack on the World Trade Center, and several 

oil spills including the 2004 Athos-I spill in Delaware Bay and the 2007 Cosco Busan spill in San Francisco 

(Kimbrough et al., 2010; Johnson et al., 2008; Lauenstein and Kimbrough, 2007). Notably, for the Deepwater 

Horizon oil spill event, the Operational Science Advisory Team highlighted the Mussel Watch Program as one of 

the two sources for pre-impact PAH data for the Gulf of Mexico (OSAT, 2010).

In this report, we provide an assessment of the Deepwater Horizon oil spill impacts on the coastal zone along 

the northern Gulf of Mexico using PAHs and metals concentrations in oyster tissue and sediment. The MWP’s 

historical monitoring data were used to provide baseline concentrations against which the magnitude and extent 

of coastal contamination from the Deepwater Horizon oil spill is assessed.

Figure 1. Map depicting locations of Mussel Watch contaminant monitoring sites sampled in May and November, 2010 for the Deepwater 

Horizon coastal contamination assessment. Shaded area depicts the combined oil slick area. Monitoring sites within the potentially oiled 

coastal areas are highlighted. Sources: U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration and National 

Park Service.

2
Table 1. Mussel Watch long-term contaminant monitoring sites sampled in May and November, 2010 for the Deepwater Horizon coastal 

contamination assessment. Sites are arranged alphabetically and by state from west to east. O = oysters (Crassostrea virginica), S = sediment.

3

Sample Collection and Analysis

Mussel Watch has 86 long-term sites in the Gulf region. Based on NOAA’s initial projections of spill trajectory 

and the determination of the Natural Resource Damage Assessment (NRDA) Topical Working Group (TWG), a 

subset of the long-term sites in the coastal zone that could be potentially oiled (Figure 1) was determined, covering 

Code Site May-10 Nov-10Code Site May-10 Nov-10

O S O S O S O S

BRFS Brazos River, 

Freeport Surfside x x BSBG Breton Sound, Bay Gardene x x

BRCL Brazos River, Cedar 

Lake x x x x LPNO Lake Pontchartrain, New Orleans x

GBYC Galveston Bay, 

Yacht Club x x x x LBGO Lake Borgne, Gulf Outlet x

GBSC Galveston Bay, Ship 

Channel x x x x MSPC Mississippi Sound, Pass Christian x x

GBTD Galveston Bay, 

Todd’s Dump x x x x MSBB Mississippi Sound, Biloxi Bay x x

GBHR Galveston Bay, 

Hanna Reef x x MSPB Mississippi Sound, Pascagoula Bay x x

GBOB Galveston Bay, 

Offatts Bayou x x MBCP Mobile Bay, Cedar Point Reef x x

GBCR Galveston Bay, 

Confederate Reef x x x x MBDR Mobile Bay, Dog River x x

SLBB Sabine Lake, Blue 

Buck Point x x PBPH Pensacola Bay, Public Harbor x x

CLLC Calcasieu Lake, 

Lake Charles x x x x PBSP Pensacola Bay, Sabine Point x x

CLSJ Calcasieu Lake, St. 

Johns Island x PBIB Pensacola Bay, Indian Bayou x x

JHJH Joseph Harbor x CBPP Choctawhatchee 

Bay, Postil Point x x

VBSP Vermilion Bay, 

Southwest Pass x x x CBJB Choctawhatchee Bay, Joe’s Bayou x x x x

ESCP East Cote Blanche, 

South Point x PCMP Panama City, Municipal Pier x x x x

CLCL Caillou Lake x x x x PCLO Panama City, Little 

Oyster Bar x x x

TBLB Terrebonne Bay, 

Lake Barre x x x x SAWB St. Andrews Bay, Watson Bayou x x x x

TBLF Terrebonne Bay, 

Lake Felicity x x APDB Apalachicola Bay, Dry Bar x x x x

BBMB Barataria Bay, 

Middle Bank x x x x APCP Apalachicola Bay, Cat Point Bar x x x x

BBTB Barataria Bay, 

Turtle Bay x x SRWP Suwannee River, West Pass x x

BBSD Barataria Bay, 

Bayou Saint Denis x x x x CKBP Cedar Key, Black Point x x

MRTP Mississippi River, 

Tiger Pass x TBNP Tampa Bay, Navarez Park x x

MRPL Mississippi River, 

Pass A Loutre x TBMK Tampa Bay, Mullet Key Bayou x x

BSSI Breton Sound, Sable 

Island x x
Standard procedures for gonadal index 

characterization in bivalves are detailed 

in Kim et al. (2006). Oysters collected in 

May were mostly in ‘late development’, 

‘fully developed’ and/or spawning with 

visible gametes, whereas oysters collected 

in November were mostly sexually 

undifferentiated or spawning with few 

or no gametes visible and, as such, are 

considered post-spawning. Because of 

this distinct difference in the stage of 

gametogenesis between pre- and postlandfall samples coupled with the fact 

that organic contaminants preferentially 

accumulate in lipids, the total PAH 

concentrations were normalized on 

the lipid fraction so as to facilitate 

comparison between the obtained values 

from two different times of the year. 

However, the November post-landfall 

samples are physiologically comparable 

to long-term Mussel Watch bivalve 

samples, which are always collected 

post-spawning and was compared as 

such with historic measurements.

the areas from the Brazos River in Texas to Tampa Bay, Florida. Due to logistics and TWG directives, a total of 

23 sites were sampled for sediment and a total of 30 sites were sampled for oysters (Crassostrea virginica) and/or 

sediment in May 2010 (pre-landfall) and November 2010 (post-landfall). Ultimately, DWH related oil slicks did 

not make landfall near all sampling sites (Figure 1).

Surface sediments (top 1 - 2 cm fraction to represent newly deposited materials) and oyster specimens were 

collected using standard NS&T procedures (Lauenstein and Cantillo, 1998). The samples were handled using strict 

documentation and chain-of-custody procedures based on the NOAA’s National Resources Damage Assessment 

(NRDA) process (http://nrdata.org/).

Both oyster tissue and sediment samples were analyzed for PAHs (Table 2). Sediment samples were not 

measured for metals because of insufficient funding and negligible concentration changes that may result from the 

exposure to oil. Oyster tissue samples from November were analyzed for trace elements (Table 2), in partnership 

with the FDA. Thus, our spill impacts assessment for metal contamination were limited to comparing the postlandfall results in tissue to those of the historical monitoring data. Site-specific assessments were made comparing 

post-landfall concentrations to the long-term data range (from 1986 – 2009) for each metal. Vanadium, a crude 

oil signature metal, is not routinely measured by the MWP so archived samples from the years 2008 and 2009 

were analyzed to allow for comparison between pre- and post- spill samples. In addition to the PAHs and metals, 

oyster tissue samples were measured for ancillary parameters such as moisture and lipid content while sediment 

samples were analyzed for total inorganic carbon and grain size. All chemical analyses followed NS&T methods 

documented in Lauenstein and Cantillo, (1998), Kimbrough and Lauenstein (2006) Kimbrough et al. (2007), and 

McDonald et al. (2006). 

Physiological processes, such as gametogenesis and spawning, can significantly influence the contaminant 

body burdens of oysters (Mix et al., 1982). Lipophilic compounds such as hydrocarbons tend to be preferentially 

concentrated in gonadal tissue which may account for up to 50% of the soft tissue (Choi et al., 1993). Thus, a 

subset of oysters collected from each monitoring site were examined for the state of gonadal development (gonadal 

index) to give an indication of the amount of gametic material in the tissues at the time of chemical analysis. 

4

Table 2. Individual PAH compounds used to compute total PAHs and oil-related 

metals measured as a part of this assessment. Metals discussed as part of this 

document are in bold. For simplicity, the term metal is used without distinction 

between true metals and metalloids.

PAHs Metals

Biphenyl Dibenzothiophene Arsenic (As)

Naphthalene C1-Dibenzothiophenes Cadmium (Cd)

C1-Naphthalenes C2-Dibenzothiophenes Chromium (Cr)

C2-Naphthalenes C3-Dibenzothiophenes Copper (Cu)

C3-Naphthalenes Fluoranthene Iron (Fe)

C4-Naphthalenes C1-Fluoranthenes/Pyrenes Mercury (Hg)

Acenaphthylene Benz[a]anthracene Manganese (Mn)

Acenaphthene Chrysene/Triphenylene Nickel (Ni)

Fluorene C1-Chrysenes Lead (Pb)

C1-Fluorenes C2-Chrysenes Antimony (Sb)

C2-Fluorenes C3-Chrysenes Selenium (Se)

C3-Fluorenes C4-Chrysenes Zinc (Zn)

Anthracene Benzo[b]fluoranthene Vanadium (V)

Phenanthrene Benzo[j,k]fluoranthene

C1-Phenanthrenes/Anthracenes Benzo[e]pyrene

C2-Phenanthrenes/Anthracenes Benzo[a]pyrene

C3-Phenanthrenes/Anthracenes Dibenzo[a,h]anthracene

C4-Phenanthrenes/Anthracenes Benzo[g,h,i]perylene

Pyrene Indeno[1,2,3-c,d]pyrene
Results and Discussion

Polycyclic Aromatic Hydrocarbons (PAHs)

Key Large Scale Findings of PAHs in Sediments

• The median concentration of post-landfall measurements is well below the national median (Figure 2).

• Post- landfall measurements are comparable to measurements in the region in 2006/2007.

• Based on the overall magnitude of total PAHs, there is no conclusive evidence of an increase in Gulf-wide PAH 

coastal sediment contamination from the Deepwater Horizon oil spill at Mussel Watch sites. A site-specific 

analysis does show areas of concern regarding PAHs and is presented later in the report.

5

Figure 2. Comparison of pre- and post-landfall total PAH measurements in sediments collected from the coastal zone of the Gulf of 

Mexico in the aftermath of Deepwater Horizon oil spill to historic measurements collected by NOAA Mussel Watch Program. ‘National’ 

(‘N’ in inset) refers to sediment collected from Mussel Watch sites around the country other than Gulf, ‘Gulf ’ (‘G’ in inset) refers to 

sediment collected solely from the Gulf of Mexico, ‘Pre- landfall’ (‘Pre- l’ in inset) refers to sediment collected from Gulf of Mexico 

in May 2010 and ‘Post- landfall’ (‘Post- l’ in inset) refers to sediment collected from the Gulf of Mexico in November 2010. The inset 

figure depicts the same data without outliers. The bottom and top of the boxplots represent the 25th and 75th percentiles respectively, the 

whiskers represent the 5th and 95th percentiles, the dots represent outliers that lie beyond the 5th and 95th percentiles, and the line in the 

middle of the box is the median.
Key Large Scale Findings of PAHs in Oysters

• Gulf-wide post-landfall tissue concentrations fall within the range of historic measurements (Figure 3).

• Based on the overall magnitude of total PAHs in oyster tissues, there is no conclusive evidence of an increase 

in tissue burden in oysters from Mussel Watch sites around the coastline of the Gulf of Mexico following 

Deepwater Horizon oil spill. 

6

Figure 3. Comparison of post-landfall total PAHs (sum of 38 individual compounds) measurements in the tissues of oysters collected 

in Nov 2010 from the coastal zone of the Gulf of Mexico in the aftermath of the Deepwater Horizon oil spill to historic measurements 

collected by NOAA’s Mussel Watch Program. ‘National’ (Fig. 4a.) depicts the overall trends in total PAH concentrations in oysters 

collected from the Gulf of Mexico, Middle Atlantic and Southeast Atlantic from 1996-2009. ‘Gulf ’ depicts the overall trends in total 

PAH concentrations in oysters collected from 30 sites from the Gulf of Mexico for the Deepwater Horizon oil spill assessment with (Fig. 

3b.) and without (Fig. 3c.) outliers. The bottom and top of the boxplots represent the 25th and 75th percentiles respectively, the whiskers 

represent the 5th and 95th percentiles, the dots represent outliers that lie beyond the 5th and 95th percentiles, and the line in the middle of 

the box is the median. 
Key Findings from Pre- and Post-Landfall Lipid-Normalized Oyster Tissue PAH Analysis

• The lipid-normalized total PAH (Figure 4) concentrations in oysters indicated that post-landfall measurements 

at the site BBMB in Barataria Bay, Louisiana and at the SAWB site in St. Andrews Bay in Florida were 

substantially higher than pre-landfall measurements. 

• Sites BBMB and SAWB were in coastal areas where spilled oil reached the shoreline (Figure 1). Further research 

is warranted to explain these observations.

7

Figure 4. Bar chart depicting pre- and post-landfall lipid normalized total PAH concentrations (ng/g lipid wt.) in oyster tissue from select Mussel 

Watch sites in the coastal zone of the Gulf of Mexico. The sites within the potentially oiled zone lie between the two dotted lines from site VBSP 

to site SAWB. Sites BBMB and SAWB (*) had substantially higher post-landfall PAH concentrations than pre-landfall measurements.
Key Findings from Site Specific Oyster Tissue PAH Analysis

• The post-landfall total PAH concentrations at the majority of sites are comparable to historic measurements 

(Table 3).

• The highest concentrations (marked in red) were found at the Middle Bank in Barataria Bay, Louisiana (site 

BBMB), the Watson Bayou in St. Andrews Bay, Florida (site SAWB) and the Ship Channel in Galveston Bay, 

Texas (site GBSC; located outside potentially oiled zone). The post-landfall concentration at site BBMB is 

much higher than the site-specific concentrations of recent years, although not the highest concentration 

ever observed at that site. The Watson Bayou site is located near a small shipyard and the Ship Channel 

in Galveston Bay sees extensive vessel traffic. Both locations could have PAH impacts independent of the 

Deepwater Horizon spill. Further sampling is urged at all four locations to better understand these patterns.

Key Findings from Site Specific Sediment PAH Analysis

• Based on site-specific concentrations listed in Table 4, the majority of sites have concentrations that are 

comparable to historic measurements.

• The sites that have relatively higher post-landfall concentrations compared to pre-landfall concentrations are 

marked in red: SLBB in Sabine Lake, Texas and PCMP at the Municipal Pier in Panama City. 

• NS&T site SLBB is outside the potential oiling zone identified in Figure 1.

• Site PCMP was potentially oiled, but the survey nature of these sampling efforts make it difficult to form 

conclusive evidence of oiling based on May and Nov 2010 concentrations. Intensive sampling should be 

conducted at this site. It also appears that the May 2010 concentration was significantly lower than what was 

historically observed, potentially due to flushing events due to seasonal rainfall and tidal patterns, and may not 

be representative.

8
9

Table 3. Historic PAH concentrations (ng/g dry weight) in oyster tissue from the Gulf of Mexico. Grey rows denote sites within the 

potentially oiled zone as depicted in Fig. 1. Values in red denote large differences in concentration between data from November 2010 

and historical data.

Site General Location Specific Location State 96/97 98/99 00/01 02/03 04/05 06/07 08/09 Nov-10

BRCL Brazos River Cedar Lakes TX 823 509 594 496 947 686 - 183

GBCR Galveston Bay Confederate Reef TX 711 491 625 333 583 434 380 333

GBTD Galveston Bay Todd's Dump TX 877 1104 557 2079 1639 864 177 134

GBYC Galveston Bay Yacht Club TX 1356 1763 2327 1076 2490 517 518 298

GBSC Galveston Bay Ship Channel TX - 2343 4161 3623 - 1711 810 1994

CLLC Calcasieu Lake Lake Charles LA 2636 564 234 3198 932 1466 2271 710

VBSP Vermilion Bay Southwest Pass LA 421 562 119 380 286 189 212 107

CLCL Caillou Lake Caillou Lake LA 46 521 324 217 241 279 49 97

TBLB Terrebonne Bay Lake Barre LA 470 79 55 49 218 197 73 94

BBMB Barataria Bay Middle Bank LA 2056 965 378 850 705 331 183 1793

BBSD Barataria Bay Bayou Saint Denis LA 290 493 117 360 423 268 162 137

MSPC Mississippi Sound Pass Christian MS 367 2839 188 455 595 5368 646 91

MSBB Mississippi Sound Biloxi Bay MS - 4244 188 3851 924 866 683 213

MSPB Mississippi Sound Pascagoula Bay MS 366 379 139 318 368 576 553 306

MBCP Mobile Bay Cedar Point Reef AL 826 156 228 142 190 204 184 124

MBDR Mobile Bay Dog River AL 2742 1423 549 790 1166 939 1022 307

PBPH Pensacola Bay Public Harbor FL 1754 1204 261 307 357 566 566 445

PBSP Pensacola Bay Sabine Point FL 721 132 191 80 187 198 - 131

PBIB Pensacola Bay Indian Bayou FL - 626 105 33 138 174 194 176

CBJB Choctawhatchee Bay Joe’s Bayou FL 3032 2487 493 16477 2371 1267 1357 285

CBPP Choctawhatchee Bay Postil Point FL 1447 1092 284 708 446 306 325 317

PCLO Panama City Little Oyster Bar FL 448 861 180 196 358 - - 189

PCMP Panama City Municipal Pier FL 5865 241 2026 992 1356 - 2914 342

SAWB St. Andrews Bay Watson Bayou FL 6753 1071 3106 4905 1205 1445 475 1877

APDB Apalachicola Bay Dry Bar FL 266 1027 146 101 336 122 58 113

APCP Apalachicola Bay Cat Point Bar FL 929 330 346 130 335 263 330 215

SRWP Suwannee River West Pass FL - - - 152 192 103 55 110

CKBP Cedar Key Black Point FL 40 413 106 110 127 73 52 104

TBNP Tampa Bay Navarez Park FL 1291 653 394 221 376 766 682 188

TBMK Tampa Bay Mullet Key Bayou FL 395 104 169 118 116 89 141 136
Table 4. Historic PAH concentrations (ng/g dry weight) in sediment from the Gulf of Mexico. Grey rows denote sites within the potentially 

oiled zone depicted in Fig. 1. Values in red denote large changes in concentration from May to November.

10

Site General Location Specific Location State Gulf 96/97 Gulf 06/07 May-10 Nov-10

BRCL Brazos River Cedar Lakes TX 294 359 251 141

BRFS Brazos River Freeport Surfside TX 4109 920 143 154

GBCR Galveston Bay Confederate Reef TX 286 284 379 195

GBOB Galveston Bay Offatts Bayou TX 3475 12509 14489 14086

GBTD Galveston Bay Todd's Dump TX 183 326 183 33

GBYC Galveston Bay Yacht Club TX 51 179 170 159

GBSC Galveston Bay Ship Channel TX - 1276 693 653

GBHR Galveston Bay Hanna Reef TX 191 236 224 230

SLBB Sabine Lake Blue Buck Point LA 40 183 82 742

CLSJ Calcasieu Lake St. Johns Island LA 65 542 - 134

CLLC Calcasieu Lake Lake Charles LA 297 263 383 263

JHJH Joseph Harbor Bayou Joseph Harbor Bayou LA 122 356 - 33

VBSP Vermilion Bay Southwest Pass LA - 56 - 80

ECSP East Cote Blanche South Point LA - - - 303

CLCL Caillou Lake Caillou Lake LA 81 203 367 105

TBLB Terrebonne Bay Lake Barre LA 132 - 296 181

TBLF Terrebonne Bay Lake Felicity LA 137 - 242 267

BBMB Barataria Bay Middle Bank LA 480 723 425 652

BBSD Barataria Bay Bayou Saint Denis LA 150 166 283 72

BBTB Barataria Bay Turtle Bay LA - - 327 343

MRTP Mississippi River Tiger Pass LA 1241 - - 104

MRPL Mississippi River Pass A Loutre LA 631 - - 371

BSSI Breton Sound Sable Island LA 651 - 864 504

BSBG Breton Sound Bay Gardene LA 126 - 344 106

LBGO Lake Borgne Gulf Outlet LA - - - 297

LPNO Lake Pontchartrain New Orleans LA 2257 - - 213

CBJB Choctawhatchee Bay Joe's Bayou FL 292 2323 5158 150

PCLO Panama City Little Oyster Bar FL 326 - - 501

PCMP Panama City Municipal Pier FL 2392 - 33 2689

SAWB St. Andrews Bay Watson Bayou FL 1833 - 3301 2335

APDB Apalachicola Bay Dry Bar FL 121 52 197 210

APCP Apalachicola Bay Cat Point Bar FL 1700 149 16 174
11

Figure 5. Comparison of pre- and post-landfall concentrations of vanadium in oyster tissue. Bar chart depicts pre-landfall vanadium 

concentrations in oyster tissue collected in 2008/2009. Overlaid stars represent site-specific vanadium concentrations in oysters collected 

in Nov 2010. 

Metals

In this report we focus our discussion on mercury, nickel, and vanadium, which are the most prevalent crude 

oil-related metal contaminants (Nadkarni, 1991; Osuji and Achugasim, 2010). Iron is also commonly associated 

with oil, but due to its commonly high background concentration in bivalves (unpublished Mussel Watch data, 

http://egisws02.nos.noaa.gov/nsandt/index.html#), iron was not used in this report as an indicator of oil of possible 

oil related contamination. All metal values are reported as total metal concentrations (i.e. not individual metal 

speciation).

Key Findings from Site Specific Oyster Tissue Vanadium Analysis

• At most of the monitoring sites, vanadium concentrations in post-landfall oyster samples were at comparable 

levels or lower than pre-landfall values (Figure 5). At some sites however, post-landfall vanadium levels were 

elevated relative to pre-spill values. Vanadium concentrations in post-landfall oyster samples were higher than 

pre-spill values at sites in Galveston Bay (GBSC, GBTD), Terrebonne Bay (TBLB), Mississippi Sound (MSBB, 

MSPB), Mobile Bay (MBCP), Pensacola Bay (PBPH, PBIB) and Apalachicola Bay (APCP). 

• Aside from the sites in Galveston Bay and Apalachicola Bay, all of the aforementioned high concentration sites 

were located in the potentially oiled coastal area where oil and tar balls have been observed. Further study is 

recommended to explain this pattern.
Key Findings from Site Specific Oyster Tissue Nickel Analysis

• At most of the monitoring sites, post-landfall nickel values in oyster were within historic concentration ranges. 

At some sites however, post-landfall nickel levels were elevated relatively to pre-spill values. 

• As illustrated in Figure 6, nickel concentrations in post-landfall oyster tissue were higher than pre-spill values 

at sites in Caillou Lake (CLCL), Terrebonne Bay (TBLB), Mississippi Sound (MSPC), Mobile Bay (MBCP, 

MBDR), Pensacola Bay (PBIB), Choctawhatchee Bay (CBPP), Panama City coastal area (PCLO, PCMP) and 

Apalachicola Bay (APDB). 

• Many of these high concentration sites were located in the potentially oiled coastal area where oil and tar balls 

have been observed (Figure 1). Further study is warranted to explain these observations.

• The U.S. FDA has established the maximum permissible action level of 80 ug.g-1 nickel wet weight in shellfish 

for seafood safety (FDA, 1993). Maximum nickel concentrations in post-landfall oyster tissue were well below 

the FDA action level and we estimate nickel concentrations did not cause seafood safety concerns.

12

Figure 6. Site-specific comparisons of post-landfall nickel concentrations (star) in oyster tissue to long-term (1986 – 2009) concentration 

ranges (boxplot). The upper and lower limits of the boxplots represent the 25th and 75th percentiles respectively, the whiskers represent 

the 5th and 95th percentiles, and the line in the middle of the box is the median.
Key Findings from Site Specific Oyster Tissue Mercury Analysis

• All post-landfall mercury concentrations in oyster tissue were within or below long-term site specific ranges 

(Figure 7).

• The U.S. FDA has established the maximum permissible action level of 1.0 μg.g-1 mercury wet weight in shellfish 

for seafood safety (FDA, 1993). Our results indicated that mercury concentrations in oyster tissue were below 

the FDA action level and are not a current food safety concern at these sites. 

13

Figure 7. Site-specific comparisons of post-landfall mercury concentrations (star) in oyster tissue to long-term (1986 - 2009) concentration 

ranges (boxplot). The upper and lower limits of the boxplots represent the 25th and 75th percentiles respectively, the whiskers represent the 

5th and 95th percentiles, and the line in the middle of the box is the median.
Overall Summary

• Comparison of the overall magnitude of total PAHs in sediments and oysters to historic Mussel Watch data 

indicates that there is no conclusive evidence of an increase in Gulf-wide PAH sediment contamination from 

the Deepwater Horizon oil spill.

• Site-specific total PAH data for sediment and oysters indicate the possibility of oiling at a few sites. Further 

sampling at these sites is needed to determine the origin, extent, and impact of contamination.

• In general, post-spill concentrations of oil-related trace metals were found to be within the site-specific longterm ranges based on Mussel Watch monitoring data. However, in a few instances post-landfall concentrations 

exceeded long-term maximum concentrations. These sites deserve further attention to more specifically 

examine these patterns.

• Concentrations of major oil-related metals such as vanadium, nickel and mercury were also mainly within 

their respective site-specific long-term range. However, at some sites located within oiled coastal areas postspill concentrations were relatively higher than historical maximum concentrations, again suggesting the need 

for further study.

• Relative to the FDA’s maximum permissible action levels for shellfish consumption (FDA, 1993), post-landfall 

concentrations and long-term levels of all potentially toxic metals that NS&T monitored as a part of the 

Deepwater Horizon impact assessment were below associated action levels. 

14

Acknowledgments

Robert Warner, W. Edward Johnson, Cliff Cosgrove (NOAA) assisted with field work. Juan Ramirez (TDIBrooks) provided laboratory Quality Assurance support for PAH analysis across different programs. Greg Piniak 

provided helpful comments of a scientific and editorial nature on this document. Logistical field support was 

provided by Jim Culter of Mote Marine Laboratory, Meagan LaPeyre of Louisiana State University, Dale Stevens 

of NOAA NMFS Southeast Fisheries Science Center Pascagoula Lab, and through a contract with Quaternary 

Resource Investigations, LLC.
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