MINIMAL FOOD WEB USE OF DEEPWATER HORIZON OIL IN LOUISIANA ESTUARINE FOOD WEBS

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1 MINIMAL FOOD WEB USE OF DEEPWATER HORIZON OIL IN LOUISIANA ESTUARINE FOOD WEBS Brian Fry 1 D. Justic 1 Charles S. Milan 1 Phillip H. Riekenberg 1 Erick Swenson 1 R.E. Turner 1 Laurie C. Anderson 2 Carrol J. Michael 2 1 Oceanography & Coastal Sciences, LSU 2 Geology and Geophysics, LSU

2 Exxon Valdez 5% of DH Deepwater Horizon 120% of Ixtoc natural oil seepage in 1 year, entire Gulf of Mexico, 134,000 tonnes Deepwater Horizon, 602,000 tonnes in 3 months (200x background)

3 Barataria Bay NOLA, Barataria Bay, June 26, 2010 Especially wave action associated with Tropical Storm Alex brought in oil to Barataria Bay in late June 2010 Macondo 252 oil spill, Spilling April 20 July million barrels (780,000 m 3 ) total spilled. This is about 1.2*Ixtoc spill in , and half the size of the Kern Co. oil spill in California, National Geographic, Port Fourchon, June 30, 2010

4 Here we are In Mobile AL Data Sets New Orleans Breton Sound Barataria Bay We had two NGI projects focused on Louisiana estuaries near the oil spill: a)riverine and Estuarine Carbon Export to the Coastal Ocean (RECECO), Northern Gulf of Mexico (with Turner and Justic) H1) Barataria Bay is a net sink for atmospheric CO 2 on an annual basis, but may be a seasonal source of CO 2 during some months. b) Impact of DH Oil Spill on the Louisiana Coastal Environments, Oil Spill Effects on Ecosystem Respiration for two Louisiana Estuaries (Susan Welsh lead PI) H2) Spilled oil is increasing ecosystem respiration and the heterotrophic status of two estuaries (Breton Sound and Barataria Bay) that are situated near the Deepwater Horizon rig.

5 Data Sets Water Quality Salinity and ph Respiration Oiled vs. unoiled δ 13 C (-22 vs. -27 ) Barnacles Mussels Δ 14 C (-1000 vs. +20 ) Barnacles Geukensia demissa Balanus eberneus & B. amphitrite

6 Data Sets Water Quality Salinity and ph Respiration Oiled vs. unoiled δ 13 C (-22 vs. -27 ) Barnacles Mussels Δ 14 C (-1000 vs. +20 ) Barnacles Geukensia demissa Balanus eberneus & B. amphitrite

7 Barataria Transect Jul2002-Mar2011: June through August average +/- 1 SD Previous 30 day average precipitation (cm) Pre Macondo 225 During Macondo 225 Previous 7 day average precipitation (cm) Previous day maximum wind speed (m s -1 ) Previous day average wind speed (m s -1 ) Average air temperature (centigrade) Average Mississippi River discharge (m 3 s -1 / 10 3 ) Previous 3 day Davis Pond discharge (m 3 s -1 / 10 6 ) Value Data sources: LA-DNR, NCDC, USACOE, USGS

8 Barataria Transect Jul2002-Mar2011: June through August average +/- 1 SD 30.0 Pre Macondo 225 During Macondo Salinity (psu) Station Data source: R. E. Turner, LSU

9 Barataria Transect Jul2002-Mar2011: June through August average +/- 1 SD 9.0 Pre Macondo 225 During Macondo ph Station Data source: R. E. Turner, LSU

10 Data Sets Water Quality Salinity and ph Respiration Oiled vs. unoiled δ 13 C (-22 vs. -27 ) Barnacles Mussels Δ 14 C (-1000 vs. +20 ) Barnacles Geukensia demissa Balanus eberneus & B. amphitrite

11 New Orleans Caernarvon Diversion Breton Sound Estuary N km Barataria Estuary Gulf of Mexico

12 Respiration Rates New Orleans Caernarvon Diversion Breton Sound Estuary N km Barataria Estuary Gulf of Mexico 24 hour dark respiration mmol oxygen m -3 d control potential oil impact September Caernarvon August Barataria October Barataria There was no evidence for enhanced respiration due to oil consumption in the water column; measured rates in both estuaries were within the median range for respiration rates for estuaries of mmol oxygen m -3 d -1.

13 Data Sets Water Quality Salinity and ph Respiration Oiled vs. unoiled δ 13 C (-22 vs. -27 ) Barnacles Mussels Δ 14 C (-1000 vs. +20 ) Barnacles Geukensia demissa Balanus eberneus & B. amphitrite

14 New Orleans Caernarvon Diversion Breton Sound Estuary N Barataria Estuary km Gulf of Mexico 2000 vs Barataria Barnacles 13 C δ 13 C shell 2010 Fractionation 2010 Tissue 2000 Shell 2000 Tissue 2000 Fractionation Fractionation at 100% Oil Salinities were higher in 2000 than 2010, and so shell carbon isotopes were higher in Once these salinity effects are accounted for as fractionation = shell- tissue isotope values, there is no difference or trend towards oil incorporation in the 2010 collections.

15 Ok, barnacles are not using oil, but what about Geukensia demissa mussels actually living in oiled marshes? New Orleans Caernarvon Diversion Breton Sound Estuary N Barataria Estuary km Terrebonne Bay terr 53 pre oil terr 53 oil free terr 49 near oil terr 50 oiled Gulf of Mexico Tissue Shell Shell-Tissue Fractionation Shell-Oil Fractionation bar no oil 67 Barataria Bay bar no oilbar no oil bar oil Close-up of results for Geukensia; hard to see any oil incorporation terr 53 pre oil terr 53 oil free terr 49 near oil Tissue Shell Shell-Tissue Fractionation Shell-Oil Fractionation terr 50 oiled bar no oil 67 bar no oil 68 bar no oil 65 bar oil 66

16 Data Sets Water Quality Salinity and ph Respiration Oiled vs. unoiled δ 13 C (-22 vs. -27 ) Barnacles Mussels Δ 14 C (-1000 vs. +20 ) Barnacles Geukensia demissa Balanus eberneus & B. amphitrite

17 New Orleans Caernarvon Diversion Breton Sound Estuary Barataria Estuary N km Gulf of Mexico C Station Number along Barataria Transect, starting at Barataria Pass (the beach at Grande Terre) Open circles are pre-oil controls from May 2000; closed circles are potential oil impact, August Small arrows show sites for shell 14 C analysis.

18 New Orleans Caernarvon Diversion Breton Sound Estuary N km Barataria Estuary Gulf of Mexico 25 controls potential oil impact C Caernarvon Barnacle Tissues 2010 Barataria Barnacle Tissues 2000 Barataria Barnacle Tissues 2010 Barataria Barnacle Shells 2010 Errors are 95% confidence limits. No significant differences to be found so 0.0% oil use by barnacles and 0.0% oil-derived CO 2 incorporation into shells.

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20 Conclusions 1. Oil incorporation into estuarine metabolic cycles and food webs is very minimal. There may be two main reasons, a) oil was weathered at sea before coming ashore so easy-tometabolize components were lost offshore, and b) estuaries are high-productivity systems, so a little bit of oil does not make much difference in terms of total carbon. 2. A previous study of the Exxon Valdez oil spill in Alaska shows similar low incorporation results. There is probably a distinction between toxic effects that require only very minor amounts of oil and food web effects that require large amounts of oil to be metabolized by bacteria that are then grazed efficiently. 3. A speculation is that oil incorporation may be much more important in the deep sea. Metabolic rates are low in the deep sea and food is often limiting, so a little bit of oil might have a much greater food web impact in those deep and hard-to-study offshore systems.

21 Thank you

22 Druffel, E. R M.; Beaupré, S.; Griffin, S.; Hwang, J. Variability of dissolved inorganic radiocarbon at a surface site in the Northeast Pacific Ocean. Radiocarbon 2010, 52, data data data y = x R² = 1 Series1 Linear (Series1) extrapolated extrapolated correction factor

23 Microbial Degradation Hydrocarbons Head, Jones, and Röling Marine microorganisms make a meal of oil. Nature Reviews Microbiology. 4:

24 Graham et al Oil carbon entered coastal planktonic food web during the Deepwater Horizon oil spill. Env. Rsch. Letters

25 Oil C in Coastal Food Webs: Prince William Sound Coffin, R.B.; Cifuentes, L.A.; Pritchard, P.H. Assimilation of oil-derived carbon and remedial nitrogen applications by intertidal food chains on a contaminated beach in Prince William Sound, Alaska. Mar. Environ. Res. 1997, 44,