Oil Effects on Marine Organisms

Chase DA, Edwards DS, Qin G, Wages MR, Willming MM, Anderson TA, Maul JD. 2013. Bioaccumulation of petroleum hydrocarbons in fiddler crabs (Uca minax) exposed to weathered MC-252 crude oil alone and in mixture with an oil dispersant. Science of The Total Environment 444:121-127. Find it Online*
Fiddler crabs are of high value to their ecosystem because they are benthic detritivores that have strong ecological links between the marine, marsh, and even terrestrial environments.  Due to the nature of the fiddler crab, they may be a source of nutritional transfer between these areas.  Fiddler crabs were subject to exposure of chemically dispersed and non-dispersed oil to compare how the oil is transferred through an organism’s system.  Chemically dispersed oil has a smaller droplet size and this created an enhanced diffusion across the gut of the crab, compared to the larger, or non-dispersed oil droplets.  The smaller oil droplets (i.e., chemically dispersed oil) were harder to eliminate because the pollutant was more efficient at permeating through crab tissues.  This could grossly impact predators of the fiddler crab or even hamper all the roles this crab provides (e.g., redistribute nutrients, biogeochemical cycling, and bioturbators).

Passow U, Ziervogel K. Marine snow and associated microbial processes as drivers for oil transformation in surface Gulf of Mexico waters. Frontiers in Microbiology: In Press. Find it Online*
Marine snow is usually small, accumulated particles of detritus, feces, bacteria, phytoplankton, and biominerals that are responsible for the downward (vertical) transport of organic matter within the ocean.  Marine snow in the Gulf of Mexico (GoM) after the BP oil spill was noticeably different, mainly due to densities and settling rates.  GoM snow had: (1) higher mucus content due to the increased amount of oil-degrading bacteria, (2) a higher rate of coagulation due to the physical properties of oil, (3) rapidly degraded phytoplankton, therefore increasing aggregates.  Future studies need to be completed to assess the impact of GoM snow on the pelagic and benthic organisms that will use it as a food source.

Mitra S, Kimmel DG, Snyder J, Scalise K, McGlaughon BD, Roman MR, Jahn GL, Pierson JJ, Brandt SB, Montoya JP et al. . Macondo-1 well oil-derived polycyclic aromatic hydrocarbons in mesozooplankton from the northern Gulf of Mexico. Geophysical Research Letters 39(1):L01605. Find it Online*
Mesozooplankton are organisms that are larger than phytoplankton, but smaller than zooplankton and they are usually food for juvenile fish and shrimp.  Mesozooplankton were studied to compare polycyclic aromatic hydrocarbon (PAH; i.e., the carcinogen portion of oil) concentrations from the BP oil spill, as opposed to the concentrations found naturally from oil seeps in the northern Gulf of Mexico.  There were no systemic trends in PAHs within mesozooplankton, be it by depth or distance away from the wellhead.  PAHs were found in mesozooplankton well after the wellhead was capped (i.e., July 15, 2010); these concentrations persisted longer than expected.  It is noted that the presence of PAHs in mesozooplankton covered an extensive area, but was patchy in location.  The study suggests BP oil spill PAHs were transferred a nutritional level higher into the zooplankton.

Fodrie FJ, Heck KL, Jr. 2011. Response of Coastal Fishes to the Gulf of Mexico Oil Disaster. PLoS ONE 6(7):e21609. Find it Online*
Fish species that inhabited seagrass as a nursery habitat showed no immediate impacts directly after the Deepwater Horizon oil spill.  This may be due to a large portion of the oil that was retained at deeper depths.  There was actually an increase in the catch rates of seagrass-associated fish and this could be contributed to several factors (e.g., fisheries closure, fish may be buffered from oil due to foraging techniques, higher fatalities amongst fish larvae predators).  More research should include the chronic effects of fish subject to oil exposure.

Ortmann AC, Anders J, Shelton N, Gong L, Moss AG, Condon RH. 2012. Dispersed Oil Disrupts Microbial Pathways in Pelagic Food Webs. PLoS ONE 7(7):e42548. Find it Online*
A mesocosm experiment was developed to examine the oil and dispersed oil impact towards the Gulf of Mexico microbial community.  With the addition of oil, there was an increase in ciliate biomass (i.e., an indicator for phytoplankton) and this suggested that the transfer of carbon to higher trophic levels was likely.  The addition of dispersant resulted in an increase of bacterial biomass and a significant hindrance of ciliates.  Reduced primary producer (i.e., phytoplankton) biomass would cause a decline in the grazing efforts of zooplankton and could affect regional food webs along the Gulf shelf.

Rico-Martinez R, Snell TW, Shearer TL. 2013. Synergistic toxicity of Macondo crude oil and dispersant Corexit 9500A to the Brachionus plicatilis species complex (Rotifera). Environmental Pollution 173(0):5-10.
Corexit 9500a (i.e., the deepwater application of chemical dispersant in the BP oil spill) & light crude oil are more or less equivalent in toxicity to marine rotifers, but when mixed the toxicity increases by a multiple of 52.  Dispersed oil and dispersants are also extremely toxic to soft/hard shell coral species.  Chemically dispersed oil is more dangerous than mechanically (i.e., naturally) dispersed oil because it allows for the carcinogenic portions of oil, polycyclic aromatic hydrocarbons (PAHs), to be bioconcentrated more easily.  The dispersant to oil ratio in the Deepwater Horizon remediation effort was 1:130.

Chanton JP, Cherrier J, Wilson RM, Sarkodee-Adoo J, Bosman S, Mickle A, Graham WM. 2012. Radiocarbon evidence that carbon from the Deepwater Horizon spill entered the planktonic food web of the Gulf of Mexico. Environmental Research Letters 7(4):045303. Find it Online*
Oil and natural gas contamination from the BP oil spill has entered the plankton food web through small and larger types of phytoplankton (i.e., 125 and 600 µm).  Carbon abundance was used as an indicator by radioactive tracers.  The entrance to the planktonic food web most likely occurred through bacterial degradation that was incorporated into the food web themselves.

Beazley MJ, Martinez RJ, Rajan S, Powell J, Piceno YM, Tom LM, Andersen GL, Hazen TC, Van Nostrand JD, Zhou J et al. . 2012. Microbial Community Analysis of a Coastal Salt Marsh Affected by the Deepwater Horizon Oil Spill. PLoS ONE 7(7):e41305. Find it Online*
A study has found that salt marsh vegetation in Alabama trapped incoming oil from the Deepwater Horizon incident.  The oil within the vegetation had a higher concentration compared to open inlets near that same region; although, the oil on the vegetation decreased faster than within those open inlets.  The main reason was due to the plant rhizosphere (i.e., root zone) that promoted plant uptake, increased aeration in the root zone, and enzymes responsible for degradation (e.g., oil mineralization, detoxification of organic pollutants).  Anaerobic degradation is another factor as the oxygen-depleted conditions beneath the rhizosphere enable sulfate reduction, denitrification, and menthanogenesis. 

Finch BE, Wooten KJ, Faust DR, Smith PN. 2012. Embryotoxicity of mixtures of weathered crude oil collected from the Gulf of Mexico and Corexit 9500 in mallard ducks (Anas platyrhynchos). Science of The Total Environment 426:155-159. Find it Online*
The BP oil spill coincided with bird nesting periods indigenous to the Gulf of Mexico region; a study of oil & dispersant impact on mallard duck eggs ensued.  Fresh crude oil is more toxic to the eggs than weathered (i.e., older; affected by natural processes) crude oil.  This is because weathered crude oil contains a reduced ratio of lighter PAHs or polycyclic aromatic hydrocarbons (i.e., carcinogenic compounds).  Also, fresh crude oil has a higher toxicity to the eggs than a combination of weathered crude oil and dispersant.  Elevated oil to dispersant mixtures (50:1) were higher in toxicity than the lower oil to dispersant mixtures (10:1).  When comparing the effects of the two mixtures, there was no significant difference between the impacts on egg development.  However, fresh crude oil applied to the eggshell affected the frequency of abnormalities in birds.  This is likely attributed to higher proportions of lighter PAHs, which can penetrate eggshells and eggshell membranes.


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