| DEEPWATER HORIZON AND FISH DEVELOPMENT: A STORY OF TRANSPORT, EXPOSURE, DISPERSANTS AND GENE EXPRESSION |
| KLEINOW, K. Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA 70803, kklein7@lsu.edu |
| The Deepwater Horizon incident released large amounts of Louisiana light sweet crude oil into the Gulf of Mexico. Before reaching coastal zones that serve as nurseries for many fish species, significant alterations to the oil occurred during ascension thru the water column and in transit. Due to the character of the released Louisiana light crude, distance and weathering a major component of petroleum-derived products reaching coastal nurseries occurred as stable water-in-oil emulsions (WIO) or mousse. Mousse with near neutral buoyancy, protracted persistence and an elastic surface film offered unique oil transport capabilities from far offshore to near-shore coastal zones. Upon contact with coastal features compliant mousse layered onto surfaces important for substrate breeding fishes. Studies were performed with zebrafish (Danio rerio)(ZF) as a model to examine the developmental significance of mousse relative to direct contact, indirect exposure, transport and persistence of toxicity. WIO resulted in high levels of developmental toxicity in ZF. The dispersant Corexit alone did not elicit significant embryonic abnormalities or death at the concentrations examined, but at higher concentrations potentiated WIO embryonic toxicity. Direct contact exposure with WIO elicited greater developmental toxicity than water-intermediated exposures with the same material at the same dose. Delays in hatch evident with WIO exposure were accompanied by debris accumulation in the periembryonic space and reduction of chorion dissolution necessary for hatch. Cardiac edema, yolk-sac edema, axial changes and lack of functional swimbladder were evident. Axial changes were most common with non-contact exposures. Direct contact WIO embryonic toxicity followed a general, but non-stoichiometric dose-response relationship (proportionally more toxic at lower doses). Air exposed, aged and dried WIO retained developmental toxicity similar to a freshly exposed surface of the same material. Buttered mousse immersed under flowing water and subject to degrading conditions was capable of eliciting significant developmental toxicity over many months. Gene array data suggested that early exposure (0-48hrs) was inclined to affect genes involved in neurological system processes while late exposures (48-96hrs) triggered genes associated with responses to a chemical stimulus. Collection of mousse from multiple sites of varying distances from the well head (64-320 km) at multiple times elicited similar gene array responses in embryos exposed to buttered WIO. The largest responses noted were for biotransformation and oxidative stress systems. These results suggest that transported then buttered WIO may pose risk to early life stages of substrate breeding fish coming in direct contact with this material. |
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