A major new initiative in this proposal is to carry out DWH oil and Corexit 9500 exposure studies designed to establish sublethal responses of such exposures in multiple pathways (dietary, water, and sediment) in marine fish, and microbes. Short-term effects of oil spills on fishes are generally clear and readily documented. Long-term effects and recovery processes of impacted species and ecosystems are much more difficult to recognize and demonstrate. Readily-recognizable endpoints that serve as measures of effect are not necessarily pertinent in terms of long-term ecological relevance.
To address this critical issue, researchers are using a suite of endpoints that allow bridging exposure-related observations along a continuum of responses. Molecular biomarkers provide avenues by which scientists can directly measure biologically significant responses such as immune system function, acute-phase protein responses, fertility potential and genotoxicity. They empirically assess effects of a stressor, rather than simply identifying whether an organism has been exposed. Second, many biomarkers are very sensitive, allowing documentation of the onset of harmful effects long before the critical stage is reached. There is ample literature documenting the impacts of oil spills on various biomarkers of exposure and their ultimate effects on marine fishes. A study of killifish from the oil-impacted nearshore environments has linked PAH exposures to genomic changes and alterations in protein expression.
Studies from a number of previous oil spill events such as Exxon Valdez clearly demonstrate immune system suppression can persist in marine fishes more than ten years after the initial event. Naturally, a decrease in ability to exhibit a competent immune response will jeopardize the sustainability of a population. Further, exposure to PAHs can have significant sublethal effects on reproductive capacity of individuals. In fishes, PAHs are metabolically transformed, but the metabolites are toxic and can cause cell damage, mutagenesis, teratogenesis, and carcinogenesis. Fish immune cells and organs associated with the circulatory system partly act as filter and are exceptionally vulnerable to toxicants via this route of exposure but also via the neuro-endocrine system. The critical questions are (1) how can immunotoxic effects be assessed most effectively and efficiently?, (2) what are the mechanisms leading to immunotoxicity?, and (3) what are the implications for immunocompetence and fitness?
Our researchers are answering these questions and more at the Mote Marine Aquaculture Park and at Wageningen University with ongoing exposure studies.
If you are an investigator with C-IMAGE, you can visit the Geodata Portal for access to the exposure study data and experiment timeline.