Using both field- and laboratory-derived data, we will identify specific fish biomarker responses central to the mission of rapidly assessing the environmental impact of DHOS-related hydrocarbon and dispersant discharges in the north-central Gulf of Mexico (GoM). Fish biomarker research principally has focused on Fundulus heteroclitus in the Atlantic, but we propose to explore those same tried-and-true biomarkers in the phylogenetically-related Fundulus grandis; a ubiquitous keystone endemic of GoM bay shores, marsh ponds, and tidal creeks that promises to be a reliable, yet underexplored, indicator of ecosystem functioning and environmental health. Hydrocarbons and their metabolites are known agents of immune suppression resulting in enhanced pathogen susceptibility and hematopoietic dysfunction in fishes.
Additionally, hydrocarbon exposure is known to significantly impact the oxidative status of higher order vertebrates resulting in extreme disruption of biochemical homeostasis. Hence, we predict that F. grandis, like F. heteroclitus, will exhibit specific biomarker responses:
- Pathological changes to liver, kidney, gill and
- Induction of selected metabolic biomarkers and acute phase reactants in liver [proposed biomarkers include Cyp1A, CYP2N2, MT2, and CRP]
The laboratory component of this research will not only serve to validate these field results, but also to provide more conclusive data on the impact of single (hydrocarbon) or synergistic (hydrocarbon and dispersant) toxicants on induction of stress responses in F. grandis.
Field data:25 F. grandis will be collected concurrently from 3 oiled and 3 non-oiled sites
Field-extracted tissues (liver, gill, kidney) will be fixed immediately in 10% formalin for histopathology. Liver samples will be placed in RNAlater TissueProtect® tubes for assessment of putative biomarkers Cyp1A, CYP2N2, MT2, and CRP by measurement of mRNA expression in 100 randomly selected subsamples using RT-PCR. Oxidative stress response testing will be conducted on serum collected with heparin for separation and antioxidant analysis of both proteinated and deproteinated fractions.
Laboratory data: 100 adult, SPF F. grandis in 40 L aquaria (14 hr-photoperiod, fed daily, temp 27°C, pH 7.2, hardness 80 mg/L CaCO3, nitrite 0.005 mg/L, ammonia 0.0mg/L) will be divided into 3 groups (n=30 each; 10 unassigned) and exposed to
- MC252 crude,
- MC252 crude plus dispersant, and
- Control, no crude or dispersant
Tissues will be fixed in 10% formalin for histopathology and in RNAlater for quantification of biomarker RNA expression.