The most productive oyster reef and many areas historically productive for oysters, blue crabs (and other macroinvertebrates), and finfish on the Alabama coast were exposed or potentially exposed to oil for several weeks during the active spilling of oil from the Deep Water Horizon rig. These resources may continue to be exposed to oil, oil-derived substances of various forms, and chemical dispersants after the initial oil spill.
We propose the following questions and scientific approach to understand the recovery of macrofauna as part of the affected coastal marine ecosystem of the northern Gulf of Mexico:
General questions & hypotheses:
- How do we measure and define exposure and subsequent recovery of marine invertebrate and vertebrate macrofauna?
- We hypothesize that a suite of independent tracers can be applied to measure and define the effects of oil-exposure and habitat contamination on macrofauna by quantifying biological effects on key sentinel species in the field and lab.
- We hypothesize that greater exposure to oil and oiled habitats will result in detection of:
- Reduced growth and/or survival
- Increased stable isotope ratios and expression of stress-related proteins
- Corresponding changes in gene regulation, endocrine function, membrane composition [phospholipid fatty acids, sterols], and shell and otoliths trace element composition.
- We hypothesize that controlled lab analyses of these indicators at known exposure levels will generate dose-response relationships to calibrate field data and better define exposure and recovery in the natural environment.
- On what spatial and temporal scales can recovery be measured in macrofauna representing different habitats and feeding habits?
- We hypothesize that comparing data from key sentinel species collected before, during, and in a time series after the release of oil, will distinguish and define biological responses for baseline, impact, and recovery conditions.
- We hypothesize that comparison of hydrocarbon (PAH) concentrations in water, sediments, and animal tissues through time with known timing and spatial distributions of surface oil will link biological responses to oil-derived substances
Summary of approach:
We propose to define and measure exposure of macrofauna to oil and oil-derived substances, including dispersant, by applying a suite of independent tracers to measure biological effects on three sentinel species; oysters (Crassostrea virginica), blue crabs (Callinectes sapidis), and Gulf menhaden (Brevoortia patronus). These species represent different key feeding habits and habitats, including deposit and suspension feeding, as well as benthic, pelagic, sedentary, and motile lifestyles. All three species are commercially important to the region. We propose to combine rigorous complementary field and lab studies to define exposure and the temporal and spatial scales of recovery. Lab analyses will be useful to calibrate and interpret field data, while field sampling will ground-truth lab analyses.