This RAPID proposal brings together a collaboration among Universities in states affected by the Deepwater Horizon (DH) oil release. With the millions of gallons of oil released, the use of dispersants and the likelihood of movement of the subsurface oil "bloom" into bays and estuaries, an unprecedented anthropogenic impact on human and natural populations may result. This study will define the physiological and evolutionary impact of the DH oil release using the fish Fundulus grandis, a natural inhabitant of estuaries along the Gulf of Mexico. By applying cutting edge technologies, the genetic effects of man's impact on this environment will be described and, thus, provide the baseline data to document the effect of oil pollution on genetic diversity and effectiveness of remediation in limiting negative biodiversity consequences of the spill.
These data will inform society about the short and long-term impacts of the DH oil spill, which has not been possible prior to the recent innovation in genomic techniques. The application of genomic technology provides insights into the genes affected by DH oil and whether cleanup efforts effectively minimize loss of genetic diversity. Thus, this research should provide the evidence of the effectiveness of BP cleanup efforts. Additionally, by measuring the impact of DH oil on fish genomics, additional information will be gathered regarding the genes that matter for human health. Simply put, by measuring the genes in fish that survive exposure to DH oil, genes that may also be important for human health will be identified.
Using killifish – an abundant marsh fish – we measured how their biology changed over time (pre-oil compared to post-oil) and across sites (some that got hit by oil and others that didn’t). The biology that we studied was genome expression (the turning on and off of genes to make proteins that do the work of the cell), gill morphology, and development. In terms of genome expression, one can think of the genome as the computer processor of the cell. The genome expresses specific genetic programs to determine the function of a cell. So if you can measure what gene programs are running, you can tell what the cell is doing. For example, just as a computer processor would turn on virus containment software if it detected a computer virus, the genome turns on specific genetic programs, for example if it detects contaminants. We detected that a genome program – a specific suite of genes - that is specifically turned on by the toxic components of oil was turned on in fish coincident with the timing and location of oil contamination. We know that the turning on of this genetic program is what leads to toxicity. And just as a computer would be harmed if it couldn’t contain damage from a computer virus, the genome programs being altered may also be diagnostic that something is wrong with the cell. For example, we also detected profound down-regulation of reproduction genes. Impacts on reproduction are what would precede impacts on populations. At the structural level, we also found that the gills were quite dramatically malformed, and this gill damage coincided with the arrival of oil, and coincided with the genome expression response. Gills, as you might imagine, are pretty important for the health of the fish – they support gas exchange just like our lungs do, among many other important functions in fish such as ion transport and waste excretion. So a fish with damaged gills is probably in big trouble. Importantly, though these effects were apparent and clearly linked to oil exposure, these animals were not carrying around high concentrations of oil contaminants in their tissues – if you wanted to eat these fish, they would have officially been deemed "safe to eat" based on chemical testing and safe consumption standards. However, being safe to eat does not mean that you are performing normally, reproducing normally, or developing or growing normally. These important biological effects can be detected even though chemical testing of their tissues, and the waters they are swimming in, comes up "clean". It doesn’t take much chemical to cause these important effects. Finally, continuing work in our labs indicates that exposures to sediments contaminated with DWH oil (collected from field sites), causes severe abnormalities in developing killifish embryos. Importantly, these developmental impacts persist for sediments collected after more than a full year following contamination. We know from decades of research on the Exxon Valdez that sediments can act as reservoirs for long-term exposures to low-level but toxic concentrations of oil – sediment-associated oils can extend toxic effects over long periods of time and delay population recoveries. Since these shallow marsh habitats are important spawning grounds for MANY Gulf species, including the economically important ones, this is of concern. We did our studies using killifish because they are the most abundant fish in Gulf marshes, are ecologically important, and are relatively sensitive to the toxic effects of oil. We use them as our "canary in the coal mine". We don’t eat killifish, but many other species do – so they are an important forage species. Though we are seeing these impacts in killifish, at this time we don’t know what this means for other species – we just haven’t done this work in other species. However, for animals that share the same habitat as killifish (shallow marsh habitat as many species do), they would be at similar risk of exposures and effects that we are seeing in killifish. We don’t know what the long-term population-level consequences of these exposures and effects are going to be for killifish. These types of effects may take generations to emerge, as they did for species ultimately impacted by the Exxon Valdez oil spill in Alaska, so we might not be able to detect population-level effects for years. But if there were to be population-level effects, these are the types of effects that you’d expect to be seeing in the short term. That is, effects on reproduction and development are predictive of longer-term population-level effects. This all means we must keep a watchful eye on these populations, measure effects across generations, measure effects on reproduction, development, growth, and performance, so that if population-level effects do ultimately emerge, we will be able to link them back to the DWH spill event.
