The consortium "Relationships of Effects of Cardiac Outcomes in fish for Validation of Ecological Risk" (RECOVER) consists of seven co-PIs from four institutions: University of Miami, FL, University of Texas at Austin, Port Aransas, University of North Texas, and University of California, Riverside.
Proposed consortium activities are an integration of studies at the molecular, cellular, organ level and whole animal physiology as well as behavioral studies at different life stages for two important Gulf of Mexico predatory fishes, the coastal redfish and the pelagic mahi-mahi.
Studies by the RECOVER members and others have revealed that exposure to water accommodated fractions of oil during early development results in malformation of hearts in fish embryos and larvae, which likely results in mortality or reduced cardiac performance in surviving individuals. Furthermore, the members of RECOVER have demonstrated that such surviving individuals display reduced swimming capabilities even 25 days after being transferred to non-contaminated water. Their findings also demonstrate that, in addition to reduced cardiac performance, factors that affect swimming efficiency contribute to this reduction in swimming capacity. The RECOVER team has demonstrated that acute exposures to later life stages (juveniles and young adults) also result in reduced swimming performance, an observation that cannot be attributed to malformed hearts but possibly impaired heart function. At present, it is not known if swimming performance recovers after termination of exposure. Swimming capacity is critical for vital functions like prey capture, predator avoidance, and spawning migrations, but it is currently unknown if any of the above observations translate to fitness in surviving animals. RECOVER members and others have also demonstrated that the ultraviolet (UV) component of natural light has the potential to significantly enhance toxicity of polycyclic aromatic hydrocarbons (PAHs) found in crude oil by more than an order of magnitude. This UV enhancement of PAH toxicity places the above observations of effects at relatively low PAH levels under artificial light conditions in a crisp perspective and suggests that effects under natural field conditions might have been more pronounced than those observed in the laboratory.
On this background, the RECOVER members propose to develop a greater understanding of the molecular and cellular underpinnings of oil-induced toxicity in developing fish embryos, larvae, and young juveniles and how the observed cardiac malformations affect heart function. Similarly, the mechanisms responsible for impaired swimming performance of later life stages following short-term exposure will be examined. While the impacts of oil exposure on cardiac development and swimming performance are undeniable, it is unclear if recovery from such effects may occur and, if so, what the rate and extent of recovery may be. The RECOVER team will measure, not only heart rate, but also stroke volume and thus cardiac output in different life stages of fish in an attempt to understand what limits swimming performance in oil-exposed fish. Alternative mechanisms to account for impaired swimming performance, including reduced swimming efficiency, impaired calcium cycling in skeletal muscle and/or mitochondrial uncoupling, will also be pursued.
Sophisticated molecular approaches and organ level and whole animal physiology will combine to establish an Adverse Outcome Pathway to determine the cellular mechanisms responsible for effects observed to date. Such approaches may also unveil molecular mechanisms of toxicity that point to previously undiscovered higher order effects of oil/PAHs that can be employed as weight of evidence parameters for ecological risk assessments. Finally, the population level significance of even subtle oil-induced impacts on swim performance will be determined through examinations of predator-prey interactions.
The ultimate goals of the RECOVER activities summarized above are to:
- Provide a near complete mechanistic understanding of physiological effects of exposure to crude oil and PAHs. Such an understanding will provide a solid foundation for predicting effects on other species under other environmental conditions (UV penetration, temperature, salinity, oxygen tension, etc.)
- Provide insight into best practices for managing future spills involving other species and different physical-chemical environmental parameters.
- Furthermore, the proposed studies of potential reversal of induced effects seek to determine to what extent individual organisms are able to recover from damage induced by exposure to crude oil/PAHs.
- Finally, the proposed studies of predator-prey interactions, the first of their kind, examining oil/PAH impacts on fish, aim to inform population ecologists and thus assist with ecosystem effect predictions.
Project Research Overview (2015):
An overview of the proposed research activities from the GoMRI 2015 Meeting in Houston.
Direct link to the Research Overview presentation.