The consortium “Relationships of Effects of Cardiac Outcomes in fish for Validation of Ecological Risk II” (RECOVER II) work primarily under the third of the GoMRI research themes 3. Environmental effects of the petroleum/dispersant system on the sea floor, water column, coastal waters, beach sediments, wetlands, marshes, and organisms; and the science of ecosystem recovery. However, RECOVER II’s activities are also relevant for themes 2. Chemical evolution and biological degradation of the petroleum/dispersant system and subsequent interactions with coastal, open ocean and deep-water ecosystems and 5. Impacts of oil spills on public health including behavioral, socioeconomic, environmental risk assessment, community capacity, and other population health considerations and issues. RECOVER II is comprised of 10 internationally recognized co-PIs from 5 universities all with extensive relevant experience. The co-PI team spans newly appointed assistant professors through experienced full professors and counts leading experts in all relevant fields. The productivity and international recognition of our co-PI team is illustrated clearly by a combined 1081 publications and > 27,000 citations in the peer-reviewed literature.
The RECOVER II activities represent a unique and integrative approach encompassing studies at the molecular, cellular, organ, whole animal and population level placed in the context of the Gulf of Mexico (GOM) physical and chemical environment. The overarching objective is to gain what may be the most comprehensive understanding of oil impacts on any single organism, an objective that we pursue for a costal and a pelagic GOM fish species. This legacy will provide an exceptionally strong foundation for predicting biological endpoints most at risk during future oil spills in the context of relevant environmental factors (light, temperature, dissolved organic carbon, oxygen and currents). The RECOVER II team works almost exclusively on two important GOM predatory fishes, the coastal red drum and the pelagic mahimahi (mahi). Notably, the RECOVER partner institutions have established facilities, brood stocks and expertise to produce and raise all life stages of mahi (University of Miami) and red drum (The University of Texas at Austin) and have extensive experience with experimental work on both species.
Studies by RECOVER I, at the molecular level, revealed that development and function of sensory nervous systems are at risk during oil exposure of early life stages (ELS). Data providing phenotypic anchoring for these results are emerging, revealing impaired olfactory and visual capabilities following oil exposure. Since sensory acuity is critical for recruitment, prey capture, predator avoidance and con-specific interactions (including spawning), we propose to investigate the mechanisms of oil impaired sensory function at the molecular, organ and intact animal levels. Observations to date suggest sensory systems may be as sensitive to oil impacts as the cardiovascular system with the two acting in parallel to reduce overall fitness of exposed fish.
While significant strides have been made with respect to cardiotoxicity in oil exposed fish, several questions remain unanswered and will be addressed largely at the cellular level. Pelagic fish perform vertical migrations exposing them to temperature variation. Our early data from popup satellite tagged mahi reveal 10ºC fluctuations daily, which will influence cardiac function and we predict sensitivity to oil. Characterization of interactions between temperature and oil cardiotoxicity may serve impact assessments and response strategies for future oil spills.
A clearer understanding of oil effects under laboratory conditions is emerging, but we still know very little about how these effects combine to influence animals in the wild with consequences at the population level. This type of question is often addressed in mesocosms but mesocosm experiments are not suited for pelagic top predators. We will perform the ultimate experiment to measure the combined consequences of cardiovascular, sensory, and additional unknown effects on wild mahi in their natural environment. This experiment employs popup satellite tagging on non-exposed and oil exposed mahi allowing for an integrative assessment of oil impacts on habitat utilization, migration, and spawning behavior. To our knowledge, this approach has never been attempted for any fish exposed to contaminants, yet our recent experience with popup tagging of mahi demonstrate feasibility. The interpretation of habitat utilization data from oil exposed and non-exposed fish will benefit from our extensive data on metabolic rates at specific temperatures and swim speeds.
Impaired cardiovascular function at the organ level leads to predictions of limited ability to cope with high temperature and hypoxia at the organismal level, predictions we will examine thoroughly. The outcome of these efforts will inform future impact and risk assessments of oil spills in the context of relevant environmental parameters.
In addition to development and function of the heart and sensory organ systems, we have demonstrated that oil exposure results in altered embryo buoyancy, which is important for vertical distribution in the wild and thus dispersal and recruitment at the population level. Environmental parameters, such as UV light and dissolved organic carbon (DOC) enhance and mitigate oil toxicity, respectively. In addition, these factors interact and their interactions are influenced by dispersants such as Corexit. The impacts of temperature, UV, DOC and dispersants on oil toxicity to early life stages of mahi will be addressed experimentally also at sublethal levels where we will quantify impacts on specific gravity. Oil, in interaction with some of these environmental parameters, increase specific gravity leading up to hatch, which will have implications for vertical distribution, dispersal, and survival of larvae. The dispersal of embryos and larvae is critical for population health and will be modelled in the context of the DWH biophysical and biochemical environment. The model, which largely exists, will be parameterized by data from the above experiments and data from (our) past NRDA efforts and ongoing GoMRI work to allow for synthesis of population level impacts to pelagic top predators, another GoMRI legacy resulting from RECOVER activities.
Finally, ongoing studies have revealed that sublethal oil exposure of adult fish confer an epigenetically inherited increased resistance to subsequent exposures to oil to F1 offspring, an outcome which has never been considered for pelagic fish, despite the real-world relevance of such studies in the context of an oil spill. Powerful molecular tools employed also by RECOVER II to address mechanistic underpinnings as well as the molecular mechanisms conferring the suspected increased resistance in F1 offspring from oil exposed mahi. Potential tradeoffs and costs associated with epigenetically derived tolerance to oil such as altered tolerance to hypoxia and energy allocation to spawning will be also be examined.
Collectively, then, our studies will uniquely span from molecular to population levels, focused on two Gulf of Mexico species, one costal and one pelagic, of economic and ecological importance.
Standing on the shoulders of RECOVER’s intense and successful outreach program, RECOVER II continue to capitalize on a strong presence on the web and in various social media. We propose to continue monitoring the impact of our outreach efforts to allow for adjustments to ensure maximum reach and impact. Our recently developed virtual lab (available in the app store), a tool for middle and high school students and educators, is particularly exciting as it greatly enhances our outreach footprint at little cost. Several additional modules are planned under RECOVER II and a web domain for the app is secured and ensure yet another GoMRI legacy in the form of a broad outreach impact far beyond the life of GoMRI funding.
Although the proposed RECOVER II activities are designed specifically to understand impacts of oil contamination, many measurements on un-exposed red drum and mahi provide novel and extremely valuable baseline information about keystone predators in coastal and oceanic environments. This information, another GoMRI legacy, will form a vital component for the understanding of GOM ecosystems and beyond – mahi occupy circum-global temperate, subtropical and tropical pelagic environments.
Finally, the integrative nature of our activities combined with our iconic study species, continue to attract some of the very best graduate students and postdocs. The breadth of our studies and mentoring strategies aim to prepare this next generation of scientists for careers in academia, teaching or government positions where truly long-term impacts of our efforts will be manifested. Best management practices and the scientific method form the basis for all RECOVER II scientific, project and data management, outreach and education as well as training and mentoring approaches.