Dana L. Wetzel

Toxicity of Deepwater Horizon Source Oil and the Chemical Dispersant, Corexit® 9500, to Coral Larvae

Acute catastrophic events can cause significant damage to marine environments in a short time period and may have devastating long-term impacts. In April 2010 the BP-operated Deepwater Horizon (DWH) offshore oil rig exploded, releasing an estimated 760 million liters of crude oil into the Gulf of Mexico. This study examines the potential effects of oil spill exposure on coral larvae of the Florida Keys. Larvae of the brooding coral, Porites astreoides, and the broadcast spawning coral, Montastraea faveolata, were exposed to multiple concentrations of BP Horizon source oil (crude, weathered and WAF), oil in combination with the dispersant Corexit® 9500 (CEWAF), and dispersant alone, and analyzed for behavior, settlement, and survival. Settlement and survival of P. astreoides and M. faveolata larvae decreased with increasing concentrations of WAF, CEWAF and Corexit® 9500, however the degree of the response varied by species and solution. P. astreoides larvae experienced decreased settlement and survival following exposure to 0.62 ppm source oil, while M. faveolata larvae were negatively impacted by 0.65, 1.34 and 1.5 ppm, suggesting that P. astreoides larvae may be more tolerant to WAF exposure than M. faveolata larvae. Exposure to medium and high concentrations of CEWAF (4.28/18.56 and 30.99/35.76 ppm) and dispersant Corexit® 9500 (50 and 100 ppm), significantly decreased larval settlement and survival for both species. Furthermore, exposure to Corexit® 9500 resulted in settlement failure and complete larval mortality after exposure to 50 and 100 ppm for M. faveolata and 100 ppm for P. astreoides. These results indicate that exposure of coral larvae to oil spill related contaminants, particularly the dispersant Corexit® 9500, has the potential to negatively impact coral settlement and survival, thereby affecting the resilience and recovery of coral reefs following exposure to oil and dispersants.

Contaminant blubber burdens in Atlantic bottlenose dolphins (Tursiops truncatus) from two southeastern US estuarine areas: Concentrations and patterns of PCBs, pesticides, PBDEs, PFCs, and PAHs

Polychlorinated biphenyls (PCBs), chlorinated pesticides (i.e., dichlorodiphenyltrichloroethane (DDT) and its metabolites, chlordanes (CHLs), dieldrin, hexachlorobenzene (HCB), and mirex), polybrominated diphenyl ethers (PBDEs), perfluorinated chemicals (PFCs), and polyaromatic hydrocarbons (PAHs) were measured in blubber biopsy samples collected from 139 wild bottlenose dolphins (Tursiops truncatus) during 2003-2005 in Charleston (CHS), SC and the Indian River Lagoon (IRL), FL. Dolphins accumulated a similar suite of contaminants with summation operatorPCB dominating (CHS 64%, IRL 72%), followed by summation operatorDDT (CHS 20%, IRL 17%), summation operatorCHLs (CHS 7%; IRL 7%), summation operatorPBDE (CHS 4%, IRL 2%), PAH at 2%, and dieldrin, PFCs and mirex each 1% or less. Together summation operatorPCB and summation operatorDDT concentrations contributed approximately 87% of the total POCs measured in blubber of adult males. summation operatorPCBs in adult male dolphins exceed the established PCB threshold of 17mg/kg by a 5-fold order of magnitude with a 15-fold increase for many animals; 88% of the dolphins exceed this threshold. For male dolphins, CHS (93,980ng/g lipid) had a higher summation operatorPCBs geomean compared to the IRL (79,752ng/g lipid) although not statistically different. In adult males, the PBDE geometric mean concentration was significantly higher in CHS (5920ng/g lipid) than the IRL (1487ng/g). Blubber summation operatorPFCs concentrations were significantly higher in CHS dolphins. In addition to differences in concentration of PCB congeners, summation operatorPBDE, TEQ, summation operatorCHLs, mirex, dieldrin, and the ratios summation operatorDDE/ summation operatorDDT and trans-nonachlor/cis-nonachlor were the most informative for discriminating contaminant loads in these two dolphin populations. Collectively, the current summation operatorPCB, summation operatorDDT, and summation operatorPBDEs blubber concentrations found in CHS dolphins are among the highest reported values in marine mammals. Both dolphin populations, particularly those in CHS, carry a suite of organic chemicals at or above the level where adverse effects have been reported in wildlife, humans, and laboratory animals warranting further examination of the potential adverse effects of these exposures.

PAH Exposure in Gulf of Mexico Demersal Fishes, Post-Deepwater Horizon

Following the 2010 Deepwater Horizon (DWH) blowout, we surveyed offshore demersal fishes in the northern Gulf of Mexico (GoM) in 2011-2013, to assess polycyclic aromatic hydrocarbon (PAH) exposure. Biliary PAH metabolites were estimated in 271 samples of golden tilefish (Lopholatilus chamaeleonticeps), king snake eel (Ophichthus rex), and red snapper (Lutjanus campechanus), using high performance liquid chromatography with fluorescence detection. Mean concentration of naphthalene metabolites in golden tilefish (240 μg g(-1)) was significantly higher (p = 0.001) than in red snapper (61 μg g(-1)) or king snake eel (38 μg g(-1)). Biliary naphthalene metabolite concentration decreased over the study period in red snapper (58%) and king snake eel (37%), indicating likely episodic exposure, while concentrations were persistently high in golden tilefish. Naphthalene metabolite levels measured in golden tilefish are among the highest concentrations measured in fishes globally, while concentrations for red snapper and king snake eel are similar to pre-DWH levels measured in GoM species. In contrast, concentrations of benzo[a]pyrene metabolites were similar for all three species (p = 0.265, mean 220 ng g(-1)) and relatively low when compared to GoM, global data and previous oil spills. These data support previous findings that fish life history and physiology play significant roles in exposure and uptake of PAH pollution.

Tracking the Hercules 265 marine gas well blowout in the Gulf of Mexico

On 23 July 2013, a marine gas rig (Hercules 265) ignited in the northern Gulf of Mexico. The rig burned out of control for 2 days before being extinguished. We conducted a rapid-response sampling campaign near Hercules 265 after the fire to ascertain if sediments and fishes were polluted above earlier baseline levels. A surface drifter study confirmed that surface ocean water flowed to the southeast of the Hercules site, while the atmospheric plume generated by the blowout was in eastward direction. Sediment cores were collected to the SE of the rig at a distance of ∼0.2, 8, and 18 km using a multicorer, and demersal fishes were collected from ∼0.2 to 8 km SE of the rig using a longline (508 hooks). Recently deposited sediments document that only high molecular weight (HMW) polycyclic aromatic hydrocarbon (PAH) concentrations decreased with increasing distance from the rig suggesting higher pyrogenic inputs associated with the blowout. A similar trend was observed in the foraminifera Haynesina germanica, an indicator species of pollution. In red snapper bile, only HMW PAH metabolites increased in 2013 nearly double those from 2012. Both surface sediments and fish bile analyses suggest that, in the aftermath of the blowout, increased concentration of pyrogenically derived hydrocarbons was transported and deposited in the environment. This study further emphasizes the need for an ocean observing system and coordinated rapid-response efforts from an array of scientific disciplines to effectively assess environmental impacts resulting from accidental releases of oil contaminants.

Linkage Mapping and Comparative Genomics of Red Drum (Sciaenops ocellatus) Using Next-Generation Sequencing

Developments in next-generation sequencing allow genotyping of thousands of genetic markers across hundreds of individuals in a cost-effective manner. Because of this, it is now possible to rapidly produce dense genetic linkage maps for nonmodel species. Here, we report a dense genetic linkage map for red drum, a marine fish species of considerable economic importance in the southeastern United States and elsewhere. We used a prior microsatellite-based linkage map as a framework and incorporated 1794 haplotyped contigs derived from high-throughput, reduced representation DNA sequencing to produce a linkage map containing 1794 haplotyped restriction-site associated DNA (RAD) contigs, 437 anonymous microsatellites, and 44 expressed sequence-tag-linked microsatellites (EST-SSRs). A total of 274 candidate genes, identified from transcripts from a preliminary hydrocarbon exposure study, were localized to specific chromosomes, using a shared synteny approach. The linkage map will be a useful resource for red drum commercial and restoration aquaculture, and for better understanding and managing populations of red drum in the wild.

Species‐specific metabolism of naphthalene and phenanthrene in 3 species of marine teleosts exposed to Deepwater Horizon crude oil

The 2 most abundant polycyclic aromatic hydrocarbons (PAHs) measured in Deepwater Horizon crude oil, naphthalene and phenanthrene, and their associated homologs have both been shown to be acutely toxic in fish. Although fish have a relatively high metabolic capacity for PAHs, hydroxylated PAH (OH-PAH) derivatives formed during the initial metabolic response can negatively impact the health of fish. Species-specific metabolism of naphthalene and phenanthrene was evaluated in 3 marine teleosts, red drum (Scianops ocellatus), Florida pompano (Trachinotus carolinus), and southern flounder (Paralichthys lethostigma). Fish were exposed to Deepwater Horizon crude oil by intraperitoneal injections at time 0 and 48 h, with bile sampling events at 24 and 72 h post injection. The data suggested metabolic induction in Florida pompano and red drum, whereas southern flounder may have demonstrated metabolic fatigue. By 24 h post injection, overall profiles of red drum and southern flounder were dominated by hydroxylated phenanthrene metabolites; conversely, the Florida pompano profiles were dominated by monohydroxylated naphthalenes. In addition, Florida pompano had faster overall relative biotransformation rates, suggesting their potential decreased susceptibility to adverse effects. Red drum and southern flounder had much lower relative biotransformation rates, indicating their probable susceptibility to adverse outcomes after naphthalene and phenanthrene exposures. To our knowledge, the present study is the first to investigate monohydroxylated PAHs in fish exposed to Deepwater Horizon oil. Environ Toxicol Chem 2017;36:3168-3176.

Effects of mosquito control pesticides on competent queen conch (Strombus gigas) larvae.

Pesticides are applied seasonally in the Florida Keys to control nuisance populations of mosquitoes that pose a health threat to humans. There is, however, a need to investigate the effects of these pesticides on non-target marine organisms. We tested naled and permethrin, two mosquito adulticides used in the Keys, on a critical early life-history stage of queen conch (Strombus gigas). We conducted 12-h exposure experiments on competent (i.e., capable of undergoing metamorphosis) queen conch larvae using environmentally relevant pesticide concentrations. We found that there was little to no mortality and that the pesticides did not induce or interfere with metamorphosis. However, after introduction of a natural metamorphic cue (extract of the red alga Laurencia potei), a significantly greater proportion of larvae underwent metamorphosis in the pesticide treatments than in those with the alga alone. In addition to the morphogenetic pathway that induces metamorphosis when stimulated, there thus appears to be a regulatory pathway that enhances the response to metamorphic triggers, as suggested by the increased sensitivity of the queen conch larvae to the algal cue after pesticide exposure (i.e., the pesticides stimulated the regulatory pathway). The regulatory pathway probably plays a role in the identification of high-quality habitat for metamorphosis, as the increased response to the algal cue suggests. Aerial drift and runoff can carry these pesticides into nearshore waters, where they may act as a false signal of favorable conditions and facilitate metamorphosis in suboptimal habitat, thus adversely affecting recruitment in nearshore queen conch populations.