GCRL

The BP Deepwater Horizon oil spill has great potential to negatively affect estuarine fish populations.
In order to assess possible impacts of this event, a series of sublethal lab experiments
were performed, using the economically and ecologically important species spotted seatrout
(Cynoscion nebulosus). Larval and juvenile spotted seatrout were exposed to sublethal concentrations
of high energy water accommodated fraction (HEWAF), chemically enhanced water
accommodated fraction (CEWAF), or dispersant alone in an acute exposure. Response to exposure
was evaluated with quantative polymerase chain reaction (qPCR) to examine expression
of cytochrome P-4501A (CYP1A). Growth of larvae and juveniles over the duration of the experiment
was measured as an index of physiological response. Our data showed that the different
life stages respond differently to crude and dispersed oil, with larval spotted seatrout affected
most by CEWAF, while juvenile spotted seatrout were affected to a greater extent by HEWAF.
In both cases, the treatment with the highest CYP1A levels resulted in the greatest reductions
in growth.

Energy exploration in the Gulf of Mexico (hereafter, Gulf) has resulted in the addition of numerous oil and gas production platforms that create structurally complex habitat in an area otherwise dominated by barren mud/sand bottom. How these artificial structures affect fish populations is largely unknown, and there is ongoing debate regarding their value as surrogate habitats for ecologically and economically important reef fish species. Thus, the purpose of this study was to characterize trends in Red Snapper Lutjanus campechanus reproductive potential in the western Gulf at oil and gas platform reefs relative to reproductive potential at natural banks. Red Snapper (n = 1,585) were collected during 2013-2015 from standing platforms, decommissioned platform artificial reefs, and natural banks by using standardized vertical line gear. Comparisons of gonadosomatic index, male : female ratios, batch fecundity, annual fecundity, spawning frequency, and number of spawning-capable individuals indicated that Red Snapper reproductive biology was similar among natural bank, standing platform, and artificial reef habitats. These results suggest that in terms of reproductive output, fish inhabiting artificial reefs are functionally similar to similar-aged fish on natural banks. This work can be used to make informed management decisions and suggests that there are benefits to converting decommissioned platforms into designated artificial reefs. Future studies should consider site-specific characteristics, such as depth, vertical relief, and proximity to other structures, to elucidate how habitat characteristics may influence reproduction, ultimately improving future artificial reef deployments for fisheries enhancement in the western Gulf.

Increased loadings of nitrogen (N) from fertilizers, top soil, sewage, and atmospheric deposition are important drivers of eutrophication in coastal waters globally. Monitoring seawater and macroalgae can reveal long-term changes in N and phosphorus (P) availability and N:P stoichiometry that are critical to understanding the global crisis of coral reef decline. Analysis of a unique 3-decade data set for Looe Key reef, located offshore the lower Florida Keys, showed increased dissolved inorganic nitrogen (DIN), chlorophyll a, DIN:soluble reactive phosphorus (SRP) ratios, as well as higher tissue C:P and N:P ratios in macroalgae during the early 1990s. These data, combined with remote sensing and nutrient monitoring between the Everglades and Looe Key, indicated that the significant DIN enrichment between 1991 and 1995 at Looe Key coincided with increased Everglades runoff, which drains agricultural and urban areas extending north to Orlando, Florida. This resulted in increased P limitation of reef primary producers that can cause metabolic stress in stony corals. Outbreaks of stony coral disease, bleaching, and mortality between 1995 and 2000 followed DIN enrichment, algal blooms, and increased DIN:SRP ratios, suggesting that eutrophication interacted with other factors causing coral reef decline at Looe Key. Although water temperatures at Looe Key exceeded the 30.5 °C bleaching threshold repeatedly over the 3-decade study, the three mass bleaching events occurred only when DIN:SRP ratios increased following heavy rainfall and increased Everglades runoff. These results suggest that Everglades discharges, in conjunction with local nutrient sources, contributed to DIN enrichment, eutrophication, and increased N:P ratios at Looe Key, exacerbating P limitation, coral stress and decline. Improved management of water quality at the local and regional levels could moderate N inputs and maintain more balanced N:P stoichiometry, thereby reducing the risk of coral bleaching, disease, and mortality under the current level of temperature stress.