The distribution of larval fishes of the Charleston Gyre Region off the southeastern United States in winter shaped by mesoscale, cyclonic eddies

Serial, cyclonic, mesoscale eddies arise just north of the Charleston Bump, a topographical rise on the continental slope and Blake Plateau, and characterize the U.S. outer shelf and upper slope in the region of the Charleston Gyre. This region was transected during the winters of 2000, 2001, and 2002, and hydrographic data and larval fishes were collected. The hydrodynamics of the cyclonic eddies of the Charleston Gyre shape the distribution of larval fishes by mixing larvae from the outer continental shelf and the Gulf Stream and entraining them into the eddy circulation at the peripheral margins, the wrap-around filaments. Over all years and transects (those that intercepted eddies and those that did not), chlorophyll a concentrations, zooplankton displacement volumes, and larval fish concentrations were positively correlated. Chlorophyll a concentrations were highest in filaments that wrapped around eddies, and zooplankton displacement volumes were highest in the continental shelf–Gulf Stream–frontal mix. Overall, the concentration of all larval fishes declined from inshore to offshore with highest concentrations occurring over the outer shelf. Collections produced larvae from 91 fish families representing continental shelf and oceanic species. The larvae of shelf-spawned fishes—Atlantic Menhaden Brevoortia tyrannus, Round Herring Etrumeus teres, Spot Leiostomus xanthurus, and Atlantic Croaker Micropogonias undulatus—were most concentrated over the outer shelf and in the continental shelf–Gulf Stream–frontal mix. The larvae of ocean-spawned fishes—lanternfishes, bristlemouths, and lightfishes—were more evenly dispersed in low concentrations across the outer shelf and upper slope, the highest typically in the Gulf Stream and Sargasso Sea, except for lightfishes that were highest in the continental shelf–Gulf Stream–frontal mix. Detrended correspondence analysis rendered groups of larval fishes that corresponded with a gradient between the continental shelf and Gulf Stream and Sargasso Sea. Eddies propagate northeastward with a residence time on the outer shelf and upper slope of ∼1 month, the same duration as the larval period of most fishes. The pelagic habitat afforded by eddies and fronts of the Charleston Gyre region can be exploited as nursery areas for feeding and growth of larval fishes within the southeastern Atlantic continental shelf ecosystem of the U.S. Eddies, and the nursery habitat they provide, translocate larvae northeastward

Simulating Deep Oil Spills Beyond the Gulf of Mexico

As deep-sea oil exploitation increases worldwide, the probability of another Deepwater Horizon (DWH) blowout also increases. The DWH disaster directly impacted the coastal communities of the Gulf of Mexico (GoM) with 11 deaths and the release of 172.2 million gallons of gas-saturated oil, covering over 1000 miles of coastline and contaminating an estimated 300,000 million cubic meters of GoM water. In the aftermath of the DWH blowout, the question of what a similar event would look like outside the GoM is of fundamental importance. Anticipating the extent and potential environmental impact of major spills in other locations becomes important for effective oil preparedness and response, including coordination of emergency response between neighboring countries. Avoiding deep-sea drilling in environmentally sensitive and some of the world’s most biodiverse and productive fishing areas is also of upmost importance. The west coasts of Cuba and West Africa may be two of the most environmentally sensitive areas across the North Atlantic, yet exploitation of deepwater oil reservoirs has already started or is imminent. Northwest Cuba holds abundant coral reefs characterized by uniquely high diversity and fish biomass, and the region is also home of multi-species spawning aggregations, crucial for the persistence of fish populations. In addition, this area contains Cuba’s most important lobster fishery grounds. A major oil spill occurring in NW Cuba is thus likely to have deleterious impacts on the biodiversity and seafood resources of the region. The West African coastal upwelling system is an extremely productive area, harboring one of the world’s main “hot spots” in terms of fish abundance and biomass. This important system is most likely also a crucial mechanism regulating the climate, and an oil spill in this area could thus have severe local and global impacts. Here we simulate a DWH-like spill in two deepwater prospect blocks offshore Cuba and Senegal, West Africa, and evaluate their extent and impact against the DHW oil spill hindcast as a benchmark. These two hypothetical spills are not locally contained and are both severe, yet we find distinctive differences between their impact on the coastline, the seafloor, and the water column. Overall, the Senegal deep blowout scenario seems to be the most impactful with the highest sedimented and beached oil mass; the Cuba deep blowout scenario is the second worst, with the highest impact in terms of oiled area and volume. In this context, our study demonstrates that if another DWH occurred in a different region, poorly regulated emergency responses for international waters at the time of the spill could result in more detrimental impacts on marine ecosystems and coastal communities compared to the DWH. Here, we bring forward, quantify, and visualize the possible outcomes of another mega-spill similar to the DWH in two strategic locations to increase the awareness of decision-makers and the public to such implications. Since oil exploration is not expected to decrease in the near future, we urge governments to focus on establishing international agreements protecting sensitive marine resources and areas