From May 17 to 26, if you are looking for me, I’ll be out fishing. The second cruise for this project of this field season will begin on May 17 on the R/V Southern Journey (owned and operated by NOAA’s National Marine Fisheries Service) and will focus on collecting our two target species—red snapper (Lutjanas campechanus) and tomtate (Haemulon aurolineatum). The tomtate is a small fish that is in the middle of the food chain, whereas, the red snapper is a commercially fished species that is near the top of the food chain
.We will be collecting these fish species from 15 reefs and banks in the northwestern Gulf of Mexico to the east of the Flower Garden Banks National Marine Sanctuary. We are studying the relationship of the fishes at the different locations and comparing their genetic relationships, overall health, diet, and age. With this information, we hope to better understand whether the populations of these species at each bank are a single population or several different populations. This type of information is important for resource managers so that they can effectively manage and conserve fish populations.
Marine animals that live on the reefs and banks of the northwestern Gulf of Mexico have propagules (i.e., eggs, larvae, or juveniles) that often move or disperse to other reefs and banks transported by ocean currents. Because it is difficult to track a single egg or larva, we are modeling the oceanic currents that affect the reefs and banks located on the outer continental shelf in the northwestern Gulf of Mexico.
The reefs and banks we are studying are located at depths of 30 to 150 meters (100 to 490 feet) and very little is understood about the various physical processes (e.g., current direction and velocity) at these depths. Preliminary models indicate that water dynamics over short distances 1–10 kilometers (sub-mesoscale circulation) is more intense off the central and west Louisiana shelf than on the Texas portion of the shelf. Understanding sub-mesoscale circulation dynamics is important as this helps us reliably predict where and how larvae disperse or migrate.
We are collecting samples on this cruise of two sea fans, a black coral, and a sponge and will analyze them to determine their genetic and chemical information. This information will be combined with circulation models of larval dispersal that my lab is developing to better characterize the key habitats for our target species and determine if the various populations found on different reefs and banks are related.
“You must be a great diver.” I often receive this comment whenever meeting someone new. As a marine chemist who studies seafloor environments, I have yet to use my SCUBA skills at work. Who then, is the great diver involved? The technologies with which I work. On our cruise, we are using the remotely operated vehicle (ROV) Global Explorer (owned and operated by Oceaneering International, Inc.) to sample animals, including corals and sponges, which serve as local biodiversity hotspots and habitats for other organisms within the northwestern Gulf of Mexico.
The animals we are studying live at mesophotic depths down to 150 meters (492 feet), beyond the reach of standard SCUBA divers. The corals and sponges we seek could, in principle, be reached by highly skilled technical divers, who may be able to reach maximum depths of approximately 100 meters (328 feet), where pressures exceed 10 times that at the Earth’s surface. For this cruise, we are using the ROV Global Explorer because it provides ample bottom time, which is critical for exploration of unfamiliar areas.
We are working around the clock, with a goal of completing approximately 6–8 ROV dives every 24 hours. During every dive, the ROV Global Explorer collects video of the seafloor ecosystems with an onboard 4K ultra-HDTV camera, equipped for low-light environments. In this ocean ‘twilight zone,’ the photo flux is 15 to 300 times less than in more familiar, shallow reef environments, so the ROV uses LED lighting to illuminate the scene.