By Sandra Brooke, Associate Research Faculty, Florida State University Coastal and Marine Lab
From the tip of Miami to North Carolina, the deep seafloor is comprised of hundreds of miles of rugged peaks, ledges, and mounds, which are scoured and swept clean of sediment by the ever-present, powerful Gulf Stream current. Deep-sea corals thrive in this cold, dark, hostile environment, creating large complex structures that provide shelter, feeding, and nursery habitat to countless other invertebrates and fishes.
This bright yellow glass sponge (Hertwigia sp.) is one of many different sponge species found in the southeastern United States. They are so named for the glass-like silicon spicules that support their skeletons. Image courtesy of Brooke et al. 2005, NOAA-OER Florida Deep Corals. Download larger version (jpg, 3.6 MB).
The dominant deep coral in this region is Lophelia pertusa, the most common deep coral in the North Atlantic. Coral larvae settle on rocky substrates and grow into small colonies. Over time, colonies grow larger and the outside branches block the flow of water, oxygen, and food to the inner colony, which then dies and is colonized by tiny encrusting and burrowing animals. The colonies break apart, and live coral overgrows the dead foundation. Over thousands of years, this process creates massive mounds that are comprised of a dead coral matrix, with live corals primarily on the tops and current-facing slopes of the mounds. The dead coral provides complex habitat for other corals, sponges, bryozoans, and many other species of invertebrates and fishes.
The bright red squat lobster (Eumunida picta) is often seen among the live coral colonies, with its arms raised to grab anything edible that passes by. Image courtesy of Brooke et al. 2005, NOAA-OER Florida Deep Corals. Download larger version (jpg, 2.3 MB).
During this DEEP SEARCH cruise, we will be working offshore from southern Virginia to north Florida at depths of 200 meters (656 feet) and greater. Parts of this area have been mapped and studied using submersibles and remotely operated vehicles (ROVs), but there are vast unexplored areas that most likely support deep-sea corals and their associated communities. Our study has many objectives, including characterizing communities associated with these coral habitats, from large fishes and invertebrates down to microbes; understanding the population structure and connectivity of different coral species; and looking at how the reefs may influence the fauna that live in nearby sediments and water column.
Live Lophelia colonies are bright white to slightly pink in color, which distinguishes them from the underlying darker dead coral matrix. The dead coral is a natural part of the deep reef ecosystem and provides valuable habitat for many associated invertebrates and fishes. Image courtesy of Brooke et al. 2005, NOAA-OER Florida Deep Corals. Download larger version (jpg, 3.1 MB).
My research will focus on life history strategies and timing of reproductive cycles in the dominant coral species. It was originally thought that deep-sea environments were constant, with none of the seasonal changes that drive reproduction in shallow water animals. This is not the case; there are indeed seasonal signals that reach the deep sea, and many deep-sea animals have seasonal reproductive cycles. Why is this important? Corals are sessile animals, which means they cannot move. The only way they can colonize other locations is to produce planktonic larvae that are carried by ocean currents. Understanding when these larvae are released and how far they can travel helps us understand how different habitats are connected with each other, and how quickly they may be recolonized if damaged. I am also interested in how corals respond to fluctuations in environmental conditions such as temperature and sediment concentrations. This information will provide insight into the vulnerability of different coral species to future ocean conditions and the effects of human activities.
Much of our study area was designated a Coral Habitat Area of Particular Concern by the NOAA National Marine Fisheries Service and is managed by the South Atlantic Fisheries Management Council. Information generated by our study will be provided to the Council and other federal agencies to help manage and conserve these ecologically and economically important ecosystems.
