The diversity and abundance of high-latitude reefs, like those found off the Aleutial Islands, rival those seen in tropical coral reefs.
Microbial Ecology of Deepwater Corals in the Aleutian Islands
The Aleutian Islands are a string of volcanic islands that stretch from Alaska toward Russia, dividing the North Pacific Ocean from the Bering Sea. This is not the first place that comes to mind when you think of collecting corals for research. Since 2002, however, fisheries scientists from the National Oceanic and Atmospheric Administration (NOAA)'s Auke Bay Laboratory have been documenting deep-water coral and sponge reefs in waters hundreds of meters deep off these islands. The diversity and abundance of these high-latitude reefs rival those seen in tropical coral reefs.
This summer, Christina Kellogg, of the U.S. Geological Survey (USGS)'s Center for Coastal and Watershed Studies in St. Petersburg, FL, was invited to participate in a cruise aboard the research vessel Velero IV to collect deep-water coral samples for microbial-ecology studies. The corals were collected with the submersible Delta, using a custom device designed by Chris and her husband, Peter Richardson, that allows half of the sample to be preserved at depth. This design "stops the clock" on the sample and allows Chris to determine whether any dramatic shifts occur in the microbial community as a result of changes in temperature, pressure, and light during transport of the corals to the surface.
Coral-associated microbes have just begun to be studied in shallow-water corals, and it has been suggested that microbes may perform various functions, including nutrient cycling, nitrogen fixation, and production of antibiotics to protect the coral from disease-causing micro-organisms. The deep-water corals that make up the Aleutian reefs are mainly gorgonians (soft corals) that live in cold dark waters and lack the photosynthetic algal symbionts (zooxanthellae) that tropical corals depend on for their energy. The absence of zooxanthellae makes the potential role of microbes (bacteria, fungi, archaea) even more interesting. The microbes may help feed these corals, similar to the chemosynthetic bacterial symbionts that feed hydrothermal-vent worms. The microbial communities of these cold-adapted corals are also likely to contain novel organisms, which will not only increase our understanding of microbial diversity but could also be a source of novel enzymes or pharmaceuticals.