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DISCOVRE - Diversity, Systematics and Connectivity of Vulnerable Reef Ecosystems Project:

Microbial Ecology of Deep-Sea Coral Ecosystems

Microbial Biofilms

Microbes are ecosystem architects! All underwater surfaces are rapidly covered by a thin layer of living things (biofilm), starting with microbes. The mixed community of bacteria in a particular biofilm can determine what other organisms will later choose to settle and grow in that spot. In this way, the microbes affect the eventual community structure of the visible fauna (things like sponges, anemones, and corals).

As part of the Mid-Atlantic Canyons work, settling plate experiments were deployed and recovered to determine what types of microbial biofilms form on different surfaces. Stacks of settling plates were made by spacing apart blocks of natural surfaces like limestone (calcium carbonate) and sandstone, as well as stainless steel (to mimic a shipwreck). These settling plates were mounted on weighted metal frames holding scientific instruments (benthic landers) that were placed on the sea floor at the head and mouth of both Baltimore and Norfolk Canyons. The experiments were deployed during our first cruise in August 2012. The settling plates in Baltimore Canyon were retrieved during our research cruise in May 2013 and the settling plates in Norfolk Canyon were retrieved during a cruise in August 2013.

The objective was to leave the settling plates in place for 8-12 months to accumulate biofilms that can now be analyzed to determine their microbial composition by DNA sequencing. We will look for differences in microbial communities based on the substrate type (limestone, sandstone or steel), the depth (canyon heads vs. canyon mouths), and between Baltimore and Norfolk Canyons.

Settling plate stack   Dr. Christina Kellogg attaching a settling plate stack to a benthic lander using cable ties.
Above Right: Dr. Christina Kellogg attaching a settling plate stack to a benthic lander using cable ties. Photo credit: Eric Hanneman. [larger version]

Left: Each settling plate stack has one plate each of limestone, stainless steel, and sandstone, spaced apart by PVC pipe. Each plate is roughly 5 inches x 5 inches x 0.25 inches (12.7 cm x 12.7 cm x 0.6 cm) and the PVC spacers are 4 inches (10 cm). Photo credit: Christina Kellogg/USGS. [larger version]

Benthic lander on deck with settling plates attached.   Deploying a benthic lander in Norfolk Canyon
Above Left: Benthic lander on deck with settling plates (indicated by white arrows) attached. Photo credit: Christina Kellogg/USGS. [larger version]

Above Right: Deploying a benthic lander in Norfolk Canyon, where it will live underwater for 8-12 months. Photo credit: Christina Kellogg/USGS. [larger version]

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