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2010 Deep Sea Coral Cruise - west coast
Mission info 2007 Nancy Foster Cruise
 

Blog June 16, 2010:
School of Rockfish

Peter Etnoyer, NOAA NCCOS
Sean Rooney, Washington State University-Vancouver

Crinoids and green ball sponges photographed by the ROV
Crinoids and green ball sponges photographed by the ROV.
In high school, our science teachers always told us, "electricity and water don't mix," but here we are, day after day, sending a electrically-powered robotic vehicle over the side and into the sea, hoping it works when it gets to the bottom. Yesterday we finally reached the seafloor at about 300 ft (100 meters) depth. We stayed for six hours, crossing about 2-1/2 miles (4 kilometers) of rocky reef habitat to survey one site out of several we'd planned to see. We expected to see lots of corals, but here, corals were not abundant. The colonies (Swiftia beringi) were small, possibly new recruits. However, we encountered a high diversity of fish and invertebrates.

Several dark-blotched rockfish nestled in a Primnoa colony from Olympic Coast 2006 Expedition.
Several dark-blotched rockfish nestled in a Primnoa colony from Olympic Coast 2006 Expedition.
Interestingly, we saw many of the same animals we would expect to see in coral-rich habitats. In 2006, on another the Olympic Coast expedition, we encountered many large Primnoa coral colonies at nearby sites of similar depth. Rockfish were abundant, with some resting among the coral branches. Invertebrates such as squat lobsters, sea stars, and crinoids were seen with the corals, seeking shelter or taking advantage of their perch to feed on plankton in the passing currents. One reason we study these corals is to understand the nature of the relationship between the coral colonies and the species nearby.

A yelloweye rockfish in a boulder habitat at 100 meters depth.
A yelloweye rockfish in a boulder habitat at 100 meters depth.
On yesterday's dive, we also observed many fish, including numerous yelloweye, canary, yellowtail pygmy, and silver-gray rockfish. Most were hiding in the rocks and boulders. Some juveniles had settled on the rubble substrate. Squat lobsters and shrimp were also present on the rubble and in the rocks. They survive in the absence of coral colonies. However, animals may be more vulnerable to predators in the absence of corals. These are questions that still need to be addressed.

A juvenile rockfish rests in the rubble with squat lobsters, sponges, and a partially hidden brittlestar.
A juvenile rockfish rests in the rubble with squat lobsters, sponges, and a partially hidden brittlestar.
Corals were conspicuously absent at this site, though hard substrate was present. Why? We don't know. We must continue the research. The question here is: "how important are deep-sea corals to the survival of other species?" We know corals provide nursery habitat. We have seen organisms and their prey taking shelter in the coral branches. Corals are important in their own right, too. Coral colonies and the species associated with them are beautiful, long-lived, and slow-growing. To scientists, every colony tells a story, here at the bottom of the sea.

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