DISCOVRE 2008

Cruise Log: 10/08/2008    

International Expedition to Deep Coral Ecosystems

Furu Mienis, Tjeerd van Weering, Gerard Duineveld (NIOZ), Andrew Davies (SAMS)

Let us start by introducing ourselves. We are scientists from the Netherlands Institute for Sea Research (NIOZ) and the Scottish Association of Marine Science (SAMS). We all study cold-water coral reefs on the European margins of the Northeast Atlantic. To study the environmental constraints and measure all manner of different parameters close to the seafloor, we have developed bottom landers. These landers are free-falling, dropped from the surface to land on the seafloor, and can be deployed from several days to over a year. During the USGS DISCOVRE cruise, we plan to deploy two landers for five days to test them and to give us some background information of the environment. Before we leave Viosca Knoll, we will leave the landers on the seafloor for a year.

Our collaboration with UNC-W started almost two years ago when Steve Ross joined one of our cruises on the R/V Pelagia to a cold-water coral area close to Ireland. This year we had the opportunity to join this cruise to the cold-water corals in the Gulf of Mexico, and we're all very excited about it. We hope to contribute to the research done in this area by bringing in a new dimension to the research. The landers are fully autonomous; once they are on the sea bottom, they collect data wherever they've landed until we decide to recover them. The landers are being deployed on and next to a coral site. This means that we can measure any differences in conditions near the seafloor on the coral site compared to the site without corals.

Cruise preparations started four months ago with the packing and shipping of a large sea container. Inside contained all of our gear, including the lander frames. After six weeks we received a message that the container had safely arrived in Pascagoula, MS. On the 29th of September we flew to New Orleans, well in advance of the cruise to have enough time to setup and prepare the landers. To make our lives easier, we did most of the construction and programming before we left port.

We brought two different types of landers. Both landers have a frame made of aluminium with glass spheres attached to the frame for buoyancy. However, the lander needs to sink to seafloor and stay there. Therefore both landers carry large weights. When we want to retrieve the landers, we send an acoustic signal to a release that drops the weight. The landers then slowly drift to the surface carrying back valuable data from the seafloor.

Both landers measure near-bottom temperature, salinity, the amount of particles in the water column, current speeds, current directions and are equipped with cameras. All data collected by the landers are stored on data disks. Monday morning, we deployed the landers at almost 500 metres in the Gulf of Mexico and hopefully we will retrieve them within five days to get our first data. Today we were really lucky because we got a view of one of the landers with the ROV. The data coming from the landers, combined with water column studies hopefully will give us a first insight into the hydrodynamic conditions around the cold-water corals in the Gulf of Mexico.

Deploying the BOBO lander into the ocean. - (photo credit: USGS DISCOVRE Expedition) - click to enlarge

Image of BOBO lander on the seafloor in the Gulf of Mexico. Notice that image is obscured by particles in the water, also known as marine snow. - (photo credit: USGS DISCOVRE Expedition) - click to enlarge