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Happy Australia Day to all. We’re spending a quiet one on the Aurora, with work continuing. We only have a few days left of work before we head for home so we’ve postponed the party. Once we’re on the way home, and people come off shift, we’ll celebrate. The wind has dropped and the fog is back – we hope your Australia Day has a bit more sun than ours. We spent the night running a line of stations across a 1000m deep channel carved by the Mertz Glacier during previous ice ages, then across some shallow banks to the edge of the continental shelf. We did two stations over the steep slope there to take some more photos of what is living on the sea floor. One of the aims of the voyage is to study how ocean currents affect what lives where. On a previous voyage, we discovered remarkably diverse and dense communities of corals and other organisms at depths of 400-800m on the continental slope. These two areas were later protected by being declared Vulnerable Marine Ecosystems. On the present voyage we have been mapping out where these coral gardens are found, and not found, and seeing how this relates to ocean currents. So far, the evidence seems to support our hypothesis that the corals grow where dense water produced in winter polynyas cascades off the shelf and into the deep sea. These dense waters transport small particles of food that are scavenged by the filter feeders. We’re measuring what is suspended in the water by shining a light beam through the water and measuring how much light is transmitted and how much is blocked by particles. These measurements show the dense water is often full of particles. We’ve also been able to use the camera on the CTD to take photos of these particles, or “marine snow,” which show up as a cloud of fuzzy balls. The images don’t look too exciting, but it is amazing that we can actually see this material drifting down through the water column.
REGARDS: Steve, Fred and Penny
Map
A map showing Australia and Antarctica. The map shows the journey of one voyage that has occured in the season, with each route highlighted in a distinct colour.