ABOARD THE RVIB N. B. PALMER, ON THE SOUTHERN OCEAN– Adios Punta Arenas, Chile. Hello Research Vessel and Ice Breaker, Nathaniel B. Palmer (RVIB NBP). We, the crew, support staff and scientists of the NBP Iceberg Cruise III, left port in Punta Arenas on March 6th to begin our 40-day cruise to study the water column around free-floating icebergs. This is our third cruise, after two others on December 2005 and June 2008. We are making our way through the Straits of Magellan, past the Southern tip of Argentina into the Drake Passage, and on into the Weddell Sea where our group in particular will be focusing on the phytoplankton, plants living in the ocean that react to the presence of icebergs.

The RVIB NB Palmer at the dock at Punta Arenas, Chile.

As we sail south we cross different water masses. First, the coast of Argentina with a shallow continental margin, only 50 meters deep east of Tierra del Fuego, with cold sub-Antarctic waters of 8 degrees Celsius or 40 degrees Fahrenheit. A day later we enter into deep waters of several thousand meters, the West Wind Drift that circulates all around Antarctica. We cross the Antarctic Polar Front and in a few hours we find ourselves in cold Antarctic waters, close to freezing temperatures. Continuing on our voyage we cross the Southern Front of the Antarctic Circumpolar Current. As we move from water mass to water mass, the ocean continues looking blue to our eyes but the plankton changes.

Picture this: You are on a 4-day road trip (the approximate time that it takes us to reach our iceberg and waters of study from Punta Arenas). You travel through different zones and see different plants and animals during your trip as you travel through coastal foothills, to the valley, and onto the higher mountain alpine zones. The diversity of plants and animals in the ocean goes through similar changes as we go on our 4 day voyage to the Southern Ocean and pass through different water masses, each containing characteristic species.

Dinoflagellates or cells with a cellulose cover, a top and bottom capsule (or theca), and a central groove (or cingulum) with a flagellum are common in oceanic waters.

To study these plankton changes we collect water from the sea water intake on board the ship. Small cells with flagella are abundant in open waters north of the Polar Front. Diatoms, large and with a siliceous cover, are found closer to Antarctica. Diatoms will be part of our studies in the next few weeks, being the preferred food of the Antarctic krill and growing in diverse forms and sizes around and on the icebergs.

Diatoms such as this Thalassiosira species abound in cold Antarctic waters. Thalassiosira means “thalassos” or “sea” from the greek meaning oceanic species.

Stations sampled along a transect from South America to North West Weddell Sea. Columns are: Date, hour, minute, Latitude degrees, latitude minutes, longitude degrees, longitude minutes, sample number.