PUNTA ARENAS, CHILE– Late last night we arrived at Punta Arenas, Chile. This marks the end of our Iceberg 3 cruise. We have finished analyzing the samples, re-calibrating instruments and we are now ready to start packing. We leave in 4 days; in the interim we will do an inventory of supplies, clean instruments, enter data and pack to be ready to leave on the 19th. Some of us are going back home, others will travel for a few days in the South of Chile or as far north as Ecuador.

Earlier today we met to share our findings during the cruise and plan data analysis and publication of results. Each of us gave a 5 minute (sometimes extending to 15 minute) presentation. It was impressive to see how much we had learned. We have now data that shows the changes in physics, chemistry and biology in the wake of an iceberg, we have improved the comparison of areas affected and not affected by the presence of an iceberg and we can tell how different the iceberg imprint in surface waters is at different times of the year in the North West Weddell Sea (summer, fall and winter). We have accomplished our goal of testing the release of iron to surface waters and the response of phytoplankton and bacteria. This was done not only by measurements in the ocean at different distances from icebergs but also through experiments with iron additions.

These photos show some of the wide variety of icebergs we saw in the northwest Weddell Sea. Notice the blue ice in this iceberg.

The black stripes in this “dirty” iceberg are caused by sediments trapped in the ice.

It was decided we will meet next month in Monterey, California. At that time we expect to have a more in-depth analysis of data that will allow us to synthesize findings in a more comprehensive way. Science carried out in interdisciplinary groups is based not only on results from the individual researchers but also on how well we can combine our findings to describe the iceberg system.

Until the next one!

ABOARD THE RVIB N. B. PALMER, ON THE SOUTHERN OCEAN– As most unicellular phytoplankton algae, diatoms usually reproduce by division. One cell becomes two after mitosis; the two new algae are called “daughter cells”. Once in a long while diatoms go through sexual reproduction. After meiosis the new daughter cells have a recombined genetic material. What brings this phenomenon? Some scientists think that the cell division (or asexual reproduction) produces silicon valves smaller and smaller until size can become a problem. Stress is another factor thought to affect reproductive strategy. Cells under unfavorable conditions for growth, when nutrients run out, undergo meiosis to increase their change of survival.

Corethron criophilum after cellular division through asexual reproduction.

The dominant diatom around the C18A iceberg is undergoing sexual reproduction. It is easy to see this process under the microscope as Corethron criophilum is large and the changes are striking. In cell division two smaller cells are seen at the extremes of the valve in cingular view, or along the cylinder. The auxospore is produced after fertilization of male and female gametes, leaving the mother cell.

Auxospore leaving a diatom frustule after sexual reproduction and fertilization.

Is the iceberg affecting phytoplankton in such a way to start sexual reproduction? Or does Corethron criophilum under stress due to diminishing light days as the fall season advances? These are questions we are asking ourselves. Detailed analysis of samples under the microscope once we are home will shed light on the first question. The importance of changing season on Corethron criophilum cannot be assessed during a 40-day cruise. Several months of study in the field would be needed. This is a question that might remain open and maybe can be answered in future cruises.

ABOARD THE RVIB N. B. PALMER, ON THE SOUTHERN OCEAN– C18A is a large iceberg, rectangular, shaped almost like a surf board, 18 km long and 6 km wide. It takes us about 4 hours at 11 knots to navigate around it. Working around the iceberg will keep us busy for the next week. There are eight Principal Investigators and their collaborators studying different aspects of the iceberg, the waters around it including our group that concentrates on the phytoplankton. Others measure zooplankton, bacteria, fishes, birds, chemistry, nutrients for plants and bacteria (like iron and what particles fall from the iceberg to the ocean bottom). We all share an interest in seeing how animals and plants are influenced by a large iceberg due to its melting of cold and fresh water. More information on different aspects of this project can be found at www.mbari.org/expeditions/antarctic09.

Our first study area: the iceberg C18A that formed off the Ross Sea shelf in 2003.

Corethron criophilum abounds here. This diatom is rather spectacular, a cylinder about 100 micrometers long (0.1 millimeters or 0.000394 inches) only seen under the microscope. Sometimes we can see some specs floating in the water but most times they are invisible to the naked eye. At each end of the cylinder there is a crown of spines, shorter at one end than at the other one, giving the cell an asymmetrical look. This species is most common in waters around the Antarctic Peninsula but can be found in other cold areas, like the Arctic Ocean.

Corethron criophilum seen from the side.

Corethron criophilum seen from the front. The crown of spines surrounds the valve edges.

Not much phytoplankton is present in these waters. A combination of being away from the continent or sea ice combined with the beginning of autumn could be the reason of the sparse community. To study these cells we concentrate them with a net of very fine mesh, 20 micrometers: we count them to estimate their concentration, describe their morphology, extract their cellular content for photosynthetic pigments and total carbon. When their abundance is low we concentrate larger water volumes, close to 200 Liters, or 52 gallons.

Is Corethron criophilum affected by the presence of the iceberg? Does the mixing of waters that bring nutrients from deep water favor its growth? If so, we expect to see more and healthier cells closer, as opposed to farther away from the iceberg. The iceberg itself can also bring nutrients when melting and enrich surrounding waters. We call this phenomenon “natural fertilization”. Experiments under controlled conditions with the addition of selected nutrients will help us answer this question.

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.

MCMURDO STATION, ANTARCTICA– In our webcast with John Weller recently, he showed some photos of a group of bat stars and close-up of the top of one of them. Bat stars are common sights on the bottom of Antarctic seas, clustering under holes and cracks in the ice where seals congregate. They scavenge seal droppings or bits of food left over from the seal’s fishy meals; nothing in the ocean goes to waste.

Photo (c) John Weller.

We were curious about the structures on the back of the little bat star (also known as a cushion star) so I wrote to my former advisor at U.C. Santa Cruz, John Pearse. Dr. Pearse did his doctorate scientific research in Antarctica on these invertebrate creatures whose scientific name is Odontaster validus. He emailed me back the other day and explained what was on the upper surface of the cushion star.

Photo (c) John Weller.

The pink flower-like structures are called paxillae and they create a space for water to circulate across the surface of the stars making it easier to absorb oxygen from the water. The purplish bud-like structures are called papulae, or “skin gills.” They extend from the inside of the star’s body cavity and have lots of tiny beating hairs, called cilia, that also help the animal absorb oxygen and get rid of waste products.

It’s curious that in such richly oxygenated water as found in the Ross Sea, these animals need two structures to aid their respiration. Dr. Pearse notes that there’s probably an interesting story there for some future invertebrate zoologist in Antarctica to investigate.

Cassandra Brooks is a marine scientist and science writer based in California. She’s studied Antarctic marine resources since 2004 at Moss Landing Marine Laboratories (MLML) and with the Antarctic Marine Living Resources (AMLR) Program.

Cassandra Brooks first began studying Antarctic toothfish in 2004 as part of her master’s thesis at Moss Landing Marine Laboratories. Antarctic toothfish are large, deep-sea predatory fish found only in the ice-laden waters surrounding Antarctica. Biologists who were fascinated with their ability to live in these freezing waters were the first to study these fish. It turns out that Antarctic toothfish have special proteins in their bodies that act like anti-freeze to keep their blood from freezing, thus enabling the fish to live in the icy waters off Antarctica.

Commercial fishermen took notice of the Antarctic toothfish only in the last ten years when populations of its sister species, the Patagonian toothfish, became depleted. Patagonian toothfish are found in the northern waters of the Southern Ocean, off the tip of South America and around sub-Antarctic islands. Both species of toothfish are more commonly known by their market name “Chilean Sea Bass,” though they bear no relation to sea bass. The depletions of Patagonian toothfish were likely caused by the large illegal pirate fishery, which has been estimated at up to 70 percent of the total harvest of this species.

As the subantarctic waters where the Patagonian toothfish lives were overharvested, vessels moved further south, into the remote and pristine waters of the Ross Sea, Antarctica, in search of the Antarctic toothfish. The commercial catch of Antarctic toothfish has increased steadily over the last ten years, even though very little is known about the basic biology of this fish. Cassandra’s work focuses on life history and population structure of this species. Her goal is to provide information on their age, growth, and spatial distribution to the toothfish’s managing body (CCAMLR) in order to facilitate sustainable management of this large Antarctic species.

Antifreeze Fish

Some of the coldest ocean waters on earth, where temperatures fall below the freezing point of fresh water, are found in the Southern Ocean surrounding Antarctica. Nearly every fish on the planet would freeze to death if it tried to brave such harsh conditions. The Antarctic toothfish, however, thrives in this icy environment. How does it do it?

Antarctic toothfish have evolved remarkable traits that allow them to survive in sub-freezing waters. One of these traits is a slow heartbeat—a beat only once every six seconds. The main secret of these unique fish, though—who have a natural lifespan of 40 years and can weigh in at over 200 pounds when full-grown—lies in a special protein that acts like antifreeze. By making this unique antifreeze glycoprotein, the Antarctic toothfish are able to keep their blood from freezing. It’s a remarkable evolutionary solution to surviving in the frigid waters of the Antarctic.

One of the most amazing things about these Antarctic antifreeze fish is their corollary in the Arctic, where waters reach similar subfreezing temperatures. There, fish carry a similar but different antifreeze protein—evolutionarily distinct from that of the Antarctic toothfish. What this means is that fish at both ends of the planet evolved similar antifreeze survival strategies through completely different methods.
For more on this awesome evolutionary achievement, please visit our Origins site here.

Background on AMLR

The United States is one of 25 nations that are bound by the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). CCAMLR is an international treaty, the aim of which is to conserve marine life in the Southern Ocean and to ensure the harvesting of marine resources is done in a sustainable manner without disrupting the Antarctic ecosystem. The United States Antarctic Marine Living Resources (AMLR) program is responsible for collecting scientific information that will be used to develop and support US policy regarding the conservation and management of the marine resources in the waters surrounding Antarctica. For over 20 years, scientists with the AMLR program have investigated the effects of krill, crab and finfish fisheries on the ecosystem, including the effects on seal and seabird populations. The Antarctic Ecosystem Research Division (AERD), located at the Southwest Fisheries Science Center branch of NOAA Fisheries, manages the AMLR Program.

When Cassandra goes to sea with AMLR, she primarily studies zooplankton under Dr. Valerie Loeb, a marine biologist at Moss Landing Marine Laboratories (MLML) and a contact scientist for AMLR. Valerie studies the abundance, demography, and distribution patterns of krill, and is head of the krill and zooplankton component of the AMLR program. Valerie and the AMLR crew study krill because these small (approximately 2–2.5 inches, or 5-6 cm) shrimp-like crustaceans are the most abundant and important food source in Antarctica. The whales, seals, fish, and seabirds in the Southern Ocean all depend on krill for their survival.