6 March, 1999
March 6, 1999
Hello from the Nathaniel B. Palmer! Today, we moved east along the Walgreen Coast toward Pine Island Bay. We had to use satellite images to help guide us between an area filled with pack ice and another area known as the Thwaites Iceberg Tongue. The Thwaites Glacier flows into the Amundsen Sea about 30 miles East of Mount Murphy, Marie Byrd Land. Seaward of the glacier is a large, floating glacier tongue and an extensive grounded iceberg tongue. These features stick out nearly 100 miles into the Amundsen Sea, and we have to make sure and avoid them. We saw lots of really cool icebergs all day today. In addition, I saw about four minke whales. One of them was even breaching (jumping up and landing on its back)!
Let's take some time to look at yesterday's question: "What other types of critters can be found in the waters surrounding Antarctica?" Of course, you already know about the whales, seals and penguins. There are also over 270 species of fish. Several species of these fish are interesting because of their ability to survive in sub-zero waters without freezing. Much like the insects we discussed yesterday, they have something like antifreeze in their blood. One such fish that is common in McMurdo Sound is called the Antarctic cod. These fish live up to 1500 feet below the surface and can weigh up to 125 pounds!
Another large, predatory group of fish are known as ice fish. They have clear blood and a pale flesh, which gives them their name. The reason that their blood is clear is that they have no red blood cells! Red blood cells normally carry oxygen, so these fish must have other adaptations to get the oxygen that they need to survive. They have several such adaptations, including more blood, a larger heart, more gill surface area, and the ability to exchange oxygen through their tails. A lot of scientists have studied these unique fish!
Squid are not fish, but they are very common swimmers in the southern waters. There are at least 20 species of squid in Antarctica, and they play an important part in the food chain for whales, seals, and birds. Some of these squid (like the giant squid) live in very deep waters and are very difficult to study. Squid vary greatly in their adult size -- measuring from only an inch long to as long as 60 feet! Squid move very quickly in the water, and they have excellent vision. They have several defense mechanisms to protect themselves. The best known of these is the ability to squirt black "ink" out to blind or confuse predators.
There are many other marine invertebrates that live on the ocean floor of the Antarctic waters. Creatures such as sea stars, corals, barnacles, clams, snails, sponges, sea cucumbers, worms, and sea spiders can be found on or in the sediments. Because they live on the sea floor and don't swim, they are considered benthic organisms. Other invertebrates are in the water, but they are too small or too weak to swim against the currents. Because they primarily drift with the currents, they are considered planktonic organisms. A few species of Antarctic zooplankton (animal plankton) include jellyfish and some foraminifera. PJ has been studying benthic foraminifera (forams) for her doctoral research.
There are also marine plants in the Southern Ocean. In the intertidal areas of the southern islands, giant kelp form thick bands like forests that protect the shores from rough seas. Other types of marine plants drift with the currents and are called phytoplankton (plant plankton). Diatoms are a common example of these tiny, single-celled plants that are at the bottom of the ocean food chain. Diane is conducting research on diatoms. Diatoms are also the organisms that turn the mud in our cores a green color.
Although we've already mentioned krill, I want to take a few minutes to make sure that you know what they are. Krill are the most important planktonic animal in the Southern Ocean. They feed on phytoplankton, and they are the prey of almost all the larger organisms in the sea . . . including fish, seals, whales, and birds (especially penguins). "Krill" is actually the Norwegian name for Euphausia, a type of pink-colored shrimp. They can grow to be about two and a half inches long. Large swarms may involve several million tons of krill and have densities as high as 10,000 organisms per cubic meter. Krill are a potentially valuable source of protein for human use, and they are easily collected with large nets. They may be cooked and peeled, or made into things like fish paste or livestock feed. Today, up to 400,000 tons of krill are caught commercially each year, mostly from the South Atlantic Ocean.
Some people have written to ask if we eat fish from the Southern Ocean for dinner. In fact, we had fish tonight . . . but not from the these waters! All living species in and around Antarctica are protected. In 1961, 12 countries (including the United States) signed the Antarctic Treaty. Today there are 43 member nations that have signed this treaty and agreed to work together to protect the unique environment that exists below 60 degrees South Latitude. Another treaty was passed in 1964 that specifically protects all animal and plant species in Antarctica. Even people doing scientific research have to have special permits to collect or kill any Antarctic wildlife (except in an emergency as food). In 1982, yet another treaty was enacted that set catch limits and defined fishing seasons and fishing methods for those parts of the Southern Ocean that aren't protected by the Antarctic Treaty (north of the boundary for the Treaty, and south of the Antarctic Convergence). This treaty, the Convention for the Conservation of Antarctic Marine Living Resources, regulates the harvest of both krill and fish. Monitoring is done on a regular basis to make sure that the allowable catches do not affect the populations of birds, seals, or whales.
Well, that's about all we have time for today. For tomorrow, we'll look at this new question: How do you suppose that we get fresh water for drinking, cooking, and washing on the Nathaniel B. Palmer? Thanks for all of the great questions! I love hearing from you!
Latitude: 72 degrees 52 minutes South
Longitude: 110 degrees 04 minutes West
Temperature: -6.3 degrees C
Barometer: 970.0 mb
Wind Speed: 22.1 knots
Wind Direction: 158 degrees (from the Southwest)
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