27 December 2008 Size Is Not Everything!

KrillIt is so easy to imagine a place on the Earth in terms of the charismatic animals that live there. Monkeys in tropical jungles, colorful fish on coral reefs, dolphins in the sea, polar bears in the Arctic and penguins in the Antarctic. Each spring and fall, the Fingerlakes Institute in Geneva, NY invites me to bring my students out on Seneca Lake aboard their research vessel and most of the students expect to see and study the fish that the lake is famous for. Instead, when we fly our underwater camera over the lake bottom we see a slightly cloudy "soup" of plankton being filtered by a carpet of mussels covering the lake bottom. The vast majority of the life in every ecosystem is small, microscopic life that makes up the critical base of the food chain. Here in Southern Ocean off the coast of Antarctica, some of the science teams have come to study the ways microscopic algae use the nutrient rich water to grow. We have sampled sea ice that is the color of tea because it is filled with microscopic plants called diatoms. We have seen areas where the cleanest seawater in the world is turned to a soupy green with blooming algae. In fact, some of the open water areas near the coast of the Amundsen Sea may be the most productive natural ocean water in the world because of the upwelling of nutrients from the sea floor.

The critical link in the Antarctic food chain is the animal that can eat the microscopic algae and in turn become food for penguins, seals and whales. Ecologists call these members of the food chain "primary consumers" because they are the first to eat the green plants and move the nutrients up to higher trophic levels. Around here, we call them krill. These 4cm crustaceans swim in swarms through the icy water to filter and eat the algae. They could be described as giant zooplankton because they feed directly on phytoplankton. In the photo below you can see that they look like their shrimp relatives with a nearly transparent body and a large tail for swimming backwards through the water. More important are the bent, feather-like appendages in the front of the krill that it uses to net and filter the microscopic plants from the water. If you look inside the head, to the left of the two black eyes, you can see the krill's stomach, filled with green algae. Krill are, by far, the most abundant animal in Antarctica. Young krill can live inside the crevices in the bottom of the sea ice and adult krill form enormous swarms near the surface that are big enough to satisfy the appetites of the whales that travel all the way here just to feed on them. The most abundant seal in the world are the crabeaters here in Antarctica (I can see 5 on the sea ice outside the window right now!). Crabeater seals have specially designed teeth that allow them to gulp mouthfuls of krill and strain out the seawater through the gaps in their teeth. The penguin droppings I have seen on the ice make it clear that krill are the number one item on their menu too.

The moral of this story is, all of the big, cute and famous animals of Antarctica, are here because the krill are here. The krill are here because the algae is here. And, this part of the ocean is rich in algae because the nutrient rich, deep sea water is being forced to the surface as the more dense, cold, salty polar surface waters are sinking to the bottom.

So, the next time you marvel at my photos of seals and penguins remember to thank the krill, the diatoms and the gravity that make Antarctica so full of life.

The beauty is in the details.

Just as the fine details of the krill above tell stories about how it finds food, the details in the icebergs reveal part of the hidden stories that the icebergs tell about how they form and how big they really are. And, icebergs are beautiful to look at!

Making memories on the ice,

Jeff Peneston