Deborah Bronk and a colleague drill through sea ice on the Chuckchi Sea to take water samples.Today, the Chukchi Sea is a shallow, productive water body that supports large blooms of phytoplankton following ice-out each spring and into the long days of summer. These algal blooms nurture a rich bottom-dwelling community of clams, worms, and other filter feeders. Together, these organisms sustain the fish, walrus, and seals that local subsistence hunters harvest for food.
But climate change threatens to upset this finely balanced ecosystem. As permafrost melts with continued warming, the runoff of "humics" into the coastal Arctic Ocean is increasing. "Humics," says Bronk, are "organic remains from plants that make the water in our neck-of-the-woods tea colored."
Bronk says that addition of humics to the Chukchi Sea will likely shift the focus of productivity from phytoplankton to bacteriabad news for the many animals that rely on phytoplankton for food, and for organisms higher up the food chain, including the native Inupiat. Bacteria are simply too small for filter feeders to capture.
Scientists think that humic-laden waters will favor bacteria, says Bronk, because "humics shut off the light that phytoplankton need for photosynthesis, and provide organic matter, which bacteria use for energy."
A shift from phytoplankton to bacteria could also further enhance climate change in the region. Today, the Arctic's coastal zones are thought to be carbon "sinks," areas where the net result of photosynthesis by phytoplankton is to draw carbon dioxide from the atmosphere into the ocean. With more humics and a shift to bacteria, these regions could become carbon "sour
|Contact: David Malmquist|
Virginia Institute of Marine Science