May 27, 2009

Ten Major Rivers The Focus Of Research

The Faculty of Biosciences at the University of Helsinki includes a project focusing on the ten major rivers in the world. Academy Research Fellow Anssi Vähätalo's group addresses the journey of riverine organic to the oceans and in particular the photochemical decomposition of organic carbon caused by sunlight.

The research project sheds new light on the mechanisms of the carbon cycle on the global scale and it enhances understanding of the links between continents and oceans. Partners along the major rivers send the water samples in 40-litre canisters to Viikki. The first samples from the Parana and Mississippi rivers have already arrived, and samples from rivers including the Mekong, Amazon and Lena are expected. All samples are taken during peak flow.

In the background is the painstaking research by Vähätalo's group into the cycle of organic carbon. When organisms die a part of their organic matter transforms into dissolved form and leaches into aquatic ecosystems. In the aquatic ecosystems dissolved organic matter is "food" for bacteria, which are eaten by zooplankton which itself serves as food for fish. However, much of dissolved organic matter is biologically recalcitrant and eventually flows to the ocean.

Sunlight keeps the ocean crystal clear?

Although the organic matter transported to the ocean is biologically recalcitrant, we can find only small fraction of it in the ocean.  This phenomenon can also be seen with the naked eye: oceans are not cloudy brown as are many lakes; the open waters of oceans are some of the clearest water systems on our planet. Vähätalo hypothesizes that sunlight is responsible for the decomposition of riverine dissolved organic matter in the ocean. Sunlight, which filters efficiently through clear seawater, decomposes organic matter back into carbon dioxide. The most important research findings are expected in the first half of next year.


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