Flow Cytometry at Sea

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The oceans constitute one of the world’s largest resources, covering over 70% of the surface of the globe. They are known to play a major role in climate as the source of water for cloud formation and as a sink and transporter of heat absorbed from the sun’s rays. It is now becoming clear that the oceans also have a biologically based role to play in climate through the cycling of carbon from the atmosphere to the ocean floor. Carbon dioxide (the major greenhouse gas) is drawn down from the atmosphere into the surface waters of the ocean by biological processes (Watson et al. 1991), where it is converted to organic carbon. Much of the organic carbon is recycled by the activity of the planktonic activity in surface waters. However, some of the organic carbon is lost from the surface and sinks to the sea bed where it ultimately becomes incorporated into the sediment. The biosynthetic conversion of carbon dioxide to organic carbon is carried out by the activity of single-celled plants, the phytoplankton. These cells are of microscopic size and are ubiquitous in the surface waters of the marine environment where they are often present in large numbers (Smetacek 1981; Porter et al. 1985; Fenchel 1988). Phytoplankton use carbon dioxide dissolved in the water to form proteins, carbohydrates and lipids through photosynthesis.