Hessen, D.O., E. van Donk, M. De Lange
Abstract:
There is an intimate interplay between light, nutrient and cell biochemistry in phytoplankton. Phytoplankton cells exposed to UV-radiation undergo a series of physiological changes that affect both cell-wall and intracellular morpology as well as a number of biochemical pathways and products. Not only do these effects influence overall primary production and phytoplankton community structure, they also affect the grazers and the entire food-web in numerous ways. Of the most prominent changes reported are reduced uptake of inorganic nutrients, reduced photosynthesis various genomic effects, loss or immobilization of flagella, increased cell wall thickness and halted cell division and concomitant increases in cell volumes and accumulation of intracellular starch and lipids. There are also reports on effects on fatty acid composition, yet this response is somewhat contrasting. Finally, there is a set of papers describing loss of orientation abilities owing either to damage on photosensitive cells or flagella. From the various cellular and biochemical changes, a set of hypothetical effects on zooplankton grazers may be deduced. There are some reports indicating that these effects could be severe. This review summarize current knowledge within this field focussing qualitative effects, and also poses new links between the field of photobiology and more conventional ecology.
(University of Oslo, Dept. of Biology, P.O.Box 1027 Blindern, N-0316 Oslo, Norway)
*******