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Abstracts - S11 Stofomsætning i det marine miljø
75. Temperature influences on phytoplankton community size structure
Erik Askov Mousing, Marianne Ellegaard, Katherine Richardson
Center for Macroecology, Evolution and Climate, Department of Biology, University of
Copenhagen
eamousing@bio.ku.dk, me@bio.ku.dk, kari@science.ku.dk
Smaller phytoplankton species becomes increasingly dominant as temperature increases. In the
ocean, this has usually been interpreted as being an indirect effect because increasing temperature,
through resulting stratification, has a negative effect on nutrient availability in the euphotic zone.
Recent studies, however, have hinted at the possibility of a direct effect of temperature on
community size structure. Using a size-fractionated global dataset, we investigate phytoplankton
community size structure in relation to temperature and inorganic nutrient concentrations in an
attempt to discern the individual effects of these two factors. The main patterns show an increase in
the relative importance of small cells with increasing temperature and a decrease in the importance
of small cells with increasing concentrations of total inorganic nitrogen and phosphate. We
empirically demonstrate that temperature has both a nutrient-independent and a nutrient-mediated
effect on phytoplankton community size structure. Phytoplankton size is an important factor
influencing the biological pump with less carbon being transported to the interior of the ocean when
the phytoplankton community is dominated by small cells. Failing to appreciate the nutrientindependent
temperature effect might lead to underestimation of the effect of temperature on the
carbon sink in a warming ocean.
Program 17. danske havforskermøde, 99