Temperature-Correlated Changes in Phytoplankton Community Structure Are Restricted to Polar Waters.
Globally distributed observations of size-fractionated chlorophyll a and temperature were used to incorporate temperature dependence into an existing semi-empirical model of phytoplankton community size structure. The additional temperature-dependent term significantly increased the model's ability to both reproduce and predict observations of chlorophyll a size-fractionation at temperatures below 2°C. The most notable improvements were in the smallest (picoplankton) size-class, for which overall model fit was more than doubled, and predictive skill was increased by approximately 40%. The model was subsequently applied to generate global maps for three phytoplankton size classes, on the basis of satellite-derived estimates of surface chlorophyll a and sea surface temperature. Polar waters were associated with marked decline in the chlorophyll a biomass of the smallest cells, relative to lower latitude waters of equivalent total chlorophyll a. In the same regions a complementary increase was seen in the chlorophyll a biomass of larger size classes. These findings suggest that a warming and stratifying ocean will see a poleward expansion of the habitat range of the smallest phytoplankton, with the possible displacement of some larger groups that currently dominate. There was no evidence of a strong temperature dependence in tropical or sub-tropical regions, suggesting that future direct temperature effects on community structure at lower latitudes may be small.
Laboratoire des Sciences de l'Environnement Marin, Institut Universitaire Européen de la Mer, Place Nicolas Copernic, Plouzané, France; School of Geographical Sciences, University of Bristol, Bristol, United Kingdom.
Ben A
BA
Ward
D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D017753:Ecosystem; D008962:Models, Theoretical; D010839:Phytoplankton / Q000254:growth & development*; D011156:Population Density; D012621:Seasons; D012623:Seawater / Q000737:chemistry*; D013696:Temperature
D002734:Chlorophyll; D000077194:Chlorophyll A