PARENT SESSION
Oral Session # 51: Limnology II: Plankton; Carbon.
Presiding: K Forshay
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 101.

Resource-based niches of phytoplankton functional groups.

Litchman, Elena^*,1, Klausmeier, Christopher¹, Schofield, Oscar², Falkowski, Paul², ¹ School of Biology, Atlanta, GA, USA² Institute of Marine and Coastal Sciences, New Brunswick, NJ

ABSTRACT- Phytoplankton community composition profoundly affects patterns of carbon and other major element cycling as well as the structure of aquatic food webs. Can we predict spatial and temporal occurrence and dominance of major functional/taxonomic groups of phytoplankton? A significant step would be to define the ecological niches of major taxa. To characterize resource-based niches, we compiled a database of nutrient-dependent growth and uptake parameters for different species of marine and freshwater phytoplankton belonging to major taxa: diatoms, dinoflagellates, coccolithophores, green algae and cyanobacteria. Parameters describing nutrient uptake and growth were significantly different among taxonomic groups. Generally, diatoms are the best nutrient competitors, while dinoflagellates are the worst. Our database reveals important physiological constraints on the evolution of various traits that confer nutrient competitive abilities: the maximum uptake rates of nitrate were positively correlated with the minimum nitrogen quota and nitrogen half-saturation constant. Parameters describing nutrient uptake and growth were significantly correlated with cell size: carbon-specific maximum uptake rates decreased nonlinearly with cell size in a group-specific way.

Key words: niche, phytoplankton, functional groups