Aquatic Sciences Meeting, Albuquerque 2001

SS44 Auto-Heterotrophic Coupling Across Trophic Gradients In Lakes and Oceans (Spatial and Temporal Connections)

Date: Monday, February 12, 2001, Time: 2:00:00 PM

Location: Sandia/Santa Ana

Cotner, J, B, Univesity of Minnesota, Saint Paul, USA, cotne002@umn.edu

Biddanda, B, A, University of Minnesota, Saint Paul, USA, bbiddan@sfwmd.gov

VARIABLE ROLE OF BACTERIOPLANKTON ACROSS ECOSYSTEM TYPES

Heterotrophic bacteria are a significant planktonic component in aquatic ecosystems and play a major role in biogeochemical processes. The relative importance of heterotrophic bacteria to material and energy fluxes is maximized in oligotrophic ecosystems and decreases in eutrophic ecosystems. We conclude that competition with autotrophs for dissolved nutrients and competition with heterotrophs for organic carbon play important roles in determining the relative abundance and impact of heterotrophic bacteria in aquatic systems. Oligotrophic systems have low nutrient concentrations, with high proportions of dissolved nutrients in organic form, which favors bacteria over phytoplankton. In eutrophic systems, increased relative concentrations of inorganic nutrients and increased relative concentrations of particulate organic carbon select for autotrophs and phagotrophic heterotrophs over bacteria. In oligotrophic systems, auto- heterotrophic interactions are tightly coupled because the dominant heterotrophs are similar in size, growth rates, and have similar nutrient composition to the dominant autotrophs, small phytoplankton. In eutrophic systems, increased productivity passes through zooplankton that are larger, and have slower growth rates than the autotrophs, leading to more potential for de-coupled auto- and heterotrophic production and increased export production.

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Aquatic Sciences Meeting, Albuquerque 2001

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