Sabine Flöder

Publications (2)4.21 Total impact

• Article: Competition between benthic and pelagic microalgae for phosphorus and light – long-term experiments using artificial substrates

  Annika Pasternak, Helmut Hillebrand, Sabine Flöder
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  ABSTRACT: Benthic and pelagic microalgae inhabiting shallow lakes compete mainly for the limiting resources phosphorus and light. The availability of these resources depends on the spatial structure of the algal habitats. Pelagic microalgae use phosphate that is dissolved in the water column, and in turn their biomass affects the light intensity that reaches benthic microalgae. Benthic algae are able to use sediment-associated nutrients and nutrients that are recycled within the algal mats. To investigate competition between benthic and pelagic microalgae in shallow lakes, we performed two microcosm experiments with a three-factorial design. Phosphorus concentration in both the artificial substrates and the water column as well as light intensity were manipulated. The manipulated factors significantly affected Chl a and particulate phosphate concentrations of the experimental communities. In both experiments, benthic algae dominated during the entire time. Irrespective of light intensity, phosphate concentrations in the sediments and in the water column, pelagic algae were unable to become competitively superior by producing a biomass that was dense enough to shade the benthic algal community. Nutrients dissolved in the water column were effectively used by benthic microalgae, which reduced their availability for pelagic algae. The assumption that increasing the nutrient concentration in the water column would result in the loss of benthic communities was not confirmed.
  Aquatic Sciences 04/2012; 71(2):238-249. · 2.11 Impact Factor
• Article: Competition between pelagic and benthic microalgae for phosphorus and light

  Sabine Flöder, Anja Combüchen, Annika Pasternak, Helmut Hillebrand
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  ABSTRACT: In freshwater ecosystems production of both pelagic and benthic microalgae tends to be limited by phosphorus and light. However, the availability of these resources to pelagic and benthic communities differs due to differences in habitat structure. In a well mixed epilimnion individual phytoplankton cells should receive similar light intensities and nutrient concentrations per unit time. Benthic microalgae colonize substrates forming three-dimensional mats. Their access to nutrients and light is partially determined by the vertical architecture of the mat and often restricted to the canopy layer algae. In addition, algal mats will always be shaded by the phytoplankton inhabiting the water column above. We investigated competition between pelagic and benthic freshwater microalgae in a three factorial experiment, in which we manipulated phosphorus concentration, light intensity and the source of the inoculum (pelagic, benthic and benthic-pelagic). We found significant and interacting effects of phosphorus, light and inoculum on algal biovolume, chlorophyll-a concentration and cellular phosphorus content. When cultured separately, both benthic and pelagic microalgae benefited from the enhanced supply of phosphorus and light (higher biovolume, Chl-a). In combined culture, pelagic microalgae benefited from the increased light supply and became dominant irrespective of whether high or low phosphorus concentrations were added. In contrast, benthic microalgae profited from low light intensity combined with high nutrient concentrations. Cellular phosphorus contents in benthic and in mixed cultures were highest under low light supply, whereas in pelagic cultures no signifi- cant differences in cellular phosphorus content were detected.
  Aquatic Sciences 11/2006; 68(4):425-433. · 2.11 Impact Factor