Document: OWE-3-52-8

Effects of species diversity and environmental variability on community and ecosystem properties in an aquatic microcosm experiment.

PETCHEY, O.*, T.CASEY, L.JIANG, J.JOHNSON, Y.KATO and T.MCPHEARSON

Rutgers University, New Brunswick, NJ 08901 ¹

Abstract:
Having shown that single species population dynamics were affected by temporal autocorrelation (none or positive) of environmental variability, we looked for effects on species coexistence and ecosystem function. Aquatic microbial microcosm communities initially contained 2, 4, 6, or 8 bacterivore species (with 4 species compositions at each diversity level) and experienced constant, random, or correlated temperature treatments. We measured species presence/absence, species abundance and biomass, bacterial density, community respiration, and decomposition rate during the second and final week of the 6 week experiment. The proportion of initial species remaining at the end of the experiment was unaffected by environmental variability, but proportionally more species were lost from diverse communities. This suggested that environmental variability did not affect species coexistence in this community, and that fewer than 8 species could coexist in this system. Total biomass increased with realized species diversity as expected by the sampling effect and/or species complementarity, but environmental variability had no effect on total biomass. Neither realized diversity nor environmental variability affected community respiration, and decomposition and bacterial abundance responded differently during weeks 2 and 6. Other than the obvious increase in total biomass with diversity, the treatments have weak or no effects on static community properties. Dynamic community properties, measured by proportional changes in biomass, community respiration, and decomposition from week 2 to week 6 were also analyzed. Total biomass generally decreased during the period from week 2 to 6, more so in less diverse communities. Community respiration also decreased from week 2 to 6, but more so in diverse communities. Decomposition decreased without any influence of diversity, but was significantly different in one autocorrelated temperature treatment. These results suggest that increased diversity reduced temporal changes in biomass, supporting hypotheses that predict stabilizing influences of diversity on aggregate community properties. This result was, however, not consistent among different community/ecosystem properties, and was not strongly affected by environmental variability.

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This abstract is being presented at: 1:45 PM in session:
Oral Session #11: Trophic Cascades.