科研之友
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摘要
Although theoretical mechanisms permitting phytoplankton co-existence have been extensively examined, few empirical field tests exist. Competition theory predicts greater diversity when species occupy heterogeneous habitats creating spatial niches. In a whole-lake experiment, we deepened thermoclines in two of three lake basins to examine alterations to the degree to which major algal groups showed spatial overlap (SO), in the vertical water column, and the consequences for diversity. Deeper thermoclines were expected to lead to less SO if species selected different depth positions in the water column in the absence of a thermal barrier, but to lead to greater SO if increased entrainment of phytoplankton in the mixed layer occurred. Increased diversity was expected to accompany less SO. Phytoplankton SO was determined using spectral group depth profiles from a FluoroProbe, and community diversity was estimated using high-performance liquid chromatography-estimated pigment diversity on daily samples taken over a 3-week focal period during the stratified summer period. SO declined and deep chlorophyll maxima were thicker when thermoclines were deepened. Unexpectedly, increases in SO preceded increased diversity by 5-7 days in all basins. This response likely arose from positive growth by most species within the unmanipulated deep chlorophyll maximum. The surprising result of our study, although supported by some theory, stresses the importance of large-scale field tests to validate hypotheses generated by resource-ratio theory.
- 出版日期2014-8
