[Effects of Phytoplankton Classifications on the Relationship Between Phytoplankton Community and Environment in Summer Subtropical Reservoirs, Southern China].

ABSTRACT

Phytoplankton communities are sensitive to environmental changes and are used to assess water quality and ecosystem states. However, their responses to environment are affected by the classifications. To understand the impact of different classifications, the response relationship between phytoplankton communities and environment were compared with five phytoplankton classifications (species, genus, phyla, morphology-based functional groups, and functional groups) by investigating eight reservoirs in summer in the southern subtropical region. The eight reservoirs were mesotrophic and their environment was characterized by a high temperature (32.6±1.1)℃ and low light bioavailability (Zeu/Zm was 0.48±0.28). The variance of dissolved nutrients contributed to the main environmental differences between the eight reservoirs. The environmental gradient, in terms of dissolved nutrients concentration, was significantly higher than in terms of total nutritional status, temperature, and light bioavailability (P<0.05). The number of species and genus was higher but their biomass was lower than those of other classifications. This contributed to the higher Bray-Curtis distance and lower species gradient (SCBD) and location gradient (LCBD) of phytoplankton communities with species and genus classifications than other classifications. A statistical analysis showed that only the phytoplankton community gradient with MBFG and phylum classifications was significantly correlated with environmental gradient, in particular the gradient of pH value and PO43--P concentration. A significant regress was detected between the TSI gradient and the phytoplankton community gradient with MBFG and phylum classifications. In conclusion, as the variance of environment stemmed from the supply of nutrients, the response of the phytoplankton community classified with MBFG and phylum was more sensitive than other classifications.