Community structure in epilinmetic and metalimnetic phytoplankton assemblages

Epilimnetic and metalimnetic phytoplankton communities were compared to assess the relative importance of autogenic and allogenic factors regulating community composition and structure. In the epilimnion, opportunistic species were predominant, and as a result there was considerabletemporal change in the community as measured by the community coefficient. In the metalimnion, however, temporal changes in the community coefficient were small compared with changes along the vertical gradient. It appears that non-equilibrium dynamics caused by short term changes in physical processes might be regulating the phytoplankton community in the epilimnion, and vertical niche partitioning along the vertical gradient was minor compared with temporal changes of community structure. The metalimnion supported communities with a more persistent structure over time, although vertical resource partitioning between density layers resulted in considerable change of community structure with depths.