The phytoplankton community dynamics and the processes influencing phytoplankton community structure were investigated in Beatrix Bay, Pelorus Sound, New Zealand. The particular focus was on bottom-up resource acquisition driving phytoplankton dynamics in this coastal ecosystem. Sampling for water column structure, nutrient concentration, and phytoplankton community composition was done over two years in conjunction with experiments that manipulated nutrient concentration and light levels, to test how these affected phytoplankton community dynamics seasonally.