Over time, a variety of views have been formed on the structure of ecological communities. A. At any given place and time a particular group of phytoplankton species dominates, but the group that has dominance changes in pattern of seasonal succession that is repeated on an annual basis. B. Seasonal succession, unlike terrestrial ecological succession, results in a climax community, which can last indefinitely provided the right environmental conditions persist. C. Organic chemicals released by the dominant phytoplankton species, including toxins and vitamins, may influence successions by inhibiting or promoting the populations of other phytoplankton species. D. Seasonal succession among phytoplankton populations are influenced by a number of factors including water temperature, nutrient levels, and the activities of selective grazers. E. Certain species of phytoplankton release concentrated toxins that can kill other species of phytoplankton. F. Laboratory experiments have shown that, in temperate seas, temperature is the primary factor in phytoplankton species composition.