DIFFERENTIAL ATTRIBUTES OF PHYTOPLANKTON ACROSS THE TROPHIC GRADIENT - A CONCEPTUAL LANDSCAPE WITH GAPS

I provide a conceptual landscape of attributes of phytoplankton relate d to trophic gradients, by reviewing 69 papers and books on eutrophica tion, with special reference to the ecology of the phytoplankton. Fort y-eight ecological variables such as total phosphorus and Chi-a, are u sed, each related to the trophic gradient measured. They are subdivide d in structural features of the phytoplankton, functional or dynamic f eatures, and other relevant properties of the plankton community. Only twelve of the forty-eight variables are statistically related to trop hic gradient. In most cases, variability across a trophic gradient is only nominally described. Less attention is given to functional, struc tural or dynamic variables. Some associations occur because the variab les are interrelated, for example, photosynthesis and Chi-a, or becaus e the mathematical comparison is between a whole factor and a part of it. Many important environmental features which trigger or affect phyt oplankton behaviour are independent of trophic state. Therefore, troph ic states might be viewed as a multi-dimensional space, the axes of wh ich are defined by the various independent variables, and not merely a simple gradient of fertility. The alternative approaches to the searc h for pattern are either the single global pattern (which seeks to exp lain the ecological behaviour of phytoplankton in all freshwater syste ms) or multiple local patterns (where only a small set of specific var iables is solved for each question and system). If the ultimate goal i s a paradigm of phytoplankton dynamics, biomass models, and tools for the prediction.