Temporal and Spatial Scales in Phytoplankton Ecology. Mechanisms, Methods, Models, and Management

This article is essentially a review of the temporal and spatial scales of variability in both marine and freshwater planktonic environments and the algal responses to those scales. I assert that there are problems with our present understanding of these scales and the use of inappropriate assumptions concerning the occurrence of steady-state conditions. In a nonsteady-state environment the concepts of limiting nutrients must be changed, and the extrapolation from culture to field conditions is fraught with problems. In this paper I review the evidence for the existence and importance of small-scale, high frequency and large-scale, low frequency variation in the planktonic environment and show that such variation fundamentally affects our understanding of existing processes. Methodology and models must also reflect the true scales of variability which exist. I show that there are, at present, problems with our understanding of planktonic processes which greatly affect our ability to manage water quality. New concepts and models are urgently needed. Finally I propose a new model of community structure and process in variable environments which accounts for the correct 'algal' scales of perturbation and response and allows certain predictions to be made. It is possible to reconcile certain problems and controversies in the literature by the use of such a model. An enhanced ability to manage planktonic systems should result from an improved understanding of the true scales of variability which exist.Key words: lakes, oceans, phytoplankton, communities, nutrients, models, management, eutrophication, fluctuations, scales