The relationship between mesoscale phytoplankton heterogeneity and hydrographic variability

The notion that mesoscale phytoplankton heterogeneity results from hydrographic variability was tested, in the basis of data gathered in 9 cruises in diverse marine environments, to provide an explanation for cross-system differences in the extent of phytoplankton heterogeneity. This analysis showed that differences in the extent of phytoplankton heterogeneity are closely related to differences in the extent of hydrographic heterogeneity in moderately complex systems, but not in hydrographically complex systems (e.g. estuarine systems). Thus, phytoplankton heterogeneity was greatest in systems with intermediate hydrographic heterogeneity, and failed to increase in more complex environment. Thus limited phytoplankton heterogeneity in hydrographically complex system, such as estuaries, can be partially attributed to delay in phytoplankton growth response following perturbations. We thus conclude that phytoplankton growth and, therefore, growing conditions appear to have a dominant bearing on the extent of mesoscale phytoplankton heterogeneity in moderately complex systems, whereas phytoplankton heterogeneity in systems with complex hydrography is primarily controlled by physical processes.