Photosynthetic and cellular photoadaptive characteristics of three ecotypes of the marine diatom, Skeletonema costatum (Grev.) Cleve

Abstract

Physiological variation among genetically distinct clones of Skeletonema costatum (Grev.) Cleve, representative of the prevalent seasonal populations of this species in Narragansett Bay, were examined to determine the nature of their optimal survival strategies in response to changes in light intensity. The clones were found to exhibit significant differences in growth rates, cellular pigment content, PSU-RCI and PSU-RCII numbers per cell, ratios of RCI/RCII and photosynthetic capacities per cell. Respiration rates and I c values did not vary among clones. The variation among clones for many characteristics were similar in magnitude to those previously reported for differences among species. No single photosynthetic feature dominated or predicted the photoadaptive mechanism in any clone examined. Large clonal differences in photoadaptive features suggest that the evolution of the seasonal ecotypes of S. costatum was not a recent phenomenon. The integration of cell-dependent and cell-independent photosynthetic features in each clone and, by inference, the genetic groups which they represent, partially accounts for the seasonal pattern of abundance distinct allochronic populations in the Narragansett Bay ecosystem.