• allozymes;
  • electrophoretic bands;
  • genetic variation;
  • Narragansett Bay;
  • seasonal populations;
  • Skeletonema costatum


Clones of Skeletonema costatum (Grev.) Cl. isolated from Narragansett Bay, R.I., during different seasons were grouped according to their electrophoretic banding patterns. The growth rates, pg chlorophyll · cell−1, carbon uptake · cell−1· h−1, and carbon uptake · pg chl−1· h−1 were measured at 20°C, in a 14:10 h L:D cycle at 180 μE · m−2· s−1. Statistically significant sources of variation were found among groups of clones in growth rate, pg chl · cell−1, and carbon uptake · pg chl−1· h−1. It was concluded that there is a significant relationship between the physiological characteristics of clones isolated from populations in different seasons and patterns of genetic variation inferred from the electrophoretic studies. However, genetic diversity detected by banding patterns tends to underestimate the total genetic diversity in natural populations. The groups of clones most common in summer bloom populations had significantly higher growth rates, lower values of pg chl · cell−1, and higher rates of carbon uptake · pg chl−1· h−1 at 20°C than did the group of clones most common in winter bloom populations. However, differences among groups in these parameters at 20°C alone cannot account for the seasonal cycling of genetically variable populations of Skeletonema in Narragansett Bay. The range of growth rates among clones of this species is 0.1–5.0 divisions · d−1 under a single set of temperature and light conditions. Chlorophyll concentrations range from 0.2–1.7 pg chl · cell−1 and carbon uptake · pg chl−1· h−1 varies by a factor of 7 among clones. The range of physiological variation in this species means that it is difficult to use laboratory studies of single clones to analyze the responses of natural populations of Skeletonema.