Photosynthetic response of Gonyaulax tamarensis during growth in a natural bloom and in batch culture

The photosynthetic behavior of the dinoflagellate Gonyaulax tamarensis was investigated using single-cell isolation techniques at various stages during growth in a natural bloom in Salt Pond, Massachusetts, USA, and in laboratory cultures. Cell-specific photosynthetic capacity (PrnaxCen) increased from 0.25 to 0.32 ng C cell-' h-' during bloom development, then dropped sharply to 0.19 ng C cell-' h-' a few days prior to bloom decline. For G. tamarensis cultures grown to nitrogen depletion, both Pmax,,,, and cell-specific light harvesting efficiency (aceu) decreased several-fold as soon as NOSin the media fell to zero. Several lines of evidence are presented that suggest that nitrogen limitation played an important role in the decline of the G. tamarensis bloom despite the fact that ambient n~trogenous nutrient concentrations did not become depleted In the pond.