Aquatic Sciences Meeting, Albuquerque 2001

SS13 Mixotrophic Plankton - Combining Phototrophic and Heterotrophic Nutrition

Date: Friday, February 16, 2001, Time: 10:00:00 AM

Location: Acoma/Zuni/Tesuque

Coe, A, L, University of Maryland, Cambridge, USA, acoe@hpl.umces.edu

MacIntyre, H, L, University of Maryland, Cambridge, USA, macintyr@hpl.umces.edu

EFFECT OF SEDIMENT PORE WATER ON THE PHOTOSYNTHETIC PHYSIOLOGY OF THE DINOFLAGELLATE PROROCENTRUM MINIMUM DURING PROLONGED DARKNESS

Growth of the bloom-forming dinoflagellate Prorocentrum minimum can be stimulated relative to autotrophic controls in the presence of sediment pore-water rich in dissolved organic carbon (DOC) and ammonium. The same pore water can enhance the loss of photosynthetic competence when P. minimum is subjected to prolonged darkness. When cells in log-phase growth or stationary phase are deprived of light, the photosynthetic responses show a rapid suite of changes, with declines in cellular pigmentation and potential light absorption, and in the maximum quantum yield of photosynthesis and the light-saturated rate of photosynthesis. On a return to light, severely compromised cells lack the ability to re-acclimate and bleach rapidly. The loss of photosynthetic potential in darkness is accelerated in the presence of sediment pore water rich in ammonium and DOC, presumably because the deleterious effects of high ammonium outweigh the advantage of heterotrophic uptake of DOC that is seen under growth in the light. This outcome is relevant to the dynamics of bloom populations in Chesapeake Bay, where sinking blooms may be subject to aphotic conditions in or near the sediment.

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Aquatic Sciences Meeting, Albuquerque 2001

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