Pyramimonas amylifera Conrad (Prasinophyceae): seasonal dynamics of a wild population, and the effects of temperature and salinity on growth and survival in culture

Temperature, salinity and abundance of Pyramimonas amyliferawere monitored over a 1-year period in a tidal salt marsh pool.The organism reached two peaks of abundance, the first in latefall before ice covered the pool, and the second in late winterafter the ice had melted. Cysts, but no oc-toflagellate stagesof this organism, were found in the pool in summer. The resultsof growth experiments on a clone of this organism isolated fromthe pool indicate that a temperature between 10 and 15 C isoptimal. A temperature between 20 and 25 C is the maximum tolerableby this clone. The "short-term" salinity tolerance range ofthis clone was found to decrease with increasing temperature,a phenomenon which could affect the fitness of the organismas a tide pool inhabitant. The field and laboratory data indicatethat although temperature and salinity were factors affectingthe abundance of P. amylifera in the pool, other factors notconsidered in the study must have also been important. ^*Present address: Department of Biology, University of SouthFlorida, Tampa, Florida, U.S.A. 33620. (Address for reprints)