Dynamics of community structure and phosphate status of picocyanobacterial populations in the Gulf of Aqaba, Red Sea
Limnol. Oceanogr., 50(1), 2005, 363-375 | DOI: 10.4319/lo.2005.50.1.0363
ABSTRACT: We monitored the genetic diversity and phosphate (P) status of Prochlorococcus and Synechococcus populations during an annual cycle (1999-2000) in the Gulf of Aqaba, Red Sea, using DNA probes and antibodies against the protein PstS, a molecular marker of P stress. The usual spring Synechococcus bloom was not observed in this year, and the picophytoplankton was dominated by Prochlorococcus from April to December. A single high light (HL)- adapted ecotype of Prochlorococcus, HLII, dominated, and this dominance extended even to the base of the euphotic zone for much of the year. Low light (LL)-adapted ecotypes only appeared between July and October and were confined to waters deeper than 50 m. The Synechococcus population was also dominated by a single clade (clade II), with the exception of a peak of clade III genotypes in June. Highest PstS expression from the collective Synechococcus and Prochlorococcus populations, indicative of P stress, was observed during the acutely oligotrophic summer, whereas low expression occurred during the winter and spring. Prochlorococcus abundance appeared unaffected by P stress and only decreased with the beginning of winter mixing, whereas P stress might have caused the decline of the Synechococcus population in May 1999.