Seasonal dynamics of phytoplankton in the Gulf of Aqaba, Red Sea

Abstract

Seawater samples were collected biweekly from the northern Gulf of Aqaba, Red Sea, for Phytoplankton analysis during the period May 1998 to October 1999. Microscopic counts and HPLC methods were employed. Procaryotic and eucaryotic ultraplankton dominated throughout most of the year, with larger nano-and microplankton making up only 5% of the photosynthetic biomass. Moderate seasonal variations in the 0-125 m integrated Chl a contrasted with a pronounced seasonal succession of the major taxonomic groups, reflecting the changes in the density stratification of the water column: Prochlorococcus dominated during the stratified summer period and were almost absent in winter. Chlorophyceae and Cryptophyceae were dominant during winter mixing but scarce or absent during summer. Diatoms and Synechococcus showed sharp and moderate biomass peaks in late winter and spring respectively, but remained at only low Chl a levels for the rest of the year. Chrysophyceae, Prymnesiophyceae and the scarce Dinophyceae showed no clear seasonal distribution pattern. The implications of alternating procaryotic and eucaryote dominated algal communities for the Red Sea pelagic food web are discussed.

Environmental properties of the southern Gulf of Aqaba, Red Sea, Egypt

“…In the northern Gulf of Aqaba, chlorophyll a showed homogeneous vertical distribution down to 400 m depth, with a concentration around 0.2 µg l ) and between 50-75 m depth in spring. The subsurface high chlorophyll a is a common phenomenon in the Gulf of Aqaba, and was reported in summer at 50 -100 m in the northern Gulf (Cornils et al, 2005;Al-Najjar et al, 2006) and in different layers over the year in the southern Gulf of Aqaba (El-Sherbiny et al, 2007).…”

Occurrence of brackish water phytoplankton species at a closed coral reef in Nansha Islands, South China Sea

“…Only at class-level analysis are available and some important taxonomic groups are mixed, for example, both diatoms and dinoflagellates are classed as the 'brown' algae (Blanco et al, 2008). Moreover, quantitative tests of the agreement between pigment analysis and microscopic analysis in natural waters are scarce, due to difficulties in precisely converting microscopic estimates of phytoplankton cell number, volume and pigment contents into carbon (Al-Najjar et al, 2007 and references therein). Therefore, research on the phytoplankton taxonomic composition and distribution in coral ecosystem is still fundamental and necessary for understanding the biodiversity of the coral reef ecosystem and monitoring the status of the habitat.…”

Nitrogen and phosphorus limitation of oceanic microbial growth during spring in the Gulf of Aqaba

“…During winter the Gulf is subjected to benthic injections of nitrogen that maintain the nitrogen: phosphrous ratio (N:P) close to the 'Redfield ratio' (N:P = 16) (Häse et al 2006). At this time, eukaryotic algae dominate but growth is limited by light availability with deep mixing (Lindell & Post 1995, Stambler 2005, Al-Najjar et al 2007). Water column stratification initiated during the spring traps nutrients in the high-light surface waters resulting in phytoplankton blooms, typically cyanobacteria and diatoms (Lindell & Post 1995, Al-Najjar et al 2007).…”

“…At this time, eukaryotic algae dominate but growth is limited by light availability with deep mixing (Lindell & Post 1995, Stambler 2005, Al-Najjar et al 2007). Water column stratification initiated during the spring traps nutrients in the high-light surface waters resulting in phytoplankton blooms, typically cyanobacteria and diatoms (Lindell & Post 1995, Al-Najjar et al 2007). As spring progresses into summer, the phytoplankton community becomes increasingly dominated by picoeukaryotes and prochlorophytes (Lindell & Post 1995, AlNajjar et al 2007, Stambler 2006.…”