Abstract
Phytoplankton quantification was conducted in Sanya Bay from January 2005 to February 2006. A submersible in situ spectrofluorometer, which permits the differentiation of four algal groups (green algae, diatoms and dinoflagellates, cryptophytes and cyanobacteria) was used. Seasonal variation of total chlorophyll a concentration showed that high value appeared in summer and low concentration occurred in spring. Diatoms and dinoflagellates group was the predominant phytoplankton all year in the Bay. The stable stratification of phytoplankton vertical distribution came into being in July. During the stratification event, the total chlorophyll a concentration of deep layer was much higher than the surface; cyanobacteria and cryptophyta groups decreased and almost disappeared, however, the concentration of green algae and diatoms and dinoflagellates groups increased. In deep layer, the concentration of diatoms and dinoflagellates group increased sharply, which was about eight times more than that in the surface layer. The vertical profiles character of phytoplankton showed that from inshore stations to outer bay the stratification of phytoplankton vertical distribution gradually strengthened. Dissolved inorganic nutrient especially phosphate and inorganic nitrogen and cold-water upwelling were the main regulating factor for phytoplankton distribution.
Highlights
Phytoplankton, as the primary producer in food webs, is the basic biological resources of marine ecosystem
The validation studies for the determination of the total chlorophyll a and composition of phytoplankton communities compared to the standard laboratory methods for phytoplankton quantification, concentration of chlorophyll a and microscopy analysis were carried out
A high correlation between chlorophyll a levels using different methods was found in all types of phytoplankton community
Summary
Phytoplankton, as the primary producer in food webs, is the basic biological resources of marine ecosystem. Beutler et al (2002) presented a device (FluoroProbe, bbe-Moldaenke, Kiel, Germany) that was able to discriminate four spectral classes of phytoplankton (default ‘green’ - green algae, ‘blue’ - phycocyanin containing cyanobacteria, ‘brown” – diatoms, dinoflagellates, and ‘mixed’ - cryptophyta) according to their fluorescence excitation spectra and determined their quantity in units μg chlorophyll a per ml. The submersible fluorometer was used widely for the in situ monitoring of phytoplankton communities in marine and freshwater environments and have been accepted as a quick, simple, and useful tool for quantification of phytoplankton organisms (Serra et al, 2007; Arnaud et al, 2008; Blanco et al.,2008; Znachor et al, 2008; Ziegmann et al, 2010; Izydorczyk et al, 2009)
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