THE PHYTOPLANKTON OF THE HUGUANGYANMAAR LAKE

Annual investigations on the community of phytoplankton and physicochemical factors were carried out in the HuguangyanM aar Lake, Zhanjiang, Guangdong Province ofChina. The results showed that a total of 260 species of the phytoplankton (includ ing variety and form) belonged to 99 genus were found, with 119 species em erging in spring, 121 species in summer, 150 species in autumn and 122 species in winter. Among which, 20 genus includ ing 43 species belonged to Cyanophyta,accounting for 1615% of all species, 20 genus including 79 speciesw ere Bacillariophyta, accounting for 3014%,49 genus including 117 species were Chlorophyta, accounting for 45%, 2 genus including 8 species were Pyrrophyta, accounting for 311%, 2 genus including 2 species were Euglenophyta, accounting for 018%, 2 genus including 6 species were Chrysophyta, accounting for 213%, 3 genus including 4 species were Xanthophyta, accounting for 115%, and 1 genus including 1 species wasRhodophyta, accounting for 014%. There were 40 widespread species in all year, with 15 species being Cyanophyta, 6 species being Bacillariophyta, 14 species being Chlorophyta, 3 species being Pyrrophyta, and both species being Chrysophyta and Xanthophyta respectively. T here w eremutual 57) 78 species in each assembly o f both seasons while Jaccard index was 0128) 0142 dom inant species ( Y > 0102) presented through the year and belonged to Cyanophyta(13 species), Chlorophyta(8 species) and Bacillariophyta( 8 species) respectively, with 8 species in spring, 16 species in summer, 13 species in autumn and 11 species in winter, in which Chroococcusm nor,Microcystis flos-aquae, Pleurocapsa fuliginosa and Chlorella vulgaris were annually w idespread species. The most dominant species were Cyanophyta in spring,summer and autumn, but the most ones were Bacillariophyta in winter. The average cell abundance of phytoplankton ranged from 613 @ 104 ind /L to 5611 @ 104 ind /L, with the maxmium in spring, the second in winter and the minmium in summer.The averages of Shannon-weaver index and evennessw ere 4153 and 0165 respectively, with the maxmium in winter,follow ed by autumn, summ er and spring; the species were very abundant1There were the dominant populations of os, Bmand Am in the comm unity o f phytoplankton, accom panied by typically subtrop ical character1The elem ent P was the only lmiiting factor of nutrit ion in whole year accord ing to the ratio ofN /P, but both N and P were lmi iting factors of nutrition based on the absolute value ofN and P1The com prehens ive analysis indicated that the nutritional types ofwater quality belonged to subtropical oligotrophic types in this lake.