Community structure and environmental adaptation of the planktonic larvae in Beibu Gulf

Abstract:

Seasonal species composition,abundance variations of the planktonic larvae were investigated during four cruises conducted in the Beibu Gulf,between Feb 1998 and May 1999. A total of 15 groups of planktonic larvae were identified,including Macruran larva,Alima larva,Ophiopluteus larva,Brachyura zoea,Brachyura megalopa and other Brachyura larva,six dominant groups,and other common groups. There were four groups which occurred all year round while the others occurred in some seasons. The results from 4 seasonal cruises suggested that the abundance of planktonic larvae in the Beibu Gulf ranged from 0.02 to 7.65 ind/m³ and averaged 0.50 ind/m³. The average abundance of planktonic larvae was 0.86,0.40,0.32,0.12 ind/m³ in summer,spring,autumn and winter respectively. The density centre was moving anticlockwise from the northeast of the Gulf in spring to the northwest in summer and autumn,then back to the northeast in winter. The K-dominance curves suggested that the community diversity of the planktonic larvae decreased from spring,winter,summer to autumn in sequence,but the range of seasonal variations was not so obvious. And the canonical correspondence analysis (CCA) showed that the abundance of planktonic larvae was affected greatly by the sea water temperature and pH,but less by the salinity and DO.