Spatial-temporal distribution of chlorophyll a in the Zhelin Bay——A large-scale maricultural area

Chlorophylla around the Zhelin Bay-a large-scale maricult ure(with 19 sampling stations),eastern Guangdong,where the harmful algal blooms most frequently occurred,was investigated from July 2001 to July 2002.The results showed that concentrations of chl.a in the sampling stations range from 0.01 to 3.26 mg/m³,with an annual average of 0.56 mg/m³.The concentration of chl.a in the investigated area was higher in the Huanggang River and the out side of the bay than that in the inside,consequently resulted in that chl.a was greater in the outer and eastern bay than those in the inner and western bay. Based on the data from the related investigations,the Zhelin Bay is a bay with high nutrients and low chlo-rophylla.Such pattern might be mainly due to the low water exchange,low illumination and feeding of seashells caused by large-scale mariculture.There was a significant seasonal variation in chl.a during the investigation.The highest was found in August 2001,and the lowest in January and July 2002.The concentration of chl.a in July 2002 was equal to only 10% of that in July 2002.Such large difference occurred between consequent years might be related to 2001~2002 El Niño event,which resulted in low precipitation around the eastern Guangdong and the consequent largely decrease of PO₄-P and increase of total suspension materials in July 2002 in the Zhelin Bay compared with those in July 2001.