大规模增养殖区柘林湾叶绿素a的时空分布

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

柘林湾是粤东一个大规模海水增养殖区和赤潮重灾区.2001年7月至2002年7月对柘林湾及其周边水域(共设19个站位)进行的叶绿素a含量周年调查结果表明,调查海区叶绿素a站位实测值年变化为0 01~3 26 mg/m3,均值为0 56 mg/m3.平面分布的基本格局表现为湾顶黄冈河内与湾口外侧海域的叶绿素a含量明显高于湾内的,湾内外侧和东部水域的叶绿素a含量明显高于湾内内侧和湾西部的.结合同步调查的水化数据得知,柘林湾是一个高营养盐、低叶绿素的海湾,其原因可能与高密度、大规模海水增养殖业引起的水流不畅、水下光照减弱和养殖贝类的摄食等有关.柘林湾叶绿素a含量的季节变化显著,最高值出现在2001年夏季8月,最低值出现在冬季1 月和2002年7月,其中2002年7月的叶绿素a含量仅为2001年7月的1/10左右.这种巨大的年际间变化显然与2001~2002年厄尔尼诺现象导致粤东地区于2002年春夏期间气候异常、干旱少雨、径流剧减和调查海区浊度大幅升高有关.

Chlorophyll a around the Zhelin Bay-a large-scale mariculture (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/m^(3)), with an annual average of 0.56 mg/m^(3). The concentration of chl. a in the investigated area was higher in the Huanggang River and the outside 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 chlorophyll a. 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 Nio event, which resulted in low precipitation around the eastern Guangdong and the consequent largely decrease of PO (4)-P and increase of total suspension materials in July 2002 in the Zhelin Bay compared with those in July 2001.