虾池拟柱胞藻爆发的生态因子调查

2002～2003年,在广东珠三角地区凡纳滨对虾(Litopenaeus vannamei)低盐度养殖虾池水体生态的调查过程中发现部分虾池爆发拟柱胞藻(Cylindrospermopsis raciborskii).在调查的低盐度虾池中,共统计20个拟柱胞藻爆发的虾池,其种群密度平均高达7.74×10⁷ filaments·L^-1,平均优势度达47.0%.虾池水体平均水温为30.3℃,pH为8.9,盐度1.4,透明度19cm,化学耗氧量为24.3mg·L^-1.拟柱胞藻爆发的虾池水体环境表现为高水温、高pH、高有机质、低盐度且水体不断被搅动;通常爆发在对虾养殖的中后期富营养化水体.调查发现大量的拟柱胞藻对虾池其它藻类和微生物菌群表现一定的抑制作用,蓝纤维藻和小环藻等少数藻种可与拟柱胞藻形成共优势种.拟柱胞藻为广东珠三角凡纳滨对虾低盐度虾池重要优势藻种,且以螺旋型为主.

Investigation on the ecological factor in Cylindrospermopsis raciborskii bloom in low salty prawn ponds

Very high cell densities of Cylindrospermopsis raciborskii were detected in low salinity prawn ponds for Litopenaeus vannamei in Pearl River Delta areas,Guangdong Province,South China from 2002 to 2003.More than 20 prawn ponds were surveyed,and the density of C.raciborskii reached to 7.74×10⁷ filaments·L^-1,with an average dominance of 47%.The water temperature in the prawn ponds was 30.3℃;pH is 8.6;salinity was 1.4‰; transparency was 19 cm and the chemical oxygen demand(COD) was 24.3 mg·L^-1.It is obvious that C.raciborskii bloom occurs in the environmental condition of high water temperature,high value ofpH,high level of COD and low salinity;moreover,stirring the water in the ponds facilitates the forming of C.raciborskii bloom.In general,the bloom occurs in the middle or late term of water eutrophication in the prawn ponds. C.raciborskii cells can restrain the growth of other algae and microbes in the prawn ponds;some other algal species such as Dactylococcopsis acicularis and Cyclotella sp.can dominate with C.raciborskii.The spiral C.raciborskii is the dominant algal species in the low salinity prawn ponds in Pearl River Delta area,South China.