Abstract:Biomass size distributions of zooplankton in the Laizhou Bay,Bohai Sea, were analyzed based on the samples collected by plankton nets (mesh size of 160μm and 500μm) in May and June, 2011. Results showed that, in both months, zooplankton individuals from samples were in the size range of -3~10 (in logarithmatic carbon unit), and continuous Sheldon-type biomass size spectra without gaps were found similarly. But in May, Sheldon-type biomass size curve was composed of two major domes attributed by small copepod Acartia bifilosa and meso-individuals, Calanus sinicus, Sagitta crassa respectively. While in June, it had only one remarkable dome attributed by meso-individuals, C. sinicus and S. crassa. Total zooplankton biomass in June was much lower than that in May as the A. bifilosa declined greatly. Moreover, the production and P/B of zooplankton were calculated as 75 mg C/m2•d, 0.20 for May and 24 mg C/m2•d, 0.16 for June. Normalized biomass size spectra were also constructed on a double log plot and fitted closely with a linear regression line with equations y = -0.962 9x +14.893 (R2=0.60) for May and y=-0.906 3x+12.832 (R2 = 0.80) for June. According to theoretical Borgmann model (1987), the fish biomass is predicted to be 0.57 gC/m2 in the size range of 14~16 in May and 0.1 gC/m2 in the size range of 12~25 in June.
