Effects of different proportions of silver carp and bighead carp on phytoplankton community structure and water quality in ponds
To study the effects of different proportions of silver carp and bighead carp on phytoplankton community structure and water quality,three experimental groups were set up,with proportions of silver carp and bighead carp of 1∶1(group A),3∶7(group B)and 1∶9(group C),respectively.Each group with two replicates(A1,A2;B1,B2;C1,C2)was equipped with the same density of piceus,crucian carp,carp,dace and cat-fish at the same time.The cul-ture period was 194 days.The results showed that a total of 53 genera of phytoplankton from 6 phyla were identified in 7 sampling sessions in the three ponds,among which the green algae were the most abundant,accounting for 40.3％of the total number of species;The total density of phytoplankton ranged from 30.07 to 123.83 × 104 ind·L-1,and the bio-mass ranged from 0.49 to 2.51 mg·L-1.The diversity index H showed that group B was light pollution,and group A and C were β-medium pollution.The evenness index J showed that group A was heavily polluted,while group B and C were α-medium polluted.The richness index D showed that groups A,B and C were all lightly polluted.The content of CODMn and TN in group B was lower than that in other groups,but the water quality standard rate was the highest.In general,the'3∶7'ratio of silver carp and bighead carp is beneficial to the diversity of phytoplankton communities and ecological health of multi-species fish mixed freshwater ponds.
phytoplanktonsilver carp and bighead ratiocommunity characteristicswater quality
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