| In order to assess the toxic effects of pyrethroid pesticides on marine organisms and marine environments,and to understand the influence of pyrethroid pesticides on primary production of marine ecosystem,the toxicities of cypermethrin on the growth of three important harmful agla bloom species Chattonella marina,Scrippsiella trochoidea,Skeletonema costatum and seaweed Gracilaria lemaneiformis were studied.The toxic effects of cypermethrin on biochemical parameters including contents of pigment,such as chlorophyll a(chl.a) and phycoerythrin(PE), soluble sugar,soluble protein,malonyldiadehyde(MDA) and activity of superoxide dismutase superoxide dismutase(SOD),were measured as well.Meanwhile the absorption and adsorption ability of G lemaneiformis on cypermethrin were studied.Results showed that,in mono-species culture condition,cypermethrin obviously accelerated the growth of microalga at concentration below 10μg·L-1,and inhibited the growth significantly when concentrations were over 50μg·L-1.However over-compensation growth occurred in the late exposure period under high cypermethrin concentrations.Under co-culture condition,S.costatum was the most sensitive species to cypermethrin,nest sensitive species was C.marina,and S.trochoidea had the strongest resistance.C.marina had the similar growth curve with the control group at the lowest concentration group(1μg·L-1),and growth rates were lower than that in control group at concentration over 5μg·L-1.The growth of S.trochoidea accelerated at lower concentrations(≤10μg·L-1) and was inhibited at higher ones (≥50μg·L-1).The growth of S.costatum was severely inhibited under the conjunct stress of cypermethrin and co-cultures,and the cell densities were less than 10%of the control group.All of the biochemical parameters were sensitive at the early 6-12 h exposure stages,and became to be stable after 24 h or 48 h exposure in both mono-cultures and co-cultures.The contents of Chl.a,soluble sugar,soluble protein and the activity of SOD were induced at lower concentrations(≤5μg·L-1),and were initially inhibited and then recovered at high concentrations (≥50μg·L-1).However,MDA content increased significantly with the increasing of concentrations.Results showed that the inhibition of SOD activity and cellular inclusions and the damage of cell membrane structure might be the important reasons for the toxicity of cypermethrin to algal cells.The results showed that all biochemical parameters measured in this study were sensitive to cypermethrin.Furthermore SOD and MDA were more sensitive.The lowest effective concentrations of cypermethrin to SOD activity and MDA content of were both 10μg·L-1 for C. marinas,were 5μg·L-1 and 1μg·L-1 respectively for S.trochoidea,and were both 5μg·L-1 for S. costatum.While the inhibition concentrations on growth and other biochemical parameters were all 50μg·L-1.Therefore,SOD and MDA of microalga might be capable to be used as biomarks for early warning of cypermethrin pesticide contamination.The sensitivity of G lemaneiformis to cypermethrin was much lower than marine algae. Cypermethrin obviously accelerated the growth of G lemaneiformis at concentration below 50μg·L-1,and inhibited the growth significantly over 500μg·L-1.All biochemical indicators, including the cellular contents of PE,Chl.a,soluble sugar and soluble protein,MDA and SOD activity,were sensitive to cypermethrin.SOD activity and MDA content were the most sensitive parameters with the lowest effective concentrations of 5μg·L-1.Cypermethrin decomposed fast in water that 50%-70%was decomposed within 96 hours,and the degradation rate increased slightly to 52%-73%in cultures with G lemaneiformis.Results showed that the removal rates of G lemaneiformis to cypermethrin were too low to function as an effective bio-filter.On the other hand,the pollution of cypermethrin would be decrease to the safety levels in marine environments,due to its quick self degradation. |
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