Toxicity of some pesticides to aquatic organisms
2005
Bajet, C.M. | Navarro, M.F.P. | Kumar, A., Philippines Univ. Los Banos, College, Laguna (Philippines). Crop Protection Cluster
The toxicity of selected pesticides to local aquatic organisms like tilapia, shrimps (Macrobrachium lar) and duckweed (Limna sp.) was studied. The choice of pesticides was based on the residues detected from tributaries to Laguna and Taal Lakes [Philippines]. Pesticides identified as having high risk of offsite migration based on PIRI (Pesticide Impact Rating Index), a computer software which ranks the pesticides based on risks, were also tested. The toxicity and effect on Tilapia at early and fingerling stages were presented. The pesticides arranged in decreasing order of toxicity to tilapia fingerlings were as follows: lambda cypermethrin deltamethrin triazophos methamidophos cypermethrin diuron profenophos niclosamide inidacloprid. The pyrethroids (A alphapermethrin, deltamethrin and lambda cyhalothrin) and organophosphates (triazophos and methamidophos) were all toxic to tilapia, causing 50 percent mortality at less 10 microg/L LC50 (96 h). Changes in fish size, yolk sac distribution, morphology, among others, were observed on newly hatched fish fingerlings which developed from tilapia treated with chlorpyrifos, deltamethrin, lambda cyhalothrin, butachlor, 2,4D and profenophos. The decreasing order of toxicity of pesticides to shrimp collected in Laguna Lake is as follows: lambda cyhalothrin deltamethrin chlorpyrifos profenophos butachlor carbaryl imidacloprid. Lambda cyhalothrin and deltamethrin were the most toxic to both tilapia and shrimps, among the pesticides tested. Duckweed was found to be a good indicator of herbicide movement. The herbicides, butachlor and diuron were generally more toxic to duckweed than the insecticides tested. The presence of herbicides resulted in growth inhibition, as indicated by either fewer fronds number or lesser frond surface area.
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