Genetoxic stress induced by intensive aquaculture activities in Taal Lake (Philippines) on circulating fish erythrocytes using comet assay and micronucleus test.

Abstract

The present study determined the genotoxicological effects of intensive fish cage aquaculture in Taal Lake (Philippines) on Nile tilapia (Oreochromis niloticus) erythrocytes using the comet assay and micronucleus test. Water and sediment samples were collected from three sampling sites namely: Gonzales, Bañaga, and Balakilong, which are non-aquaculture, moderate aquaculture, and heavy aquaculture respectively. About 1 ml blood was extracted by caudal puncture in five samples of O. niloticus per site. The extracted blood was immediately processed for micronucleus test while the rest was transferred into citrated tubes, then transported for the comet assay. The highest incidence of tail moments, micronuclei and nuclear abnormalities was detected in Balakilong. The nuclear abnormalities of erythrocytes included blebbed, notched and lobed nuclei. The gradient established by cumulative results of the comet assay and micronucleus test is as follows: Balakilong > Bañaga > Gonzales. Using post-hoc analyses, the two aquaculture sites showed no significant differences in both mean tail moment and frequency of nuclear abnormalities. The observed genotoxic responses were discussed in relation to the presence of contaminants such as ammonia and copper, which have settled in the sediments from unconsumed feeds. Results of the study demonstrate that fish cage aquaculture has a harmful impact on lake quality. It is recommended that a concentration-based analysis of the effects of ammonia and copper be conducted in controlled laboratory set-ups to obtain a finer analysis concerning the genotoxic potential of these contaminants, either individually or as mixtures.