Gerris spinolaeLethierry and Severin (Hemiptera: Gerridae) andBrachydeutera longipesHendel (Diptera: Ephydridae): Two Effective Insect Bioindicators to Monitor Pollution in Some Tropical Freshwater Ponds under Anthropogenic Stress
The abundance patterns of two insects,Gerris spinolaeandBrachydeutera longipes, were found to be affected by abiotic aquatic factors including free carbon dioxide, dissolved oxygen, BOD, and phosphate concentrations prevailing in four tropical freshwater ponds, three of which being anthropogenically stressed. Regression analysis between each individual-independent water quality variable and insect abundance demonstrated a significant positive correlation in each case betweenB. longipesabundance and BOD, phosphate, free CO2, and algae dry weight, while a significant negative correlation of each of these variables was found withGerris spinolaeabundance. Moreover, a significant negative correlation ofB. longipesabundance was calculated with dissolved oxygen concentration, whileG. spinolaeabundance exhibited a positive correlation with the same. Thus,G. spinolaeappears to be a pollution sensitive, effective bioindicator for healthy unpolluted ponds, whileB. longipeshas potential as a pollution-resistant insect species indicative of pollution occurrence.