RNA/DNA ratio of crabs as an indicator of mangrove habitat quality

Abstract

1. Pollution of mangrove ecosystems puts their future and that of local communities at risk. Only the use of informed and integrative approaches will successfully maintain and restore these valuable ecosystems. 2. Biochemical indicators of organism physiological condition have been widely used to evaluate habitat quality and for early detection of the impact of stressors. Mangrove crabs may be useful bioindicators of the quality of mangrove habitats, as they are characteristic and ecologically important organisms in mangrove environments. 3. The physiological condition (evaluated by the RNA/DNA ratio) of Perisesarma guttatum (Grapsidae) and Uca annulipes (Ocypodidae) was assessed to determine its potential as an indicator of habitat quality in one polluted and two relatively unpolluted Mozambican mangroves, during the rainy and dry seasons. 4. Both species showed seasonal effects on RNA/DNA ratio, but only U. annulipes was significantly affected by pollution. RNA/DNA ratio of U. annulipes may thus be a useful indicator of pollution and seasonality in mangrove habitats. There was a synergistic negative effect of the rainy season and pollution on the RNA/DNA ratio of U. annulipes. Due to higher DNA, rather than lower RNA contents, the RNA/DNA ratio of P. guttatum was always significantly lower than that of U. annulipes. 5. The knowledge gathered in this study can be used in integrative strategies, policies and programmes aiming to sustain, maintain and restore mangrove areas, and for the evaluation of mangrove habitat quality. Copyright © 2009 John Wiley & Sons, Ltd.