Behavioural Responses of the Mangrove Fiddler Crabs (Uca Annulipes and U. Inversa) To Urban Sewage Loadings: Results of a Mesocosm Approach
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Elsevier
Abstract
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The study aimed at investigating the effects of sewage loadings on the behaviour of two fiddler crabs species
maintained in a system of experimental mesocosms, built in a mangrove area in Tanzania and inundated
with different seawater/sewage mixtures. Our results show that sewage loads led to a modification
of the overall activity budget of the crab community as a result of increased hypertrophic conditions
(high COD, increased chlorophyll-a concentrations). During their activity period, crabs inside contaminated
mesocosms seemed to satisfy their feeding demand faster than those of the control cells, spending
a significant longer time in other activities like courtship and territorial defence. Apart from being a good
biological indication of ecosystem eutrophication, such a reduced foraging activity by fiddler crabs also
depresses their sediment bioturbation activity, important factor for the health of mangrove systems, suggesting
practical implications regarding the efficiency of mangrove-based wetlands for treatment of
domestic sewage.
Keywords
Sewage, East Africa, Mangrove, Fiddler crab, Behaviour, Ecosystem engineer