Influence of environmental cycles upon a seagrass caridean shrimp assemblage

ABSTRACT. – Seagrass meadows are an ecologically and economically important resource throughout the Indo-Pacifi c bio-region, but ecological understanding of their faunal assemblages remains largely lacking, with faunal research mostly focussed upon studies of fi sh. The present study investigated the short-term temporal dynamics of caridean shrimp in relation to diel, tidal and lunar cycles. Such assemblages are important given their link between primary production and higher trophic levels such as fi sh. Caridean shrimp were found to be at maximal abundance and diversity (Hill’s N2) at night and during the waxing moon, increasing by a factor of 4 at night, with assemblage structure signifi cantly infl uenced by both these factors. Although subtle changes in daily tidal height had little effect upon caridean assemblages, it is thought that the lunar changes that consequentially affect tides (spring to neaps) were key infl uences upon why caridean shrimp are in greater abundance during the waxing moon. Discussed is the potential for caridean shrimp to undertake inter-habitat migrations in relation to these environmental cycles.