MEPS 504:193-205 (2014)  -  DOI: https://doi.org/10.3354/meps10761

ABSTRACT: Temporal variations in stable isotope ratios and fatty acid composition were examined in 3 crustacean species and their potential food sources in a temperate estuary. We hypothesized that the shrimp Palaemon peringueyi, the mud prawn Upogebia africana and the sand prawn Callichirus kraussi have disparate diets due to interspecific differences in metabolism and feeding mode and that diets of the crustaceans all change temporally due to variations in available food. The species with the most variable diet was expected to have the greatest niche differentiation. We sampled the 3 crustaceans and their food sources on occasions spanning 4 seasons. The diet of P. peringueyi changed from a dominance of benthic microalgae in spring and winter to increased contributions of particulate organic matter (POM) in summer, with preferential sequestration of 22:6ω3. U. africana showed a stable dependence on estuarine POM as the main source of its energy, while C. kraussi relied more on marine POM, except in winter, when benthic microalgae was an important energy source. The 2 infaunal prawns showed elevated proportions of 16:1ω7 and 20:5ω3 throughout most of the year, probably originating from diatoms. P. peringueyi showed a different preferred diet than the 2 prawns, resulting in an isotopic niche segregation from the infaunal prawns, but the fatty acid niche of the shrimp overlapped with the prawns. Stable isotope values revealed the temporal variations in the origins and proportions of different food sources contributing to the diet of each species, while fatty acid data provided information on finer-scale trophic interactions. Temporal variations in estuarine consumer diets should be considered in estuarine food web studies whenever possible.

KEY WORDS: Benthos · Diet · Niche · Temporal variation · Shrimps · Prawns · South Africa