Mangrove Leaves are Not an Important Source of Dietary Carbon and Nitrogen for Crabs in Temperate Australian Mangroves
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The carbon and nitrogen stable isotope ratios of the mangrove sesarmid crabs Parasesarma erythrodactyla, Paragrapsus laevis, and Helograpsus haswellianus were measured from sites in arid and humid temperate Australia, and compared with potential food sources. Crab stable isotope ratios were uniform and consistent with published values from subtropical Queensland. Fresh and decomposed leaves of the dominant mangrove Avicennia marina were discounted as a potential food source, being too depleted in their δ13C and δ15N signatures compared to crabs to have made a substantial contribution to the diet. A three-source mixing model indicated that fine benthic organic material was the primary food source. Mangrove epiphyte and highly decomposed mangrove leaf material were too depleted in δ15N to be contributing to crab diet.
KeywordsEstuarine Food habits Isotope Sesamaridae Trophic
The authors acknowledge Mrs. Gitanjali Katrak, School of Biological Science, Flinders University, SA for collecting crab and mangrove leaves from Middle Beach mangrove forest, SA. Dr. Suzanne Hollins (ANSTO) for advice and logistic support. The Department of Environment Climate Change and Water (NSW) provided access to the Towra Point sites. Crab samples were collected under NSW Scientific Collection Permit P06/0005. The helpful comments of two anonymous referees are gratefully acknowledged.
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