Leaf-burying crabs: Their influence on energy flow and export from mixed mangrove forests ( Rhizophora spp.) in northeastern Australia

Abstract

Field experiments which compared the decomposition rate of leaves of the mangrove Rhizophora stylosa Griff, in the presence and absence of the leaf-consuming crab Sesarma messa (Campbell) showed that, by burying and consuming leaves, crabs had a highly significant effect on weight loss from leaves. Seasonal measurements of the rates of leaf litter fall and leaf removal (= burial plus consumption) by crabs during day- and night-time periods of low tide in low to mid-intertidal mixed Rhizophora forest showed that crabs could remove at least 154g·m −2·yr −1 or 28% of the annual leaf fall of 556g·m −2·yr −1. Crabs consumed >78% of the leaf material within 6 h of burial. These results show that an earlier attempt to measure detrital export from mangrove forests in northeastern Australia over-estimated export by at least 22% by ignoring leaf removal by crabs. In addition, the results indicate that current models of energy flow in mangrove forests, based mainly on work in Florida, must be altered to include the leaf litter → crab trophic link in order to describe accurately the food chains of mangrove forests in the Indo-West Pacific region.