MEPS 310:15-24 (2006)  -  doi:10.3354/meps310015

Movement of carbon among estuarine habitats: the influence of saltmarsh patch size

Michaela A. Guest1,2,3,*, Rod M. Connolly1,2

1Centre for Aquatic Processes & Pollution, and School of Environmental & Applied Sciences, Gold Coast Campus, Griffith University, PMB 50, Gold Coast Mail Centre, Queensland 9726, Australia
2Cooperative Research Centre for Coastal Zone, Estuary and Waterway Management, Queensland 4068, Australia
3Present address: Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, GPO Box 252-49, Hobart 7001, Tasmania, Australia

ABSTRACT: We used carbon stable isotopes to examine the influence of the size of saltmarsh patches on the trophic contribution of saltmarsh grass and mangroves to 2 species of resident crabs (Parasesarma erythrodactyla and Australoplax tridentata). Crabs were collected at different distances across the saltmarsh–mangrove interface at each of 10 saltmarshes of different sizes (0.01 to 8.10 ha) adjacent to mangrove forests (each >4 ha). The δ13C values of crabs at all 10 marshes fitted a sigmoidal curve, with rapidly changing δ13C values across the saltmarsh–mangrove interface (the transition zone). The size of saltmarsh patches had a significant effect on δ13C values of P. erythrodactyla collected in the saltmarsh, with a similar trend shown by A. tridentata. On large saltmarshes (>0.4 ha), δ13C values of crabs (P. erythrodactyla, –15.9‰; A. tridentata, –15.4) collected >5 m onto the saltmarsh matched that of the saltmarsh grass Sporobolus virginicus (–15.5). Carbon movement and assimilation by crabs was limited to <5 m. On small saltmarshes (<0.3 ha), δ13C values of saltmarsh crabs (–18.1 and –16.8, respectively) were depleted, indicating assimilation of carbon from S. virginicus, but also from a more depleted allochthonous source, e.g. mangroves (–28.1), microphytobenthos (–23.7), or phytoplankton (ca. –20). Saltmarsh patch size did not affect the extent of carbon movement or assimilation by crabs in mangroves. Given that habitat patch size can influence pathways of carbon supply to invertebrates, the role of estuarine habitats in food webs cannot be assumed to be independent of the size and configuration of habitats.

KEY WORDS: Landscape ecology · Trophic ecology · Stable isotopes · Avicennia marina · Crustacea

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