Movement of carbon among estuarine habitats and its assimilation by invertebrates
- 464 Downloads
We measured the extent of movement of carbon and its assimilation by invertebrates among estuarine habitats by analysing carbon stable isotopes of invertebrates collected along transects crossing the boundary of two habitats. The habitats were dominated by autotrophs with distinct isotope values: (1) mudflats containing benthic microalgae (mean −22.6, SE 0.6‰) and (2) seagrass and its associated epiphytic algae (similar values, pooled mean −9.8, 0.5‰). Three species of invertebrates were analysed: a palaemonid shrimp, Macrobrachium intermedium, and two polychaete worms, Nephtys australiensis and Australonereis ehlersi. All species had a similar narrow range of isotope values (−9 to −14‰), and showed no statistically significant relationship between position along transect and isotope values. Animals were relying on carbon from seagrass meadows whether they were in seagrass or on mudflats hundreds of metres away. Particulate organic matter collected from superficial sediments along the transects had similar values to animals (mean −11.1, SE 1.3‰) and also showed no significant relationship with position. The isotope values of these relatively immobile invertebrates and the particulate detritus suggest that carbon moves from subtidal seagrass meadows to mudflats as particulate matter and is assimilated by invertebrates. This assimilation might be direct in the case of the detritivorous worm, A. ehlersi, but must be via invertebrate prey in the case of the carnivorous worm, N. australiensis and the scavenging shrimp, M. intermedium. The extent of movement of carbon among habitats, especially towards shallower habitats, is surprising since in theory, carbon is more likely to move offshore in situations such as the current study where habitats are in relatively open, unprotected waters.
KeywordsCrustacea Estuary Polychaeta Stable isotopes Trophic subsidy
We thank R. Diocares for mass spectrometry assistance and the marine ecology group at Griffith University for improving the manuscript. We gratefully acknowledge funding support from Fisheries R&D Corporation and the Cooperative Research Centre for Coastal Zone, Estuary and Waterway Management.
- Boto KG, Bunt JS (1981) Tidal export of particulate organic matter from a North Australian mangrove system. Estuar Coast Shelf Sci 16:379–402Google Scholar
- Glasby CJ, Hutchings PA, Fauchald K, Paxton H, Rouse GW, Watson-Russell CW, Wilson RS (2000) Class polychaeta. In: Beesley PL, Ros GJB, Glasby CJ (eds) Polychaetes and allies. Fauna of Australia, vol 4A. CSIRO Publishing, Melbourne, pp 1–196Google Scholar
- Kneib R (2000) Saltmarsh ecoscapes and production transfer by estuarine nekton in the southeastern United States. In: Weinstein MP, Kreeger DA (eds) Concepts and controversies in tidal marsh ecology. Kluwer, DordrechtGoogle Scholar
- Nixon SW (1980) Between coastal marshes and coastal waters: a review of 20 years of speculation and research on the role of salt marshes in estuarine productivity and water chemistry. In: Hamilton P, MacDonald KB (eds) Estuarine and wetland processes. Plenum, New York, pp 437–525Google Scholar
- Odum WE, Heald EJ (1972) Trophic analyses of an estuarine mangrove community. Bull Mar Sci 22:671–738Google Scholar
- Odum WE, Fisher JS, Pickrel JC (1979) Factors controlling the flux of particulate organic carbon from estuarine wetlands. In: Livingston RJ (ed) Ecological processes in coastal and marine systems. Plenum, New York, pp 69–79Google Scholar
- Peterson BJ, Howarth RW (1987) Sulfur, carbon, and nitrogen isotopes used to trace organic matter flow in the salt-marsh estuaries of Sapelo Island, Georgia. Limnol Oceanogr 32:1195–1213Google Scholar
- Twilley RR (1988) Coupling of mangroves to the productivity of estuarine and coastal waters. In: Jansson BO (ed) Coastal-offshore ecosystem interactions. Springer, Berlin Heidelberg New York, pp 155–180Google Scholar
- Walsh CJ (1994) Ecology of epifaunal caridean shrimps in the Hopkins River estuary, and the role of estuaries in the life history of the atyid Paratya australiensis in south-eastern Australia. PhD thesis, Deakin University, p 276Google Scholar