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Marine Ecology Progress Series

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MEPS 369:193-204 (2008)  -  DOI:

Stable isotope monitoring of benthic–planktonic coupling using salt marsh fish

Brian Fry1,*, Matthew Cieri2, Jeff Hughes3, Craig Tobias4, Linda A. Deegan5, Bruce Peterson5

1Department of Oceanography and Coastal Sciences, LSU, Baton Rouge, Louisiana 70803, USA
2Maine Department of Marine Resources, PO Box 8, McKnown Point Road, West Boothbay Harbor, Maine 04575, USA
3Department of Biological Sciences, Wellesley College, 106 Central Street, Wellesley, Massachusetts 02481, USA
4Department of Earth Sciences, University of North Carolina-Wilmington, Wilmington, North Carolina 28403, USA
5Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA

ABSTRACT: Salt marshes are important coastal ecosystems whose trophic function can be monitored with stable isotopes of abundant fish biosentinel species such as the mummichog Fundulus heteroclitus and the Atlantic silverside Menidia menidia. We compared movement patterns and feeding biology of these species in the summers of 1999 and 2000 in the Rowley River salt marsh estuary north of Boston, Massachusetts, USA. A 15N tracer addition experiment showed that fish of both species were more resident than transient, with mummichogs resident at scales of 1 km or less. Natural abundance stable isotope C, N, and S distributions showed that mummichogs feed more strongly in the benthic food web while silversides feed more in the planktonic food web, with % benthic feeding respectively averaging 58 ± 5 and 32 ± 3% (mean ± 95% confidence limit, CL). For both species, isotope results indicated considerable individual specialization in foraging behavior, likely related to use of channel habitat versus use of the marsh. Power analysis showed that measuring 3 composite samples each comprising 10 to 15 individual fish should provide relatively low errors of 0.5‰ (95% CL) or less around stable isotope averages. Use of such composite samples in monitoring programs will allow detection of significant temporal and spatial changes in benthic-planktonic coupling for salt marsh ecosystems, as recorded in average fish diets. Analyzing some individual fish also is recommended to obtain more detailed information on fish food sources, feeding specializations, and end-member isotope values used in estimating importance of benthic and planktonic food sources.

KEY WORDS: Stable isotope analysis . Salt marsh . Fish . Monitoring . Power analysis . Benthic microalgae . Spartina

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Cite this article as: Fry B, Cieri M, Hughes J, Tobias C, Deegan LA, Peterson B (2008) Stable isotope monitoring of benthic–planktonic coupling using salt marsh fish. Mar Ecol Prog Ser 369:193-204.

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