Biogeographic and nearshore–offshore trends in isotope ratios of intertidal mussels and their food sources around the coast of southern Africa

Hill, J.M. and McQuaid, C.D. and Kaehler, S. (2006) Biogeographic and nearshore–offshore trends in isotope ratios of intertidal mussels and their food sources around the coast of southern Africa. Marine Ecology Progress Series, 318 . pp. 63-73. ISSN 0171-8630

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There are broad differences in oceanography and primary production around the southern African coast that are likely to give rise to major differences in trophic pathways. Stable isotope ratios provide integrated information on trophic relationships, yet there has been limited research on geographic variation in isotopic composition of marine consumers and their food. In this study, δ13C and δ15N of suspended particulate matter (SPM), intertidal mussels and common macroalgae along the southern African coastline were explored. Nearshore–offshore isotope trends as well as biogeographic and temporal patterns in isotopic ratios of mussel tissue, macroalgae and SPM were investigated at 12 sites along the coast from Namibia to the Mozambique border. SPM exhibited overall trends of nearshore 13C depletion from south-west to north-east along the coastline and from nearshore (0 km) to offshore (10 km) waters, in both cases suggesting a shift from a nearshore signature strongly influenced by macroalgal detritus to one more representative of oceanic phytoplankton. With one exception it was possible, using discriminant analysis, to categorize mussel populations into 4 geographic groups, on the basis of both carbon and nitrogen signatures: the east coast, the south-east coast, the south-west coast and the west coast. Macroalgae showed no consistent biogeographic trends and need to be examined in greater detail to relate nearshore SPM values to living macroalgal signatures. A linear mixing model indicated that mussels along the entire coastline generally demonstrated more than 50% dependence on nearshore carbon and nitrogen, emphasizing the importance of nearshore primary production to intertidal consumers.

Item Type:Article
Additional Information:Currently restricted, the full-text of this article will become accessible in 2011
Uncontrolled Keywords:δ13C; δ15N; Biogeographic trends; Diet; Mussels; Stable isotope analysis; biogeography; bivalve; discriminant analysis; food availability; geographical variation; intertidal community; isotopic ratio; nearshore environment; oceanography; primary production; suspended particulate matter; Mozambique; Namibia; Southern Africa; Sub-Saharan Africa
Subjects:S Agriculture > SH Aquaculture. Fisheries. Angling
Q Science > Q Science (General)
Q Science > QL Zoology
G Geography. Anthropology. Recreation > GC Oceanography
Divisions:Faculty > Faculty of Science > Zoology & Entomology
ID Code:1655
Deposited On:04 May 2010 07:31
Last Modified:06 Jan 2012 16:21
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