New Zealand Journal of Marine and Freshwater Research abstracts
Macroinvertebrate diet in intertidal seagrass and sandflat communities: a study
using C, N, and S stable isotopes
Daniel Leduc1
P. Keith Probert1
Russell D. Frew2
Catriona L. Hurd3
1 Department of Marine Science
2 Department of Chemistry
3 Department of Botany
University of Otago
P.O. Box 56
Dunedin, New Zealand
email: ledda951@student.otago.ac.nz
Abstract Most seagrass community food-web studies using stable isotopes
have been carried out in subtidal habitats during one sampling event. We used
C, N, and S stable isotopes to characterise the diet of the dominant macroinvertebrates
found in intertidal Zostera capricorni and sandflat communities of southern
New Zealand in late summer and winter. The range of d13C and d34S values for Z.
capricorni was wide (>5‰), which highlights the importance of accounting
for spatial and temporal variability in primary producer isotopic signatures.
The range of d15N values for Z. capricorni was comparatively small (<1‰).
Mixing models based on d13C and d15N signatures suggested that Z. capricorni was
a potentially important contributor (24–99%) to the diet of most consumers
sampled at the seagrass site, whereas microphytobenthos dominated the diet of
the same consumers at the sandflat site. The main exception was the bivalve Austrovenus
stutchburyi, which had a diet consisting mostly (up to 85%) of Ulva and Polysiphonia spp.
at both sites. S isotopes proved to be of limited use owing to the difficulty
of sampling microphytobenthos and to potential non-dietary sources of 34S-depleted
sulfur to consumers. Mixing models also suggested that Z. capricorni contributed
more to the diet of deposit feeders in August (late winter) than in March (late
summer).
Keywords intertidal; food web; Zostera capricorni; Austrovenus
stutchburyi; macroinvertebrates; detrital pathway; New Zealand; temporal
variation
New Zealand Journal of Marine and Freshwater Research, 2006, Vol. 40:
615–629
0028–8330/06/4004–0615 © The Royal Society
of New Zealand 2006
M06042; Online publication date 15 November 2006. Received 12 July
2006; accepted 13 September 2006
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