Benthic faunal responses to variations in patch density and patch size of a suspension-feeding bivalve
Journal of Experimental Marine Biology and Ecology
Vol. 216, Issue. 1-2, pp.171-189, 1997
Robert B. Whitlatch a , Anson H. Hines b, Simon F. Thrush a, Judi E. Hewitt a and Vonda Cummings a
a National Institute of Water and Atmospheric Research, 100 Aurora Terrace Road, P.O. Box 11-115 Hamilton New Zealand
b Smithsonian Environmental Research Centre, P.O. Box 28 Edgewater, MD 21037 USA
Responses of benthic macrofauna and epibenthic predators/sediment disturbers to controlled density (0, 12, 120, 600 and 1200 individuals m -2 ) and patch size (0.25, 1.0 and 9.0 m 2 ) manipulations of the venerid bivalve Austrovenus stutchburyi (Gray) were examined on an intertidal sandflat. Bivalve density manipulations greater than 600 m -2 had a mixed influence on macrofauna colonisation; two species were reduced, three enhanced and three were unaffected. There was no clear functional group-related pattern as to which species were affected by Austrovenus . The most pronounced influence of high bivalve densities was the reduction in the abundance and alteration of the size-structure of post-set (ca. 250-360 mm) tellinid bivalves, Macomona liliana Iredale. Patch size manipulations of Austrovenus had no measurable effect on macrofauna colonisation, probably because patch density (120 bivalve m -2 ) was too low. While a variety of epibenthic predators were present at the study site, Austrovenus stutchburyi mortality estimates in both experiments were relatively low (0.01-0.03% individuals lost day -1 ) and were independent of both density and patch size. In contrast, the proportion of nipped bivalve siphons was relatively high (11-37%) in both experiments. While proportions of nipped siphons were similar across the range of manipulated densities, siphon browsing was more than 2 times higher in 9.0 m 2 plots than 0.25 m 2 plots. Scale-dependent foraging of sub-lethal marine benthic predators is previously unreported and our results illustrate the necessity for conducting studies on predator-prey dynamics at ecologically meaningful spatial scales for both the predator and prey species.
Author Keywords: Sandflat; Colonisation; Adult-juvenile interaction; Patch dynamics