Estuaries and Coasts DOI 10.1007/s12237-014-9857-7
Spatial Distributions of Grazing Activity and Microphytobenthos Reveal Scale-Dependent Relationships Across a Sedimentary Gradient Daniel R. Pratt & Conrad A. Pilditch & Andrew M. Lohrer & Simon F. Thrush & Casper Kraan
Received: 14 February 2014 / Revised: 29 June 2014 / Accepted: 8 July 2014 # Coastal and Estuarine Research Federation 2014
Abstract The density, spatial structure and functional roles of macrofaunal and microphytobenthic (MPB) communities change across sedimentary gradients. Grazing by macrofauna can impose considerable top-down control on MPB biomass at the scale of the animal’s feeding ambit (cm scale), yet how relationships between deposit feeders and MPB scale up across such transitional environments (10’s m scale) is poorly understood. We determined the relationship between sediment chlorophyll-a concentration (a proxy of MPB biomass), distance to feeding traces (a proxy of recent deposit feeding activity) made by the tellinid bivalve Macomona liliana (at cm scale) and macrofaunal densities (at 10’s m scale) across a sediment mud content gradient. Correlative relationships, estimated by generalised least-squares regression, between recent deposit feeding activity and MPB biomass were scale dependent and significant only at the site (10’s m) scale. MPB biomass declined by 28 % as coverage of feeding traces increased from 2 to 28 %, with feeding trace area contributing significantly to variation in chlorophyll-a (std. coefficient= −0.24, p=0.01). However, the interaction term between the Communicated by Richard W. Osman D. R. Pratt : C. A. Pilditch Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton, New Zealand D. R. Pratt (*) : A. M. Lohrer : S. F. Thrush : C. Kraan National Institute of Water and Atmospheric Research, P.O. Box 11-115, Hamilton, New Zealand e-mail:
[email protected] S. F. Thrush Institute of Marine Science, University of Auckland, Private Bag 92019, Auckland, New Zealand C. Kraan Biometry and Environmental System Analysis, University of Freiburg, 79106 Freiburg, Germany
density of the suspension-feeding clam Austrovenus stutchburyi and sediment mud content explained a larger amount of the variability (std. coefficient=0.72, p
