biological vs. physical mixing effects on benthic food web dynamics生物和物理混合对底栖生物食物网动力学的影响.pdf

Biological vs. Physical Mixing Effects on Benthic Food Web Dynamics 1 2 1 2 2,3 Ulrike Braeckman *, Pieter Provoost , Tom Moens , Karline Soetaert , Jack J. Middelburg , Magda Vincx1, Jan Vanaverbeke1 1 Department of Biology, Marine Biology Section, Ghent University, Ghent, Belgium, 2 Netherlands Institute of Ecology (NIOO-KNAW), Centre for Estuarine and Marine Ecology, Yerseke, The Netherlands, 3 Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands Abstract Biological particle mixing (bioturbation) and solute transfer (bio-irrigation) contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria) and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter assimilation by the metazoan lower part of the food web through niche establishment (i.e., ecosystem engineering) or rather deprives them from food sources, is so far unclear. We investigated the effects of the ecosystem engineers Lanice conchilega (bio- irrigator) and Abra alba (bioturbator) compared to abiotic physical mixing events on survival and food uptake of nematodes after a simulated phytoplankton bloom. The 13C labelled diatom Skeletonema costatum was added to 4 treatments: (1) microcosms containing the bioturbator, (2) microcosms containing the bio-irrigator, (3) control microcosms and (4) microcosms with abiotic manual surface mixing. Nematode survival and subsurface peaks in nematode