MEPS 399:173-186 (2010)  -  doi:10.3354/meps08336

Role of macrofauna functional traits and density in biogeochemical fluxes and bioturbation

Ulrike Braeckman1,*, Pieter Provoost2, Britta Gribsholt3, Dirk Van Gansbeke1, Jack J. Middelburg2, Karline Soetaert2, Magda Vincx1, Jan Vanaverbeke1

1Ghent University, Department of Biology, Marine Biology Section, Krijgslaan 281/S8, 9000 Ghent, Belgium
2Netherlands Institute of Ecology (NIOO-KNAW), Centre for Estuarine and Marine Ecology, PO Box 140, 4400 AC Yerseke,  The Netherlands
3Center for Geomicrobiology, Department of Biological Sciences, Aarhus University, Ny Munkegade, Building 1540, 8000 Aarhus C, Denmark

ABSTRACT: The importance of different functional traits of macrobenthos in benthic processes of the Southern Bight of the North Sea was investigated to estimate the effects of density declines and species loss on benthic ecosystem functioning. Two laboratory experiments were performed: before (winter, temperature = 10°C) and after (summer, temperature = 18°C) sedimentation of the spring phytoplankton bloom. Single species treatments of key species (Abra alba, Lanice conchilega and Nephtys sp.) with different functional traits were added to microcosms at 3 density levels (natural, lower, lowest) to account for possible density declines. Sediment–water exchanges of oxygen and nutrients, denitrification and bioturbation were measured. In absence of fauna, benthic mineralisation in the summer experiment was 2.0 times higher than in winter. Fauna stimulated microbial respiration more in summer (up to 100% in L. conchilega treatments) than in winter (negligible fauna effect). As chlorophyll a concentrations were similar in both seasons, the stronger fluxes in summer must be explained by a higher macrobenthic activity owing to the elevated temperature and better condition of the animals. Stimulation of mineralisation by the 3 species in the microcosms was different, and behaviour-related. Owing to its irrigation activity, the tube dweller L. conchilega had more pronounced influences on benthic respiration, nutrient release and denitrification than did the biodiffusers, A. alba and Nephtys sp. A. alba appeared to be a more effective bioturbator than Nephtys sp. Processes such as benthic respiration, nutrient fluxes, denitrification and bioturbation seem to be related to animal densities and therefore decreases in densities can possibly have implications for ecosystem functioning.

KEY WORDS: Ecosystem functioning · Macrobenthos · Functional traits · Density · Temporal variability · Lanice conchilega · Abra alba · Nephtys sp.

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Cite this article as: Braeckman U, Provoost P, Gribsholt B, Van Gansbeke D and others (2010) Role of macrofauna functional traits and density in biogeochemical fluxes and bioturbation. Mar Ecol Prog Ser 399:173-186

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