Bioturbation, ecosystem functioning and community structure

Abstract

The effect of community structure on the functioning of the ecosystem is an important issue in ecology due to continuing global species loss. The influence of infaunal community structure on the functioning of marine systems is proposed here to act primarily through bioturbation of the sediment. Nutrient concentration in the water column, generated by release from the sediment, was used as a measure of ecosystem functioning. In situ and laboratory experiments showed a significant difference in nutrient concentrations with different species treatments. Bioturbation profiles showing the incorporation of tracer particles also differed between communities with different dominant species. The behavioural differences between infaunal species, generating different modes and rates of bioturbation, are therefore proposed to influence nutrient release. The presence and quantity of bioturbating infauna also influenced the amount of sediment suspended in the water column. The increase in surface area available for microbial activity may generate an increase in nutrient cycling. Abiotic influences on sediment structure, such as flow, may have a similar effect on nutrient concentration. Annular flumes used in both laboratory and in situ experiments to generate flow conditions produced a significant increase in ammonia (NH 4 -N) production in macrofaunal treatments. Flow may influence the behaviour of macrofaunal species, causing changes in NH 4 -N production through modifying bioturbation of the sediment.

Bioturbation and bioirrigation extend the open exchange regions in permeable sediments

“…We conclude that the effect of large burrowing macrofauna is closely linked to the hydrodynamic regime. Large-scale in situ approaches are necessary to detect the full spectrum of bioturbation and bioirrigation effects on the seafloor (Biles et al 2002) because results may diverge from those found in the laboratory (e.g., Papaspyrou et al 2007). At least in semi-exposed fine sands, where a pit-and-mound topography generated by bioturbating infauna is frequently obliterated by water movements, the continuous bioturbation may lead to the maintenance of high sediment permeability that facilitates elevated benthic-pelagic fluxes and thereby affects sedimentary habitat characteristics.…”

“…Manipulated laboratory microcosms are a commonly used approach for the study of the effects of macrofauna on benthic metabolism and sediment-water exchange (e.g., Banta et al 1999), but the exclusion of physical forces has been shown to affect the magnitude of macrofaunal effects (Papaspyrou et al 2007). In situ experimental works remain few (Huettel 1990;D'Andrea et al 2002), presumably due to difficulties in manipulating species composition and measuring oxygen fluxes in an open and fluid system (Biles et al 2002). Moreover, small-scale approaches may alleviate possible effects of macrofaunal activities due to lateral particle and pore-water exchange between manipulated plots and the surrounding sediment, especially in dynamic environments like intertidal sand flats.…”

Influence of temperature on surface sediment disturbance by freshwater fish: a microcosm experiment

“…Benthivorous fish species (e.g., Cyprinus carpio, Abramis brama) are also known to influence directly and indirectly water quality (i.e., nutrients, suspended solids and organic matter) and biological communities (e.g., macrophytes, phytoplankton, zooplankton and macro-invertebrates) through nutrients and organic matter release from the resuspension of sediments to the water column due to bioturbation (i.e., by feeding) but also excretion (Breukelaar et al, 1994;Persson and Svensson, 2006a;Roozen et al, 2007;Matsuzaki et al, 2009). Hence, changes in SSD by benthic fish in response to water warming could lead to a wide range of disturbances in ecosystem functioning, among which changes in primary productivity by a spatial redistribution of the micro-phytobenthos (Orvain et al, 2004), increases of the water turbidity (Breukelaar et al, 1994;Matsuzaki et al, 2009), changes in nutrient recycling (Biles et al, 2002;Ieno et al, 2006), modifications in the texture of the sediment (Montserrat et al, 2009) or redistribution of macro-invertebrates in the first centimetres of the substrate (Persson and Svensson, 2006b;Maire et al, 2010).…”

Novel method to concurrently sample the planktobenthos and benthos

“…The rate of nutrient cycling depends not only on depth, ocean currents, and seafloor properties but also on the associated biological communities (Biles et al 2002). The MAPS seems an appropriate method with which to study benthic-pelagic coupling, as it facilitates the segregated collection of animals from the seafloor and immediately above.…”