Sediment reworking by marine benthic species from the Gullmar Fjord (Western Sweden): Importance of faunal biovolume

Abstract

In order to compare and quantify sediment reworking activities by different species/functional groups of macrofauna, a laboratory experiment was carried out with species from the Gullmarsfjord (Western Sweden). Monospecific communities of Amphiura filiformis, Echinocardium cordatum, Scalibregma inflatum and Abra nitida were introduced in experimental mesocosms, with identical densities (795 ind. m−2), for 10 days. Sediment reworking was studied by quantifying downward and upward movements of fluorescent inert tracers (luminophores). Luminophores with different colour were initially deposited both at the sediment surface and within the sediments. Population biomass and biovolume were also determined. Surface tracers reworking coefficients ranged from 0.6 to 2.2 cm2 y−1 and 0.9 to 4.1 y−1, respectively for the biodiffusive-like and non-local transports. Calculated biodiffusive-like coefficient was between 1.0 and 2.3 cm2 y−1 for the deep tracers. For both tracers, the E. cordatum population presented the highest reworking coefficients. Among the morphological and/or ethological parameters that could determine overall patterns of reworking and differences between species, results have shown a direct relationship between the apparent biodiffusive mixing and the biovolume of the individuals (Db=0.35 ⁎ Biovolume). This suggests that the biovolume of macrofauna may allow a rough estimate of the biodiffusive-like reworking intensity of particles deposited on the sediment surface.