Preliminary Data on the Bioturbation Activity of Hediste Diversicolor (Polychaeta, Nereididae) from the Loire Estuary, France

ABSTRACT

The ragworm Hediste diversicolor (O. F. Müller, 1776) plays a key role in the estuarine water-sediment interface. This scientific project comes under the framework of the International network Nereis Park Experiment gathering 27 laboratories from all over the world. The experiments were carried out concurrently in spring 2007 using a common protocol. In the Loire estuary, the samples were collected in the intertidal zone of the Saint-Nazaire Bridge. During the field experiment, we estimated the surface area of the burrow walls (Sb) value varied from Sb = 0.26 m2.m-2 to 2.18 m2.m-2 (mean Sb = 0.75 m2.m-2), and the pumping rate (Pr) value from Pr = 0.9 l.d-1m-2 to 7.7 l.d-1 m-2 (mean value Pr = 2.7 l.d-1m-2). The density and the biomass of H. diversicolor populations largely controlled the amount of reworked sediment. In the laboratory, we estimated the pseudo-diffusive mixing, Db value varied from Db = 1.2 to 1.6 (mean Db = 1.5). The non-local transport (r) from the upper layers to the bottom of the tubes varied from r = 1 to 7.2 (mean r = 4.3). A positive relationship could be established between Db and the temperature while on the contrary a negative relationship could be established between the Db and biomass. It seems that small individuals are more efficient reworkers than big ones.

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