The effects of marine sand and gravel extraction on the macrobenthos at a commercial dredging site (results 6 years post-dredging)

Abstract

2005. The effects of marine sand and gravel extraction on the macrobenthos at a commercial dredging site (results 6 years post-dredging). e ICES Journal of Marine Science, 62: 145e162.Benthic recolonization was investigated at a site historically used for the extraction of marine sand and gravel. The main objective was to assess the effects of different levels of dredging intensity on the recolonization of benthic fauna and sediments. Preliminary observations from this study indicated that the fauna within an area of seabed exposed to high dredging intensities remained in a perturbed state some 4 years after the cessation of dredging. Thereafter, annual monitoring surveys of the benthos and sediments at the ''treatment'' and ''reference'' sites have followed the recolonization process. Results from univariate and multivariate data analyses show that distinct differences in the nature of assemblages at sites exposed to high and lower levels of dredging intensity persist at least 6 years after the cessation of dredging. This paper presents the physical and biological findings 6 years after dredging, together with a generic framework for evaluating postcessation recolonization studies.

Sand, rarer than one thinks

“…Damage is more severe in small river catchments. The same applies to threats to benthic ecosystems from marine extraction (Krause et al, 2010;Desprez et al, 2010;Boyd et al, 2005).…”

“…Dredging and extraction of aggregates from the benthic (sea bottom) zone destroys organisms, habitats and ecosystems and deeply affects the composition of biodiversity, usually leading to a net decline in faunal biomass and abundance (Desprez et al, 2010) or a shift in species composition. Long-term recovery can occur only where original sediment composition is being restored (Boyd et al, 2005).…”

The Puck Bay as an example of deep dredging unfavorably affecting the aquatic environment

“…Dredging has many deleterious environmental effects (Johnston 1981). Simultaneously, its impact depends on the intensity and method of dredging, as well as the environmental condition of the dredge area (Boyd et al 2005, Robinson et al 2005. Direct results of dredging include defaunation of sediment, changes in seabed topography and sediment structure (Gilkinson et al 2003, Seiderer andNewell 1999), release of nutrients and toxins from the sediment to the water column (Falcão et al 2003, Riemann and Hoffman 1991, Su et al 2007, Vale et al 1998, increase in water turbidity (Black andPary 1994, Wu et al 2007).…”

Biogeomorphology of coastal seas

“…However, by knowing the patchy distribution of tube-building worms and the morphodynamics behavior, only correlative relationships could be determined and no causal relationships could be proven. In order to prove causal relationships, the recovery after a human interference in both the morphological and biological system should be monitored, for example after a shore face nourishment , after sand-mining in a sand wave field (Boyd et al, 2005) or after the construction of the Zandmotor in the Netherlands (Mulder and Tonnon, 2010). In general, the benthic community is completely killed after such human interferences (Baptist et al, 2008).…”