Marine Research Findings of the VECTORS Project

This website provides access to the research results of the VECTORS project, which can be used to support marine management decisions, policies and governance as well as future research and investment. VECTORS was a large scale project that brought together more than 200 expert researchers from 16 different countries. It examined the significant changes taking place in European seas, their causes, and the impacts they will have on society.

Habitat alteration and community changes by aggregate extraction

The extraction of marine aggregates may represent a challenge for biodiversity if mining projects are carried out in under-represented areas within the geographical area and / or if they impact sensitive species or habitats (spawning grounds, nursery areas, biogenic reefs etc.). The original habitat of the geographical area off Dieppe is constituted of dunes of coarse shelly sands colonised by a characteristic community with Amphioxus. Big bivalves (dog cockle) and foraging fish species (sandeels) inhabiting this sediment are the dominant prey for fish predators like seabass and plaice; sandeels are the dominant fish species of the reference habitat.

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After ten years of extensive extraction, the number of EUNIS habitats and associated communities has increased with creation of new structural and functional habitats.

The extraction perimeter is characterised by the presence of pebble crests created during exploitation (EUNIS Habitat A5.121). These crests are quickly colonised by an epifauna of opportunistic species like the tubicolous worm Pomatoceros which represents more than 90 % of the new benthic community; the main accompanying species are the crabs Pisidia and Galathea which are the dominant prey species for black seabream, cod and gurnards which characterise the new fish community of the extraction site.

The regular occurence of cod in the extraction areas both in Dieppe and in Baie de Seine is of interest as this species is on the red OSPAR list of threatened species. This occurence has a trophic explanation, as fallow areas constitute important feeding areas.

The surrounding area which is regularly affected by the deposition of fine sands from overspill, shows a finer sediment cover than the original coarse sand, but this sediment is more unstable in the local context of strong tidal currents; only a few species, characterising fine mobile sands (errant annelids, small bivalves) inhabit this deposition area (EUNIS Habitat A5.231) with sole and plaice as main predators.

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Mitigation measures such as low dredging intensity, zoning, and no screening are able to minimize impacts and favour positive interactions for an integrated marine management

A low intensity of extraction can:

  • reduce the impact on the main fish population parameters (species richness, abundance, biomass)
  • provide temporary feeding areas for sole, cod and black seabream (movement into more suitable habitats)
  • increase habitat diversity favouring resilient species of economical value (sole, red mullet)
  • have potential benefits for some OSPAR threatened or protected species (cod) and habitats (Sabellaria reefs)
  • limit the propagation of the invasive mollusc Crepidula.
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In coarse sediments of the eastern Channel, an appropriate extraction strategy can minimise the degradation of the biodiversity and of the function of the marine environment.

  • A low extraction intensity (< 1 h.ha-1.year-1) limits the impact on benthos and fish communities and accelerates the functional restoration of the disturbed area by promoting the benthic recolonisation (Dieppe, Baie de Seine)
  • A spatio-temporal zoning (fallow areas) is favouring the opportunistic recolonisation by epifaunal species which are preys for commercial species like cod, gurnards and black seabream (Dieppe, Baie de Seine);
  • This zoning is an opportunity to increase the local number of habitats (Dieppe).

 

Lead Author:

Michel Desprez
(despzmike@wanadonospamo.fr)
University of Rouen (UR)
Date of research: January 2015

Related articles:

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The Baltic ATLANTIS model and global change

The drivers of a common sole population 

Activities influencing fisher location choice 

Baltic cod recruitment and predation

Changes in herring larvae and environment 1957-2010

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 266445
© Vectors 2015. Coordinated by Plymouth Marine Laboratory.