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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 496463
Title Ecosystem-based design rules for marine sand extraction sites
Author(s) Jong, Maarten F. de; Borsje, Bas W.; Baptist, Martin J.; Wal, Jan Tjalling van der; Lindeboom, Han J.; Hoekstra, Piet
Source Ecological Engineering 87 (2016). - ISSN 0925-8574 - p. 271 - 280.
DOI https://doi.org/10.1016/j.ecoleng.2015.11.053
Department(s) IMARES Ecosystemen
IMARES Onderzoeksformatie
IMARES Maritiem
Aquatic Ecology and Water Quality Management
Publication type Refereed Article in a scientific journal
Publication year 2016
Keyword(s) Bed shear stress - Demersal fish - Epifauna - Infauna - Macrozoobenthos - Sand extraction - Sediment characteristics - Sedimentation rate
Abstract

The demand for marine sand in the Netherlands as well as globally is increasing. Over the last decades, only shallow sand extraction of 2m below the seabed was allowed on the Dutch Continental Shelf (DCS). To guarantee sufficient supply and to decrease the surface area of direct impact, the Dutch authorities started to promote sand extraction depths over 2m for sand volumes over 10 millionm3. The ecological effects of deep sand extraction, however, are still largely unknown. Therefore, we investigated short-term effects (0-2.5y) of deep sand extraction (20-24m) and compared these with other case studies such as, regular shallow sand extraction on the DCS (2m) and an 8m deepened shipping lane. For intercomparison between case studies we used tide-averaged bed shear stress as a generic proxy for environmental and related ecological effects. Bed shear stress can be estimated with a two-dimensional quadratic friction law and showed a decrease from 0.50 to 0.04Nm-2 in a borrow pit in 20m deep water and extraction depths up to 24m. Macrozoobenthos in a borrow pit with a tide-averaged bed shear stress of around 0.41Nm-2 is expected to return back to pre-extraction conditions within 4-6 year. When tide-averaged bed shear stress decreases below 0.17Nm-2 enhanced macrozoobenthic species richness and biomass can occur. Below a tide-averaged bed shear stress of 0.08Nm-2, increasing abundance and biomass of brittle stars, white furrow shell (Abra alba) and plaice (platessa platessa) can be expected. Below 0.04Nm-2, an overdominance and high biomass of brittle stars can be expected whereas demersal fish biomass and species composition may return to reference conditions. Next to changes in faunal composition, a high sedimentation rate can be expected. Ecological data and bed shear stress values were transformed into ecosystem-based design (EBD) rules. At higher flow velocities and larger water depths, larger extraction depths can be applied to achieve desired tide-averaged bed shear stresses for related ecological effects. The EBD rules can be used in the early-design phases of future borrow pits in order to simultaneously maximise sand yields and decrease the surface area of direct impact. The EBD rules and ecological landscaping can also help in implementing the European Union's Marine Strategy Framework Directive (MSFD) guidelines and moving to or maintaining Good Environmental Status (GES).

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