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Spatial patterns in gravel habitats and communities in the central and eastern English Channel

Spatial patterns in gravel habitats and communities in the central and eastern English Channel
Spatial patterns in gravel habitats and communities in the central and eastern English Channel
The distribution of sediment type and benthic communities in the central and eastern English Channel is shown to be polarised around a distinctive local hydrodynamic feature. The seabed in the region includes an extensive area of gravel substrate which is both an important habitat for benthic marine fauna and a valuable source of material for the marine aggregate industry. Effective management of the area is predicated on an understanding of whether it represents a single homogeneous unit, or several different units that may need to be managed in different ways. The aim of this study was to provide information that would inform such management decisions. Spatial patterns in gravel habitats and communities were studied by investigating the physical environment through modelled and empirical data, and the distribution of infauna and epifauna along an east-west trending transect. A common spatial pattern was observed in both physical and biological parameters, but rather than indicating a simple longitudinal gradient, there was a distinct polarisation around a central feature, a bedload parting (BLP) zone situated between the Isle of Wight and Cotentin peninsula. Sediments and communities at the eastern and western ends of the transect were more similar to each other than to those in the middle. The strong hydrodynamic regime in the BLP area controls sediment distribution, transporting finer material, mainly sand, away from the mid transect area. The pattern in sand content of the substrate mirrors the magnitude of the potential bedload transport, which is complex in this region due to the interplay between the M 2 and M 4 tidal constituents and produced a series of erosional and depositional zones. The structure of benthic communities reflected the local substrate and hydrodynamic conditions, with sponges observed among the stable substrates and stronger currents that characterised the mid transect area, while infauna became more diverse towards the ends of the transect where substrates were more mobile. We conclude that the area should not be considered as a homogeneous unit for management purposes, despite its apparent uniformity on contemporary seabed sediment maps.
Aggregate dredging, Benthos, Gravel, Seafloor mapping, United Kingdom
0272-7714
118-128
Coggan, Roger
ba28145e-50b1-40e9-9d0f-6b45e07fb426
Barrio Froján, Christopher R.S.
4935e7ee-ac0f-41bd-b00b-2c5806561d74
Diesing, Markus
384e066e-5654-4514-8317-50e681b114d5
Aldridge, John
b6c032b3-89ec-40ca-b3b1-e562cba93b7d
Coggan, Roger
ba28145e-50b1-40e9-9d0f-6b45e07fb426
Barrio Froján, Christopher R.S.
4935e7ee-ac0f-41bd-b00b-2c5806561d74
Diesing, Markus
384e066e-5654-4514-8317-50e681b114d5
Aldridge, John
b6c032b3-89ec-40ca-b3b1-e562cba93b7d

Coggan, Roger, Barrio Froján, Christopher R.S., Diesing, Markus and Aldridge, John (2012) Spatial patterns in gravel habitats and communities in the central and eastern English Channel. Estuarine, Coastal and Shelf Science, 111 (10), 118-128. (doi:10.1016/j.ecss.2012.06.017).

Record type: Article

Abstract

The distribution of sediment type and benthic communities in the central and eastern English Channel is shown to be polarised around a distinctive local hydrodynamic feature. The seabed in the region includes an extensive area of gravel substrate which is both an important habitat for benthic marine fauna and a valuable source of material for the marine aggregate industry. Effective management of the area is predicated on an understanding of whether it represents a single homogeneous unit, or several different units that may need to be managed in different ways. The aim of this study was to provide information that would inform such management decisions. Spatial patterns in gravel habitats and communities were studied by investigating the physical environment through modelled and empirical data, and the distribution of infauna and epifauna along an east-west trending transect. A common spatial pattern was observed in both physical and biological parameters, but rather than indicating a simple longitudinal gradient, there was a distinct polarisation around a central feature, a bedload parting (BLP) zone situated between the Isle of Wight and Cotentin peninsula. Sediments and communities at the eastern and western ends of the transect were more similar to each other than to those in the middle. The strong hydrodynamic regime in the BLP area controls sediment distribution, transporting finer material, mainly sand, away from the mid transect area. The pattern in sand content of the substrate mirrors the magnitude of the potential bedload transport, which is complex in this region due to the interplay between the M 2 and M 4 tidal constituents and produced a series of erosional and depositional zones. The structure of benthic communities reflected the local substrate and hydrodynamic conditions, with sponges observed among the stable substrates and stronger currents that characterised the mid transect area, while infauna became more diverse towards the ends of the transect where substrates were more mobile. We conclude that the area should not be considered as a homogeneous unit for management purposes, despite its apparent uniformity on contemporary seabed sediment maps.

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More information

Published date: 1 October 2012
Additional Information: Funding Information: This study draws on work funded by the UK's Department for Environment, Food and Rural Affairs under the project ME1102 ‘Broadscale mapping of hard substrates in the central English Channel: providing an evidence base to support regional management of aggregate resources and the designation of SACs relating to Annex 1 reef habitats’. We acknowledge the provision of data from studies funded by Marine Environmental Protection Fund (MEPF) ; a research programme delivered by the Aggregate Levy Sustainability Fund in the UK, specifically MEPF project 04/01 ‘The Eastern English Channel Marine Habitat Map ( James et al., 2007 ) and MEPF 08/02 ‘The South Coast Regional Environmental Characterisation’ ( James et al., 2010 ). We also wish to acknowledge the contribution to the video analysis work made by Matthew Curtis of Cefas, the statistical advice provided by Jon Barry (Cefas) and the constructive comments provided by three anonymous referees.
Keywords: Aggregate dredging, Benthos, Gravel, Seafloor mapping, United Kingdom

Identifiers

Local EPrints ID: 479894
URI: http://eprints.soton.ac.uk/id/eprint/479894
ISSN: 0272-7714
PURE UUID: e2450a1a-505f-4d91-8263-b2771b13869f
ORCID for Christopher R.S. Barrio Froján: ORCID iD orcid.org/0000-0001-5562-5508

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Date deposited: 28 Jul 2023 16:43
Last modified: 18 Mar 2024 04:11

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Contributors

Author: Roger Coggan
Author: Christopher R.S. Barrio Froján ORCID iD
Author: Markus Diesing
Author: John Aldridge

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