Marine Ecology Jetty Es Chapter 10

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Hinkley Point C Preliminary Works 10 - 1 Environmental Statement

Temporary Jetty Development November 2010

10 MARINE ECOLOGY

10.1 Introduction

10.1.1 This Chapter of the ES provides an assessment of the potential impacts to marine

ecology in respect of the proposed temporary jetty during the construction, operation

and subsequent dismantling and restoration phases. In addition it considers the impacts

associated with removal of the jetty and site reinstatement should the IPC not grant a

DCO. Where appropriate, mitigation measures are proposed to reduce potential adverse

impacts.

a) Scoping of Assessment

Scoping

10.1.2 An Environmental Scoping Report for the jetty development was produced in March

2010 (Ref 10.1), which provided a summary of baseline environmental conditions for the

study area and information on likely environmental effects relating to marine ecology.

10.1.3 A Scoping Opinion (Ref 10.2) was received from the Marine Management Organisation

(MMO) in June 2010 (see Appendix 5-1, Volume 4). This Scoping Opinion included

responses from a range of organisations, including the Environment Agency, Natural

England, the Countryside Council for Wales (CCW), Somerset County Council and West

Somerset and Sedgemoor District Councils. In relation to marine ecology the Scoping

Opinion raised a number of points, notably a requirement to consider if the works could

impact on Sabellariareef orCorallinaturfs on the foreshore (see Section 10.5), as well

as a requirement for a thorough assessment to be carried out of potential cumulative

impacts (see Chapter 25). The Scoping Opinion has been taken into account during the

preparation of this Chapter (see Annex 10.1 at the end of the Chapter).

Consultation

10.1.4 The assessment of impacts on marine ecology as reported in this Chapter has been

informed by detailed consultations with relevant bodies dating back to 2008.

10.1.5 On 3 November 2008 an initial meeting was held with Natural England and Somerset

County Council) to discuss and agree the proposed scope and range of near shore and

offshore marine ecological surveys to be undertaken. A Method Statement was issued

prior to the meeting and Natural England confirmed that it was content with the

proposed surveys but requested a full 12 months baseline survey period for certain key

species.

10.1.6 A subsequent meeting was held with Natural England and CCW on 16 January 2009. It

was agreed that the Revised Method Statement for Marine Ecology (revised following

the initial meeting) would be sent to Natural England and CCW for any further comment.

CCW raised the issue of potential impacts to Welsh Special Areas of Conservation

(SACs), including the River Wye, River Usk and River Tywi, partly designated for the

following fish species: sea lamprey Petromyzon marinus, brook lamprey Lampetra

planeri, twaite shad Alosa fallax, Atlantic salmon Salmo salar and bullhead Cottus

gobio. However, due to the limited nature of the potential impacts associated with the

jetty development and the distance of the works from these features, separate

assessments have not been undertaken for these sites (see Section 10.5).


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10.1.7 Comments were received on the proposed marine ecology methodology (CCW 09/02/09

and Natural England 12/02/09) but no further changes to survey design were requested

other than the previously agreed extension of the survey period. Natural England agreed

that marine mammals could reasonably be addressed through desk-based assessment.

10.1.8 A series of meetings were held with the Marine Authorities Liaison Group (MALG) to

discuss all stages of the assessment and the jetty development engineering and

construction design. MALG members include the Centre for Environment, Fisheries and

Aquaculture Science (Cefas), CCW, Natural England, Environment Agency, MMO,

Somerset County Council, Sedgemoor District Council, Royal Society for the Protection

of Birds (RSPB), Crown Estates, English Heritage and West Somerset Council. A

summary of marine ecology issues discussed at these meetings is presented in Annex

10.2 (located at the end of this Chapter).

10.1.9 Following a meeting between EDF Energy and the Environment Agency and Natural

England on 23 July 2010, the Environment Agency provided a written response dated 6

August 2010. The marine ecology elements of this response are also reviewed in

Annex 10.2.

Assessment Content

10.1.10 The assessment of impacts on marine ecology receptors arising from the jetty

development has been undertaken for the study area and uses the best practices and

standard methodologies as described in Section 10.3.

10.1.11 The baseline conditions described in Section 10.4 are based on a number of surveys

undertaken by EDF Energy of the wider scale environmental and ecological

characteristics up to 15km from the application site as well as others that focussed on

the proposed working areas both offshore and in the inter-tidal zone at Hinkley Point.

10.1.12 Impacts on marine ecology are assessed in Section 10.5. This includes potential

impacts on marine ecology receptors. Appropriate mitigation measures that are aimed

at reducing the impact of the proposed jetty on marine ecology receptors are identified in

Section 10.6. The residual impacts following implementation of the mitigation measures

are presented in Section 10.7. A summary of the impact assessment in tabulated form

is provided in Section 10.8.

10.1.13 The cumulative effects on marine ecology are assessed and set out in Chapter 25. For

this assessment, the effects of the proposed jetty works are assessed cumulatively with:

the site preparation works; the Hinkley Point C Project; and

other relevant plans and projects.

b) Objectives of Assessment

10.1.14 The assessment had the following objectives:

identify marine ecology receptors within the study area that may potentially be

affected by the jetty development;

characterise the baseline environmental and ecological conditions against which

any potential impacts can be measured;


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assess the impacts on marine ecology receptors of the jetty developments

construction, operation, dismantling / restoration and, if no DCO consent is granted,

removal and site reinstatement phases;

provide information to inform any Habitat Regulations Assessment (HRA) (this

assessment will be submitted after the application for a HEO);

recommend mitigation measures, if determined necessary, to reduce the jettydevelopments impacts on marine ecology; and

assess the residual impacts of the jetty development on marine ecology.

10.2 Legislation, Policy and Guidance

a) International Legislation and Policy

The Ramsar Convention of Wetlands of International Importance 1971 (Ref 10.3)

10.2.1 The Ramsar Convention on Wetlands of International Importance 1971 provides the

framework for national action and international co-operation for the conservation and

considerate use of wetlands and their resources. Suitable wetlands are designated forinclusion in the List of Wetlands of International Importance. Many Ramsar sites are

also Special Protection Areas (SPAs) classified under the Birds Directive (see below) as

a result of selection of sites of importance to waterbirds within the UK. Of relevance to

the proposed development is the Severn Estuary Ramsar status. The Severn Estuary

Ramsar site is designated due to a number of attributes, including: the high tidal range,

the presence of Annex I habitats protected under the Habitats Directive (see below), the

presence of unusual estuarine communities (reduced diversity and high productivity),

the run of migratory fish between the sea and river via the estuary, the fish of the whole

estuarine and river system which is one of the most diverse in Britain, and wildfowl and

wader assemblages and species/populations of international importance. The

Bridgwater Bay National Nature Reserve (NNR) was designated a wetland ofinternational importance under the Ramsar Convention. Although this designation

applies to ornithological interest, this interest is in part dependent on the marine food

resources that are described and assessed in this Chapter and the Convention is

therefore of relevance in that respect.

The Convention on Biological Diversity 1992 (Ref 10.4)

10.2.2 This Convention focuses on the conservation of all species and ecosystems and

therefore provides protection to all biodiversity. The Convention requires the

development of national strategies, plans or programmes for the conservation and

sustainable use of biodiversity. In accordance with this the UK developed Biodiversity

Action Plans (BAPs) (see below for further information). For inter-tidal and sub-tidalzones, Species, Habitat, and Biodiversity Action Plans have been developed and are

considered in the evaluation of features potentially affected by the development. The

action plans provide guidance for the conservation and management of biodiversity

within the natural environment and are taken account of in this impact assessment.

The Oslo Paris (OSPAR) Convention for the Protection of the Marine Environment of the

North-East Atlantic (Ref. 10.5)

10.2.3 Annex V of the Convention provides a framework for contracting parties to develop their

own conservation measures. Article 2 requires parties to take necessary measures to

protect and conserve the ecosystems and the biological diversity of the maritime area,and to restore, where practicable, marine areas which have already been adversely


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affected. Guidelines have been developed for the selection and management of Marine

Protected Areas and a series of Ecological Quality Objectives are being developed.

b) European Legislation

EC Directive on the Conservation of Wild Birds (2009/147 EC) (Ref 10.6)

10.2.4 The Birds Directive aims to protect all wild birds, their eggs, nests and habitats within

the EC. It also provides for the protection, management and control of all species of

naturally occurring wild birds that are considered rare or vulnerable within the EC as

listed in Annex I of the Directive. Under the Directive the most suitable areas for the

conservation of these species (land and sea) are classified at EU level as SPAs. In

England and Wales the Directive is implemented under the Wildlife and Countryside Act

1981 (as amended) and the Conservation of Habitats and Species Regulations 2010.

Of specific relevance to the proposed development is the Severn Estuary SPA.

10.2.5 The Severn Estuary qualifies as an SPA under Article 4.1 of the Birds Directive because

it is classified as a wetland of international importance regularly supporting at least20,000 waterfowl. In addition, it supports internationally important populations of over

wintering birds and birds on passage (see Chapter 11). Although this designation

applies to ornithological interest, this interest is in part dependent on marine food

resources that are described and assessed in this Chapter and the Directive is therefore

of relevance in this respect.

EC Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora

(92/43/EEC) (EC Habitats Directive) (Ref 10.7)

10.2.6 Under the Habitats Directive, Special Areas of Conservation (SACs) can be designated

to maintain or restore the habitats listed in Annex I and the species listed in Annex II of

the Directive to favourable conservation status. Favourable Conservation Status is

defined in the context of habitats as the establishment of conditions which will ensure

that the extent and range of the habitat and the populations of the species within that

habitat will be maintained or increased over time. In relation to species; the viability,

population size and range of the species should be maintained in the long term. In

England and Wales the Directive is implemented under the Conservation of Habitats

and Species Regulations 2010. Of specific relevance to the proposed development is

the Severn Estuary SAC.

10.2.7 The designation of the SAC is due primarily to the presence of the Annex I habitats:

'Atlantic salt meadows', 'estuaries' and 'mudflats and sandflats not covered by seawater

at low tide'. The Annex I habitats: 'sandbanks which are slightly covered by seawater allthe time' and 'reefs' are also present as qualifying features, but are not the primary

reasons for the designation. The site is also designated due to the presence of the

Annex II species: twaite shad Alosa fallax, sea lamprey Petromyzon marinusand river

lamprey Lampetra fluviatilis.

The Water Framework Directive (2000/60EC) (Ref 10.8)

10.2.8 The Water Framework Directive (WFD) is the framework European legislation relating to

the protection of water quality and ecological status of freshwaters and coastal waters

and is, therefore, of relevance to the assessment of impacts on marine ecological

receptors.


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10.2.9 The WFD provides a mechanism by which disparate regulatory controls on human

activities that have the potential to impact on water quality may be managed effectively

and consistently. In addition to a range of inland surface and groundwaters, the WFD

covers transitional waters (estuaries and lagoons) and coastal waters up to one nautical

mile from mean low water (the baseline from which territorial waters are measured).

10.2.10 Under the WFD all UK surface waters have been identified as waterbodies with

meaningful typologies that relate to physical and ecological characteristics. Based upon

ecology and water quality, these water bodies have been classified as falling into one of

five status classes. The WFD requires that all inland and coastal waters must reach at

least good status by 2015 and defines how this should be achieved through the

establishment of environmental objectives and ecological targets for surface waters.

EU Marine Strategy Framework Directive (Ref 10.9)

10.2.11 The objective of the EUs Marine Strategy Framework Directive is for EU marine waters

to achieve good environmental status by 2021 and to protect the resource base upon

which marine-related economic and social activities depend. This Directive constitutesthe environmental component of the EUs future maritime policy which has been

designed to achieve the full economic potential of the oceans and seas while conserving

the marine environment and is therefore of relevance to the assessment of impacts on

marine ecological receptors.

10.2.12 Under the Directive, each Member State within a marine region is required to develop

strategies for their marine waters. These strategies must contain a detailed assessment

of the state of the environment, a definition of good environmental status at a regional

level and the environmental targets and the establishment of monitoring programmes.

Cost-effective measures must be drawn up which include an impact assessment which

details a cost-benefit analysis of the proposed measures.

European Eel Regulation (Ref. 10. 10)

10.2.13 This Regulation established measures for the recovery of the stock of European eel.

The UK submitted 15 Eel Management Plans for approval by the European Commission

in December 2008. These plans are set at the River Basin District level, as defined

under the Water Framework Directive 2000/60/EC, covering England and Wales,

Scotland and Northern Ireland.

10.2.14 Eel Management Plans have been implemented from 2010 for the Severn Catchment

(Ref 10.11) and for South West England river basins, including the River Parrett (Ref

10.12), which aim to provide an escapement of silver eel biomass that is at least equalto 40% of the potential escapement to be expected in the absence of anthropogenic

influence. In addition, the European Eel Regulation requires that a system is in place to

ensure that by 2013, 60% of eel less than 12cm long which are caught commercially

each year are used for restocking in suitable habitat.

c) UK Legislation

10.2.15 The following environmental legislation is applicable to the proposed development:


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The Water Environment (Water Framework Directive) (England and Wales) Regulations

2003 SI 3242 (Ref 10.13)

10.2.16 The Regulations provide the mechanism to implement river basin districts within

England and Wales in accordance with the WFD Directive. The Regulations require a

new strategic planning process to be established for the purpose of managing,protecting and improving the quality of water resources. Since the jetty development

could affect water quality, which could in turn indirectly affect marine ecology, the

Regulations are therefore of relevance herein.

The Conservation of Habitats and Species Regulations (2010) (Ref 10.14)

10.2.17 The Conservation of Habitats and Species Regulations 2010 (the Habitats Regulations)

consolidate and update the Conservation (Natural Habitats, &c.) Regulations 1994. The

1994 Regulations transposed Council Directive 92/43/EEC on the Conservation of

Natural Habitats and of Wild Fauna and Flora (EC Habitats Directive) into national law.

The Regulations implement the Habitats and Birds Directives (described earlier) and

make provision for the protection and management of sites, including the control ofpotentially damaging operations that may affect designated sites.

10.2.18 The Severn Estuary European Marine Site (EMS) is not a statutory site designation but

comprises the Severn Estuary SAC, SPA and Ramsar site. It represents a management

unit for those parts of Natura 2000 sites which extend beyond the Site of Special

Scientific Interest (SSSI). Advice on management and protection of the constituent

designated sites is provided by Natural England and CCW under Regulation 33 of the

Conservation (Natural Habitats, &c.) Regulations 1994 (now part of the Conservation of

Habitats and Species Regulations 2010).

The Wildlife and Countryside Act 1981 (as amended) (Ref 10.15)

10.2.19 The Wildlife and Countryside Act 1981 Act (as amended by the Countryside and Rights

of Way Act 2000 (CRoW)) (the Act) consolidates and amends existing legislation to

implement the Bern Convention and the Birds Directive. The Act strengthens provisions

under the National Parks and Access to the Countryside Act 1949 to establish National

Nature Reserves (NNRs) in England and Wales. The legislation provides for the

designation, protection and management of NNRs which can be established on land and

land covered by water so can therefore extend into the inter-tidal zone but not below low

water (e.g. the Bridgwater Bay NNR). These areas can be designated for their flora,

fauna or geological interests. The Act provides for the designation of SSSIs and Marine

Nature Reserves. The Bridgwater Bay SSSI is designated for a number of reasons

including the inter-tidal mudflats and saltmarshes and associated communities, theinternationally and nationally important numbers of over-wintering and passage migrant

wildfowl and waders and a number of other features.

Countryside and Rights of Way Act 2000 (Ref 10.16)

10.2.20 The Countryside and Rights of Way Act increases protection for SSSIs and strengthens

wildlife enforcement legislation (and is therefore of relevance to the assessment of

impacts on marine ecological receptors).

The Marine and Coastal Access Act 2009 (Ref 10.17)

10.2.21 The Marine and Coastal Access Act 2009 (the Act) aims to enable better protection of

marine ecosystems and prevent a decline in marine biodiversity. The Act sets out


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provisions for more coherent planning in the marine environment in terms of issuing

consents and permits for activities in the marine and coastal environment. It provides

for enhanced protection of the marine environment and biodiversity, improved

management of freshwater and migratory fisheries in England and Wales and improved

access to the English coast. The Act contains provisions to allow for the designation of

Marine Conservation Zones (MCZs) and the creation of a network or Marine ProtectedAreas (MPAs). As one of the Acts aims is to protect marine ecosystems it is of

relevance to the consideration of the impacts of the jetty development on marine

ecology.

Salmon and Freshwater Fisheries Act (Ref 10.18)

10.2.22 The Salmon and Freshwater Fisheries Act 1975 (SAFFA) applies to salmon, trout

(including sea trout) and freshwater fish and, following implementation of the Marine and

Coastal Access Act (2009) (Ref 10.17), smelt and lampreys, This legislation is therefore

of relevance to the assessment of impacts on marine ecological receptors.

d) National Policy

Planning Policy Statement (PPS9): Biodiversity and Geological Conservation (Ref

10.19)

10.2.23 PPS9 sets out the Governments national planning policies on the protection of

biodiversity and geological conservation. Government objectives in relation to

biodiversity and geological conservation aim to conserve, enhance and restore

biodiversity, and promote sustainability. The aims and objectives of PPS9 are intended

to be delivered via Local Development Frameworks implemented by local planning

bodies.

10.2.24 PPS9 establishes a series of key principles that local planning authorities should adhere

to ensure that the potential impacts of planning decisions on biodiversity and geological

conservation are fully considered. This is accompanied by Office of the Deputy Prime

Minister (ODPM) Circular 06/2005 which provides administrative guidance on the

application of the law relating to planning and nature conservation.

10.2.25 The guidance advises that a strategic approach to the conservation, enhancement and

restoration of biodiversity and geology should be taken, recognising the contribution that

sites, areas and features (both individually and in combination) make to conserve these

resources.

10.2.26 The UK Biodiversity Action Plan (UK BAP) provides a detailed plan for the protection ofbiological resources and involves the implementation of Species Action Plans, Habitat

Action Plans and Local BAPs.

10.2.27 PPS9 advises that a key aim of planning decisions should be to prevent harm to

biodiversity and geological conservation interests. Adequate mitigation measures

should be put in place where necessary. Where a planning decision would result in

significant harm to biodiversity and geological interests which cannot be prevented or

adequately mitigated, then appropriate compensation measures should be sought.

10.2.28 With regard to SSSI designation the guidance states that where a proposed

development on land within or outside a SSSI is likely to have an adverse effect,

planning permission should not normally be granted. Where an adverse effect on thesites notified special interest features is likely, PPS9 advises that an exception should:


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only be made where the benefits of the development clearly outweigh both the impacts

that it is likely to have on the features of the site that make it of special scientific interest

and any broader impacts on the national network of SSSIs.

10.2.29 Networks of natural habitats are considered within PPS9 to represent a valuable

resource. To reflect their importance, emphasis is placed upon Local Planning

Authorities to maintain networks by avoiding or repairing the fragmentation and isolation

of natural habitats through policies in plans.

UK Biodiversity Action Plan (Ref 10.20)

10.2.30 The UK BAP is the UK response to the Convention on Biological Diversity 1992. The

UK BAP describes the UKs biological resources and commits to a detailed plan for the

protection of these resources. Within the plan a list of priority species and habitats is

developed, for which specific action should be taken to conserve these species and

habitats. The implementation of the BAP is the responsibility of various statutory and

non-statutory organisations. This is a requirement of the Countryside and Rights of Way

Act 2000.

Eel Management Plans

10.2.31 Eel Management Plans have been implemented for the Severn Catchment and the

River Parrett (Refs 10.11 and 10.12).

e) Regional Policy

10.2.32 On 6 July 2010 the Secretary of State for Communities and Local Government revoked

all Regional Strategies with immediate effect under section 79(6) of the Local

Democracy, Economic Development and Construction Act 2009. This includes the

Regional Planning Guidance for the South West (RPG10).

10.2.33 Therefore, Regional Strategies no longer form part of the development plan for the

purposes of section 38(6) of the Planning and Compulsory Purchase Act 2004.

However, EDF Energy will continue to have regard to development plan documents,

saved policies and any old style plans that have not lapsed, as well as national policy

where relevant.

Somerset and Exmoor Joint Structure Plan 1996 2016 (Ref 10.21)

10.2.34 The Joint Structure Plan (JSP) provides the strategic base for all land use planning in

the combined area covered by Somerset and the Exmoor National Park for the periodup to 2016. The JSP policies relevant to marine ecology in the vicinity of the proposed

development include Policy 1: Nature Conservation and Policy 15: Coastal

Development.

10.2.35 Policy 1 on Nature Conservation states that the biodiversity of Somerset (and the

Exmoor National Park) would be protected, conserved, restored, enhanced, and

managed in accordance with the UK and relevant regional and local BAPs. Spatial

target habitats are provided for coastal sand dune, coastal vegetated shingle, and

Sabellaria alveolatareef. Maintenance target areas are set for coastal sand dune and

coastal vegetated sand dune, however, the full extent ofS. alveolatareef is not known.

A target has been set to mitigate the natural loss of coastal sand dune, although

establishment and restoration targets are ongoing for coastal vegetated shingle and S.alveolatareef.


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10.2.36 Policy 15 on Coastal Development principally considers development on the coast and

emphasises the importance of protecting and enhancing natural marine resources

including those afforded international protection.

f) Local Policy

The West Somerset District Local Plan 2006 (Ref 10.22)

10.2.37 The Planning and Compulsory Purchase Act 2004 made a number of changes to the

planning system at the local level and, as a consequence, the West Somerset Local

Development Framework (LDF) (Ref 10.23) will replace the West Somerset District

Local Plan. However, until that time, policies in the West Somerset District Local Plan

have been saved for use in the planning process.

10.2.38 The objective that is defined in the Local Plan relating to nature conservation is: to

protect and where possible enhance the diversity of wildlife and habitats including

important landscape features in West Somerset. The policies in the Local Plan relating

to biodiversity are: NC/1 relating to effects on SSSIs; NC/2 relating to the protection ofsites of international importance; NC/3 relating to sites of local nature conservation

interest; NC/4 relating to species protection; and NC/5 relating to important wildlife

habitats.

Local Biodiversity Action Plan (LBAP) (West Somerset) (Ref 10.24)

10.2.39 Under the West Somerset biodiversity action plan, coastal vegetated shingle and S.

alveolatareefs are identified as priority habitats.

10.3 Methodology

a) Introduction

10.3.1 The baseline environmental studies and surveys and the impact assessment for marine

ecology have been conducted in accordance with all relevant best practices and

standard methodologies.

10.3.2 The identification of marine ecological impacts throughout the EIA process has been

based on guidelines provided by the Institute of Ecology and Environmental

Management (IEEM) (Ref 10.25). In this case the EIA methodology has been modified

to ensure generic consistency with the other Chapters in this ES and follows best

practice guidance.

10.3.3 The main elements of the EIA methodology include:

evaluation of marine ecological baseline information;

characterisation of potential impacts;

assessment of magnitude and significance of impacts;

proposal of mitigation measures appropriate to impacts; and

identification of residual impacts.

10.3.4 The elements of the jetty development which may have implications for marine ecology

were identified and assessed.


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10.3.5 Impacts were assessed after taking into consideration aspects of project design, good

practices and protective measures which would be implemented as part of the

development (e.g. compliance with discharge consents).

b) Study Area

10.3.6 The study area for the inter-tidal marine ecology surveys for the Hinkley Point C Project

is outlined in Ref 10.26 (Volume 4, Section 10, Part B) (local scale studies stretching

from the western boundary of the development site to 100m east of the existing Hinkley

Point B water intake) and in Ref 10.27 (widescale studies from up to 8km north of the

River Parrett Estuary to 15km west of Hinkley Point). The sub-tidal study area is set out

in Ref 10.26 (Volume 4, Section 10, Part B) (local scale studies around proposed

intake and outfall locations), BEEMS (2009b) (Ref 10.28) and BEEMS (2009c) (Ref

10.29) (widescale studies within a radius of approximately 15km from the proposed

Hinkley Point C nuclear Power Station).

10.3.7 The main surveys of relevance to the impact assessment for this Chapter are the local

scale inter-tidal surveys, as identified above. These data have been supplemented withspecific surveys to record the presence of Corallina within the same study area, and

sub-tidal Sabellaria studies within a short distance offshore along the Hinkley Point

foreshore (see Figures 10-4 and 10-5, Volume 3). These studies identified and mapped

the location and extent of receptors of conservation importance, such as Sabellariaand

Corallina, which could be potentially impacted by the jetty development. The surveys

also provided information regarding receptors which could be present further afield, such

as diadromous fish and marine mammals; however, the main area of concern is the

Hinkley Point foreshore and the nearshore sub-tidal zone.

c) Baseline Environment Assessment

Marine Receptors

10.3.8 Marine ecological receptors were identified through:

a review of historical and recent data gathered specifically for the development;

desk-based assessment and modelling; and

consultation with Natural England, CCW and the Environment Agency, as detailed

in Section 10.1.

10.3.9 The baseline environmental assessment for marine ecology included the following

receptors:

microscopic plants, animals and fish larvae (phytoplankton, zooplankton, and

ichthyoplankton);

plants and animals on and in the sediment in offshore locations (sub-tidal benthic

flora, epifauna and infauna);

fish that live on or near to the sea bed and within the water column (benthic,

demersal and pelagic fish); and

inter-tidal fish, invertebrates and algae on the foreshore in front of and to the west of

Hinkley Point B.

10.3.10 A comprehensive review of the survey and sampling programmes undertaken for the

assessment is provided in the APEM Final Baseline Report (Ref 10.26) (Volume 4,

Section 10, Part B).


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10.3.11 A two-year sampling programme was implemented to collect marine environmental

information for Hinkley Point and Bridgwater Bay. Field data were obtained from a

number of surveys and sources to collate a representative baseline marine ecology data

set for the area of potential impact around Hinkley Point.

10.3.12 The sampling commenced in February 2008 and included:

animals in the sediment in offshore locations (sub-tidal benthic infauna);

animals on the sediment in offshore locations (sub-tidal benthic epifauna);

fish that live on or near the sea bed (benthic/demersal);

fish larvae and eggs;

inter-tidal surveys from approximately 8km north of the River Parrett to

approximately 15km west of Hinkley Point; and

inter-tidal fish and epifauna.

10.3.13 These investigations were combined with mapping of the sea bed substrate and

physical studies (e.g. investigations of current speed, sediment load etc.). The results

were used to characterise the area and produce biotope maps for the area of potentialimpact.

d) Impact Assessment Methodology

10.3.14 The generic approach adopted for this impact assessment is presented in Chapter 5.

The specific methodology adopted for assessing the potential and actual environmental

impacts to marine ecology are outlined below.

Impact Magnitude

10.3.15 In addition to the generic guidance in Chapter 5, the following guidelines for the

assessment of magnitude in relation to impacts on marine ecology have been adopted

(Table 10.1).

Table 10.1 Guidelines for the Assessment of Magnitude

Magnitude Guideline

High The change permanently affects the ecological function of the habitat/speciesby reducing the ability to sustain the habitat or population levels of species ofinterest across its whole area. The integrity of the habitats/species and theconservation status of any of the designations are compromised. Habitats andspecies are degraded to the extent that locally rare populations and habitats

are lost and protected species and habitats experience widespread change.

Impacts not limited to areas within and adjacent to the development.

Medium Habitats/species are degraded to the extent that they experience a reductionin extent or number of individuals. The change substantially affects theecological structure and function of the habitat/species on a local scale but isnot likely to have an effect at a regional scale. Although it is not likely topermanently affect the integrity of the receptor it may change the evaluation ofthe habitat/species in terms of conservation status.

Impacts limited to the areas within and adjacent to the development.


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Magnitude Guideline

Low The quality and availability of habitats and species experience some limiteddegradation. Disturbance to population size and occupied area is within therange of natural variability and there is not expected to be any permanenteffect on the integrity and/or key attributes of the receptor. The change isunlikely to change the evaluation of the habitat/species in terms ofconservation status.

Impacts limited to the area within the development.

Very Low Although there may be some impacts on individuals it is considered that thequality and availability of habitats and species would experience little or nodegradation. Any disturbance would be in the range of natural variability andthere would be no short-term or long-term effects on the integrity or keyattributes of the receptor.

Activities predicted to occur occasionally and for a short period. Impacts likely

to be reversible and not likely to coincide with sensitive life stages.

Impacts limited to the area within the development.

Receptor Value

10.3.16 In addition to the generic guidance in Chapter 5, an additional guideline definition of

value specific to marine ecology has also been proposed (Table 10.2). The overall

value rating is a combination of the generic and specific guidance.

Table 10.2 Guidelines for the Assessment of Value

Definition Value

High Feature / receptor possess key characteristics which contribute considerablyto the distinctiveness, rarity and character of the site / receptor, e.g.designated features of International/National designation / importance (SAC,SPA, Ramsar, SSSI, UK BAP etc.).

Feature / receptor possess important biodiversity, social/community value and/ or economic value.

Feature / receptor is rarely sighted.

Medium Feature / receptor possess key characteristics which contribute considerablyto the distinctiveness, rarity and character of the site / receptor, e.g.designated features of Regional / County designation / importance (RegionalBAP, SSSI, Local Nature Reserves).

Feature / receptor possess moderate biodiversity, social / community valueand / or economic value.

Feature / receptor is occasionally sighted.


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Definition Value

Low Feature / receptor only possess characteristics which are of District or Localimportance. Feature / receptor not designated or only designated at thedistrict or local level, e.g. Local Nature Reserve.

Feature / receptor possess some biodiversity, social/community value and / oreconomic value.

Feature / receptor is relatively common.

Very Low Feature / receptor characteristics do not make a contribution to the characteror distinctiveness locally. Feature / receptor not designated.

Feature / receptor possess low biodiversity, social / community value and / oreconomic value.

Feature / receptor is abundant.

e) Uncertainties, Limitations and Assumptions

10.3.17 The assessment herein is based on available ecological information which has been

largely derived from baseline surveys conducted for the Hinkley Point C Project.

Methods used for the surveys adopted best practice including those outlined in the

Marine Monitoring Handbook (Davies et al. 2001; Ref 10.30) which incorporates the

recommendations of the Handbook for Marine Inter-tidal Phase 1 Survey and Mapping

(Wyn et al. 2000; Ref 10.31). Aspects of the UK National Marine Monitoring Programme

Green Book (NMMP 2003; Ref 10.32) were also taken into account. These documents

provide detailed standard methodologies for inter-tidal and sub-tidal sampling.

10.3.18 It should be noted that the surveys constitute a sample of a large and complex estuarine

system which, although undertaken throughout the year to allow for seasonal variations

(frequency depending upon survey subject), does not equate to continuous monitoring.

Variability in habitats and species may not therefore be fully recorded. However, it is

considered that the surveys were sufficiently well scoped and frequent to adequately

characterise the habitats and species main species and habitats present for this impact

assessment.

10.4 Baseline Environmental Characteristics

a) Introduction

10.4.1 This section presents the baseline environmental characteristics for the areas

designated for jetty development and surrounding area with specific reference to marine

ecology. The location of the area proposed for the jetty development is shown on Figure

10-1, Volume 3.

10.4.2 The Severn Estuary has one of the largest tidal ranges in the world, reaching in excess

of 13m at Avonmouth, a regime classified as hypertidal. The extreme tidal and turbidity

regimes of the Severn Estuary make it unique amongst British estuaries, with the

physical environment strongly influencing the distribution and productivity of the

biological assemblages present.

10.4.3 A consideration of these physical key features is provided in Chapter 9 and summarised

in Table 10.3 below.


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Table 10.3 Key Physical Features of the Severn Estuary

Key Features:Physical

Comment

Large funnel shaped

estuary facing theAtlantic

Influences fish species (particularly migratory) and other physical

features, particularly tidal regime.

Large branchingestuary

Sub-estuaries absorb energy at tidal frequencies, but input energy atlonger frequencies because of river flow variation. The Parrett, Uskand others are not insignificant regarding freshwater influx into thesystem.

High salinityvariation

Seasonal and tidal variation Parrett significantly adds to this in theHinkley Point area.

Hypertidal Rare at global scale others include the Bay of Fundy (Canada),the Seine and the Somme (France).

Periodic energyinputs

Spring to Neap changes are major in magnitude, resulting in asystem with a major component of fortnightly change (as well asother tidal periods). Long periods of low winds reduce thesuspended solids concentrations, at least in surface waters. Thesedimentary system is therefore periodic, which directly effects thelight regime (hence production), the benthic habitats and thus thebenthos.

Waves dominant inshallow water

In shallow areas, waves are dominant over the effects of tidalcurrents. Most important in the Hinkley Point area are the inter-tidaland shallow flats where it is waves that are mostly responsible interms of mobilising and/or changing the physical environment andthus affecting the biota.

Areas of exposedrock

Large portions of the Bristol Channel and lower Severn Estuaryarecharacterised by exposed rock (see the figure provided in Appendix9-9, Volume 4).

Physics makeschange in sub-tidalhabitats the normnot the exception

Changes to the sediment transport system have the potential toinduce major changes in habitat. Changes in sediment distribution(natural and manmade) are likely and these would affect habitats by definition.

Highly turbid unique in UK

High concentrations of sediment are present within the water column(in both permanent and temporary suspension and is intermittently

deposited) but there is relatively little contribution from rivers or fromthe outer Bristol Channel.

Entrance to Parrett mobile banks

The mouth of the Parrett has a variety of inter-tidal and sub-tidalbanks, which consist of layered sediments and are extremelymobile. They thus tend to have low density biota.

Existing Parrettplume impact oninter-tidal area

Freshwater run-off peaks are significant in that they affect the extentof the existing Hinkley Point B power station thermal plume acrossBridgwater Bay.

Periodic majorchanges in bedelevation

Erosion/deposition cycles occur naturally and periodically, especiallyin the outer Bridgwater Bay.


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Key Features:Physical

Comment

Residual circulation Tidal averaging of flows shows strong outward residual flow fromFlat Holm to the south side of channel off Kilve. Recirculation cellsoccur to north and south. This could trap persistent contaminants or

effluent, and provides routes for fish migration. Crudely summarisedas: fish in north, out south. This feature persists to Holm Island.Given the small magnitude of any residual circulation compared tothe regular tidal flows the significance of this feature is uncertain.

Benthic productiondominated by inter-tidal compared tosub-tidal

Due to a combination of the distribution of tidally driven bed shearforces and the extreme levels of turbidity present in the watercolumn, there is an apparent discontinuity in ecological productionwith little sub-tidally and that, over the soft inter-tidal areas, drivenlargely by microphytobenthos. The balance of primary production isthus skewed towards the inter-tidal zone.

Contains sub-

systems which arerelatively simple

The Bridgwater Bay ecosystem is relatively simple with few species

dominant. Mysids, crabs and brown shrimp (Crangon) are importantlinks in the food chain.

Migratory fishcorridor

Important for a number of species of conservation interest (shad,salmonids, eel, lampreys).

Impoverished sub-tidal benthos

Extremely poor compared to other estuaries, because of periodichighly mobile sea bed.

Highly productiveinter-tidal soft shorebenthos

Stable highly productive mud flats. The mudflats are of two generaltypes: (1) eroding Holocene muds and clays, which are relativelyresistant to erosion and able to form a habitat for infauna, and (2)periodically layered mobile sands and muds.

10.4.4 The Severn Estuary is recognised as an important conservation area and supports a

number of international, national and local designations for wetland habitats, bird

populations and the presence of other habitats and species of conservation interest.

Hinkley Point is fronted by a rocky foreshore with large areas of inter-tidal mudflats to

the east, and saltmarsh areas bordering the River Parrett. These inter-tidal areas are of

importance due to their role in supporting large numbers of over-wintering wildfowl.

10.4.5 The assemblages of organisms found in both inter-tidal and sub-tidal habitats are

characteristic of other UK estuaries in terms of the number and types of species present,

but are generally impoverished in terms of abundance. This is the direct result of high

tidal shear forces resulting in chronic sediment surface instability and extremely highturbidity levels.

10.4.6 The inter-tidal zone in front of, and on either side of, Hinkley Point B is dominated by a

shelving rocky shore with low abundances of organisms and low macroalgae biomass,

although patchy areas of high macroalgal cover are present. Sub-tidal habitats in the

vicinity of Hinkley Point consist of extensive areas of muddy sediments. The main

habitats of ecological importance on the foreshore are turfs of the red alga Corallina sp.

and those formed by tubes of the honeycomb worm Sabellaria sp.; aggregations of

these particular species can provide habitat for many other organisms and thus increase

local biodiversity. In its reef form, Sabellaria is listed as an Annex I species, protected

under the Habitats Directive. Although sub-tidal habitats exist within the study area that

are likely to be suitable forSabellariareef, no such formations have been identified.


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10.4.7 Sub-tidal habitats are dominated by just a few species including bivalve molluscs,

polychaete worms and crustaceans. The dominant sub-tidal epifaunal species observed

is the brown shrimp Crangon crangon, and this species also has high abundance

relative to others within the inter-tidal zone. This species provides an important food

source for a number of fish species (e.g. cod, flatfishes, sea bass) and birds.

10.4.8 The high turbidity of the water column limits the primary production of phytoplankton

within the Severn Estuary. As such, densities of phytoplankton and zooplankton, and

the number of different species which can tolerate these conditions, have been found to

be relatively low when compared with other coastal waters. The sub-tidal benthic flora is

relatively homogenous in the vicinity of Hinkley Point and is dominated by inter-tidal

microalgae (microphytobenthos) which had been washed into sub-tidal areas. Remote

sensing studies provided evidence for the potential presence ofSabellaria reef in some

sub-tidal areas with some sections confirmed by means of ground-truthing.

10.4.9 Seven diadromous fish species are known to migrate through the Severn Estuary;

Atlantic salmon, twaite shad, allis shad, river lamprey, sea lamprey, sea trout and eel, all

of which are afforded protection under European Directives and/or national legislation.These species were either absent or recorded in low numbers at the Hinkley Point B

intake location and were not recorded during the local or widescale trawl surveys.

10.4.10 Some of the commercial fish species were caught in relatively large numbers; and the

most abundant species recorded at the cooling water intake screens at Hinkley Point B

to date have been sprat, whiting, sand goby, poor cod, Dover sole, pout, common sea

snail, bass, flounder and dab. The following ten UK BAP marine species (commercial

fish BAP) are found within the estuary: cod, herring, plaice, sole, whiting, blue whiting,

hake, horse mackerel, ling and saithe (coalfish). Fish populations were found to be

dominated by marine migrant species which spend most of their time at sea and a

number of months within the estuary. In addition, the majority of fish caught during

surveys were juveniles supporting the view that Bridgwater Bay is an importance

nursery area for juvenile fish. Few fish larvae or eggs were collected within the water

column during ichthyoplankton surveys although inter-tidal fish surveys found a number

of fish species utilised inter-tidal areas including species of potential commercial

importance such as sea bass. There is, however, little commercial fishing activity within

the Severn Estuary.

10.4.11 There are no resident populations of marine mammals within the estuary although a

number of species are thought to use the estuary as a feeding area during different

times of the year. The harbour porpoise is the most commonly recorded marine

mammal species in the Bristol Channel.

b) Statutory Designations

Severn Estuary SAC

10.4.12 The proposed development is situated at Hinkley Point adjacent to Bridgwater Bay

within the Bristol Channel (see Figure 1-2, Volume 3). The Severn Estuary is a SAC

(designated under the EC Habitats Directive (Ref 10.7)). The SAC has a western extent

which is slightly east of Hinkley Point (Figure 11-2, Volume 3). Its designation is due to

the presence of the following habitats and species:

10.4.13 Annex I Habitats (primary features)


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Atlantic saltmeadows - Glauco-Puccinellietalia maritimae;

estuaries; and

mudflats and sandflats not covered by seawater at low tide.

10.4.14 Annex I Habitats (present)

sandbanks which are slightly covered by seawater all the time; and

Sabellariareefs.

10.4.15 Annex II Species (primary features)

twaite shad - Alosa fallax;

river lamprey - Lampetra fluviatilis; and

sea lamprey - Petromyzon marinus.

Severn Estuary SPA

10.4.16 The Severn Estuary occupies 24,663ha and was designated as a SPA in 1995. Itcomprises a range of different habitat types including: extensive inter-tidal mudflat and

sandflat, sub-tidal sandflat, saltmarsh, rocky platforms and islands. The estuary

qualifies as a SPA, under Article 4.1 of the Birds Directive, because it is classified as a

wetland of international importance regularly supporting at least 20,000 waterfowl.

10.4.17 In addition, it supports internationally important Annex I populations of overwintering

Bewicks swan (C. columbianus bewickii), curlew (N. arquata), dunlin (C. alpina alpina),

pintail (A. acuta), redshank (T. totanus) and shelduck (T. tadorna), and passage species

including ringed plover (C. hiaticula).

c) Marine Ecological Receptors

10.4.18 This section outlines baseline conditions based, in large, on Refs 10.26, 10.29, 10.30

10.33 and 10.34. In addition, the description draws on the findings of the long term

Severn Estuary Data Set (SEDS) data (Ref 10.35), which is the culmination of routine

sampling of fish and invertebrate catches over many years at Hinkley Point B.

Phytoplankton

10.4.19 Due to the very high suspended sediment concentrations, the photic depth in the

estuary is confined to the immediate surface waters, which greatly limits the primary

production of phytoplankton (Cloern, 1987 (Ref 10.36), Joint & Pomroy, 1981 (Ref

10.37), Joint, 1984 (Ref 10.38), STPG, 1989 (Ref 10.39)). Although somephytoplankton are present in the highly turbid sections of the Bristol Channel, primary

production rates are far greater in the less turbid areas. Inter-tidal sediments in the

Severn Estuary are known to support microphytobenthic populations, which are

frequently dominated by diatoms (Underwood, 1994; Ref 10.40). The re-suspension of

these algae (and the substrates they inhabit) has been demonstrated in the Eems

estuary, a large, physically dynamic estuary similar to the Severn (e.g. De Jonge & van

Beusekom, 1995 (Ref 10.41)). This suggests that it is largely re-suspended

microphytobenthos that contributes to the phytoplankton recorded in the Severn

Estuary.

10.4.20 There is limited published information available regarding phytoplankton populations in

the Bristol Channel and Severn Estuary. Rees (1939; Ref 10.42) and Underwood (1994;

Ref 10.40) provide some data on phytoplankton species recorded in the inner Bristol


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Channel. Of the diatom species indicated in these records some species are primarily

benthic (e.g. Actinoptychusspp., Bacillaria paxillifer, Gyrosigma spp., Melosira arctica

and all the Nitzschia species), while planktonic species include Asterionella spp.,

Chaetocerosspp, Ditylum brightwellii, Odontella spp. and Helicotheca tamesis. This

suggests that at least some of phytoplankton component has a microphytobenthic origin.

10.4.21 In total 21 species were recorded off Hinkley Point from the phytoplankton surveys

carried out between November 2008 and October 2009. The most frequently recorded

species between November 2008 and July 2009 was the diatom Odontella regiawhich

was present at all, or nearly all, of the sites on each occasion. This species also had the

greatest density with the highest values recorded in July 2009 (reaching up to 1006

individuals per m3). However, this species was not recorded in the August and October

2009 samples, with Paralina sulcatabeing present at all sites in August and Odontella

sinensis present at nearly all sites during October. The densities of phytoplankton

varied among sampling periods with the highest phytoplankton densities recorded in

July 2009, at a mean density of 278 individuals per m3

(which was mainly due to high

numbers of O. regia). However, when compared with other British coastal waters,

phytoplankton densities were relatively low, which is likely due in part to the highturbidity of the Bristol Channel (water transparency of 10cm) (Ref 10.39).

10.4.22 The most frequently recorded species, Odontella regia, is regarded as a planktonic form.

This species was found to occur in a low light group of algae at Helgoland in the North

Sea (Ref 10.40) suggesting it may be capable of growth within the extreme conditions of

the Severn Estuary. In contrast, G. delicatulaand S. unipunctataare more typical of

coastal waters, suggesting they may have been transported into the estuary.

Zooplankton

10.4.23 The limitation of primary production due to elevated turbidity levels within the Severn

Estuary has the potential to reduce production of any zooplankton which feed on these

microscopic plants (Ref 10.36, Ref 10.37 and Ref 10.38). Estuarine zooplankton,

however, are primarily detritivores and it is considered that the main factor limiting

zooplankton growth within this system is the need to process high levels of solids for

relatively little gain.

10.4.24 Surveys of zooplankton were carried out by the Institute for Marine Environmental

Research (IMER) between 1971 and 1981 (Williams 1984; Ref 10.43). Williams

reviewed these data to describe the species assemblages, biomass and seasonal

cycles of zooplankton in the Bristol Channel and Severn Estuary. The assemblages

found were typical of estuaries in northern latitudes, both in terms of their abundance

and species composition. However, species diversity of the zooplankton in the BristolChannel, and in the Severn Estuary in particular, has been found to be relatively low

when compared to other coastal shelf areas around the UK (Collins & Williams 1981;

Ref 10.44).

10.4.25 The permanent planktonic animals (holoplankton) in the Bristol Channel are

predominantly copepods, as is the case for many other estuaries in the UK (Ref 10.43).

The temporary plankton (meroplankton) are represented by phyla such as decapods,

molluscs, echinoderms, annelids and fish (Ref 10.43). The dominant species are the

calanoid copepods which have been recorded in maximum densities in July following

increases in abundance in March, April and May (Refs 10.41 and 10.42). Mysids

(particularly Schistomysis spiritus) also constitute a large part of the total zooplankton

biomass in summer (approximately 80%) (Refs 10.45 and 10.43).


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10.4.26 Salinity is an important environmental variable affecting zooplankton distribution, along

with temperature variation. The powerful tidal movements also have a considerable

influence (Refs 10.44 and 10.42). When considering the biomass of zooplankton in the

Bristol Channel and Severn Estuary, Rees (1939; Ref 10.42) identified a gradient from

high biomass at the seaward extent to low values further upstream. This gradient was

more pronounced in spring for the omnivores and in summer for the carnivores(reflecting the pattern of food availability). Peaks in omnivorous zooplankton biomass

occurred throughout the year. The carnivores, e.g. Sagitta spp. tended to be more

abundant in the latter half of the year when biomass was similar to that recorded for the

omnivores.

10.4.27 Entrainment sampling for zooplankton from the Hinkley Point B station has recorded a

total of 43 taxa between April 2007 and June 2009. Few species were recorded in

samples from the intake screens at Hinkley Point B during January and February 2009

which is likely to be due to reduced salinities within this area during the winter months

(Bamber & Henderson, 1994; Ref 10.45). The most abundant group over this sampling

period was the mysids which show a strong seasonal pattern in abundance. In addition

a notable feature of the long-term data collected at Hinkley Point has been the dramaticincrease in mysid abundance over the last 30 years. Peak mysid abundance is now

almost six times the level observed in the 1980s and 1990s (peak of ~3000 individuals

in 2008 samples in comparison with maximum of 500 individuals per sample in the

1980s and 1990s). Since the commencement of sampling, the mysid assemblage has

been dominated by three species, Schistomysis spiritus, Mesopodopsis slabberiand to

a lesser extent Gastrosaccus spinifer.

Ichthyoplankton

10.4.28 Zooplankton surveys conducted as part of the BEEMS programme were dedicated

towards gaining an understanding of ichthyoplankton (fish larvae and egg) abundance

and distribution. Overall, fish eggs from nine taxa were recorded: anchovy (Engraulis

encrasicolus), rocklings (Lotidae), gurnard (Triglidae), European sea bass

(Dicentrarchus labrax), Dover sole (Solea solea), solonette (Buglossidium luteum),

mackerel (Scomber scombrus) pilchard (Sardina pilchardus) scaldfish (Arnoglossus

laterna) and some unidentified eggs were also collected in June 2008 and May 2009.

Larvae of herring (Clupeidae), sprat (Sprattus sprattus), sandeel (Ammodytidae),

dragonet (Callionymidae), gobies (Gobiidae), Dover sole, European seabass and

solenette were also recorded (Ref 10.46). The majority of ichthyoplankton were caught

during the May 2009 surveys.

10.4.29 The most frequently recorded component of the ichthyoplankton was anchovy eggs

which were collected at over 30% of the sampling stations, with a maximum abundanceof 6.51 eggs per m

2(where abundance is standardised to the number of units under 1m

2

of sea surface). Historically, anchovy have been rarely reported in the area and its

presence here (in particular, the presence of eggs, indicating local spawning) might

indicate an increased northward distribution of the species from southern waters. The

second most abundant ichthyoplankton group was goby larvae (eggs were collected at

35% of the stations, with a maximum abundance of 2.46 eggs per m2) (Ref 10.46). High

densities of seabass larvae were recorded during the May 2009 surveys whereas

previously these had not been recorded. With the possible exception of anchovy, the

ichthyoplankton species identified during these surveys are not uncommon in coastal or

inshore waters and did not have distributions which could be construed as unusual.


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Sub-tidal Benthic Fauna

10.4.30 The benthic faunal assemblage of the Severn Estuary is generally regarded as being an

impoverished and predominantly opportunistic assemblage of species due to the mobile

muddy sediments, high tidal shears and the highly turbid conditions of the estuary

(Mettam et al. 1994 (Ref 10.47) and Langston et al. 2007 (Ref 10.48)). For example, asurvey of the fauna of the deep water channel and marginal areas of the Severn Estuary

between Flatholm Island and King Pool, upstream of Hinkley Point reported that the

fauna of the Severn Estuary Sabellaria reefs is impoverished compared to similar

habitats in the Bristol Channel and elsewhere in the British Isles (Warwick et al. 2001;

Ref 10.49). Furthermore, Warwick & Davies (1977; Ref 10.50) collected samples of the

bottom fauna at 155 stations in the Bristol Channel from Lundy Island to just above

Holme Islands, and described the area around Hinkley Point as having a reduced hard

bottom community due to strong tidal scour.

10.4.31 As a result of the high tidal shears in the estuary a component of the infauna sampled in

the surveys detailed below may include hyperbenthic species (i.e. species which live

above, but close to the substratum) which would not normally be considered as acomponent of the infauna. Tidal shear may draw these species into the sediment

temporarily. Discussion of those species caught during each survey which could be

classed as hyperbenthic is provided in the relevant sections below.

10.4.32 Across the five survey periods a total of 56 distinct macrofauna taxa and 6 meiofauna

phyla were recorded. Of these the cumaceans Diastylis bradyiand D. rathkei, mysid

species and the amphipod Photis longicaudata could be classed as hyperbenthic

species. The highest numbers of taxa were recorded in February, June and August of

2008 (26, 30 and 26 taxa respectively (Ref 10.29)). During each of the surveys, several

stations had no macrofauna in any of the Day Grab samples and overall species

richness and macrofauna abundance was considered to be low.

10.4.33 Molluscs contributed the most to the macrofaunal biomass during each quarterly survey

period (typically contributing to >90% of the total biomass), although biomass varied

considerably across surveys. Distribution of biomass across the survey sites was

uneven, however, the dominance of molluscs (e.g. the bivalves Macoma balthicaand

Nucula nucleus) suggests that these taxa have an important role in the ecosystem as a

food source for fish.

10.4.34 Across all surveys, four species were consistently the most frequently sampled (i.e.

found at the most sites) and were also sampled at the greatest densities (i.e. mean

abundance per 0.1m2) within the macrofaunal samples. These species were N. nucleus

(bivalve), (mean of 3.2 individuals per m2

); M. balthica(bivalve), (mean of 2.2 individualsper m

2); Nephtys hombergii(polychaete), (mean of 0.7 individuals per m2); and Diastylis

rathkei(crustacean), (mean of 0.6 individuals per m2) (Ref 10.29).

10.4.35 In general, both macrofaunal species number and densities were found to be highest in

nearshore locations and were lower at the sampling sites further offshore. The

macrofaunal grab sample data showed no clear link between substratum type and the

assemblage present. Few colonial species were collected from the area.

10.4.36 The number of meiofauna phyla found at most stations was relatively low. Nematoda

was the dominant phylum across surveys and sites accounting for 94% of the meiofauna

present. There was some evidence that nematode densities were highest in November

2008 (77 130 individuals per 10cm2 SD.), and lowest in June (38 65 individuals per

10cm2

SD) (Ref 10.29) although the trend was weak. The composition of meiofaunal


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assemblages with a dominance of nematodes was comparable with those encountered

in similar benthic environments worldwide (Coull, 1985 (Ref 10.51) and Probert, 1984

(Ref 10.52)). Meiofauna and nematode abundance was greatest at sites with mixed

sediments (e.g. sandy mud) as opposed to homogenous substrates of sand and mud, a

pattern which appeared unrelated to sediment depth.

10.4.37 A combination of widescale remote sensing studies and the results of the grab surveys

were used to generate a map of biotopes for the region (Figure 10-1, Volume 3 and

Table 4.2, for further details see Ref 10.26 (Volume 4, Section 10, Part B)). Biotopes

form basic mapping units and are defined according to a combination of both the

biological assemblages present and consideration of the physical characteristics of the

habitat. Biotopes were defined using the marine biotope classification of Connor et al.

(2004) (Ref 10.53). It should be noted that hyperbenthos and infauna within fluid muds

may be tidally redistributed over spring/neap cycles. Therefore, biotope descriptions

based on the assemblages of organisms present could vary considerably over relatively

short temporal scales and higher level descriptions based predominantly on sediment

type would be expected to remain more consistent across temporal scales. In other

words, habitat maps are generally a more reliable guide to the likely assemblageinvolved at any given sub-tidal locality.

Sabellaria

10.4.38 There are two species ofSabellaria in the UK, S. alveolataand S. spinulosa. The two

species have similar biology and ecology. Although individuals are not protected, they

tend to form large biogenic reefs by cementing together tubes constructed from sand. It

is the reefs themselves that are protected owing to the important ecological function they

perform. They often stabilise the sedimentary environment; provide hard substratum for

other sessile organisms to attach; can provide diverse habitat types (e.g. crevices); and

can alter local hydrodynamics, leading to accumulations of food particles for other

organisms (Holt et al. 1998; Ref 10.54). Their reefs are therefore protected under the

EC Habitats Directive (under which they are classed as Annex I biogenic habitats under

the 'Reefs' feature). The reefs are also referenced in the UK BAP which aims to:

maintain the extent ofS. alveolatareef habitats;

maintain the quality ofS. alveolatareef habitats; and

within 15 years, attempt to re-establish S. alveolatareefs in five areas where they

were formerly present.

10.4.39 A review of MarLIN habitat preferences and the sea bed surface map Figure 10-2,

Volume 3 suggest that areas dominated by mud and sand are unlikely to support the

development ofSabellariareefs in Bridgwater Bay. The recent extensive surveys havenot revealed any Sabellaria alveolata reef structures within these sandy and muddy

areas and their presence in these areas of substrate is unlikely.

10.4.40 Coarser sea bed habitats are most likely to support the development ofSabellariareefs.

Sabellaria presence has been recorded from some of the survey sites where such

substrates are present, but not in a form that would constitute reef habitat.

10.4.41 Sabellaria is, however, present in a form that would constitute reef on the lower shore

directly in front of Hinkley Point A. The distributions of the reef forms on the Hinkley

Point foreshore are directly coincident with the midfield dispersion pattern of the Hinkley

Point B power station thermal plume. Surveys carried out locally on the foreshore at

Hinkley Point report that the reefs growing within the flow of the cooling water discharge

from the power station are substantially larger, commonly greater than 15cm in height


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and over 1m across, than those recorded elsewhere in the area. In addition, the greater

size and complexity of the reefs in the outfall area have been found to support a denser

and more diverse range of associated fauna (Bamber 1995; Ref 10.55). In 1990 a

detailed survey programme was initiated to investigate these differential growth rates.

10.4.42 The results of studies undertaken between September 1991 and March 1993 indicated

that individual worms were neither larger nor more abundant at the outfall; they were not

of a different species and displayed no differential recruitment. These factors could

therefore not account for the difference in reef size. Tube building has been found to be

greatest at 15 to 20C, lower at 10C and absent at 5C. Therefore the authors

suggested that the differential growth rates could be attributed to maintenance of a

higher metabolism and tube-building activity at the outfall site as a result of constant

temperatures during the winter months. In addition, any frost-effects are limited at the

outfall. In effect, there exists a functional relationship between the warmed plume and

the distribution of the Sabellaria reefs, with the most likely explanation being that the

plume, or the overlying warmed air at low tide, has protected these reefs from extremes

of air temperature in the past (Ref 10.55). Therefore, it is likely that upon cessation of

Hinkley Point B cooling water effluent discharges this particular reef could be lost, if notimmediately then possibly following a low temperature event. Such cyclic patterns of

growth and retreat ofSabellaria, even within undisturbed habitats, are expected within

the estuarine habitat.

10.4.43 Surveys of Sabellaria reef fronting the Hinkley Point site (for the distribution of

Sabellaria, see Figure 10-4, Volume 3) show that coverage on the lower shore fronting

the Hinkley Point A power station is relatively extensive covering lower shore bedrock.

The reef in this area was generally low lying with high percentage coverage throughout

its distribution, large areas were covered with a thin layer of sediment and some of the

areas of the reef higher up the shore were overgrown with ephemeral algae. Overall,

based on the classifications summarised in Connor et al. 2004 (Ref 10.53) it was

considered that the reef in this area was generally of reduced quality, with some areas

of moderate quality in which colonies were 10cm in height.

10.4.44 Recent characterisation surveys of Sabellaria aggregations off Hinkley Point (BEEMS

2010a; Ref 10.56) indicate that Sabellaria alveolata is more widespread and abundant

than S. spinulosain this area.

Sub-tidal Epifauna

10.4.45 Impingement and entrainment studies carried out at Hinkley Point B have provided

information on the epifauna captured each month at the cooling water intake for over

two decades. Of the epifauna caught, the common brown shrimp Crangon crangonwasthe most commonly caught species and had the greatest abundances (Henderson et al.

2007; Ref 10.57). The abundance of this species varied temporally with spawning

occurring in spring and high numbers of juveniles causing abundances to peak in the

autumn (Ref 10.45 and Henderson et al. 2006 (Ref 10.58)). Winter increases in

abundance ofC. crangonwere also evident at Hinkley Point as some individuals move

seawards to avoid low winter salinities and females move inshore to brood (Ref 10.45).

The population size of C. crangon has been found to be positively correlated with

average water temperature from January to August, and negatively correlated with the

Winter North Atlantic Oscillation Index (Ref 10.58). In general, the population of this

species has remained relatively stable since the 1980s, although there was a year of

exceptional recruitment in 2002 (Ref 10.58).


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10.4.46 The preferred habitat forC. crangonis sandy and muddy ground with a grain size range

of 125 to 710m (MarLIN 2009; Ref 10.59). It is considered to be highly intolerant of

substratum loss, due to a decreased ability to forage and increased predation from

gadoids (e.g. cod). However, this species exhibits rapid growth, early maturation and

high fecundity, which would allow rapid population recovery (Ref 10.59). C. crangonwas

also found to be one of the most abundant epifaunal species during both the widescaleand local scale studies.

10.4.47 The second most abundant species caught at the intake screens was the pelagic ghost

shrimp Pasiphaea sivado (Ref 10.57). Whilst this species is considered pelagic as

opposed to strictly epifaunal it undergoes diurnal vertical migrations, moving throughout

the water column during the day and resting on the bottom at night. Other common

species caught at the intake screens included the demersal common prawn Palaemon

serratus, and pink shrimp Pandalus montagui, which have both shown a clear gradual

trend of increasing abundance in the estuary (Ref 10.57). Data from 2006 to 2007 and

previous decades, suggests that the abundance of shrimp and prawns near Hinkley

Point has increased since the 1980s. Due to a warm summer in 2006, the abundance of

species favouring warmer conditions was particularly high in 2007 with a record numberof these organisms being captured since the commencement of sampling (Ref 10.57).

Abundance of each of these species is known to vary seasonally in relation to

migrations and the timing of reproduction and the subsequent occurrence of juveniles

(Ref 10.45).

Inter-tidal Flora and Fauna

10.4.48 Hinkley Point is fronted by an area of inter-tidal rocky ledges and is flanked by further

inter-tidal rock, with occasional pockets of sediment to the west. To the east lie the

inter-tidal mudflats of Bridgwater Bay and the saltmarsh areas lining the River Parrett

Estuary.

10.4.49 In turbid estuarine environments with a restricted light regime, it is considered that

phytoplankton grow poorly in the water column, and that the microflora and macroflora

of inter-tidal areas and saltmarshes provide the greatest contribution to primary

production within the system (Radford 1994 (Ref 10.60)). In addition, sub-tidal

assemblages in the Severn Estuary and inner Bristol Channel generally have low

numbers of benthic fauna and low biodiversity (Warwick and Uncles 1980 (Ref 10.61),

Warwick 1984 (Ref 10.62), Ref 10.26 and Ref 10.29). This is due to the severe tidal

scouring, with frequent re-suspension of sediment, low primary production and variable

salinity regime. Hence, it can be expected that ecological activity in the Severn Estuary

is disproportionately concentrated in the inter-tidal zone and that any changes in the

function of the inter-tidal system could have direct impacts on the important migratorybird (and inter-tidal fish) populations, as well as other ecosystem services such as

nutrient cycling and sediment stabilisation.

10.4.50 The Severn Estuary supports an impoverished algal flora especially in terms of red

algae (Bamber & Irving 1992 (Ref 10.63), Ref 10.55, Seaby & Somes 2001 (Ref 10.64)

and Langston et al. 2003 (Ref 10.65). There are, however, small locally important red

algae communities such as the Corallina sp. run-offs in Bridgwater Bay (Ref 10.63,

Bamber & Irving 1993b Ref 10.66)). Corallinaturf habitats involving this species can be

found at Hinkley Point where they have developed on the littoral rock platforms. The

green algae Ulva lactuca can also be found associated with the Corallina turfs while

Fucus serratusis often present around the mat edges (Refs. 10.64, 10.65 and BEEMS

2008 (Ref 10.67)).


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10.4.51 A number of surveys of the foreshore at Hinkley Point have been undertaken between

1982 and 2001 (Ref 10.67 and Martin 1993a (Ref 10.68)). Some of these studies have

recorded the presence of the mussel Mytilus edulis. The results of these surveys

indicate a stable community with low faunal and floral diversity.

10.4.52 Bamber (1984; Ref 10.69) undertook core sampling of the littoral fine mud substrate to

the east of Hinkley Point. The dominant macrofaunal species was the bivalve M.

balthicaand the polychaete worm Nepthys hombergii. Juvenile gastropods and small

spionid polychaetes were also frequently found within samples.

10.4.53 Underwood (1994; Ref 10.40) described the inter-tidal epipelic (sediment surface) floral

assemblages in the Severn Estuary from samples collected between 1990 and 1991.

Diatoms comprised over 95% of the living cells in most of these samples and

occasionally the non-flagellated euglenoid Euglena deseswas also abundant. Over 60

diatom taxa were identified with 15 to 20 of these recorded regularly throughout the

survey period. Nitzschia epithymoides dominated samples from the upper and mid-

shore sites in the early summer months and Navicula pargeminaduring the spring and

autumn. Rhaphoneis minutissimawas present in relatively high numbers throughout theyear on lower shores, although in winter, this species was more abundant on upper and

mid shores. Seasonal changes in diatom assemblages were more pronounced on the

upper shores of the inter-tidal mudflats. In general these areas were dominated by

single taxa (e.g. N. epithymoidesorN. pargemina) and diversity was greatest on the

lower shore.

10.4.54 Smith (1978; Ref 10.70) surveyed eleven inter-tidal sites between Kilve (downstream of

Hinkley Point) and Sharpness (in the upper estuary) on the English side of the estuary.

All of these sites lacked macroalgae below the limit of Mean Low Water Springs (MLWS)

which is thought to be due to the effects of high turbidity and sediment scour (Langston

et al. 2003 (Ref 10.65)). Zonation of algae within the inter-tidal areas was characteristic

of that normally observed on rocky shores with species such as Pelvetia canaliculata

and Fucus spiralis inhabiting areas higher on the shore and Fucus serratus and

Ascophyllum nodosumpresent from the mid to lower shore.

10.4.55 Two communities of algae were found to be present at most of the sites surveyed. One

of these was formed by the green algae Ulva intestinalis, Ulva prolifera, Blidingia

minima, and Blidingia marginataand the fucoids Fucus vesiculosusand P. canaliculata

which dominated between the limits of mean high water neap and spring tides. Between

mean high and low water neap tides, however, a different community was formed by the

dominant species A. nodosum, F. vesiculosusand F. serratus. On occasion, F. serratus

was found to extend beyond the mean low water neap mark, however, it was never

found below the mean low water spring mark (Ref 10.70).

10.4.56 There are large fringes of saltmarsh in the estuary. Spartinaspp. is particularly common

and is abundant in Bridgwater Bay NNR (especially around the mouth of the River

Parrett) in which Spartina anglicawas planted in 1929 as a flood defence measure. In

Bridgwater Bay, this species now covers an area 3km long and 0.3 to 0.45km wide with

an area of approximately 120ha (Hubbard & Ranwell 2006 (Ref 10.71)). The total area

of saltmarsh habitat in the Severn Estuary as a whole is reported as 1,521ha, the

majority of which (75%) occurs on the English side (Ref 10.48). The saltmarshes are

regarded as significant nature conservation features and contribute to the SPA, Ramsar

and SAC designations.

10.4.57 During recent inter-tidal surveys (see Figure 10-3, Volume 3) a total of 40 macrofaunal

taxa were sampled across the 40 soft-sediment inter-tidal stations. There was a mean


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of 6.6 taxa per station and a trend of increasing species richness with increasing

elevation was noticeable in places, such as Berrow Flats. Data suggest that the areas

with the highest total macrofaunal densities were generally found along the higher-shore

regions of Berrow Flats and near the mouth of the River Parrett Estuary. Similarly,

areas with the greatest macrofaunal biomass were found to be along the upper shore

region of Brean Down and Berrow Flats and at a number of stations towards the west ofStert Flats. Initial univariate analysis indicated that neither elevation nor median

sediment grain size were useful predictors of macrofaunal biomass or numbers of

individuals. Total biomass was disproportionately dominated by relatively few taxa (i.e.

M. balthica 63%, Hediste diversicolor 15%, Hydrobia ulvae 8%). The most widely

distributed taxa were Hydrobia ulvaeand M. balthica(each observed at 36 stations) (Ref

10.72).

10.4.58 Comparison of these data with historical records suggests that current conditions may

not be universally consistent with the biotope map previously produced (e.g. EMU 2006

(Ref 10.73)). This may indicate the local sedimentary and biological environment is

heterogeneous on a smaller scale than shown on earlier biotope maps. Inconsistencies,

however, could also be due to slight differences in methodology, rather than changes inthe sedimentary environment or biological assemblages themselves.

10.4.59 Cluster analysis of the data was used to characterise six macrofauna assemblages, see

Figure 10-3, Volume 3. Of particular note are Assemblage D, Assemblage F and the

species S. alveolatathat form part of Assemblage E.

10.4.60 Assemblage D is comprised of two stations on the south bank of the River Parrett.

Assemblage D features Bathyporeia pelagica, which forms an important component of

the diet of shore birds. The majority of stations (31 of 40 stations), ranging in location

from the mid and upper shore regions of the Berrow and Stert Flats to the mouth of the

River Parrett form part of 'Assemblage F'. This mid to high shore mudflat assemblage is

critical to the overwintering bird populations and hence international legislative

protection of the Bridgwater Bay area. Although the assembl

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Marine Ecology Jetty Es Chapter 10

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