Publication 2007
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COMMISSIONED REPORT Commissioned Report No.286 Site Condition Monitoring: survey of marine features within the Sunart Special Area of Conservation (SAC) and Site of Special Scientific Interest (ROAME No. F06AC701) For further information on this report please contact: Laura Baxter Scottish Natural Heritage Great Glen House INVERNESS IV3 8NW Telephone: 01463-725236 E-mail: [email protected] This report should be quoted as: Mercer, T., Howson, C. M., and Moore, J. J. (2007). Site Condition Monitoring: Loch Sunart marine SAC and SSSI. Scottish Natural Heritage Commissioned Report No. 286 (ROAME No. R06AC701). This report, or any part of it, should not be reproduced without the permission of Scottish Natural Heritage. This permission will not be withheld unreasonably. The views expressed by the author(s) of this report should not be taken as the views and policies of Scottish Natural Heritage. © Scottish Natural Heritage 2007. COMMISSIONED REPORT Summary Site Condition Monitoring: survey of marine features within the Sunart Special Area of Conservation (SAC) and Site of Special Scientific Interest Commissioned Report No. 286 (ROAME No. F06AC701) Contractor: Mercer, T., Howson, C. M., and Moore, J. J. Year of publication: 2007 Background Loch Sunart’s intertidal zone has been included in the surrounding terrestrial Site of Special Scientific Interest (SSSI), for its intertidal reef feature, due to; its utilisation by the otter population; for the nationally scarce seagrasses, Zostera marina and Zostera noltii and for the internationally rare free living sheltered-water morphological variant of the egg wrack, Ascophyllum nodosum ecad mackaii (A.mac). The loch itself has been more recently designated as a Special Area of Conservation (SAC) for the marine feature ‘reefs’, an Annex I habitat under the 1992 Habitats Directive. The chief reason for the selection of this site is because it is one of the best examples of a complex fjordic sea lochs in the UK, experiencing a wide range of exposure to wave action, with water movement complicated by six shallow sills. Loch Sunart contains a range of bedrock reef habitats and associated communities, a number of which are very diverse and include several rare species. There are also extensive areas of soft mud, some sublittoral seagrass beds and the most extensive beds of the gaping file shell Limaria hians recorded in Scotland. Scottish Natural Heritage (SNH) in association with the other country agencies have established a series of common standards for the monitoring of sites of nature conservation interest (Anon., 1998). The purpose of this monitoring is to determine whether the desired condition of the feature(s) of interest for which the site was designated is being achieved. This can enable judgements to be made about whether the management of the site is appropriate, or whether changes may be necessary. The purpose of this project was to design and initiate a hierarchical monitoring programme for the features of interest within the SSSI and SAC, subtidal and intertidal rocky reefs, Ascophyllum nodosum ecad mackaii (A.mac) beds, and seagrass beds. There were also two secondary objectives of the field survey element and these were; to establish the current status of the northern hatchett shell, Thyasira gouldi (UK SAP species) and to establish the current status of key gaping file shell (Limaria hians) beds. The objectives were achieved using remote video, diver transects, intertidal transects, mapping methodologies, a limited grab survey and diver coring and quadrat studies. Main findings and conclusions Reef survey • The distribution of biotopes across the site was assessed by a combination of remote video and detailed transect surveys. The results showed that the vast majority of the site is in good condition with no significant change since 2001. • 53 littoral and sublittoral reef biotopes were recorded throughout the SAC as a whole, 34 of which were in the infralittoral and circalittoral. There was no evidence of a change in the biotope composition of the area as this was in broad agreement with the 2001 survey (Bates et al., 2004). • Seven littoral transects and eight sublittoral transects were studied using Phase II methodology. The shores surveyed ranged from very sheltered to moderately exposed and were generally rock slopes with supralittoral lichen zones adjacent to the terrestrial habitats, Pelvetia canaliculata (PelB) zones and barnacle zones on the upper and upper-middleshore (Sem), Ascophyllum nodosum in the middleshore (AscVS) and Fucus serratus on the lowershore. • Most of the transects studied east of Carna and in Loch Teacuis appeared to be exposed to variable salinity conditions. • Laminaria digitata (Ldig) dominated the sublittoral fringe in the mouth of the loch and Laminaria saccharina (Lsac and LsacPsaVS) in the middle zones of the loch. • Laminaria hyperborea forest (LhypR.Ft) dominated the infralittoral at one moderately exposed site in the entrance to the loch but was replaced by L. saccharina further into the loch, east of Carna. • A wide variety of circalittoral biotopes were found, including several near the mouth that were very rich in species. Some biotopes contained species of nature conservation importance such as the northern seafan, Swiftia pallida (CarSwi.LgAs) and the uncommon featherstar, Leptometra celtica and (AntAsH.Lept) and some that are common in sea lochs such as Protanthea simplex (NeoPro). • Sixteen species were recorded during the survey that were considered to be of nature conservation interest. • Serpula vermicularis (Ser) reefs were discovered in inner Loch Teacuis.This is of considerable nature conservation interest as it is only the second location in Scotland where live examples of this growth-form of these polychaete worm colonies are known to exist. Ascophyllum nodosum ecad Mackaii (A.mac) and Zostera bed survey • Ascophyllum nodosum ecad Mackaii (A.mac) beds were mapped at 6 locations. At Glenborrodale and Strontian quantitative abundance data were obtained for A.mac thalli, the associated fauna, flora, the infauna and the underlying sediment characteristics. • One Zostera noltii bed was mapped in the Doirlinn Channel and quantitative abundance data were obtained for Z. noltii, the associated fauna, flora, the infauna and the underlying sediment characteristics. The status of Zostera noltii in the loch should be further investigated on the extensive shores. • Three Zostera marina beds were mapped. The bed in Loch na Droma Buide requires further investigation as it was only discovered at the end of the survey. Thyasira gouldi and Limaria hians targeted surveys • A targetted grab survey was undertaken to investigate the status of Thyasira gouldi in the mid/upper reaches of the loch, but no T. gouldi were found. The fifteen 0.1m2 Van Veen grabs taken revealed a diverse infaunal community in places in the sediments of the loch. 259 taxa were recorded. The presence of the bivalve Thyasira gouldi in Loch Sunart must be in doubt given its absence from the grab samples taken in 2006. • The Limaria hians beds in the Laudale Narrows were investigated by diving. The constituents of the biotope (Lim) were recorded and the sediment properties of the beds were shown to be considerably modified by the bivalves’ presence. The associated infaunal community was analysed and described and it appeared to be both diverse and consistent within the biotope. Limaria hians byssus ‘nests’ create a unique habitat with biogenic reef-like properties and a characteristic and diverse infaunal community. Recommendations • 28 percent of the 155 drop-down video transects deployed recorded non-reef habitat over the 2001 Broadscale Survey (Bates et al., 2004) designated reef areas. It was not possible to measure any change in reef extent. This indicates that the Broadscale survey data may need more ground truthing surveys to be undertaken. • Depth stratification should be employed in the sampling methodology used for drop-down video zones in the infralittoral and circalittoral, in order to obtain adequate infralittoral information from future video surveys. • Even with the previously documented survey information regarding the intertidal and shallow subtidal, it proved difficult to make a judgement about biotope distribution and the condition of these features of the site on the basis of the seven/eight transects studied. It was felt that this level of information is not really adequate as a baseline for statements of biotope distribution. • Information on human impacts within the loch should be routinely collated for use in targeted monitoring. For further information on this project contact: Laura Baxter, Scottish Natural Heritage, Great Glen House, Inverness, IV3 8NW Tel: 01463–725 236 For further information on the SNH Research & Technical Support Programme contact: Policy & Advice Directorate Support, SNH, Great Glen House, Leachkin Road, Inverness, IV3 8NW. Tel: 01463 72500 or [email protected] Contents 1 Introduction 1 2 Development of the monitoring programme 3 2.1 Objectives for Sunart SAC and SSSI ............................................ 3 2.2 Common Standards Monitoring .................................................... 4 2.3 Review of previous data................................................................ 5 2.4 Human usage of Loch Sunart SAC and SSSI............................... 8 2.5 Draft Site Attribute Tables ............................................................. 9 2.6 Secondary features of the site .....................................................