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Assessing the Sensitivity of Sublittoral Rock Habitats to Pressures Associated with Marine Activities

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Assessing the Sensitivity of Sublittoral Rock Habitats to Pressures Associated with Marine Activities JNCC Report No: 589B Assessing the sensitivity of sublittoral rock habitats to pressures associated with marine activities Maher, E., Cramb, P., de Ros Moliner, A., Alexander, D. & Rengstorf, A. September 2016 © JNCC, Peterborough 2016 ISSN 0963-8901 For further information please contact: Joint Nature Conservation Committee Monkstone House City Road Peterborough PE1 1JY http://jncc.defra.gov.uk This report should be cited as: Maher, E., Cramb, P., de Ros Moliner, A., Alexander, D. & Rengstorf, A. 2016. Assessing the sensitivity of sublittoral rock habitats to pressures associated with marine activities. Marine Ecological Surveys Ltd – A report for the Joint Nature Conservation Committee. JNCC Report No. 589B. JNCC, Peterborough. Summary There are numerous human activities which occur in the marine environment. These activities can cause a variety of pressures on the seafloor habitats and the species they support. These pressures can occur in isolation or in combination, and their effects can be complex. To better understand the implications of anthropogenic pressures, it is crucial to be aware of how the pressures affect different species and functional ecological groups. The sensitivity of marine habitats has previously been assessed by Tillin et al (2010) and Tillin and Tyler-Walters (2014). Work by Tillin et al (2010) focused on the species, habitats and broadscale habitats recommended for designation within Marine Conservation Zones (MCZs) as part of a wider project (Tillin et al 2010). Tillin and Tyler-Walters (2014) focussed on systematic habitat level assessments of subtidal sedimentary habitats. Where possible, assessments were determined using available evidence and expert judgement. The aim of this project is to use the methods developed by Tillin and Tyler-Walters (2014) to assess the sensitivity of pre-defined ecological groups in sublittoral rock habitats in the UK to various anthropogenic pressures. The sensitivity assessments outlined in this report are conducted on groups of ecologically similar species which have been considered to have comparable traits likely to affect their sensitivity. The project consisted of two phases: Phase 1 – Following a literature review, ecological groups were defined based upon similarities in biological and habitat preference traits (Maher et al 2016). Phase 2 - Following a literature review, sensitivity assessments were conducted for characterising species from within the ecological groups to determine the sensitivity of the groups to pre-determined human pressures. The sensitivity assessments were tabulated based upon the findings for each of each ecological group. The ecological groups were defined in Phase 1 and are based upon 57 key and characterising Level 5 EUNIS biotopes, all of which fall beneath the umbrella of either ‘Infralittoral Rock’ or ‘Circalittoral Rock’ biotopes at EUNIS Level 2. From the selected biotopes, 76 characterising species were identified to represent sublittoral rock habitats and form the ecological groupings. The Tillin and Tyler-Walters (2014) sensitivity assessment method was applied to the ecological groups of the sublittoral rock habitats, this report outlines the findings of the the sensitivity assessments for those ecological groupings. Information regarding the resistance and resilience of the species was recorded with the objective of determining an eventual sensitivity score. The sensitivity assessments were conducted for the nine ecological groups defined in Phase 1, using this resistance and resilience evidence. Confidence in the assessments based upon the evidence used was continually appraised using the same methods as those outlined by Tillin and Tyler-Walters (2014). The rationale for each sensitivity score was recorded with relevant references to ensure transparency of the assessments. Assumptions and generalisations of the methods were outlined to summarise the limitations of the sensitivity assessment approach using the methods detailed in this report. Across sublittoral rock habitats as a whole, six pressures were assessed to be not relevant: ‘Emergence regime changes – local, including tidal level change considerations’, ‘Habitat structure changes - removal of substratum (extraction), ‘Penetration and/or disturbance of the substratum below the surface, including abrasion’, ‘Physical change (to another substratum type)’, ‘Death by injury or collision’ and ‘Noise changes’. In addition, the pressure ‘Barrier to species movement’ was only relevant to ecological groups 2 (non-predatory mobile species) and 3 (mobile predators and scavengers), due to their mobility. All of the ecological groupings were assessed as not sensitive to ‘Visual disturbance’, ‘Organic enrichment’ and ‘Nutrient enrichment’, with the exception of Group 1 (macroalgae) which was assessed as not exposed to ‘Visual disturbance’. In summary, nine pressures are not relevant or not thought to cause immediate damage to sublittoral rock habitats (not considering frequency and duration of pressure). Generally, few occurences of ‘High’ sensitivity were found; a total of 10.8% across the sensitivity assessments as a whole. Groups 3 (mobile predators and scavengers) and 4 (bivalves and brachiopods) demonstrated ‘High’ sensitivity to four pressures each while 6C (attached erect species) displayed ‘High’ sensitivity to five pressures. All groups were found to be highly sensitive to the pressure ‘Physical loss (to land or freshwater habitat)’. The pressures ‘Smothering and siltation rate changes’ and ‘Introduction of microbial pathogens’, were also found to be particularly damaging to sublittoral rock habitats, especially Group 3 (mobile predators and scavengers), Group 4 (bivalves and brachipods) and sub-group 6C (permanently/temporarily attached, erect epifauna). The tolerance of each ecological group was found to vary in response to different pressures, for example, although sub-group 6C (attached erect species) demonstrated the highest sensitivity overall it was also tolerant of many pressures. Group 4 (bivalves and brachiopods) and Group 1 (macroalgae) showed the lowest sensitivities in general with 25 and 24 pressures, respectively, recorded as either ‘Not sensitive’ or ‘Low’ sensitivity. Group 2 (non-predatory mobile fauna) and Group 3 (mobile predators and scavengers) each recorded 23 ‘Not sensitive’ or ‘Low’ sensitivity scores. The majority of the sensitivity assessments were found to be either ‘not sensitive’ (44.3%) or ‘Low’ (28.6%), with a proportion of the ‘low’ sensitivity scores attributed to the generally ‘high’ resilience of the groups. When a resilience score was ‘High’, a final score of ‘Low’ sensitivity was derived even if the resistance to a pressure was ‘Low’. As this may not capture the full vulnerability of the group, it is advised that where resistance is recorded as ‘low’, the need for management measures should be considered irrespective of the overall sensitivity assessment. Contents 1 Introduction .................................................................................................................. 1 2 Methods ........................................................................................................................ 2 2.1 Sensitivity, Resistance and Resilience .................................................................... 2 2.2 Sensitivity Assessments.......................................................................................... 3 2.3 Human Activities and Pressures ............................................................................. 5 3 Pressure Review .......................................................................................................... 5 3.1 Pressures with well-developed evidence base ........................................................ 6 3.1.1 Hydrological changes (inshore/local) ............................................................... 6 3.1.2 Physical damage (reversible change) .............................................................. 9 3.1.3 Physical pressure (other) ............................................................................... 11 3.1.4 Pollution and other chemical changes ............................................................ 11 3.2 Pressures with an intermediate evidence base ..................................................... 13 3.2.1 Pollution and other chemical changes ............................................................ 14 3.2.2 Biological pressures ....................................................................................... 16 3.3 Pressures with little or no evidence base .............................................................. 18 3.3.1 Physical pressure (other) ............................................................................... 18 3.3.2 Pollution and other chemical changes ............................................................ 20 3.3.3 Biological pressures ....................................................................................... 20 4 Sensitivity of subtidal rock habitats to human pressures ...................................... 22 4.1 Ecological group 1: Macroalgae ............................................................................ 22 4.1.1 Sensitivity assessments ................................................................................. 23 4.2 Ecological group 2: Non-predatory mobile species................................................ 32 4.2.1 Sensitivity assessments ................................................................................
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