Tillin, H. Tyler-Walters, H., 2014. Assessing the sensitivity of subtidal sedimentary habitats to pressures associated with marine activities. Phase 2 Report – Literature review and sensitivity assessments for ecological groups for circalittoral and offshore Level 5 biotopes. JNCC Report No. 512B, 260 pp.

摘要

Human activities within the marine environment give rise to a number of pressures onudseabed habitats. Improved understanding of the sensitivity of subtidal sedimentary habitatsudis required to underpin the management advice provided for Marine Protected Areas, as welludas supporting other UK marine monitoring and assessment work. The sensitivity of marineudsedimentary habitats to a range of pressures induced by human activities has previouslyudbeen systematically assessed using approaches based on expert judgement for DefraudProject MB0102 (Tillin et al. 2010). This previous work assessed sensitivity at the level of theudbroadscale habitat and therefore the scores were typically expressed as a range due toudunderlying variation in the sensitivity of the constituent biotopes.udThe objective of this project was to reduce the uncertainty around identifying the sensitivityudof selected subtidal sedimentary habitats by assessing sensitivity, at a finer scale andudincorporating information on the biological assemblage, for 33 Level 5 circalittoral andudoffshore biotopes taken from the Marine Habitat Classification of Britain and Ireland (Connorudet al. 2004). Two Level 6 sub-biotopes were also included in this project as these containuddistinctive characterising species that differentiate them from the Level 5 parent biotope.udLittoral, infralittoral, reduced and variable salinity sedimentary habitats were excluded fromudthis project as the scope was set for assessment of circalittoral and offshore sedimentaryudcommunities.udThis project consisted of three Phases.ud• Phase 1 - define ecological groups based on similarities in the sensitivity ofudcharacterising species from the Level 5 and two Level 6 biotopes described above.ud• Phase 2 - produce a literature review of information on the resilience and resistanceudof characterising species of the ecological groups to pressures associated withudactivities in the marine environment.ud• Phase 3 - to produce sensitivity assessment ‘proformas’ based on the findings ofudPhase 2 for each ecological group.udThis report outlines results of Phase 2.udThe Tillin et al., (2010) sensitivity assessment methodology was modified to use the bestudavailable scientific evidence that could be collated within the project timescale. An extensiveudliterature review was compiled, for peer reviewed and grey literature, to examine currentudunderstanding about the effects of pressures from human activities on circalittoral andudoffshore sedimentary communities in UK continental shelf waters, together with informationudon factors that contribute to resilience (recovery) of marine species. This review formed theudbasis of an assessment of the sensitivity of the 16 ecological groups identified in Phase 1 ofudthe project (Tillin & Tyler-Walters 2014).udAs a result:ud• the state of knowledge on the effects of each pressure on circalittoral and offshoreudbenthos was reviewed;ud• the resistance, resilience and, hence, sensitivity of sixteen ecological groups,udrepresenting 96 characteristic species, were assessed for eight separate pressures;ud• each assessment was accompanied by a detailed review of the relevant evidence;udAssessing the sensitivity of subtidal sedimentary habitats to pressures associated with human activitiesud• knowledge gaps and sources of uncertainty were identified for each group;ud• each assessment was accompanied by an assessment of the quality of the evidence, itsudapplicability to the assessment and the degree of concordance (agreement) between theudevidence, to highlight sources of uncertainty as an assessment of the overall confidenceudin the sensitivity assessment, and finallyud• limitations in the methodology and the application of sensitivity assessments wereudoutlined.udThis process demonstrated that the ecological groups identified in Phase 1 (Tillin & Tyler-Waltersud2014) were viable groups for sensitivity assessment, and could be used to representudthe 33 circalittoral and offshore sediments biotopes identified at the beginning of the project.udThe results of the sensitivity assessments show:ud• the majority of species and hence ecological groups in sedimentary habitats areudsensitive to physical change, especially loss of habitat and sediment extraction, andudchange in sediment type;ud• most sedimentary species are sensitive to physical damage, e.g. abrasion andudpenetration, although deep burrowing species (e.g. the Dublin Bay prawn - Nephropsudnorvegicus and the sea cucumber - Neopentadactyla mixta) are able to avoid damagingudeffects to varying degrees, depending on the depth of penetration and time of year;ud• changes in hydrography (wave climate, tidal streams and currents) can significantlyudaffect sedimentary communities, depending on whether they are dominated by deposit,udinfaunal feeders or suspension feeders, and dependant on the nature of the sediment,udwhich is itself modified by hydrography and depth;ud• sedentary species and ecological groups that dominate the top-layer of the sedimentud(either shallow burrowing or epifaunal) remain the most sensitive to physical damage;ud• mobile species (e.g. interstitial and burrowing amphipods, and perhaps cumaceans) areudthe least sensitive to physical change or damage, and hydrological change as they areudalready adapted to unstable, mobile substrata;ud• sensitivity to changes in organic enrichment and hence oxygen levels, is variableudbetween species and ecological groups, depending on the exact habitat preferences ofudthe species in question, although most species have at least a medium sensitivity toudacute deoxygenation;ud• there is considerable evidence on the effects of bottom-contact fishing practices andudaggregate dredging on sedimentary communities, although not all evidence is directlyudapplicable to every ecological group;ud• there is lack of detailed information on the physiological tolerances (e.g. to oxygenation,udsalinity, and temperature), habitat preferences, life history and population dynamics ofudmany species, so that inferences has been made from related species, families, or evenudthe same phylum;ud• there was inadequate evidence to assess the effects of non-indigenous species on mostudecological groups, andudAssessing the sensitivity of subtidal sedimentary habitats to pressures associated with human activitiesud• there was inadequate evidence to assess the effects of electromagnetic fields and litterudon any ecological group.udThe resultant report provides an up-to-date review of current knowledge about the effects ofudpressures resulting from human activities of circalittoral and offshore sedimentaryudcommunities. It provides an evidence base to facilitate and support the provision ofudmanagement advice for Marine Protected Areas, development of UK marine monitoring andudassessment, and conservation advice to offshore marine industries.udHowever, such a review will require at least annual updates to take advantage of newudevidence and new research as it becomes available. Also further work is required to testudhow ecological group assessments are best combined in practice to advise on the sensitivityudof a range of sedimentary biotopes, including the 33 that were originally examined.