4f4c4942-4343-5764-6473-313130323731 English NRW_DS109743 Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en 2026-03-03T11:17:32.473Z NRW 1.0 wel Latitude and Longitude (EPSG::4326) Monitoring the Health of the North Llyn Modiolus Reef Monitoring the Health of the North Llyn Modiolus Reef Monitro iechyd Riff Modiolus Gogledd Llyn Quadrat monitoring of the North Llyn horse mussel Modiolus modiolus reef 2009-12-31 NRW_DS110271 Modiolus Reefs are a feature of the Pen Llyn a'r Sarnau Special Area of Conservation (SAC). Information is gathered about the health of the reef through the recording of species present in fixed quadrats. Live horse mussels are hard to distinguish within the quadrat, however it is known that each live horse mussel supports one colony of the soft coral dead man's fingers Alcyonium digitatum and therefore these are used to count the number of live horse mussels present. This survey work is carried out as part of the Across Wales Diving Survey. The purpose of this data capture was to investigate the health of the reef. This contributes to reporting of favourable conservation status of the SAC feature. Data will be used in conjunction with acoustic data that looks at the extent of the feature (reef) and potential areas of damage. Modiolus Reefs are a feature of the Pen Llyn a'r Sarnau Special Area of Conservation (SAC). Information is gathered about the health of the reef through the recording of species present in fixed quadrats. Live horse mussels are hard to distinguish within the quadrat, however it is known that each live horse mussel supports one colony of the soft coral dead man's fingers Alcyonium digitatum and therefore these are used to count the number of live horse mussels present. This survey work is carried out as part of the Across Wales Diving Survey. The purpose of this data capture was to investigate the health of the reef. This contributes to reporting of favourable conservation status of the SAC feature. Data will be used in conjunction with acoustic data that looks at the extent of the feature (reef) and potential areas of damage. Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en CCW Marine Monitoring Team Countryside Council for Wales, Maes y Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW enquiries@naturalresourceswales.gov.uk http://naturalresourceswales.gov.uk/splash?orig=/ Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en Habitats and biotopes GEMET - INSPIRE themes, version 1.0 2008-06-01 geonetwork.thesaurus.external.theme.httpinspireeceuropaeutheme-theme biogenic reef quadrats modiolus modiolus biogenic reef Pen Llyn a'r Sarnau cSAC horse mussel marine monitoring (see also marine surveys) NRW Thesaurus 2025-01-08 geonetwork.thesaurus.local.theme.converted_nrw-keywords Habitat characterisation SeaDataNet Parameter Discovery Vocabulary 2024-06-19 geonetwork.thesaurus.external.theme.rdf+xml There are no access restrictions to this data. NRW may release, publish or disseminate it freely. no limitations © CNC/NRW 2011 There are no use restrictions on this data. Recipients may re-use, reproduce, disseminate this data free of charge in any format or medium, provided they do so accurately, acknowledging both the source and NRW's copyright, and do not use it in a misleading context. It is the recipient's responsibility to ensure the data is fit for the intended purpose, that dissemination or publishing does not result in duplication, and that it is fairly interpreted. Advice on interpretation should be sought where required. To avoid re-using old data, users should periodically obtain the latest version from the original source. English biota SeaVoX Vertical Co-ordinate Coverages 2021-01-06 benthic boundary layer Irish Sea Cardigan Bay Tremadog Bay GWYNEDD - GWYNEDD -4.66797282 -4.63196129 52.92621566 52.94269421 1999-01-01 2009-12-31 -30 -35 . Documents [A] Stitched mosaic images as TIFF files, video footage as mini DV tapes. [B] Analysed data in excel spreadsheet. [C] Summary of the data is held within Word Documents. [D] Photographs of quadrats held as .jpeg files. Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services 2010-12-08 This dataset has not been assessed for conformance to the referenced INSPIRE regulation. false Based on the monitoring trials see Marine Monitoring Report no. 1. Two sites were set up on the N. Llyn reef in order to monitor the health of the reef. An additional site is monitored on the Isle of Man as a comparison. In 2009 several sites of good condition were identified from multibeam and side-scan sonar images for possible additional monitoring. At these sites stratified random sampling is to be undertaken rather then marking permanent quadrats.At each of the original 2 sites on the Llyn permanent markers are in place that are used to position 0.5m by 0.5m quadrats. At each site 15 quadrats are placed on the crest of a Modiolus bioherm. Each quadrat is split into 25 cells of 100x100mm. The quadrat is filmed along each row from left to right using an underwater digital camera that stores footage on mini DV tapes. Detailed information about the setting up of the sites and standard operating procedures can be found in 'CCW Marine Monitoring Report 25b (draft): SOP 3'. Still images are extracted from the video processed and stitched into a mosaic. Live horse mussels are counted using the presence of Alcyonium digitatum as an indicator. Prior to analysis the quadrats are randomised to reduce any bias from the recorder. In addition to counting the presence of horse mussels trends in other easily recognizable species can be recorded to provide additional information about the quality and health of the reef. Other species recorded are live horse mussels common starfish Asterias rubens common brittlestar Ophiothrix fragilis sea urchin Psammechinus miliaris. Based on the monitoring trials see Marine Monitoring Report no. 1. Two sites were set up on the N. Llyn reef in order to monitor the health of the reef. An additional site is monitored on the Isle of Man as a comparison. In 2009 several sites of good condition were identified from multibeam and side-scan sonar images for possible additional monitoring. At these sites stratified random sampling is to be undertaken rather then marking permanent quadrats.At each of the original 2 sites on the Llyn permanent markers are in place that are used to position 0.5m by 0.5m quadrats. At each site 15 quadrats are placed on the crest of a Modiolus bioherm. Each quadrat is split into 25 cells of 100x100mm. The quadrat is filmed along each row from left to right using an underwater digital camera that stores footage on mini DV tapes. Detailed information about the setting up of the sites and standard operating procedures can be found in 'CCW Marine Monitoring Report 25b (draft): SOP 3'. Still images are extracted from the video processed and stitched into a mosaic. Live horse mussels are counted using the presence of Alcyonium digitatum as an indicator. Prior to analysis the quadrats are randomised to reduce any bias from the recorder. In addition to counting the presence of horse mussels trends in other easily recognizable species can be recorded to provide additional information about the quality and health of the reef. Other species recorded are live horse mussels common starfish Asterias rubens common brittlestar Ophiothrix fragilis sea urchin Psammechinus miliaris.