Volunteer Diver Seagrass Zostera marina Surveys, Llyn Peninsula and Milford Haven (2008)
In areas where conditions are suitable seagrass beds form and these are considered nationally important in the UK. Seagrasses are thought to help stabilising the seabed in addition to providing organic matter, shelter and food for a variety of fish, birds and invertebrates. Seagrass beds are vital nursery grounds for flatfish, and in some areas also for cephalopods. They are also known to be sensitive to changes in water quality and human disturbance. Seagrass beds have been designated as a UK Biodiversity Action Plan Habitat (underpinned by the Convention of Biological Diversity, Rio Earth Summit 1992), and as a Habitat of Principal Importance for the Conservation of Biological Diversity in Wales (NERC Act 2006: Section 42). The survey was due to be expanded in 2009 to other areas within the Pen Llyn a'r Sarnau Special Area of Conservation (SAC) and methodologies refined. 1. Develop methods to look at damage to seagrass beds caused by anchor chains compared to permanent moorings. 2. 'Ground-truth' aerial photographs of Porth Dinllaen and Milford Haven subtidal seagrass beds. 3. Test methods of measuring extent of large seagrass beds using volunteers. 4. Estimate density and measure depth of live seagrass in different parts of the bed. 5. Make note of any unusual feature of the seagrass bed.
- Identification
- Extent
- Distribution
- Quality
- Keywords
- Spatial Reference System
- Content
- Constraints
- Maintenance
- Metadata
Identification
- Identifier
- NRW_DS110284
- Alternative Title
-
- 2008 Seasearch Survey of the Entrances of Milford Haven, Pembrokeshire, Wales MRMCS01200000011
- Seagrass surveys in Porth Dinllaen and the Milford Haven
- Metadata Language
- English
- Lineage
-
Data is captured by using Volunteer divers who are CMAS 2 star qualified or equivalent with a minimum of 60 dives each. Anchor and density of seagrass shoots are captured by placing quadrats at 5 m intervals along a series of transects that are laid from the centre of the anchor point or seagrass bed. Transects are carried out in a north, south, west and east direction and where time allows also on NE, SW, NW and SE bearings. The number of shoots is counted in each 30 by 30 cm quadrat. In addition the condition of shoot and presence of seeds, black spot disease, snake pipefish and Sargassum muticum (and other non-native species), all of which are believed to be good indicators of the condition of the seagrass bed were recorded. The extent of the beds was also ground-truthed from aerial photographs. Areas (polygons) of suspected seagrass habitats were identified from the photos. An acoustic marker was deployed to the centroid of the polygon, divers were then deployed to the suspected outer edge of the seagrass bed and swam to the acoustic marker using a hand held acoustic homing device. Divers recorded where seagrass started and stopped, changed in seabed types, distance, depth and bearing. The method was repeated until all 8 cardinal points of the compass were complete (time allowing). Methods were tested at Porth Dinllaen as well as measures of extent, density and damaged from anchoring, whereas work in the Milford Haven concentrated on confirming the existence of seagrass beds and their deepest extent. All work carried out contributed to reporting on the features Favourable Conservation Status.
- Dataset Reference Date (Publication)
- 2008-12-31
Temporal Extent
- Begin date
- 2008-06-14
- End date
- 2008-09-12
- Topic category
-
- Biota
Extent
Extent
- Geographic Extent
- GWYNEDD - GWYNEDD
- Geographic Extent
- SIR BENFRO - PEMBROKESHIRE
))
Vertical Extent
- Medin Extent Keyword
-
benthic boundary layer
Vertical Extent
- Minimum value (metres)
- 1.28
- Maximum value (metres)
- -5.6
- Vertical CRS
Distribution
- Format Type and Description
-
-
Documents
(
)
- Specification
-
[A] Transects, density data and anchor data are MapInfo TAB files. [B] Species data held in excel spreadsheets. [C] Seasearch data held in Marine Recorder MRMCS01200000011. [D] Images as JPGs [E] Interim report as word and PDF file.
-
Documents
(
)
Quality
Data quality
- Quality Scope
- Dataset
- Conformity
- 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
- Explanation
-
This dataset has not been assessed for conformance to the referenced INSPIRE regulation.
- Degree
- false
- Lineage
-
Data is captured by using Volunteer divers who are CMAS 2 star qualified or equivalent with a minimum of 60 dives each. Anchor and density of seagrass shoots are captured by placing quadrats at 5 m intervals along a series of transects that are laid from the centre of the anchor point or seagrass bed. Transects are carried out in a north, south, west and east direction and where time allows also on NE, SW, NW and SE bearings. The number of shoots is counted in each 30 by 30 cm quadrat. In addition the condition of shoot and presence of seeds, black spot disease, snake pipefish and Sargassum muticum (and other non-native species), all of which are believed to be good indicators of the condition of the seagrass bed were recorded. The extent of the beds was also ground-truthed from aerial photographs. Areas (polygons) of suspected seagrass habitats were identified from the photos. An acoustic marker was deployed to the centroid of the polygon, divers were then deployed to the suspected outer edge of the seagrass bed and swam to the acoustic marker using a hand held acoustic homing device. Divers recorded where seagrass started and stopped, changed in seabed types, distance, depth and bearing. The method was repeated until all 8 cardinal points of the compass were complete (time allowing). Methods were tested at Porth Dinllaen as well as measures of extent, density and damaged from anchoring, whereas work in the Milford Haven concentrated on confirming the existence of seagrass beds and their deepest extent. All work carried out contributed to reporting on the features Favourable Conservation Status.
Keywords
Keywords
- Type
- Theme
Citation
- Date (Publication)
- 2008-06-01
Keywords
-
NRW Thesaurus
-
- anchor damage
- Pen Llyn a'r Sarnau cSAC
- Pembrokeshire Marine SAC
- Milford Haven
- eelgrass
- Porth Dinllaen
- zostera marina
- Type
- Theme
Citation
- Date (Publication)
- 2026-08-27
Keywords
- Type
- Theme
Citation
- Date (Publication)
- 2024-06-19
Keywords
-
IPSV Subjects List
-
- Volunteers
- Type
- Theme
Citation
- Date (Publication)
- 2020-11-18
Spatial Reference System
Content
Content Information
NRW Profile
Custom Elements
Constraints
Constraints
Limitations on Public Access and Use
- Restriction type
- Other restrictions
Access Constraints Directive
- Limitations
- no limitations
Access Constraints Text
- Other constraints
-
This data is jointly owned by NRW and Marine Conservation Society. In addition to this the following data is also considered OS derived data and is therefore jointly owned by NRW and the Ordnance Survey. There are no access restrictions on this data. However there are third party use restrictions. There are no access restrictions to this data. NRW may release, publish or disseminate it freely.
Use Constraints
- Use constraints type
- Other restrictions
- Other constraints
-
© CNC/NRW and Marine Conservation Society © Crown copyright. All rights reserved. Natural Resources Wales, AC0000849444 Data may be re-used under provision and in line with the terms of a NRW licence. Those seeking commercial re-use require a commercial licence available from the OS.
Metadata
Metadata
- File Identifier
- 4f4c4942-4343-5764-6473-313130323834 XML
- Metadata Language
- English
- Parent Identifier
-
Across Wales Diving Monitoring Project (2004)
NRW_DS109743
- Resource type
- Dataset
- Metadata Date
- 2026-09-28T13:50:40.702Z
- Metadata Standard Name
- NRW
- Metadata Standard Version
-
1.0