Seagrass, Macroalgae and Live coral from EMODnet Seabed Habitats

This data products displays seagrass, macroalgae and live coral from the existing library of habitat maps on the EMODnet Seabed Habitats map viewer.

These layers present the first attempt to map the areal extent of three Essential Ocean Variables (EOVs) in Europe

Introduction - Essential Ocean Variables from Seabed Habitats

The Global Ocean Observing System (GOOS) aims to promote common standards for data collection around the world. As part of this it has identified a series of variables that it hopes will lead to consistency and cost-effective marine monitoring, globally; these are known as 'Essential
Ocean Variables' (EOVs).

Of the ten EOVs in the 'Biology and Ecosystems' category there are three that relate to European seabed habitats, and within each EOV there are several sub-variables (specific variables that may be measured), one of which can be directly informed by habitat maps (Table 1).

Table 1. EOV variables and their sub-variables which can be mapped using data from the EMODnet Seabed Habitats portal.
EOV	Relevant sub-variable
Hard coral cover and composition	Live hard coral cover and extent
Seagrass cover and composition	Areal extent of seagrass meadows
Macroalgal canopy cover and composition	Areal extent

At the time of writing, the specification sheets for these habitats were still under development; therefore, the 3 EOV layers produced should also be seen as a “work in progress”.

EMODnet Seabed Habitats Map Viewer

EMODnet Seabed Habitats (ESBH) collates habitat maps, habitat models and habitat point data (Figure 1). It also produces a broadscale predictive map – EUSeaMap – which displays EUNIS marine habitats in European waters. A library of over 750 habitat maps have been collated to date. These maps span the extent of the Northeast Atlantic Ocean, Baltic Sea, Mediterranean Sea and Black Sea. The maps are in themed categories: EUNIS, Habitats Directive Annex 1, Composite Data Products and broad-scale predictive maps. (The maps are fully INSPIRE compliant. All maps can be freely downloaded from the ESBH portal along with metadata and confidence scores for each map).

Figure 1. Categories of maps available for download from the EBSH map viewer.

The resources on this web viewer were used in the compilation of composite layers displaying the areal extent of the three EOVs listed above.

Generating EOV layers

A list of habitats was prepared for each EOV with input from all ESBH project partners. These are presented in Appendix 1. After agreeing on the habitat lists, the relevant data for each EOV were extracted from the library of habitat maps on the portal. An R script was used to extract the data from all EUNIS habitat maps. Data from other maps types were extracted manually. The data were merged into standardised, non-overlapping polygon shapefiles and published as web mapping service (WMS) layers from the ESBH viewer.

1. Seagrass cover

Seagrasses provide essential habitat and nursery areas for many marine fauna. There are approximately 72 seagrass species that belong to four major groups: Zosteraceae, Hydrocharitaceae, Posidoniaceae and Cymodoceaceae. Zostera beds and Cymodecea meadows
are named on the OSPAR Threatened or Declining Habitats list (Appendix 2). Posidonia beds are protected under Annex I of the EU Habitats Directive (Appendix 3).

Seagrass habitat data have been collated from the following map categories from the ESBH
portal (order reflects the priority):

OSPAR threatened and/or declining habitats shapefile
Library of EUNIS habitat maps
non-EUNIS habitat maps
Annex I habitat maps
EUSeaMap (broad-scale predictive map)

Decision rules when dealing with overlaps
Layers (1), (2) and (3) are high resolution vector data. The EUSeaMap layer is a vectorised polygon layer converted from a 250 m model of predicted habitats. It was given the least priority on account of its course resolution (Figure 2a). OSPAR data was given priority over any overlapping data from EUNIS or non-EUNIS maps. In areas where 2 EUNIS maps overlapped, the map with the highest confidence was given priority (Figure 2b). In areas where there was a mosaic of live Posidonia and dead Posidonia, the
polygons displaying live Posidonia were selected for input into the final layer.

Figure 2. (a) Overlap between EUNIS habitat maps and EUSeaMap. (b) Overlaps between 2 EUNIS habitat maps with difference confidence assessment scores.

The final layer shows extent of seagrass collated by ESBH in European waters (Figure 3).

Figure 3. Collated seagrass polygon data from the ESBH map viewer used in the generation of the Seagrass EOV layer.

2. Macroalgal canopy cover

Kelp and fucoid brown algae are the dominant species that comprise macroalgal forests.Although not on any list of protected habitats, they provide many important functions including provision of nursery areas and protection from coastal erosion.
Macroalgal forest data have been collated from the following map categories from the ESBH portal (order reflects the priority):

Library of EUNIS habitat maps
non-EUNIS habitat maps

In areas where 2 EUNIS maps overlapped, the map with the highest confidence score was given
priority.
The final layer shows extent of macroalgal forests collated by ESBH in European waters (Figure 4).

Figure 4. Collated kelp and fucoid polygon data from the ESBH map viewer used in the generation of the Macroalgal Canopy Cover EOV layer.

3. Live coral

The health and areal extent of the hard coral community within a reef are direct indicators of the ability of a system to sustain the diversity of associated species. Lophelia pertusa and Coral gardens are both on the OSPAR List of threatened and/or declining species and habitats.
Live coral habitat data have been collated from the following map categories from the ESBH portal (order reflects the priority):

OSPAR threatened and/or declining habitats shapefile
Library of EUNIS habitat maps

The final layer shows extent of hard coral collated by ESBH in European waters (Figure 5).

Figure 5. Collated coral polygon data from the ESBH map viewer used in the generation of the Live Coral EOV layer.

Limitations and future improvements
There are a few key limitations with these products that are important to highlight.

1. Incompleteness

The composite maps are the most comprehensive collection of maps related to these EOVs in Europe. However, they cannot be assumed to show the true extent of the habitats, and likewise areas that are not mapped do not necessarily imply that the habitat is absent.
This is due to multiple reasons including:

We cannot guarantee that the collection of maps contains all the European seabed habitat maps in existence.
Much of the seabed has never been surveyed for these habitat types.
Whilst some surveys may have targeted these habitat types, the data may not facilitate the mapping of areal extents. For example, the Live coral layer produced is missing a lot of data, particularly in the Irish EEZ. One likely reason for the absence is that the output from Remotely Operated Vehicle (ROV) Surveys – the preferred survey technique for deep water corals – is a series of photos and a point dataset indicating the presence of a species or habitat. The format makes it difficult to translate into a polygon shapefile measuring extent. Advances in photogrammetric techniques may change this in the future but for now the best data will most likely be from a model or a point dataset.

2. Change over time is not explicit

Using the current method, if a single site has been mapped repeatedly over time, all instances of the habitat will be included from all the maps. This would lead to an overestimate of the extent of the habitat within the site if the extent had decreased over time.

3. There is no distinction between 'absent habitat' and 'no data'

It may be useful for a user to know whether a habitat is not mapped somewhere because the area hasn't been surveyed, or because it was surveyed and another habitat was present. For future versions of these composite products we recommend to:

Continue to collate individual habitat maps from surveys to provide the most comprehensive product possible.
Amend the method to make a distinction between 'absent habitat' and 'no data'.
Include a layer of point data - although points do not give an areal extent, they will help to indicate additional areas where the habitats have been observed but not necessarily mapped.
Make the time element more prominent. The current products show data from many different years presented together; however in reality the extent of the habitats may change over time as a result of natural variability or human activities.

More Information

References

European Seabed Habitats portal: https://www.emodnet-seabedhabitats.eu/

Products in product mapper

Seagrass cover: https://www.emodnet-biology.eu/geoviewer/?active_layer_ids=11992#!/

Macroalgal canopy cover: https://www.emodnet-biology.eu/geoviewer/?active_layer_ids=11991#!/

Live Coral: https://www.emodnet-biology.eu/geoviewer/?active_layer_ids=11990#!/

Authors

Eimear O’Keeffe (Marine Institute, Ireland) & Helen Lillis (Joint Nature Conservation Committee, England)

Appendix 1: Habitat lists for EOVs

Table 2 displays a list of habitat types from the EUNIS habitat classification system that the ESBH partners determined relate to
the seagrass EOV. These were used to extract the relevant polygons from the individual EUNIS habitats maps and EUSeaMap.
Also included are columns indicating with which Annex I and OSPAR habitats these habitat types might correspond.

Table 3 displays a list of habitat types from the EUNIS habitat classification system that the ESBH partners determined relate to
macroalgal cover EOV. These were used to extract the relevant polygons from the individual EUNIS habitat maps and
EUSeaMap. Also included is a column entitled “Other Habitat Maps” which lists two habitat types identified from non-EUNIS
habitat maps.

Table 4 displays a list of habitat types from the EUNIS habitat classification system that the ESBH partners determined relate to
the live coral EOV. These were used to extract the relevant polygons from the individual EUNIS habitats maps and EUSeaMap.
Also included are columns indicating with which Annex I and OSPAR habitats these habitat types might correspond.

Appendix 2: OSPAR List of Threatened and/or Declining Habitats

Table 5: Habitats selected from the OSPAR List for inclusion in the EOV layers.

Appendix 3: Marine habitats listed in Annex I of the EU Habitats Directive.

Table 6: Habitats selected from the Annex I List for inclusion in the EOV layers.