Seagrass mapping synthesis: A resource for coastal management in the Great Barrier Reef (NESP TWQ 3.2.1 and NESP TWQ 5.4, TropWATER, James Cook University)

This dataset summarises 35 years of seagrass data collection (1984-2018) within the Great Barrier Reef World Heritage Area into one GIS shapefile containing seagrass presence and absence survey data for 81,387 sites.

Managing seagrass resources in the GBRWHA requires adequate baseline information on where seagrass is (presence/absence), what species are present, and date of collection. This baseline is particularly important as a reference point against which to compare seagrass loss or change through time. The scale of the GBRWHA (1000s of kilometres) and the remoteness of many seagrass meadows from human populations present a challenge for research and management agencies reporting on the state of seagrass ecological indicators. Broad-scale and repeated surveys/studies of areas this large are logistically and financially impracticable. However seagrass data is being collected through various projects which, although designed for specific reasons, are amenable to collating a picture of the extent and state of the seagrass resource.

James Cook University’s Centre for Tropical Water & Aquatic Ecosystem Research (TropWATER) Seagrass Group (The Seagrass Group was part of the Queensland Government Department of Fisheries prior to 2013) has been collecting spatial data on GBR seagrass since the early 1980s. In this project TropWATER updated a previous synthesis of seagrass site data (NESP Project 3.1: https://eatlas.org.au/data/uuid/77998615-bbab-4270-bcb1-96c46f56f85a), with more recent data collected 2014-2018 to make this publicly available. Data included here from Cleveland Bay was used to classify seagrass community types, set desired state targets and for connecting sediment load targets to ecological outcomes for seagrass (NESP Project 3.2.1).

In making this data publicly available for management, the authors from the TropWATER Seagrass Group request being contacted and involved in decision making processes that incorporate this data, to ensure its limitations are fully understood.

Methods:
The sampling methods used to study, describe and monitors seagrass meadows were developed by the TropWATER Seagrass Group and tailored to the location and habitat surveyed; these are described in detail in the relevant publications (https://research.jcu.edu.au/tropwater). Methods for data sets collected by CSIRO are reported in Pitcher et al (2007).
1. Location – Latitudes and longitudes are from converted RADAR fix or GPS.
2. Depth – Depth for subtidal sites only estimated for each site using Beaman, R.J. (2017): High-resolution depth model for the Great Barrier Reef - 30 m (http://pid.geoscience.gov.au/dataset/115066). Depth for intertidal sites = 0.
3. Sediment – Dominant sediment type from deck description.

4. Seagrass metrics –Observers recorded seagrass presence/absence and presence/absence of each seagrass species using video transects, grabs, free diving, helicopter and walking:
- Video transect: Commonly used for subtidal meadows at each transect site. A CCTV camera was lowered to the bottom and towed at drift speed (less than one knot) for approximately 100m. Latitude/longitude represent the start of each transect. Footage was observed on a TV monitor and digitally recorded. The recording was paused at random times and frames selected to determine presence/absence for seagrass and each seagrass species. The camera sled included a small collecting net to obtain a specimen for identification.
- van Veen grab: Commonly used for subtidal meadows. A sample of seagrass was collected using a van Veen grab (grab area 0.0625 m2) to determine presence/absence for seagrass and each seagrass species at each site.
- Free diving, helicopter and walking: Presence/absence for seagrass and each seagrass species was estimated at each site, with a site representing approximately 10m2.

Geographic Information System (GIS)
All survey data were entered into a Geographic Information System (GIS) using MapInfo (generally pre-2005) then ArcMap® software. MapInfo spatial data was converted to ArcMap shapefiles. The GIS layer is a point (site) layer with a projected coordinate system of GDA94.
Seagrass site layer
This layer contains information on all data collected at assessment sites, and includes:
1. Temporal survey details – month and year when the survey occurred;
2. Spatial survey details – latitude/longitude, intertidal/subtidal, site depth in metres below mean sea level for subtidal sites;
3. Seagrass information including presence/absence of seagrass, and for each of 12 seagrass species;
4. Dominant sediment type;
5. Survey name; and
6. Sampling methods – helicopter, walking, boat with camera, diver, grab and/or sled.

Spatial limits
Seagrass data north and south of the GBRWHA were excluded from the layers and are held by TropWATER, JCU. Data were included when sites extended west of the GBRWHA boundary into coastal and estuarine water immediately adjacent. Modelled distributions are available (Coles et al 2009; Pitcher et al 2007) but not included here.

Taxonomy
Seagrass taxonomy has changed through time, with species such as Halophila ovata no longer recognised and some doubts expressed about other species whose morphology is relatively plastic. Field surveys have at times grouped species that are difficult to distinguish outside a laboratory. To address these issues we have amalgamated some species into complexes: Halophila ovata, Halophila minor, Halophila colesi/australis and Halophila ovalis are included as Halophila ovalis. Halodule pinifolia is grouped with Halodule uninervis. Data collected in winter may underestimate the extent of ephemeral species such as Halophila decipiens and Halophila tricostata. This is important if this composite is used to compare annual changes. Zostera muelleri subsp. capricorni has been abbreviated to Zostera capricorni throughout.

Base map
The base map used is courtesy ESRI 2020. Since the original surveys in 1980 there have been numerous changes to the shoreline, the most obvious being seaward encroachment of mangrove forests and reclamation for marina and coastal development. We have not edited seagrass sites to prevent older data from overlapping these features.

Data sets
Spatial data from over 200 site layers are included in this composite.
Further information can be found in this publication:
Carter, A. B., McKenna, S. A., Rasheed, M. A., McKenzie L, Coles R. G. (2016) Seagrass mapping synthesis: A resource for coastal management in the Great Barrier Reef World Heritage Area. Report to the National Environmental Science Programme. Reef and Rainforest Research Centre Limited, Cairns (22 pp). Available at http://nesptropical.edu.au/wp-content/uploads/2016/03/NESP-TWQ-3.1-FINAL...
and
Lambert, V., Collier, C., Brodie, J., Adams, M.P., Baird, M., Bainbridge, Z., Carter, A., Lewis, S., Rasheed, M., Saunders, M., O’Brien, K., (2020) Connecting Sediment Load Targets to Ecological Outcomes for Seagrass. Report to the National Environmental Science Program. Reef and Rainforest Research Centre Limited, Cairns (140pp.).

Limitations of the Data:
Data included extends back to the mid-1980s. Large parts of the coast have not been mapped for seagrass presence since that time. Technology and methods for mapping and position fixing have improved dramatically in 30 years. This layer represents the most reliable interpretation of that early data.

Spatial Extent: Seagrass data north and south of the GBRWHA were excluded from the layers. No seagrass site data exists east of the GBRWHA boundary. Data were included when sites extended west of the GBRWHA boundary into coastal and estuarine water immediately adjacent. Modelled distributions are available (Coles et al 2009; Pitcher et al 2007) but not included here.

Format:
This dataset consists of a point shapefile with a geographic coordinate system of GDA94. The site layer has been saved as a layer package with symbology representing seagrass presence/absence (Seagrass_sites_1984_2018.lpk)

Seagrass site Data:

- MONTH: Month of survey.

- YEAR: Year of survey.

- SURVEY_NAM: Description of the location of the survey.

- LATITUDE/LONGITUDE: survey site.

Seagrass information:

- PRESENCE_A: the presence/absence of seagrass where Yes = presence and No = absence.

- C_ROTUNDAT: presence/absence of Cymodocea Rotundata at the site.

- C_SERRULAT: presence/absence of Cymodocea Serrulata at the site.

- E_ACOROIDE: presence/absence of Enhalus Acoroides at the site.

- H_CAPRICOR: presence/absence of Halophila Capricorni at the site.

- H_DECIPIEN: presence/absence of Halophila Decipiens at the site.

- H_OVALIS: presence/absence of Halophila Ovalis at the site.

- H_SPINULOS: presence/absence of Halophila Spinulosa at the site.

- H_TRICOSTA: presence/absence of Halophila Tricostata at the site.

- H_UNINERVI: presence/absence of Halodule Uninervis at the site.

- S_ISOETIFO: presence/absence of Syringodium Isoetifolium at the site.

- T_CILIATUM: presence/absence of Thalassodendron Ciliatum at the site.

- T_HEMPRICH: presence/absence of Thalassia Hemprichii at the site.

- Z_CAPRICOR: presence/absence of Zostera Muelleri subsp. Capricorni at the site.

Additional site information:

- SEDIMENT: predominant type of sediment at the location, mud, gravel, reef, rock, rubble, sand, shell or not recorded.

- SURVEY_MET: helicopter, walking, boat with camera, diver, grab and/or sled

- TIDAL: intertidal or subtidal seabed at site

- DEPTH: the site depth in metres below mean sea level (dbMSL).

References:
Carter, A. B., McKenna, S. A., Rasheed, M. A., McKenzie L, Coles R. G. (2016) Seagrass mapping synthesis: A resource for coastal management in the Great Barrier Reef World Heritage Area. Report to the National Environmental Science Programme. Reef and Rainforest Research Centre Limited, Cairns (22 pp). Available at http://nesptropical.edu.au/wp-content/uploads/2016/03/NESP-TWQ-3.1-FINAL...

Lambert, V., Collier, C., Brodie, J., Adams, M.P., Baird, M., Bainbridge, Z., Carter, A., Lewis, S., Rasheed, M., Saunders, M., O’Brien, K., (2020) Connecting Sediment Load Targets to Ecological Outcomes for Seagrass. Report to the National Environmental Science Program. Reef and Rainforest Research Centre Limited, Cairns (140pp.).

Data Location:

This dataset is filed in the eAtlas enduring data repository at: data\NESP3\3.2.1_Eco-load-targets-seagrass