Subtidal benthic habitats of Yanyuwa Sea Country, Barni-Wardimantha Awara Indigenous Protected Area, Gulf of Carpentaria, Northern Territory, Australia

Full description

This dataset summarises subtidal benthic surveys in Yanyuwa Sea Country into 3 GIS shapefiles.
(1) A point (site) shapefile describes seagrass presence/absence at 849 subtidal sites surveyed by vessel.
(2) The meadow shapefile describes attributes of 46 subtidal seagrass meadows.
(3) The interpolation shapefile describes variation in subtidal seagrass biomass across the seagrass meadows.

This project is a partnership between the li-Anthawirriyarra rangers, Charles Darwin University, James Cook University, and Mabunji Aboriginal Resource Indigenous Corporation to map the subtidal habitats of the Yanyuwa Indigenous Protected Area (IPA), an area of profound importance to the Marra and Yanyuwa people and to the marine ecosystem of the Gulf of Carpentaria. Benthic habitat maps of Yanyuwa Country were produced, with a focus on seagrass. This project was funded by the NT Government Aboriginal Ranger Grant Program.

The sampling methods used to study, describe and monitor seagrass meadows were developed by TropWATER and tailored to the location and habitat surveyed; these are described in detail in the relevant publications (https://research.jcu.edu.au/tropwater).

Geographic Information System (GIS)
All survey data were entered into a Geographic Information System (GIS) using ArcGIS 10.8. Rectified colour satellite imagery of Yanyuwa Sea Country (Source: Allen Coral Atlas and ESRI), field notes and aerial photographs taken from the helicopter during surveys were used to identify geographical features, such as reef tops, channels and deep-water drop-offs, to assist in determining seagrass meadow boundaries. Three GIS layers were created to describe spatial features of the region: a site layer, seagrass meadow layer, and a seagrass biomass interpolation layer.

Site layer
This layer contains information on data collected at assessment sites. This layer includes:
1. Temporal survey details – Survey date;
2. Spatial position - Latitude/longitude;
3. Survey location;
4. Seagrass information including presence/absence of seagrass, above-ground biomass (total and for each species), percent cover of seagrass at each site;
5. Benthic macro-invertebrate information including the percent cover of hard coral, soft coral, sponges and other benthic macro invertebrates (e.g. ascidian, clam) at a site;
6. Algae information including percent cover of algae at a site and percent contribution of algae functional groups to algae cover at a site;
7. Open substrate – the percent cover of the site that had no flora or habitat forming benthic invertebrates present;
8. Dominant sediment type - Sediment type based on grain size visual assessment or deck descriptions.
9. Survey method and vessel;
10. Relevant comments and presence/absence of megafauna and animals of interest (dugong, turtle, dolphin); and
11. Data custodians.

Seagrass meadow layer
Seagrass presence/absence site data, mapping sites, field notes, and satellite imagery were used to construct meadow boundaries in ArcGIS®. The meadow (polygon) layer provides summary information for all sites within each seagrass meadow, including:
1. Temporal survey details – Survey month and year as individual columns and the survey date (the date range the survey took place);
2. Spatial survey details – Survey location, meadow identification number that identifies the reef name and the meadow number. This allows individual meadows to be compared among years;
3. Survey method;
4. Meadow depth for subtidal meadows;
5. Species presence – a list of the seagrass species in the meadow;
6. Meadow density – Seagrass meadows were classified as light, moderate, dense based on the mean biomass of the dominant species within the meadow. For example, a Thalassia hemprichii dominated meadow would be classed as “light” if the mean meadow biomass was <5 grams dry weight m-2 (g DW m-2), and “dense” if mean meadow biomass was >25 g DW m-2.
7. Meadow community type – Seagrass meadows were classified into community types according to seagrass species composition within each meadow. Species composition was based on the percent each species’ biomass contributed to mean meadow biomass. A standard nomenclature system was used to categorize each meadow.
8. Mean meadow biomass measured in g DW m-2 (+ standard error if available);
9. Meadow area (hectares; ha) (+ mapping precision) of each meadow was calculated in the GDA 2020 Geoscience Australia MGA Zone 53 projection using the ‘calculate geometry’ function in ArcMap. Mapping precision estimates (R; in ha) were based on the mapping method used for that meadow. Mapping precision estimate was used to calculate an error buffer around each meadow; the area of this buffer is expressed as a meadow reliability estimate (R) in hectares;
10. Any relevant comments;
11. Data custodians.

Seagrass meadow layer
Seagrass presence/absence site data, mapping sites, field notes, and satellite imagery were used to construct meadow boundaries in ArcGIS®. The meadow (polygon) layer provides summary information for all sites within each seagrass meadow, including:
1. Temporal survey details – Survey month and year as individual columns and the survey date (the date range the survey took place);
2. Spatial survey details – Survey location, meadow identification number that identifies the reef name and the meadow number. This allows individual meadows to be compared among years;
3. Survey method;
4. Meadow depth for subtidal meadows;
5. Species presence – a list of the seagrass species in the meadow;
6. Meadow density – Seagrass meadows were classified as light, moderate, dense based on the mean biomass of the dominant species within the meadow. For example, a Thalassia hemprichii dominated meadow would be classed as “light” if the mean meadow biomass was <5 grams dry weight m-2 (g DW m-2), and “dense” if mean meadow biomass was >25 g DW m-2.
7. Meadow community type – Seagrass meadows were classified into community types according to seagrass species composition within each meadow. Species composition was based on the percent each species’ biomass contributed to mean meadow biomass. A standard nomenclature system was used to categorize each meadow.
8. Mean meadow biomass measured in g DW m-2 (+ standard error if available);
9. Meadow area (hectares; ha) (+ mapping precision) of each meadow was calculated in the GDA 2020 Geoscience Australia MGA Zone 53 projection using the ‘calculate geometry’ function in ArcMap. Mapping precision estimates (R; in ha) were based on the mapping method used for that meadow. Mapping precision estimate was used to calculate an error buffer around each meadow; the area of this buffer is expressed as a meadow reliability estimate (R) in hectares;
10. Any relevant comments;
11. Data custodians.

Seagrass biomass interpolation layer
An inverse distance weighted (IDW) interpolation was applied to seagrass site data to describe spatial variation in seagrass biomass within seagrass meadows. The interpolation was conducted in ArcMap 10.8.

Base map
The base map used is courtesy ESRI 2024.

Limitations of the data
Recordings of dugong, turtle, and dolphin were opportunistic sightings and recorded if nearby a survey site. This presence/absence data was not collected as part of a formal structured survey of these animals and should therefore be used with caution.

Format of the data
This dataset consists of 1 point layer package, 1 polygon layer package and 1 raster file:
1. Yanyuwa Sea Country subtidal sites 2022-2023.lpk - Symbology representing seagrass presence/absence at each survey site.
2. Yanyuwa Sea Country subtidal seagrass meadow community type 2022-2023.lpk - Symbology representing dominant species (in terms of biomass) for each intertidal meadow.
3. Yanyuwa Sea Country subtidal seagrass biomass interpolation 2022-2023.lpk - Symbology representing the spatial variation in seagrass biomass within each seagrass meadow.

Data Dictionary
Yanyuwa Sea Country subtidal sites 2022-2023 (point data)
SITE (text) - Unique identifier representing a single sample site
MEADOW (text) - Unique identifier representing what meadow the sample site is located in. Blank if sample site is not located within a meadow
SURVEY_DATE (numeric) – survey date (day/month/year)
MONTH (text) – survey month
YEAR (numeric) – survey year
SURVEY_NAME (text) – Name of survey location
LOCATION (text) – Name of survey location
LATITUDE (numeric) – Site location in decimal degrees south
LONGITUDE (numeric) – Site location in decimal degrees east
TIME (numeric) – sample time (24 hours; GMT +9:30) (NT time - subtidal sites only)
DBMSL (numeric) – depth below mean sea level (metres) for subtidal sites. Intertidal sites depth recorded as 0.
TIDAL (text) – identifying if the site was in an intertidal or subtidal location
SUBSTRATE (text) – tags identifying the types of substrates at the sample site. Possible tags are Mud, Sand, Coarse Sand, Silt, Shell, Rock, Reef, Rubble and various combinations. Listed in order from most dominant substrate to least dominant.
SEAGRASS_P (numeric) – Absence (0) or Presence (1) of seagrass
SEAGRASS_C (numeric) - Estimated % of seagrass cover at sample site
SEAGRASS_B (numeric) - Estimated total biomass per square metre for sample site calculated from the mean of three replicate quadrats. Unit is gdw m-2.
SEAGRASS_SE (numeric) – standard error of biomass at sample site calculated from the three replicate quadrats used to estimate biomass at a sample site. Unit is gdw m-2.
EXCLUDE_B (numeric) – Include (0) or Exclude (1). Any site identified that needs to be excluded from contributing to the calculation of mean meadow biomass, e.g. where a visual estimate of biomass could not be optioned (i.e. no visibility at the site, only a van Veen sediment grab was used at the site)
C. rotundata (numeric) – Estimated biomass of Cymodocea rotundata at the sample site. Unit is gdw m-2.
C. serrulata (numeric) – Estimated biomass of Cymodocea serrulata at the sample site. Unit is gdw m-2.
E. acoroides (numeric) – Estimated biomass of Enhalus acoroides at the sample site. Unit is gdw m-2.
H. uninervis (narrow) (numeric) – Estimated biomass of Halodule uninervis (narrow leaf morphology) at the sample site. Unit is gdw m-2.
H. uninervis (wide) (numeric) – Estimated biomass of Halodule uninervis (wide leaf morphology) at the sample site. Unit is gdw m-2.
H. decipiens (numeric) – Estimated biomass of Halophila decipiens at the sample site. Unit is gdw m-2.
H. ovalis (numeric) – Estimated biomass of Halophila ovalis at the sample site. Unit is gdw m-2.
H. spinulosa (numeric) – Estimated biomass of Halophila spinulosa at the sample site. Unit is gdw m-2.
H. tricostata (numeric) – Estimated biomass of Halophila tricostata at the sample site. Unit is gdw m-2.
S. isoetifolium (numeric) – Estimated biomass of Syringodium isoetifolium at the sample site. Unit is gdw m-2.
T. ciliatum (numeric) – Estimated biomass of Thalassodendron ciliatum at the sample site. Unit is gdw m-2.
T. hemprichii (numeric) – Estimated biomass of Thalassia hemprichii at the
Z. muelleri (numeric) – Estimated biomass of Zostera muelleri at the sample site. Unit is gdw m-2.
TURF_MAT (numeric) – (Turf mat algae % contribution to algae cover). Algae that forms a dense mat on the substrate
ERECT_MACROPHYTE (numeric) – (Erect macrophyte algae % contribution to algae cover). Macrophytic algae with an erect growth form and high level of cellular differentiation, e.g. Sargassum, Caulerpa and Galaxaura species
ENCRUSTING (numeric) – (Encrusting algae % contribution to algae cover). Algae that grows in sheet-like form attached to the substrate or benthos, e.g. coralline algae.
ERECT_CALCAREOUS (numeric) – (Erect calcareous algae % contribution to algae cover). Algae with erect growth form and high level of cellular differentiation containing calcified segments, e.g. Halimeda species.
FILAMENTOUS (numeric) – (Filamentous algae % contribution to algae cover). Thin, thread-like algae with little cellular differentiation.
HARD_CORAL (numeric) – (Hard coral %). All scleractinian corals including massive, branching, tabular, digitate and mushroom
SOFT_CORAL (numeric) – (Soft coral %). All alcyonarian corals, i.e. corals lacking a hard limestone skeleton
SPONGE (numeric) – (Sponge %)
OTHER_BMI (numeric) – Any other benthic macro-invertebrates identified, e.g. oysters, ascidians, clams. Other benthic macro-invertebrates are listed in the “comments” attribute for intertidal and shallow subtidal camera drops, and listed as percent cover in the deepwater GIS.
OPEN_SUBSTRATE (numeric) – Open substrate, no seagrass, algae or benthic macro-invertebrates at site
*Note: SEAGRASS_C + TURF_MAT + ERECT_MACROPHYTE + ENCRUSTING + ERECT_CALCAREOUS + FILAMENTOUS + HARD_CORAL + SOFT_CORAL + SPONGE + OTHER_BMI + OPEN_SUBSTRATE = 100% of benthic cover
DUGONG (numeric) - Absence (0) or Presence (1) of dugong/s near site
TURTLE (numeric) - Absence (0) or Presence (1) of turtle/s near site
DOLPHIN (numeric) - Absence (0) or Presence (1) of dolphin/s near site
DFT_PRESENT (numeric) - Absence (0) or Presence (1) of dugong feeding trails at site. Only clearly visible and therefore assessed at intertidal sites. Subtidal sites not assessed for DFTs coded as -999
METHOD (text) – e.g. helicopter, walking, hovercraft, boat-based including camera, free diving, scuba diving, van Veen grab, sled net
VESSEL (text) – Vessel name (if known)
COMMENTS (text) – Any comments for that site
CUSTODIAN (text) – Custodian/owner of the data set
UPDATED (text) - The date the shapefile was last updated
AUTHOR (text) – Creator of GIS from the data set


Yanyuwa Sea Country subtidal seagrass meadows 2022-2023 (polygon data)
ID (numeric) - Unique identifier representing a single meadow
SURVEY_NAME (text) – Name of survey
LOCATION (text) – Name of survey location
SURVEY_DATE (text) – Sample date (day/month/year)
MONTH (numeric) – Sample month
YEAR (numeric) – Sample year
PERSISTENCE (text) – Meadow form on three categories: enduring, transitory, unknown
DENSITY (text) – Meadow density categories (light, moderate, dense)
TYPE (text) - Meadow community type determined according to seagrass species composition within the meadow
SPECIES (text) – (Seagrass species): seagrass species found within the meadow. Species are recorded as abbreviated species names such as “E. acoroides”
TOT_SITES (numeric) – (Number of survey sites): the number of sample sites within the meadow
BIOMASS (numeric) – (Seagrass biomass (gdw m-2)): Mean biomass calculated from all sites (BIO_SITES) within an individual meadow
SE (numeric) – (Standard Error (gdw m-2)): The error is a calculation of standard error of biomass from all (BIO_SITES) sites within an individual meadow
AREA_HA (numeric) – (Meadow area (Ha)): Estimated meadow size (unit: hectares)
R_M (numeric) – (Meadow mapping precision (m)): Estimated mapping precision based on mapping method.
R_HA (numeric) - (Meadow reliability estimate (Ha)): Meadow reliability estimate (unit: hectares). Expressing the error buffer around each meadow as calculated from the mapping precision estimate
SURVEY METHOD (text) – e.g. helicopter, walking, hovercraft, boat-based including camera, free diving, scuba diving, van Veen grab, sled net
VESSEL (text) – Vessel name (if known)
COMMENTS (text) – Any relevant comments for that meadow
UPDATED (date) – The date the shapefile was last updated
CUSTODIAN (text) – Custodian/owner of the data set
AUTHOR (text) – Creator of GIS from the data set

Yanyuwa Sea Country subtidal seagrass biomass interpolation 2022-2023 (interpolation layer)
Inverse Distance Weighted interpolation.
Band 1: Interpolated biomass in gdw m-2

References:
Intertidal survey (2021-2022) Report: Groom R, Carter A, Collier C, Firby L, Evans S, Barrett S, Hoffmann L, van de Wetering C, Shepherd L, Evans S, Anderson S. (2023) Mapping Critical Habitat in Yanyuwa Sea Country. Report to the National Environmental Science Program. Charles Darwin University, pp. 40. Available at: https://www.nespmarinecoastal.edu.au/wp-content/uploads/2023/07/NESP-MaC-Hub-Project-1.12_Groom-et-al-FINAL-REPORT.pdf

Intertidal survey (2021-2022) Dataset: Groom, R., Carter, A. B., Collier, C., Firby, L., Evans, S., Barrett, S., Hoffman, L., van de Wetering, C., Evans, S., Simon, S., & Anderson, S. (2023). Benthic habitats of Yanyuwa Sea Country, Barni - Wardimantha Awara Indigenous Protected Area, Gulf of Carpentaria, Northern Territory, Australia (NESP MaC Project 1.12, JCU & CDU) [Data set]. eAtlas. https://doi.org/10.26274/V6K5-2F34

eAtlas Processing:
The original data were provided as Layer Packages. The lpkg files were imported to ArcGIS and exported as shapefiles and GeoTiff. A modification was made to the Site layer to remove sensitive data (single column and two comments) at the request of the data provider. All other data are as provided.

Location of the data:
This dataset is filed in the eAtlas enduring data repository at: data\2020-2029-other\NT_JCU_Yanyuwa-Sea-Country_2022-2023

Lineage

Maintenance and Update Frequency: asNeeded