IMAS Metadata Catalogue
Changes in seagrass coverage in Cockburn Sound, Western Australia between 1967 and 1999
Changes in seagrass coverage in Cockburn Sound from 1967 to 1999 were assessed from aerial photographs using modern mapping methods with the aim of accurately determining the magnitude of change in hectares of seagrasses between 1967 and 1999.
Simple
Identification info
- Date (Creation)
- 2007-11-28
- Date (Publication)
- 2017-09-11T00:00:00
Author
The University of Western Australia (UWA)
35 Stirling Highway, Crawley
Perth
Western Australia
6009
Australia
Author
Author
DAL Science and Engineering (DALSE)
Author
Alex Wyllie and Associates Pty Ltd
Author
Kevron Aerial Surveys Pty Ltd
- Purpose
- To set up a baseline for future monitoring of seagrass loss in Cockburn Sound.
- Credit
- This project was funded by a consortium of industries and Western Australian Government Departments: Cockburn Cement Pty Ltd., Departments of Environmental Protection, Commerce and Trade and Resources Development, Fremantle Port Authority, James Point Pty Ltd., Kwinana Industries Council, Royal Australian Navy, Water Corporation of Western Australia and Waters and Rivers Commission of Western Australia.
- Status
- Completed
Principal investigator
School of Biological Sciences (SBS), The University of Western Australia (UWA) - Kendrick, Gary
School of Biological Sciences (SBS), The University of Western Australia (UWA)
35 Stirling Hwy
Crawley
WA
6009
Australia
- Spatial representation type
- Vector
- Topic category
-
- Oceans
- Biota
Extent
N
S
E
W
))
Temporal extent
- Time period
- 1967 1999
Vertical element
- Minimum value
- 0
- Maximum value
- 10
- Identifier
- EPSG::5715
- Name
- MSL depth
- Maintenance and update frequency
- Not planned
- NASA/GCMD Keywords, Version 8.5
- CAAB - Codes for Australian Aquatic Biota v2.
-
- Amphibolis antarctica
- 63 618004
- Amphibolis griffithii
- 63 618005
- Posidonia australis
- 63 617002
- Posidonia coriacea
- 63 617008
- Posidonia sinuosa
- 63 617003
- Halophila ovalis
- 63 605002
- Heterozostera tasmanica
- 63 619004
- Syringodium isoetifolium
- 63 618001
- Keywords (Theme)
-
- Benthic habitat
Resource specific usage
- Specific usage
- Data supplied for use by the Seamap Australia Project.
- ()
Resource constraints
- Classification
- Unclassified
Resource constraints
- Linkage
-
http://i.creativecommons.org/l/by/4.0/88x31.png
License Graphic
- Title
- Creative Commons Attribution 4.0 International License
- Website
-
http://creativecommons.org/licenses/by/4.0/
License Text
- Other constraints
- Cite data as: University of Western Australia & Western Australian Government (2007). Changes in seagrass coverage in Cockburn Sound, Western Australia between 1967 and 1999. Data accessed at http://metadata.imas.utas.edu.au/geonetwork/srv/en/metadata.show?uuid=81edfca0-9d59-11dc-a0ca-00188b4c0af8 on (access date).
- Other constraints
- This dataset is hosted by the Institute for Marine and Antarctic Studies (IMAS), University of Tasmania, on behalf of a consortium of industries and Western Australian Government Departments for the purposes of the Seamap Australia collaborative project (testing a national marine benthic habitat classification scheme).
- Language
- English
- Character encoding
- UTF8
- Supplemental Information
- Gary A. Kendrick, Matt J. Aylward, Bruce J. Hegge, Marion L. Cambridge, Karen Hillman, Alex Wyllie and Des A. Lord (2002) Changes in seagrass coverage in Cockburn Sound, Western Australia between 1967 and 1999. Aquatic Botany Volume 73, Issue 1, May 2002, Pages 75-87 http://dx.doi.org/10.1016/S0304-3770(02)00005-0 Kendrick, G. A., Hegge, B. J., Wyllie, A., Davidson, A., & Lord, D. A. (2000). Changes in seagrass cover on Success and Parmelia Banks, Western Australia between 1965 and 1995. Estuarine, Coastal and Shelf Science, 50(3), 341-353. DAL Science and Engineering (DALSE), University of Western Australia Botany Department, Alex Wyllie & Associates Pty Ltd, NGIS Australia & Kevron Aerial Surveys Pty Ltd 2000, Seagrass mapping Owen Anchorage and Cockburn Sound 1999, D.A. Lord & Associates Pty Ltd (DAL) Report No. 94/026/S3/2.
Content Information
- Content type
- Physical measurement
- Description
- Taxonomic identification of seagrass species
Identifier
- Name
-
Descr
- Description
- Appended to original data for styling purposes for the Seamap Australia Project.
- Name
-
Benthic habitat
- Name
-
SM_HAB_CLS
Distribution Information
- Distribution format
-
-
ESRI Shapefile
-
ESRI Shapefile
- OnLine resource
-
SHAPE-ZIP
Data via WFS - 1967 survey of Cockburn Sound seagrass in Shapefile format
- OnLine resource
-
SHAPE-ZIP
Data via WFS - 1972 survey of Cockburn Sound seagrass in Shapefile format
- OnLine resource
-
SHAPE-ZIP
Data via WFS - 1981 survey of Cockburn Sound seagrass in Shapefile format
- OnLine resource
-
SHAPE-ZIP
Data via WFS - 1995 survey of Cockburn Sound seagrass in Shapefile format
- OnLine resource
-
SHAPE-ZIP
Data via WFS - 2009 survey of Cockburn Sound seagrass in Shapefile format
- OnLine resource
-
Associated publication
Kendrick, G. A., Aylward, M. J., Hegge, B. J., Cambridge, M. L., Hillman, K., Wyllie, A., & Lord, D. A. (2002). Changes in seagrass coverage in Cockburn Sound, Western Australia between 1967 and 1999. Aquatic Botany, 73(1), 75-87. https://doi.org/10.1016/S0304-3770(02)00005-0
- OnLine resource
-
seamap:SeamapAus_WA_CockburnSound_seagrass_1967
MAP - Cockburn Sound seagrass (1967 survey)
- OnLine resource
-
seamap:SeamapAus_WA_CockburnSound_seagrass_1972
MAP - Cockburn Sound seagrass (1972 survey)
- OnLine resource
-
seamap:SeamapAus_WA_CockburnSound_seagrass_1981
MAP - Cockburn Sound seagrass (1981 survey)
- OnLine resource
-
seamap:SeamapAus_WA_CockburnSound_seagrass_1995
MAP - Cockburn Sound seagrass (1995 survey)
- OnLine resource
-
seamap:SeamapAus_WA_CockburnSound_seagrass_1999
MAP - Cockburn Sound seagrass (1999 survey)
Resource lineage
- Statement
- - Mapping of seagrasses - To determine seagrass distribution, submerged vegetation was mapped from recent and historical aerial photography. Distribution of seagrass assemblages and reef were then determined in 1999 from towed underwater video. We define assemblages of seagrasses as multi-species assemblages dominated, or characterised, by single or multiple species as determined from their relative abundance in video footage. In Cockburn Sound, the seagrass species Amphibolis antarctica, Amphibolis griffithii, Posidonia australis, Posidonia coriacea, Posidonia sinuosa, Halophila ovalis, Heterozostera tasmanica and Syringodium isoetifolium were components of the seagrass assemblages. We did not map to single species, although a single species assemblage is composed of more than 70% of that species. Results from mapping of aerial photographs and underwater video footage were then combined in a GIS to create coverage maps of seagrass assemblages, reef and unvegetated sand. We describe our maps as coverage maps, rather than maps of seagrass cover to reduce the confusion between the area covered by a single species of seagrass and the area occupied by an assemblage of seagrasses than is dominated by one or a few species. This is not presence-absence mapping, as vegetated assemblages do not exclude all unvegetated habitat. - Study area and mapped regions - Cockburn Sound is a sheltered marine embayment 16 km long × 9 km wide, and consists of a deep central basin (17-22 m deep) surrounded by shallow platforms. The shallow platforms vary in width from 50 m to 3 km and are where seagrass meadows are found (see thumbnail). The seagrass mapping area was delineated as shallow platforms to a depth of 10 m and covered an area of approximately 3667 ha. Coverage of all submerged vegetation was separately calculated for three regions called Cockburn Sound East, South and West. Cockburn Sound East encompassed most of the eastern bank from Woodmans Point to south of James Point. Cockburn Sound South contained the shallow bank near Rockingham, the southern sand flats and Careening Bay, Garden Island. Cockburn Sound West encompassed the western bank north of Careening Bay and shallow waters north of Garden Island. Benthic features are difficult to resolve from aerial photographs at depths greater than 10 m as seagrasses become sparsely distributed at these depths. Hence, the 10 m isobath and the coastline are used to delineate the mapping boundaries within each of these regions. - Data sources - In 1999, flights to acquire aerial photographs were purpose-flown in late-February to early-March when conditions were optimal. These conditions included maximum seagrass leaf cover; maximum water clarity; minimum haze from the adjacent industrial zone; minimum turbidity from dredging, river outflow or industrial activities; minimum cloud cover; weak prevailing winds; and incident sun angle at 20-30°. Colour photography with a yellow lens filter was obtained at two altitudes. High altitude imagery was collected at 10,000 m (scale, 1:55,000) for accurate ortho-rectification. The resulting imagery was used as a rectification base for the low-altitude imagery that was obtained at an altitude of 3,800 m. Mapping of the historical seagrass coverage in Cockburn Sound was conducted using rectified and mosaicked imagery obtained in: 1994 (majority of imagery obtained on 4 and 8 January 1994 and some on 6 January 1995); 1981 (imagery from 13 June 1981); 1972 (imagery from 2 May 1972); and 1967 (imagery from 20 March 1967). - Image geo-referencing and rectification - Images were initially rectified (Datum: WGS-84) using ERMapper-6.1 to a resolution of 2.0 m (Earth Resource Mapping, 2000). The images were initially scanned into three colour bands (red, green and blue). The red band of the colour images contained almost no information for marine benthic habitat, as red light was severely attenuated through the water column. The green band was better than the red, though images had low contrast due to atmospheric attenuation. The blue band provided the best contrast between vegetated and unvegetated habitats and therefore was the only band used for mapping. It was converted to 256 greyscales. Rectified imagery was processed using Geographic Resources Analysis Support System (GRASS) GIS software (Neteler, 1998). GRASS is a raster-based GIS and the 2.0 m cell size and its spatial location (spatial integrity) was strictly maintained in rectified imagery. Also the same spatial integrity was kept consistent among the rectified imagery for the different years mapped (spatial consistency). - Automated mapping - A computerised, semi-automated, greyscale segmentation mapping method called Spann-Wilson segmentation (Spann and Wilson, 1985) was employed to map submerged vegetation. Spann-Wilson combines locally adaptive segmentation (local centroid) with pre-processing using multi-level quad-tree smoothing. The segmentation method was implemented using the Xite image-processing software (The University of Oslo, 1999). The size of the moving histogram window and the number of quad-tree smoothing levels were controlled by the operator, although for this exercise were set to 324 m2 and 3-4. Spann-Wilson segmentation was very effective in defining the boundaries of seagrass meadows reefs and unvegetated sand from greyscale images. It reduced the original 256 greyscales from the aerial photographs to four greyscales. The operator then chose a greyscale which most closely coincided with the visually interpreted boundary between vegetated and unvegetated habitat. - Control rules for mapping - The vegetated areas were distinguished from the unvegetated areas as they had a distinct photo-tone of medium to dark grey. To enable consistent coverage mapping across the study area, a series of control rules were used (Kendrick et al., 2000). These control rules were as follows: - Isolated vegetated patches less than 30 m2 in area were not mapped. - Vegetated patches, that were greater than 30 m2 and less than 100 m2 were mapped as separate patches when the distance between one patch and another was greater than the diameter of the patch. - Vegetated patches, that were greater than 30 m2 and less than 100 m2 were mapped as a single meadow when the distance between one patch and another was less than the diameter of the patch. Unvegetated areas within the meadow with an area greater than 100 m2 were mapped. - Vegetated patches greater than 100 m2 were mapped and the edges of these areas were traced accurately. Unvegetated regions within these patches with areas greater than 100 m2 were mapped. The control rules were applied automatically during mapping with control rules 2?4 processed during the Spann-Wilson segmentation step to a 324 m2 moving window, and control rule 1 applied after the segmentation step to 1 km2 areas using a PERL script.
- Hierarchy level
- Dataset
- Hierarchy level
- Dataset
Platform
Identifier
- Code
- research aeroplane
Metadata
- Metadata identifier
-
urn:uuid/81edfca0-9d59-11dc-a0ca-00188b4c0af8
- Language
- English
- Character encoding
- UTF8
Point of contact
- Parent metadata
Type of resource
- Resource scope
- Dataset
- Metadata linkage
-
https://metadata.imas.utas.edu.au/geonetwork/srv/eng/catalog.search#/metadata/81edfca0-9d59-11dc-a0ca-00188b4c0af8
Point of truth URL of this metadata record
- Date info (Creation)
- 2020-09-23T10:52:27
- Date info (Revision)
- 2023-09-16T11:24:28
Metadata standard
- Title
- ISO 19115-3:2018
Overviews
Spatial extent
N
S
E
W
Provided by
Associated resources
Not available