| Summary: | Maintenance and Update Frequency: notPlanned 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. Statement: - 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 ...
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