DOI: 10.1594/pangaea.946610
title: Inshore seagrass meadows of the eastern Gulf of Carpentaria (Albany Island to Tarrant Point), Queensland, derived from field surveys conducted 21 October to 7 November, 1986

description: Approximately 18,366 ha of predominately intertidal and shallow subtidal seagrass meadows were mapped between Albany Island (Cape York) and Tarrant Point (southern Gulf of Carpentaria) in late 1986. The survey involved examination of 905 field validation points and identified 60 individual meadows.Field validation points were surveyed every 250 m along transects (perpendicular to the coast) approximately 2 – 5 km in length and 5 – 15 km apart, from shallow water to depths at which seagrasses could no longer be found. Spot-checks were also conducted at haphazard points between transects to check for continuity of meadows, habitats and bottom types. At each point, a pair of free-divers swam over a 15 m section of seabed and recorded the presence or absence of seagrass. Direct in situ observations at each point included visual estimates of the percentage of the seafloor covered by seagrass (2 replicates of a 0.25 m2 quadrat), seagrass species present, % algae cover and sediment type. Depths of survey points were recorded with an echo-sounder and a RADAR with a variable range marker was used to determine geographic position of sampling points.Boundaries of seagrass meadows were hand drawn on marine charts in the field and interpreted using one or more of the following: seagrass data at each point, extent of habitat visible from the vessel, low-tide aerial photography (1:50 000 captured between 1988 and 1992) and bathymetry. Boundaries of meadows in intertidal depths were usually mapped with greatest confidence, while boundaries in sub-tidal depths were mapped with less confidence because of: a) very gradual changes in habitat and b) poor underwater visibility. Bathymetry was used to help outline the meadow boundary between survey sites. Each seagrass meadow was assigned a qualitative mapping value (ranked 1 to 5), determined by the data sources and likely accuracy of mapping (a mapping quality rank of 1 is the highest).Twelve species of seagrass were found in the eastern Gulf of Carpentaria, including Cymodocea rotundata, Cymodocea serrulata, Halodule uninervis (wide- & narrow-leaf), Halodule pinifolia, Syringodium isoetifolium, Enhalus acoroides, Halophila decipiens, Halophila minor, Halophila ovalis, Halophila spinulosa, Halophila tricostata, and Thalassia hemprichii. Nine species were found in coastal habitats, ten around islands and seven species in rivers and estuaries. Seventeen seagrass meadow/community types were identified based on the order of species dominance. Most seagrasses in coastal areas of the eastern Gulf of Carpentaria are restricted to shallow water – mean depths of distribution for all species was less than 6 metres. Some deep water (down to 18 metres) seagrass is found in the Bamaga region but most seagrass north of Aurukun was either close inshore or restricted to estuaries. South of Aurukun almost all coastal seagrass was intertidal. Highly turbid water and mobile bottom sediment is most likely the mechanism restricting seagrass distribution. This is particularly the case between Edward river and Karumba where no seagrass was detected.