GBR - Large-scale manta tow surveys of densities of crown of thorns starfish and benthic cover by the AIMS LTMP - Spatial interpolation - 1986 - 2005 (MTSRF 1.1.5, AIMS)

Brief description

The purpose of this study is to quantify spatial and temporal changes in the density of crown-of-thorns starfish and benthic cover in the Great Barrier Reef. Broad-scale manta tow surveys have been conducted by the Long-Term Monitoring Program (LTMP) of the Australian Institiute of Marine Science since 1986, counting crown-of-thorns-starfish (COTS, Acanthaster planci).

COTS densities fluctuates over years forming southward bound ‘waves’ (the incidence of reefs with new active outbreaks moving south over time, due to the southward transport of larvae by the East Australian Current). Outbreaks in the Swains sector appear to occur independently of the main southward moving wave of COTS outbreaks. The highest overall mean number of COTS per tow was 1.17 in 1988. Active or incipient outbreaks were recorded on 16% and 11% of the reefs surveyed reefs in 2004 and 2005, respectively. The highest percentage of reefs with active outbreaks was 17%, recorded in 1987, 1999 and 2000.

Benthic cover of hard corals, soft corals and dead corals was also estimated on each tow, providing comprehensive estimates of cover around the whole perimeter of reefs.

As part of the Reef Atlas project (now the eAtlas) the manta tow observations were interpolated over the whole GBR by Glenn De'ath using Generalized Additive Models with a Quasibinomial fit. This produced a gridded version of the dataset and is available as a KML and ASCII grid file in WGS84 projection.