Small scale variation in Dictyocerid sponges in central Torres Strait, Australia (MTSRF Project 1.3.2)

Surveys for Coscinoderma sp. were done at 5 island-groups: Ugar (Stephen Island) and Erub (Darnley Island) in eastern Torres Strait; and Masig (Yorke Island), Poruma (Coconut Island) and Warraber (Sue Island) in central Torres Strait.

Sponge surveys were done at 7 or 8 randomly selected locations in each island group with each location at least 2 km apart, averaging 8 km. Each location was divided into 2 sites, approximately 200 m apart. At each site, three 30 x 1 m strip transects were quantitatively surveyed for the bath sponge, Coscinoderma sp. Transects were separated by at least 20 m and all were done between 7-11 m.

Sponges were grouped into 2 or 5 cm size classes. For any diseased sponge, the percent of infected or necrotic pinacoderm was noted. Four environmental factors (slope, %rock, %rubble and %sand) were recorded.

Tissue samples from 10 individuals of Coscinoderma sp. were collected from each island-group. In addition, 10 sponges were collected from each of two sites, Keats and Kodall islands, off Masig. Approximately 2 g of tissue from each sample was taken for DNA extraction, amplification and sequencing.

For microbial analysis, a DNA fingerprinting technique (denaturing gradient gel electropohoresis) was used to determine the stability of bacterial associations within Coscinoderma sp. across wide spatial scales.