Spatial distribution of the large foraminiferan Discobotellina biperforata, off the west shore of Moreton Island, Queensland, Australia

A hierarchical sampling study of the distribution of the large foraminiferan Discobotellina biperforata (Collins, 1958) was conducted along the west shore of Moreton Island, at Shark Spit and Tangalooma, in Moreton Bay, Queensland, between March and June 1995. D. biperforata is disc-shaped, with a test made up of organic matter, reinforced with sand grains. The species exhibits different test morphologies, the most abundant type being the biperforate which has two holes, or lunules, through its test. A less common type is the non-lunulate form, and the multiperforate and crescent-shaped types are rare. Possible abundance-substratum correlations were studied and the results indicated that D. biperforata is strongly correlated to a band of siltier and more organic-rich sediment found at the bottom of sand slopes running off Moreton Island. There was a significant difference in abundance between Tangalooma, where the mean abundance was 11.11 individuals per square meter (SD = 3.63) and Shark Spit, where it was found to be 7.73 individuals per square meter (SD = 3.06). No patchiness was apparent within the areas of siltier and organic-rich sediments. There was no significant difference in the ratio between the different forms within the areas sampled, but a size difference was apparent between locations, with larger specimens found at Tangalooma. The mean size of the specimens found was 27.7 mm in diameter. D. biperforata is the most abundant macrofaunal species in the area studied.