COMPLEX PATTERNS OF CHANGE IN THE MACROBENTHOS OF A LARGE SANDBANK FOLLOWING DREDGING .1. COMMUNITY ANALYSIS

The impact of dredging operations on the marine benthos of a large, subtropical, sublittoral sandbank (Middle Banks, Moreton Bay, Queensland, Australia) was investigated during July and Aug. 1982. Statistical comparisons (ANOVA) of species richness, total abundance, Shannon diversity and Shannon equitability were made with extensive predredging data base. Both the dredged and adjacent areas were investigated. Changes in sediments and the distribution and deposition rates of the dredge plumes were also examined. There were significant decreases (P .ltoreq. 0.025) in the species richness (from 33.0 to 16.6 mean number of species/site), total abundance (from 117.9-47.6 mean number of individuals/site) and Shannon diversity (from 4.03-3.22 mean diversity/site) within the dredged area. There were significant increases (P .ltoreq. 0.01) in species richness (from 31.2-67.9 mean number of species per site) and total abundance (from 177.7-752 mean number of individuals/site) in adjacent benthic areas. The distribution and the predicted deposition rates of the sediment plume correlated precisely with the area of enhancement (P < 0.05). The potential causal relationshp between deposition and faunal enhancement is discussed. The enhanced effect is probably a response of the benthic biota to an increase in available resources.