Bioerosion rates of the sponge Cliona orientalis Thiele, 1900: spatial variation over short distances

We studied bioerosion rates and tissue growth of the sponge Cliona orientalis Thiele, 1900. Experimental blocks grafted with sponge tissue were deployed at three sites in Moreton Bay, QLD, Australia, which have different environmental conditions. Bioerosion rates varied between 4, 5, and 10 kg m⁻² year⁻¹ when related to final tissue area and between 4, 7, and 16 kg m⁻² year⁻¹ when related to initial tissue area of the graft, which supports findings of earlier studies. Comparing results between the sites, eutrophication appeared to have the most stimulating effect and is most likely to have caused the measured differences. However, slight differences between shading and current speeds may also have played a role. Variation may have masked spatial differences of sponge growth, which were insignificant between study sites. Growth and bioerosion nevertheless followed the same trend and were weakly correlated. Habitat quality itself had no influence. Overall, the twofold difference in sponge bioerosion over a distance as short as 10 km suggests that when estimating bioerosion rates, subsamples should be tested at different locations.