caa a22 4500 445819537 CHVBK 20180317145239.0 cr unu---uuuuu 170323e20110901xx s 000 0 eng 10.1007/s00338-011-0754-2 doi (NATIONALLICENCE)springer-10.1007/s00338-011-0754-2 Diel patterns in sea urchin activity and predation on sea urchins on the Great Barrier Reef [Elektronische Daten] [M. Young, D. Bellwood] Understanding diel patterns in sea urchin activity is important when assessing sea urchin populations and when interpreting their interactions with predators. Here we employ a combination of surveys and a non-invasive tethering technique to examine these patterns in an intact coral reef system on the Great Barrier Reef (GBR). We also assess local scale variation in relative diurnal predation pressure. Surveys revealed that sea urchins were active and exposed at night. Echinometra mathaei and Echinothrix calamaris were the most abundant species with significantly higher night densities (0.21 and 0.03 ind.m−2, respectively), than daytime densities (0.05 and 0.001, respectively). Bioassays revealed that exposed adult E. mathaei (the most abundant sea urchin species) were 30.8 times more likely to be eaten during the day than at night when controlling for sites. This observation concurs with widely held assumptions that nocturnal activity is a risk-related adaptive response to diurnal predation pressure. Despite relatively intact predator communities on the GBR, potential predation pressure on diurnally exposed E. mathaei assays was variable at a local scale and the biomass of potential fish predators at each site was a poor predictive measure of this variation. Patterns in predation appear to be more complex and variable than we may have assumed. Springer-Verlag, 2011 Coral reefs nationallicence Sea urchin nationallicence Predation nationallicence Echinometra mathaei nationallicence Tethering nationallicence Ecosystem function nationallicence Young M. Australian Research Council Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, 4811, Townsville, QLD, Australia aut Bellwood D. Australian Research Council Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, 4811, Townsville, QLD, Australia aut Coral Reefs Springer-Verlag 30/3(2011-09-01), 729-736 0722-4028 30:3<729 2011 30 338 https://doi.org/10.1007/s00338-011-0754-2 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00338-011-0754-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Young M. Australian Research Council Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, 4811, Townsville, QLD, Australia aut NATIONALLICENCE 700 1- Bellwood D. Australian Research Council Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, 4811, Townsville, QLD, Australia aut NATIONALLICENCE 773 0- Coral Reefs Springer-Verlag 30/3(2011-09-01), 729-736 0722-4028 30:3<729 2011 30 338 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer