Demographic variability and long-term change in a coral reef sponge along a cross-shelf gradient of the Great Barrier Reef
R. J. Bannister A C D E , C. N. Battershill B C and R. de Nys A BA School of Marine and Tropical Biology, James Cook University, Townsville, Qld 4811, Australia.
B AIMS@JCU Tropical Aquaculture Program, James Cook University, Townsville, Qld 4811, Australia.
C Australian Institute of Marine Science, PMB 3 Townsville, Qld 4810, Australia.
D Current address: Institute of Marine Research, PO Box 1870, N-5817 Bergen, Norway.
E Corresponding author. Email: raymond.bannister@imr.no
Marine and Freshwater Research 61(4) 389-396 https://doi.org/10.1071/MF09067
Submitted: 27 March 2009 Accepted: 23 August 2009 Published: 27 April 2010
Abstract
Effects of anthropogenic inputs on corals are well documented in regard to the ecology of coral reefs. However, responses to anthropogenic changes by sponge assemblages, also a key component of coral reefs, have received less attention. This paper quantifies differences in abundance, size and distribution of the sponge Rhopaloeides odorabile across a cross-shelf reef system on the central Great Barrier Reef (GBR) from neritic to outer reef oligotrophic waters. Benthic surveys were conducted in reef habitats spatially separated across the continental shelf. The mean abundance of R. odorabile increased significantly with increasing distance from coastal habitats, with 3.5 times more individuals offshore than inshore. In contrast, the mean size (volume) of R. odorabile individuals did not differ significantly across the cross-shelf reef system. On inshore reefs, R. odorabile was restricted to depths <10 m, with a preference for shallower depths (5–6 m). On offshore reefs, R. odorabile was found as deep as 15 m and predominantly between 9 and 10 m. These demographic changes in R. odorabile populations, together with a general population size reduction from surveys made decades prior, suggest a response to anthropogenic impacts across the continental shelf of the central GBR.
Additional keywords: anthropogenic impacts, coral reefs, population dynamics, Porifera, Rhopaloeides odorabile, water quality.
Acknowledgements
This research was part of the sponge aquaculture program of AIMS@JCU, which received funding and in-kind support from the Australian Institute of Marine Science, James Cook University Advancement Program (Finfish and Emerging Aquaculture), Great Barrier Reef Research Foundation and the Coolgaree Aboriginal Corporation. We thank D. Bourne, S. Whalan and R. Hidlebaugh for assistance in the field, N. Paul for statistical advice and two anonymous referees for their constructive comments to help improve the quality of this manuscript.
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