Growth of the encrusting sponge Tedania anhelans (Lieberkuhn) on vertical and on horizontal surfaces of temperate subtidal reefs

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Contents Vol 57(1)

doi:10.1071/MF05092

Growth of the encrusting sponge Tedania anhelans (Lieberkuhn) on vertical and on horizontal surfaces of temperate subtidal reefs

N. A. Knott ^A ^B ^D, A. J. Underwood ^A, M. G. Chapman ^A, T. M. Glasby ^A ^C

^A Centre for Research on Ecological Impacts of Coastal Cities, Marine Ecology Laboratories A11, University of Sydney, NSW 2006, Australia.
^B Present address: Department of Zoology, University of Melbourne, VIC 3010, Australia.
^C Present address: NSW Department of Primary Industries, Port Stephens Fisheries Centre, Private Bag 1, Nelson Bay, NSW 2315, Australia.
^D Corresponding author. Email: nknott@unimelb.edu.au





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Marine and Freshwater Research 57(1) 95–104 http://dx.doi.org/10.1071/MF05092
Submitted: 18 May 2005 Accepted: 10 October 2005 Published online: 17 January 2006

Abstract

On subtidal reefs around Sydney (Australia), Tedania anhelans (Lieberkuhn, 1859)is a common encrusting sponge that occurs as frequently on vertical as on horizontal surfaces on most reefs, but covers more than twice the area on vertical surfaces of reefs. Faster growth, leading to the greater cover of the sponge on vertical surfaces, is a possible explanation for this difference. This was examined by experimental transplants to test the hypothesis that T. anhelans transplanted from vertical to horizontal surfaces grow more slowly than those on vertical surfaces. Over three months, T. anhelans transplanted to horizontal surfaces shrank, by 18 ± 18% and 17 ± 16% (mean ± s.e.) at two sites. Conversely, sponges on vertical surfaces grew rapidly, increasing by 40 ± 18% and 78 ± 19% at two sites. Potential artefacts owing to the experimental procedure of moving sponges between places were tested, but none was detected. These results indicated that orientation had a strong effect on the growth of T. anhelans and that growth has an important role in creating the pattern of its greater cover on vertical than on horizontal surfaces of temperate subtidal reefs.

Keywords: experimental transplant, percentage cover, Porifera, sessile invertebrate, surface orientation.