Underwater Imagery Reveals Bryozoan Habitat in Western Port, South-East Australia

Large erect bryozoan colonies significantly enhance habitat complexity and associated biodiversity. Globally, bryozoan habitats are rare and at risk from anthropogenic disturbance. This paper presents two newly described bryozoan habitats in Western Port (~70 km south-east of Melbourne, Australia) and further expands our current knowledge of bryozoan habitats in other parts of the bay. These previously unknown bryozoan habitats discovered in the North and Western Arms of Western Port are comprised of laminar forms that develop erect plates, growing large (up to 1 m in circumference and vertical relief) robust colonies and structure on cobble and shelly sand substrates in areas of high current and moderate wave energy. These bryozoan habitats are composed of two main species: Adeonellopsis sulcata (Milne Edwards, 1836) and Celleporaria foliata (MacGillivray, 1888). Colonies of A. sulcata and C. foliata were in approximately equal proportional abundance at the North Arm site, while A. sulcata dominated the Western Arm site. These bryozoan habitats support a variety of marine life, with sponges, ascidians, molluscs, echinoderms, fishes, cnidarians, smaller, non-habitat-forming bryozoan species and macroalgae recorded. The North and Western Arm bryozoan habitats differ from previously described bryozoan reefs in the Eastern Arm, which are dominated by fenestrate species forming erect rounded foliose colonies arranged in continuous linear rows and patch reefs in shallower areas of the bay. The new findings add to an emerging understanding of bryozoan habitats in Western Port (a Ramsar site of international significance), which are unique in their ecophysical setting and one of only four known such habitats in Australia. Further research is needed to determine the extent of these habitats in Western Port, the biodiversity of associated species and ecological function.