Introductions all around

A polychaete of the family Sabellidae genus Notaulax.
Image: Gary Cranitch.


7 September 2010
The research conducted by Dr Maria Capa as part of the CReefs project could contribute to understanding which marine animals pose a danger to coral reefs, as well as which geographical areas are richest in marine life and in most need of protection.
Dr Capa, a post-doctoral researcher with the Australian Museum in Sydney, is one of a team of scientists studying the diversity and biogeography of polychaete worms on the CReefs expeditions to Lizard Island and Heron Island on the Great Barrier Reef, and Ninglaoo Reef in Western Australia.
"There seem to be several species that have Indo-Pacific distributions, so they were found all around the coast of northern Australia. We're now looking at the genetics of populations to confirm this," Dr Capa says.
"We are trying to discover if there are connections between these populations, or if there are geographical boundaries, perhaps due to currents or geology or habitat," she says.
So far, there don't seem to be significant differences in most species between Lizard Island, Heron Island and Ningaloo Reef, but the polychaete team has made some interesting discoveries, particularly about introduced species.
Many polychaete species are endemic, or native, to Australia, but there are 10 species that have been identified as introduced. Polychaetes can live in substrate attached to the hulls of ships, and planktonic polychaete larvae can live in ballast water for up to a month, and so can be transported around the world.
"One species is unusual because we have found it at Cairns and Heron Island, rather than in cities with large ports. It has some identical genes to specimens found in Hawaii, so we think they are the same species, but we don't know whether if they've gone from Heron Island to Hawaii or the other way around," Dr Capa says.
Introduced species could potentially threaten marine ecosystems.
"One species of the group I am working with, for instance, Sabella spallanzanii, is a tube worm that measures about 20 centimetres long and has a large fan of branch-like tentacles. In its native habitat in the Mediterranean, these worms are widely dispersed in seagrass beds, but in southern Western Australia and in Port Philip Bay in Melbourne, they cover some areas in very high densities. They modify the environment below them, because they capture most of the small particles of food from the water, and are probably competing with native species," Dr Capa says.
She says that understanding the biogeography of endemic and introduced species could have important applications for conservation.
"For instance, if a species lives in several places in northern Australia and we want to preserve it, we might choose, for example, an area in Western Australia to preserve, and say that is a representative population of that fauna. But if there are different species in different locations, we might need to preserve an area in Western Australia, another in the Northern Territory and another in Queensland," she explains.
"CReefs is an important project because it allows us to conduct population studies, which will help us to resolve the biogeographical boundaries of the species," she says.