A Baykeeper shoreline shell survey found a large Cart-rut shell (Thais orbita) at Holloway Bend earlier this year, suggesting the species may still live in the area. This species was central to the ban on use of Tributyltin (TBT) as an anti-foulant on vessels less that 25m in Victoria in 1989.
Cart-rut shell: worse for wear but there!
International studies had shown TBT caused female shellfish to grow penises. A high incidence of the condition (known as imposex) had been recorded at Brighton Harbour in the early 1990s, but had reduced after the ban. We were delighted this week to receive photos of several “fist-sized” Cart-rut Shells on a reef offshore of Brighton.
Cart-rut shells on Brighton reef (pic: Steven Putt)
10 years after the ban was introduced, Marine Pollution Bulletin (Volume 42 # 10) reported that the relative penis size index (RPSI) of female Thais orbita in Port Phillip Bay had generally reduced. But the RPSI had increased at Williamstown, indicating that TBT from large vessels, ship maintenance activities, and release from historically contaminated sediments, continued to pollute the area.
The study concluded that while the ban remained, TBT pollution would only threaten ports areas and be unlikely to impact more widely in the Bay. Unfortunately, their study was restricted to a limited number of sites and they didn’t consider the practice of dumping dredged sediments from the Port of Melbourne into the Bay.
I read with dismay the article in the Age newspaper (14/11) of the continuing pollution of our rivers, creeks and the Bay and the role the EPA continually fails to do -In all these cases they are not protecting the environment.
http://www.theage.com.au/environment/water-issues/mobils-licence-to-spill-and-its-legal-20111113-1ndwl.html
Thanks for drawing attention to this Wendy. No doubt many others share your concerns as I do. The whole matter of the environmental effects of industrial waste on waterways needs a serious overhaul. The current approach seems to be that if there are no demonstrated human health effects (which would take serious research and money to prove!) then the effects on the environment are of no consequence. For example the Lower Yarra Fish Study conducted for the Channel Deepening project analysed muscle tissue of fish (which would be eaten by people) and ignored testing fish livers, which would contain much greater concentrations of toxins.
I have been monitoring the Cart-rut shell (Thais orbita) “eggs” and while the 12 or so adult shells moved away for at least a week, one has returned and appears to be keeping guard.
The Eleven Armed seastar has also moved after being in the same spot for at least 2 weeks.
I haven’t been able to find it again.
Fantastic that you can keep an eye on the eggs Steven. I’ll be interested to hear how they progress. Thanks for sharing!