Like most other seastars, Meridiastra calcar (aka Carpet Seastars, formerly Patiriella calcar) are slow movers and spend their whole life in localised areas. Their varied diet of algae, molluscs, detritus and dying animals provides a good living. But unlike most other seastars, Patiriella brood their young within their body, rather than shedding masses of eggs and sperm into the water. Body brooding produces far fewer offspring, but with a high chance of survival. Patiriella prefer rocky coasts, and avoid deeper waters, living in or just beyond the intertidal zone.
This survival strategy has been good for thousands on years in Port Phillip Bay, but things aren’t quite the same since North Pacific Seastars (NPS’s) were introduced to the Bay in ship ballast waters. The NPS’s are breeding machines, females pumping 20 million eggs into the water column each year. As their diet is much the same as Patiriella they compete with them (and many other species) for food.
Since NPS’s were first recorded in the Bay in the late 1990’s the official response has been simply to try to stop them spreading more widely into Victorian waters. Apart from Earthcare St Kilda’s regular community working bees to physically remove them from St Kilda Harbour there has been limited action to minimise their impacts. It will be great when other local groups follow Earthcare’s lead and mount ongoing action to remove those pesky pests from their local habitats. Check out Earthcare at http://www.earthcarestkilda.org.au/