There was time for a quick swim this morning before the wind increased too much. A moderate northerly wind and recent rain meant that the Yarra river was running heavily into the park. There was quite a current, some haloclining at times and generally poor visibility. So I concentrated on the small stuff while I was buzzed by loads of snapper. Not a disappointing dive at all. Three sea slug species in all: a couple of Oxynoe, a nice unfurled leaf-like Elysia and a large Boodlea (the one with the orange tips). Water is still quite warm (19 degrees).
Coral Reef biotope
On a side note. The following image nicely illustrates the relationship between green coral and our native sea urchins. In this picture are five sea urchins. Deakin University is removing urchins down to roughly two to four per square metre (notably, this was based on only a tiny number of transects and ignored 15 years of monitoring data that shows otherwise).
There is a worrying trend towards calling these urchins ‘pests’. Unfortunately, this has arisen from rather ill-founded publicity run by Parks Victoria and Deakin University. This is based on poor science that is misleading. As the image above clearly shows five such urchins cuddling up to an important coral. Notably, coral reef biotope isn’t recognised by the research scientists in their work.
Urchins aren’t a pest at all. That terminology is rather vulgar. They are an essential part of the local ecosystemHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More. Especially since most large abalone have been fished out, they have become the dominant herbivore. Without them, the whole system collapses. If there is any overabundance in places (though that is doubtful in Ricketts), this is also because of the total annihalation of resident reef fish and crayfish from the northern Bay in the last 70 years.
We are very lucky to have green coral habitat. If we smash urchins in the park, we lose bommies like this, that could be 200 years old.
