Sydney hard Corals

Corals are limited by two major factors. One is water temperature. Most corals do not like being below 18 degrees Celcius for long periods. South of latitude 30 or so, hard corals cannot compete with the large brown algaes such as Ecklonia and Sargassum. They are shaded and cannot compete. Corals need lots of sunshine to grow as the tiny brown algae inside contribute up to 95% of the diet. Sydney is not known for its hard corals. There are quite a few corals growing on rocks. The reefs around here are usually referred to as sponge gardens as sponges are more dominant. Quite often, sponge gardens can be much more colourful that many tropical reefs, especially deep water sponge gardens deeper tham 25 metres. Many of the sponges have brilliant vivid colours created by tiny marine algal plants living within the sponge tissues..

 

 

 
Clumped Tooth Coral Culicia coral
This Clumped Tooth Coral, Balanophyllia gemmifera is common on many of the rocky reefs around Sydney. Over the last four years, corals and sedentary lifeforms in Botany Bay have suffered from turbid water from construction of Port Botany, Desalination plant and submarine electrical cables. Turbidity makes water dirty, stops marine plants growing and starves the food chain from the bottom up. Silt from disturbed water fouls up marine life as well.. This Sydney Culicia coral is one of the most amazing types of coral in our seas. In my marine biology course, you will learn how its colonies form by producing runners just like strawberries do.
Sydney Stony coral SOlitary Tooth coral
Sydney Stony coral is usually a brown colour. This green form is less common but is due to different symbiotic algae living within the tentacles. Sydney stony coral is renowned for flourescing in ultra violet light. The Solitary Tooth Coral, Balanophyllia bairdae is common in water deeper than 15 metres. It has lightning fast reflexes when catching food. The tentacles kill prey by using three mechanisms. They stick to prey, they coil around prey and then the sting them to death. All Cnidaria have these three types of killing tentacles. Think about how a Blue Bottle tentacles sticks to your skin and coils around your arm as it stings you!