Moreton Bay's biggest sexual event

What has been described as 'the world's biggest sexual event,' the coral spawning on the Great Barrier Reef maybe about to happen in Moreton Bay.

Most corals only reproduce once a year, usually with a cue from the moon. It is unknown if the simultaneous release of eggs and volcanic style eruptions of sperm occurs in Moreton Bay like it does on the Great Barrier Reef, but WPSQ Bayside Branch are organising a boat trip to Peel Island to find out. The date is set to be shortly after the full moon in November.

What is a first of its kind, a trip to establish if coral spawning happens in Moreton Bay, should be a real adventure. It is hoped the 'snowstorm' spectacle will be seen but there is no certainty; however, a night time cruise and spotlighting may reveal other wonders like turtles and dugongs.

A little known fact to many on the mainland is that Moreton Bay supports a significant coral community. Within Moreton Bay there are 40 species of coral and at Flinders Reef, located in the northern oceanic section of the bay, 119 species have been recorded. Moreton Bay's corals are biogeographically distinct from those of the rest of the Indo-West Pacific region, as the particular group of species present in Moreton Bay are unlike any other reported. This uniqueness is a result of an overlap of tropical and sub-tropical species. While massive and brain coral are prevalent inside Moreton Bay, particularly Favia speciosa, branching staghorn species can be found at Flinders Reef and Myora. There is a general gradient from a dominance of massive coral in the southwest of the bay to branching coral in the northeast of the bay. A similar situation exists with soft coral; Alclonium sp. is dominant in the southwest while Xenia sp. and Sarcophyton sp. predominate in the northeast. 

Peel Island is a great place for corals, and is renowned as having the greatest diversity of coral within Moreton Bay. The northern areas of Peel Island are the best location to find coral. While corals are known for their beauty and for the habitat they provide for many sea creatures, they have proven valuable to science. Corals are excellent historical archives. Just like trees, they place down bands, a high density (summer growth) and low density (winter growth) band represents one year. The coral skeletal features also show up environmental conditions and by using a UV light environmental conditions can be determined at the time the coral skeleton was laid down.

Recent core samples taken during the Healthy Waterways Moreton Bay study showed quite clearly the flood event of 1974 and the peak discharges from the Brisbane River in 1988, 1989 and 1990. Such flooding and associated sediments, nutrients and freshwater have had a significant negative impact upon the coral. The shallow nature of the bay doesn't help and as a result water temperatures range from 15 to 27 degrees, with a minimum of 13 degrees and a maximum of 32 degrees, such extremes impact upon coral distribution.

However, the massive and brain corals continue to survive, likely due to their adaptation to extremes and their ability to rid themselves of silt by producing copious amounts of mucus. Unfortunately, tipping the scales against the coral survival was coral dredging, ceased in Moreton Bay in 1997, bushland destruction and increased urbanisation, therefore, increased silt and stormwater pollution and anchor damage. But the most significant decline in Moreton Bay's coral was due to the drop in the sea level that occurred about 3,000 years ago; this reduced the amount of clean oceanic water entering the bay. 6,000 to 3,000 years ago, the coral reefs in Moreton Bay were similar to those found on the Great Barrier Reef today and Mud, Green, King and Bird Island were once thriving coral cays.

Don't despair though, the CSIRO estimate by 2050 the sea level will rise between 0.2 and 0.5 m, so coral may be on the way back, and so will our shoreline. Yes, change is inevitable but the increased rate of change due to homo sapiens is the problem, and our unsustainable ways are now recorded in coral as testimony for future generations.