About bioerosion:

Coral reefs around the world are under threat from a variety of sources. Erosion and reef building are natural processes but have a natural balance which must be maintained.   This project aims to assess the rate of erosion versus the rate of building and colonisation by reef organisms. Reefs may be degraded by man induced or by natural events but certainly man is in the process of degrading many of the world's reefs.

The main problems occur from coastal deforestation and poor agriculture methods which increase nutrient and sediment outputs to the reef waters; physical construction and anchor damage or removing fish populations and other reef animals to upset the fine balance of the reef.  Many of these events may not show immediate degradation but over the long term the reef may not recruit new colonies as well, algae may overgrow corals or the skeletal structure may be weakened. This may eventually cause a change in the reef and in some cases it has resulted in a rocky algal reef replacing the original rich coral reef.

The research:

Dr Pat Hutchings has placed coral skeleton blocks at a variety of reef sites from Port Douglas to Osprey Reef. This gives the ability to check the rates of bioerosion at similar reef sites which vary in distance from the coast and human influence. The sites include reefs across the continental shelf, Lizard Island reefs,  the ribbon reefs and oceanic Osprey Reef which is 100 miles offshore and in 1000 metre deep surrounds. Coral blocks (7x5x5cm)were cut from Porites boulder corals in September 1996 and duplicate grids of 8 blocks each were placed at each site at depths of 7 - 10 metres. Two blocks from each grid are taken for analysis each year for four years.  Slices of the block are analysed for overall change in mass and the organisms boring into the corals are identified and quantified. Organisms colonizing the blocks are also of interest and will be assessed. 

Undersea Explorer crew record digital video footage and images of the bioerosion grids to assess the finer scale changes and also the animals which may be grazing on the blocks. The database constructed by Undersea Explorer and linked to the various research projects will also be of value in giving year-round data on water temperature, salinity,  nutrient levels and many other related observations. To date there has been a range of video data already collected. 

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