Reef Report for Saturday, February 21, 2015
Dugongs, Dredging and the Great Barrier Reef
In reading the news this past week I came across two beautiful photographs of dugongs, which inspired me to jot down a few lines for you.
Dugongs are marine mammals, both closely related and very similar looking to the manatee.
They are widespread, found along the coasts throughout most of the tropical indo-pacific region. In most areas, they have become quite rare, and Australia is thought to be one of the last refuges for good-sized populations of these animals, from the Great Barrier Reef coastline across the top of Australia and down the western Australian coastline.
Iíve read historical accounts of the almost what you could call great herds of these animals, moving from place to place along the Queensland coast, over time dugong populations have declined, and it appears that in most parts of their traditional range here in Australia they are still declining.
There are thought to be several reasons for the recent declines of their populations. These animals have been hunted, thatís a traditional right of coastal Aboriginal and Torres Strait Islander groups. However, there appears to be an increase in poaching, where outlaws trespass on tribal lands and hunt these animals, largely for their meat. The Australian Government has recently passed a law providing for both increased penalties and enforcement funds for illegal hunting of turtles and dugongs, thatís a great step! Letís hope that thereís follow up funding and support for the enforcement of this law.
Another reason for the decline of dugongs is reduction of the quality of their habitat. These animals are usually not found on coral reefs, but on sandy flats, where they graze on sea grasses. Any increased disturbance to these areas, by cyclones, increased sediment input, decreased water quality, or disturbance by dredging, dredge spoil dumping or seabed trawling would reduce the size and productivity of these sea grass beds. Most of these sea grass beds lie closer to the coast than the Great Barrier Reef, and have borne the brunt of any reduced water quality from the rivers and creeks that drain into the ocean here.
Part of the controversy over the proposed expansion and maintenance of ports along the Queensland coast relates to what will be done with the dredge spoils. The easiest solution is to dump them somewhere else, but thereís a lot of disagreement about the toxicity of harbor dredge spoils, and how far they move after being dumped. Thereís been a proposal to dump dredge spoils on land in one case (the Abbot Point harbor expansion) but the site where they will be dumped is a wetland, and we all know the ecological importance of wetlands to the ocean ecosystems that lie next to them, so that might not be the best idea either. Some folks remain sceptical of the governmentís commitment to end dredging and dredge spoil dumping that impacts the health of the Great Barrier Reef, and would likely reduce dugong habitat as well.
Someday I hope to see a dugong on a dive trip, that would be a great thrill, and someday I hope to learn that their populations are expanding. It seems like steps are being taken in the right direction, but I wish that laws and regulations would take that one step further, to ensure the effective protection of these animals.
The weekly reef report is written by Joel Groberg of DiveTheReef.com,
who compiles them from the many conversations he has with dive staff in the area, as well as† many other local sources in the dive
Index of all reef reports.