Planetary Coral Reef Foundation
Science Report
This reef was also studied by PCRF in 2007. Please refer to the links to the 2007 study at the top of each page for comparative data sets.
27.5 - 28.8 °C
It's hard to pin the changes on temperature, but we met with Bob Halstead in Alotau who has been diving the reefs of the Milne Bay region for at least twenty years. He had talked to us of a very warm current that had passed close to the mainland a couple of years ago - it is possible that its effects reached this far east.
The shallowest zones did become almost unbearable in the heat of the day and appropriately, there was little hard coral growth here.
There was very little bleaching on the remaining hard corals, just the occasional spot usually on turbinaria plates.
The visibility was variable but generally good, ranging from 82 to 141 feet.
Just two crown of thorns specimens were sighted during the study period, one below our study zones (around 15m deep), the other in the shallow zone.
The reef studied was the fringing reef on the north side of Uratu Island. Uratu is a small and uninhabited island, separated by a sandy channel from Kitava Island, just a couple of hundred metres away. Kitava is a coral island with a growing population, currently about 6000 people. Uratu is owned by one of the chiefs from Kitava but he is happy for all the islanders of Kitava to feel free to use Uratu as a 'party' island. The men come and fish, mostly with hand nets, building fires on the beach at the end of the day. The women come with their children to play and eat.
Very close to the beach, there are large flattened slabs of rock which evolve into submassive acropora colonies at many points, bordered by some enormous massive porites colonies. A few of these massive porites were noticed to have had some sorf of graffiti carved into them. The reef flat is smothered in mostly macroalgae close to shore, then leather corals as you move further towards the reef slope. There are many sandy patches, the hard coral coverage is very small now although you can still make out that the substrate used to be hard coral too. The reef slopes down gently to about 40 metres and continues at this depth for a fair distance.
From the very first time we put our head underwater here in Kitava, it was immediately clear that a sudden change occurred on this reef some time within about the last five years. Shapes of large hard corals are now buried under fields of Sarcophyton spp leather corals and macroalgae, mainly halimeda. Some magnificent and eerily unblemished massive porites colonies remain as do some foliaceous turbinaria colonies, although these are a little less perfect. But between the green and brown carpets, there are also new and pristine corals taking root. The change has passed, the conditions are now allowing, even encouraging, new growth but the damage caused by this event was widespread.
Corals a reasonable number of colonies had their tentacles out during the day. The most dominant genera of corals are Acropora (with a great deal of sub-massive lifeforms), porites (in many lifeforms and some beautiful specimens of massive), turbinaria, stylophora. There was surprisingly little montipora compared to other reefs in PNG.
Fish - the diversity in fish species is typical for this region and the numbers are just below average. But the noticeable aspect of the fish life here was the size of individuals - most of the fish are the smaller kinds of reef fish, only a few larger fish such as snappers or sweetlips and only an occasional pelagic (one tuna, one mackerel). There were no sharks at all. The men who fish around here show us their catches on the island of Uratu - all tiny reef fish, damsels and juvenile parrotfish.
Invertebrates Sarcophyton (mushroom leather) soft corals plagued the reef. We cannot explain how they became so prevalent although they do appear to be capable of settling on substrates that are poorly favoured by other coral reef animals eg. they appeared to be growing in just sand, something a hard coral would never be capable of. In fact, they were actually attached to a piece of dead coral or other hard substrate, but buried up to 5 centimetres below the surface.
I had one encounter with a dancing mantis shrimp beneath the transect chain! He did not scuttle away as they usually do but rather indignantly stood his ground beneath me. There was a very large amount of Tubipora, organ-pipe coral, on the reef, plus certain areas of dense coverage of Xenia - the pulsing soft coral.
Algae- the predominant algae was halimeda, but there were also significant amounts of caulerpa and padina.
There is a large tidal difference, about 3 metres and the tidal currents are strong around Kitava and Uratu. At times the water was very dense with plankton, one night with a spectacular show of (we think) shrimp glowing as they released clouds of gametes. The beach is greatly used by the people of Kitava with fires lit at least every weekend if not every night. There were great amounts of washed up coral skeleton, especially the distinguished red stoloniferous skeleton of Tubipora.
The passage between Kiriwina and Kitava, about 10 miles wide, has become a major shipping lane. We figure that these are ships travelling between Australia and Asia that do not want to pass through the Torres Straits. The stream of large ships (one was even believed by an islander to be an aircraft carrier, quite possibly an Australian naval ship on manoeuvre) was constant and in one 24 hour period we counted 19 ships passing.
In many conversations between the ship's crew and the islanders of Kitava, we pursued the cause of the event that changed this reef. There was a tidal wave that came from the south two years ago. It completely rearranged the local landscape, destroying the southern beach of Kitava and eating into the bush, plus bringing most of the beach on the southern side of Uratu to the northern side. The channel running between the two islands changed from being deep to shallow (maximum fifteen metres now). It could have been a smothering of sediment that choked the hard corals, killing them off and providing a substrate that only the leather corals and macroalgae could settle on. There were also visible effects on the fishing catches, although these have also been interfered with by foreign ships, especially the Taiwanese, sneaking into local waters to use mass-techniques.
