Researchers' Diaries
Dr Zoe Richards (Australian Museum): Corals
The level of hard coral diversity sampled during this last survey to the southern Kimberley Bioregion was considerably lower than that recorded so far in the central and northern sectors
The level of hard coral diversity sampled during this last survey to the southern Kimberley Bioregion was considerably lower than that recorded so far in the central and northern sectors. Further research on the skeletal material collected is underway but so far it appears that approximately 200 species of scleractinian coral occur in this part of the Kimberley. Generally, the coral communities were dominated by species tolerant of high sediment loads. Hence, Goniastrea spp., Goniopora spp. and Porites spp. were recorded in abundance. As observed in other parts of the inshore Kimberley, the blue coral – Heliopora coercula was also well represented.
Western Australia’s endemic species, Australomussa rowleyensis was recorded, so too was the rare species Cataphyllia jardini. The five most prevalent Acropora species in this sector were A. aspera, A. digitifera, A. granulosa, A. muricata and A. spicifera. Thickets of branching Acropora muricata were present at Mavis Reef and Acropora aspera formed such deep and extensive thickets on the huge intertidal reef surrounding White Island that in parts it is impossible to gain low-tide access.
Reef communities in this region are controlled by the tide and in particular, the amount of suspended particulate matter.
In fact we saw a rolling wave of sediment carried along by the tide during a dive (see Clay Bryce’s diary entry for a full description). This phenomenon was particularly evident when we SCUBA-dived on an isolated and unnamed reef outcrop north-west of Black Rocks. As we entered the water, shortly before high tide, water visibility was approximately 20m with an abundance of schooling reef and pelagic fishes swimming about. We could see that the steep reef slope extended up to the reef top at 14 m. The slope was dissected by narrow grooves and featured caves and ledges. Plating and encrusting hard corals and the soft corals, Sinularia and Sarcophyton dominated the reef top. At mid-dive the reef was engulfed by a very turbid, tidally-driven rolling cloud of sediment. As we ascended at the end of our survey, the turbid cloud had extended up to approximately 10 m from the surface.
I find it absolutely fascinating to learn that there is a diverse suite of corals, which can survive in these dynamic and turbid conditions, and my observations in the Kimberley to date are definitely leading me to reconsider the traditional view that corals prefer clear-water!
