WEST KIMBERLEY PLACE REPORT - Department of Sustainability ...

Populations of several other cetacean species also inhabit Camden Sound and the
Buccaneer and Boneparte archipelagos, including the recently described Australian
snubfin dolphin (Orcaella heinsohni) (Beasley et al. 2005). Snubfin dolphins have
been observed to hunt in groups, working together first to chase fish to the surface of
the water, and then to round them up by shooting jets of water from their mouths.
This unusual and complex behaviour was first recorded off the Kimberley coast.
Remarkable reefs
Along the west Kimberley coast, remarkable coral communities thrive in extreme
conditions, posing researchers many puzzles. South of Camden Sound, Montgomery
Reef is a sandstone platform encrusted with coral, which extends for around 300
square kilometres. As the tide drops, water cascades spectacularly from where it is
held in lagoons atop the reef, roaring as it pours over the platform's sheer edge. At
very low tides, Montgomery Reef is exposed above sea level by as much as four
metres. As water is lost from the lagoons, small pools are created, filled with coral
and algae. Dugongs, turtles, fish, clams and starfish can be seen in these pools,
waiting for the rising tide to release them. Montgomery Reef is one of many places in
the Kimberley where coral grows abundantly in an extreme tidal environment,
buffeted by strong currents and high water temperatures. The dynamic tidal currents
at Montgomery Reef have also made it possible for coralliths and rhodoliths to
survive here. These unusual organisms are comprised of coral or corraline algae, and
are rolled around relentlessly by the currents until they form balls of living matter,
detached from their original rock substrate. They float free, alive on all sides. Much
remains to be learned about Montgomery Reef.
Other submerged and fringing reefs and unusual coral communities occur along the
Kimberley coast, including at Cape Bougainville, Cape Londonderry, the Maret
Islands, Murrangingi Island and Napier Broome Bay. High water temperatures, strong
currents and high nutrient availability from wet season runoff contribute to rapid coral
growth. The outer parts of the fringing reefs around the Maret Islands appear to have
grown very actively in the past 6,000 years, following the Holocene sea level rise.
Corals are present on the platform and edges of the reefs. Beyond the reefs, between
12 and 30 metres below sea level, major filter feeding communities, including sponge
gardens, grow (C. Simpson, pers. comm. January 2008).
South-east of Montgomery Reef and north of Derby on Yampi Peninsula, the narrow
Yule Entrance links Walcott Inlet to Secure Bay. The tidal range here can be as much
as 11 metres, and results in turbulence, strong tidal flows and whirlpools (Burbidge et
al. 1991). Beyond Yule Entrance the tide drives straight out into the ocean, carrying
silt laden waters some six kilometres into Collier Bay, and creating a cloudy brown
river in a brilliant aquamarine sea (Chester et al. 1999).
A little south of Yule Entrance, Talbot Bay is virtually enclosed by vertical sandstone
cliffs, with only two narrow gaps allowing sea water to enter. Massive tidal
movements between the bay and the sea result in what are known as the Horizontal
Waterfalls. As the tide rises and as it drops, there can be up to 10 metres difference
between the water levels of the bay and of the ocean. Water held back by these
narrow gaps rushes through and is spectacularly expelled in a churning, roiling mass.
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