|Image: Paul and Jill|
Kimberley corals evade bleaching
Science Network Western Australia 19 Oct 12;
CERTAIN Kimberley corals appear to be resisting the extreme environmental fluctuations usually associated with coral bleaching.
UWA PhD candidate Sana Dandan has been studying corals at Cygnet Bay pearl farm, on the Dampier Peninsula north of Broome, for two years.
“During the 2010-2011 bleaching event that occurred along the Western Australian coast the Kimberley corals didn't show signs of bleaching,” she says.
“Some of the things that I looked into during my Masters’ thesis was … [if there was] any beneficial impacts on corals due to light [and] protection from extreme light.”
She says Kimberley corals in tidal pools at low tide at midday are subject to high temperatures and very high light intensity.
She also says these are the two most common factors proven to induce coral bleaching, but the corals she observed appeared to be unaffected by them.
Research is concentrating on three types of coral; Acropora aspera, Trachyphyllia geoffroyi and Favia spp, chosen for their differing physiologies.
“I have one that is branching and one that is massive [both of which] are found throughout the Pacific — Trachyphyllia geoffroyi is a bit more unique because it’s a solitary coral,” she says.
She says she is analysing various factors to characterise the environment, and then trying to discern the mechanism behind the species’ resistance to bleaching.
“The environment is very complex; you have the influence of the high light at low tides … so you have … pulses of very high stress.”
She says much of her work to date has taken the form of a growth experiment, where she has transplanted the corals on to tiles for periodic weighing.
“I’ve been measuring the growth rates on the corals to hold up against the environmental fluctuations and see if that has any impact.”
“So far I’ve found that what probably impacts them the most is in the branching corals — there’s a bit of a suppression if they get aerial exposure.
“I’ve measured a range of prominent chemistry values but they all seem to be within what you would expect under normal circumstances.”
She says she has observed several temperature drops of almost five degrees during windy or stormy weather during the study.
“If you add the minimum and the maximum [temperature] from over the year to the tidal fluctuation, that gives you more than 15 degrees [variation] — where as elsewhere one to two degrees over summer would incur a bleaching event.”