Oxygen and temperature levels examined in Kimberley reef
Written by Brooke Hunter , Science Network WA
MARINE scientists are using results from a recent reef study at Tallon Island, north of Broome, to develop predictive models for use on other reef systems in the Kimberley.
Speaking at the 2015 WAMSI Research Conference, University of Western Australia Associate Professor Ryan Lowe said the interactions occurring in these ‘tidally-forced’ reefs still remain unknown in relation to the widespread literature of wave-dominated reefs worldwide.
“There’s little known about the function and productivity of these reef systems so the goal is to really understand the nutrient dynamics in these types of environments,” he said.
A/Prof Lowe’s field program focused on detailed process-studies of the Tallon Island platform reef to understand the role of extreme environmental variability.
“We wanted to understand how the extreme environmental variability influences the benthic productivity of reef communities,” he says.
Using an array of synchronised current meters, tide gauges and thermistors (measurement and control instrument) A/Prof Lowe and his team researched primary production under extreme physical force by focusing on coral, algae and seagrass.
The results from the intensive field study, conducted three times during the dry and wet seasons, were used to measure the temperature variability across the intertidal reef.
Seagrass feels hot under the collar
A/Prof Lowe said extreme temperature variables were affecting the reef, with spatial patterns causing seagrass warming of up to almost 35 and 40 degrees Celsius.
“One of the striking things is the substantial tidal variations on these reefs,” he said.
“It is good in that it keeps these reefs from drying out during the day but it reduces the exchange of water in the ocean so it allows these extremes in temperatures and biogeochemicals to occur.”
At low tide the scientists were able to track the water mass through drifters and measure the changes in oxygen, nutrients and chlorophyll.
“From this information we can calculate influxes. From oxygen we can estimate rates in production and respiration and from the nutrients and chlorophyll we can estimate the uptake and release,” A/Prof Lowe said.
The scientists noticed extreme variations in oxygen, with primary producers such as seagrasses and algae producing a high amount during the daytime but with a noticeable decrease during the evening.
“However, we are getting twice as much post primary production in the seagrass zone as we are in the algal zone,” he says.
Listen to Ryan Lowe’s presentations at the WAMSI Research Conference 2015:
Ryan Lowe, UWA – Primary production
Ryan Lowe, UWA – Redefining sediment transport models over sensitive benthic habitats
The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley.
The WAMSI Dredging Science Node is made possible through $9.5 million invested by Woodside, Chevron and BHP as environmental offsets. A further $9.5 million has been co-invested by the WAMSI Joint Venture partners, adding significantly more value to this initial industry investment. The node is also supported through critical data provided by Chevron, Woodside and Rio Tinto Iron Ore.