WAMSI Bulletin March 2018
New Tool to Forecast Marine Response to Changes in the Kimberley
An international team of researchers has developed and tested a conservation tool for the Kimberley region, in Australia’s far northwest, that can predict how marine species may fair under different climate and development scenarios.
A range of scenarios was modelled by scientists from CSIRO and Canadian-based ALCES under different management strategies to provide some insight into the potential pattern of responses by marine species over a 35 year period until 2050.
Changes in levels of conservation effort where compared against the three biggest environmental pressures of warming, rainfall and development.
The researchers found that the dynamic Kimberley system, which is driven mostly by seagrass and algae (70%), reacted independently to many of the environmental pressures put on it.
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| Summary of result of scenario analysis |
While variations in population growth made little difference to the overall outcome, groups and elements within the marine environment were found to respond differently to climate and development pressures, some showing dramatic variation between scenarios, and others showing very little.
WAMSI project leader, CSIRO’s Dr Fabio Boschetti, recently presented his team’s findings to Department of Biodiversity, Conservation and Attractions researchers and managers in Perth. He explained that the use of modelling tools was not an ‘absolute’ prediction but attempts to say something about how the system may respond to different management decisions based on our current understanding.
“We analysed different conservation strategies ranging from doing nothing at all, to medium and high conservation efforts,” Dr Boschetti said. “Current conservation efforts are running at about medium.”
“What we did find interesting was that such a dynamic system was so independent of the forces,” Dr Boschetti said. “When we included a conservative 2.5 per cent population growth rate per year, which is quite high, we were still surprised to see it made such a small imprint on the system as a whole. It would be interesting to model spikes in evolution, such as unusual warming or rain events.”
Dr Hector Lozano-Montes (CSIRO) collated information from the results of 25 projects under the Western Australian Marine Science Institution’s (WAMSI) Kimberley Marine Research Program in order to describe the ‘system’ and develop an interactive dynamic food web based on how much marine biomass there is and where it is. This work has resulted in the development of a more detailed picture of the complete interactions that occur in the Kimberley marine system.
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| The Ecopath system |
Links:
WAMSI Project Page: www.wamsi.org.au/modelling-future-kimberley-region
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.
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Kimberley coastline key to monitoring shorebird decline
Researchers looking into the declining number of long-distance shorebirds say, while there is clear evidence that changes in Australian populations are strongly influenced by factors outside of the country, there may also be losses due to habitat pressure in the Kimberley.
A shorebird monitoring project, supported by the Western Australian Marine Science Institution, found some evidence suggesting that local habitat preferences of shorebirds in northwestern Australia have changed in response to human disturbance of roost sites, mangrove incursion on some beaches in northern Roebuck Bay.
The study, led by Danny Rogers and Chris Hassell from the Australasian Wader Studies Group, focussed on the coastlines of Roebuck Bay and Eighty Mile Beach.
Organic pollution of groundwater from Broome has contributed to algae blooms in Roebuck Bay, which may have detrimental effects on the food available to shorebirds.
“It is not yet clear whether these problems have only resulted in local relocation of shorebirds, or whether it affects their survival rates and population counts,” Danny Rogers said.
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| Bottom row: Greater Sand Plovers (Charadrius leschenualtii), Top row (one mostly hidden): Great Knot (Calidris tenuirostris) At right centre: Red Knot (Calidris canutus) (Image: Danny Rogers ) |
Shorebirds carry out long-distance annual migrations between their feeding grounds in the arctic and non-breeding grounds in the southern hemisphere.
During their non-breeding season, migratory shorebirds are broadly distributed along those parts of the northern Western Australian coast with extensive tidal flats. Especially large concentrations are in Roebuck Bay and the northern 80 kilometres of Eighty Mile Beach.
Of the 41 shorebird species occurring regularly along this coastline, 18 species occur in internationally significant numbers (>1% of the population in the East Asian – Australasian Flyway). In total, more than 635,000 migratory shorebirds depend on the tidal flats of the northwestern Australian coast.
“Given the strong external influences on shorebird numbers in Australia, it is clear that Australian-based monitoring serves an important purpose as a barometer of shorebird populations throughout the East Asian – Australasian Flyway,” Danny Rogers said. “As the most important non-breeding region for shorebirds in Australia, Kimberley coastline monitoring is a very important part of this monitoring effort.”
Links:
WAMSI Project Page: www.wamsi.org.au/pressures-migratory-shorebirds
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.
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Giant tides supply food and nutrients to Kimberley reefs
Researchers from The University of Western Australia Oceans Institute have been studying how giant tides in the west Kimberley (up to 12 metres range) flush reefs with water rich in nutrients and phytoplankton, which are food sources for seagrass, algae, coral, and other reef organisms.
In a journal article recently published in Limnology and Oceanography, the scientists, working on the Western Australian Marine Sience Institution’s (WAMSI) Kimberley Marine Research Program, showed how semidiurnal and spring-neap tidal cycles helped control nutrient availability on reefs.
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Professor Ryan Lowe, Dr Renee Gruber, and Dr Jim Falter worked on Tallon Island, a fringing reef in the Sunday Island group, with assistance from the Bardi Jawi Rangers and Kimberley Marine Research Station staff.
The researchers placed instruments on the reef to measure flow speeds and chlorophyll concentrations in waters flowing over the reef. Chlorophyll is a pigment present in green plants and is used to estimate how much phytoplankton (a food source for coral) is present.
The researchers also built a four metre high scaffold on a sandy part of the reef to hold an automatic water sampler that collected water samples throughout the tidal cycle. This study occurred over three weeks in order to measure how the conditions varied over a complete spring-neap tidal cycle.
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| Platform and water sampler on Tallon Reef during high tide (Renee Gruber) |
Many Kimberley reefs sit close to mean sea level and become “cut off” from surrounding ocean waters when the tide falls below the level of the reef crest. The researchers found that during these periods, almost all chlorophyll is grazed from the water column and reef organisms must wait for the next flood tide to feed again.
By measuring the chlorophyll entering and exiting the reef each tidal cycle, the researchers determined how much feeding occurred over the entire reef platform and estimated that phytoplankton provided ~50% of the nitrogen used by the reef community.
Although approximately 30% of reefs worldwide experience water motion driven predominantly by tides, almost all scientific studies of reefs to date have focused on locations where the flows responsible for ocean-reef nutrient exchange are driven mainly by currents generated by breaking waves.
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| Giant clams are an abundant filter-feeding organism on Tallon Reef (Renee Gruber) |
“Our results are an important first step in understanding how tides can affect the productivity and growth of reef communities,” Dr Renee Gruber said. “The physics of water motion control many aspects of an organism’s life cycle, and we must first understand the physics before we can predict how future challenges such as sea level rise and ocean warming will affect tidally-driven reefs.”
This study was also among the first to publish water quality data for the coastal Kimberley region, which is a first step in helping managers set baselines and interpret future changes in environmental condition in the broader region.
Links:
Gruber R, Lowe R, Falter J (2018) Benthic uptake of phytoplankton and ocean-reef exchange of particulate nutrients on a tide-dominated reef. Limnology and Oceanography doi: 10.1002/lno.10790
Project Page: www.wamsi.org.au/benthic-community-production
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.
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