09060: Effects of nutrient enrichment and toxic Lyngbya blooms on benthic invertebrates and migratory shorebird communities of Roebuck Bay Ramsar site

    The Greater Sand Plover is one of many migratory bird species that over-winter in Roebuck Bay. Courtesy Thomas de Silva University of Western Australia
    The Greater Sand Plover is one of many migratory bird species that over-winter in Roebuck Bay. Courtesy Thomas de Silva University of Western Australia

    Roebuck Bay is ranked in the top eight shorebird migratory stopover sites in the world.

    The Ramsar site is also a principal site for wintering shorebirds in Australasia, supporting 20 migratory and two resident species in internationally significant numbers. The importance of the site is due to its incredibly high diversity and biomass of benthic invertebrates, which situate this tropical intertidal mudflat area among the richest in the world.

    Benthic invertebrates are organisms that live in or on the sea bottom or the sediments of rivers, streams, and lakes, and have no backbone. Because the benthic community is so dependent on its surroundings, it serves as a biological indicator that reflects the overall condition of the aquatic environment. They indicate local conditions because they have limited mobility and cannot migrate to avoid stressful situations.

    Nutrient enrichment can significantly alter the biodiversity of mudflats, producing shifts in the composition of benthic invertebrates and favouring algae (cyanobacterium). In Moreton Bay, Queensland, algae blooms have been catastrophic, with seagrass loss and modification of the benthic invertebrate composition.

    In 2005 algae blooms were first recorded in Roebuck Bay, and the extent and biomass of these blooms is increasing every year. In February 2009, Lyngbya majuscula was recorded within the Ramsar site boundaries for the first time.

    With the help of funding from the State NRM Program, the University of Western Australia is determining the extent, duration, intensity and triggers of cyanobacteria blooms in Roebuck Bay, and the effects it has on benthic invertebrate diversity and the food webs of shorebirds.

    Following the study, recommendations on management actions to limit the effects of blooms will be made. The project will also assist in raising community awareness of the risks of algae blooms on human and ecosystem health.

    Investment: $ 211 561
    In-kind contribution: $ 200 095
    Delivery organisation: University of Western Australia
    Project duration: June 2010 - December 2012
    Location: Roebuck Bay, Broome

    Major project achievements

    • Identification of triggers, distribution and patterns of Lyngbya has been successful leading to:

      • A monitoring Program developed for Roebuck Bay

      • Raising community awareness of risks - both ecosystem and human

      • Inform community about the causes of Lyngbya blooms

    • Areas with high sediment nutrient concentrations have been localised.

    • Information has been used for both current campaigns and future projects.

    Lessons Learnt

    • Sufficient funding provides the technical expertise to appropriately complete projects.

    • Completion dates or milestones should be mildly flexible due to unknown errors in analytical analysis.

    • Sufficient community notice and relevance increases community volunteers.

    Project partners

    Broome Bird Observatory; Global Flyway Network; Australian Wader Studies Group; Department of Parks and Wildlife; Port of Broome; Broome Hovercraft; NRM Rangelands; Roebuck Bay Working Group.

    More information

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