Ottelia Ecology
Projects
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Engaewa Burrowing Crayfish surveys
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Cape Leeuwin Freshwater Snail survey
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Wetland vegetation monitoring
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Impacts of mosquito larvicide on non-target aquatic invertebrates
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Lower Vasse River water circulation trial
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Frederick Baldwin Lake ecological survey
Aquatic plant monitoring in the Vasse Wonnerup Wetlands
The Vasse-Wonnerup wetlands system is a Ramsar wetland of international significance for waterbird habitat. However it is at risk from nutrient enrichment, which has led to algal blooms and fish deaths for many years. Aquatic plants are important in maintaining water quality and supporting food webs, so are important in understanding ecosystem health.
Robyn Paice been assisting Murdoch University with long term annual monitoring of submerged macrophytes and macroalgae in the Vasse-Wonnerup Wetlands since 2013. Additional seasonal sampling commenced in 2017, as part of the Department of Water and Environmental Regulation's Integrated Ecological Monitoring Program, in partnership with Murdoch University.
Mexican Waterlily in the Lower Vasse River
Mexican waterlily, Nymphaea mexicana has been present as an introduced plant in the lower Vasse River for many years, but expanded rapidly during 2013-2014 to cover 1.1ha of the lower Vasse River (1.1ha). While the ongoing expansion over large areas of the river is of concern to the community and management authorities, the presence of waterlily has had a visible beneficial effect on water quality, with an absence of summer algal blooms within and adjacent to patches of waterlily.
Ottelia Ecology undertook a study to improve understanding of the effects of the waterlilies on water quality and ecology in Autumn 2017. This project was completed for the Department of Water and Environmental Regulation as part of the Revitalising Geographe Waterways program.
Toby Inlet Sediment Investigation
Over the 2019-2020 summer, Ottelia Ecology scientists undertook an extensive investigation of the nature and volume of sediments in Toby Inlet for the City of Busselton. Sediment accumulation in Toby Inlet has been of increasing concern to residents and waterway managers due to impacts on amenity, ecology and water quality. The investigation found extensive sediments have substantially reduced water depth throughout the Inlet, caused by internal organic material, such as decomposing algae, and catchment inputs. The project included an assessment of the feasibility of various techniques in removing the sediment.
Impacts of mosquito larvicide on non-target aquatic invertebrates
The City of Busselton undertakes seasonal mosquito larvicide treatment at several breeding sites, including areas of the Vasse-Wonnerup wetland system. Due to the significance of these wetlands as waterbird habitat, monitoring of non-target aquatic invertebrates was required under the EPBC Act to ensure that food resources for waterbirds are not negatively impacted by the use of larvicide.
A sampling program to fulfil this requirement was undertaken consistently from 2009 to 2015, including pre-and post-treatment sampling in treatment and control wetlands.
Aquatic invertebrate sampling over seven years has found no evidence of adverse impacts of larvicide use on non-target organisms, for either S-Methoprene or Bti.
Environmental Management Plan for mosquito control in the Vasse-Wonnerup Wetlands
To minimise the incidence of Ross River Virus amongst residents and visitors, the Shire of Busselton undertakes seasonal control of mosquitoes. An Environmental Management Plan prepared by Robyn Paice provided a detailed analysis of the potential direct and indirect impacts of larvicide and adulticide on non-target species. It detailed an adaptive management approach, including monitoring programs and trigger levels for potential impacts and associated remedial actions.