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That’ll do Lloyd Smith from Palmerston and his dog Quake wait their turn at the National Dog trials being held at Alpha Burn Station this week.
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How much is our lake worth? Tim Brewster
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The increasing presence of algae or ‘lake snow’ and its possible links to nutrients and other triggers has two of the country’s top lake experts warning of potentially long term degradation of Lake Wanaka if its catchments are not monitored and controlled effectively. Otago University research fellow, Dr Marc Schallenberg, an internationally recognised limnologist (lake researcher) has studied the lake snow issue since 2008 with two PhD students as part of a postgraduate doctorate programme he supervises. “How much is Lake Wanaka worth?” he said. The appearance of algae in the water was first noticed in 2003 by fishermen who had the substance on their lines. The university was contacted after complaints in 2007 from householders who had clogged water filters and pumps. The monitoring work has since found algae in much of the southern part of the lake up to Minaret Station. Marc said the arrival of the algae coincided with the start of the lagarosiphon reduction programme and also the increase of nutrients from fertilisers following more intensive farming in the area, but there is still
little known about how it arrived, its rate of growth and its ability to grow in other bodies of water in the area. NIWA principal scientist Dr John Clayton who helped create and currently oversees the lagarosiphon reduction programme implemented by LINZ said controlling the catchments is crucial for lake quality. “You only need to
laws/policies/planning in place to do that. Monitoring is just keeping a scientific watch over what is happening with the lake snow. This can lead us to better understanding the dynamics and drivers and consequences of lake snow. Once we understand these things, we could potentially manage the lake and catchment to prevent lake snow from
We’re not looking for blame ... we just want to look at all our options. look at Lake Taupo water quality and clarity to see how pervasive the legacy of catchment activities are even for large bodies of water,” he said in an email. He said he hasn’t seen any evidence the rotting lakeweed is a significant factor to provide nutrients for algae as some contractors have suggested. Marc said a major concern is if the algae spreads. If it became an issue in Lake Wakatipu, with its larger population reliant on the lake for water, dealing with it would be a major issue. “Maintaining or getting the lake back to a more pristine state is a matter of one: political will and two: having the
occurring. We are not at that stage yet. In fact, apart from my PhD students, Tina Bayer and Amy Weaver, nobody has been monitoring the lake snow in Lake Wanaka,” he said. Marc has inspected 70 lakes in New Zealand and has yet to find any other signs of the cyclotella algae which forms the gel. Guardians of Lake Wanaka chairperson Helen Tait said the group is motivated to get some long-term, comprehensive monitoring of the lake water. A recent application for a monitoring buoy costing $60,000 was rejected by the Central Lakes Trust, but the organisation hopes to find other funding later this year. The
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information would be relevant to other lakes in the South Island. Short-term monitoring is already the responsibility of government funded groups, so the buoy would be used to add to the data. At a water workshop for interested parties in October or November, a North Island scientist will present a case study of a lake that became degraded and then reclaimed. The group will discuss the best approach for managing the future of Lake Wanaka. “We’re aiming at the long-term monitoring of a number of factors,” Helen said. “We’re not looking for blame, we don’t want people to come along and be attacked or beleaguered, we just want to look at all our options,” she said. Lake snow is an algal growth that looks like floating snowflakes. Formed by microscopic algae called cyclotella, it secretes large amounts of sticky polysaccharides causing the algae and other microscopic organisms to clump together to make visible ‘flakes’. Why this happens and what effects it has on the lake ecosystem and fishery are still unknown.