Cyanobacteria occurs naturally - a statement repeated often. Makes it sound ok and something we just have to live with. The toxic algae, also known as cyanobacteria, occurs naturally but increases rapidly during summer months So I did some further reading: Mike Joy - But worse than that, too many nutrients can sometimes lead to the growth of toxic bacteria mats, known as cyanobacteria. They can and have killed dogs and can make people sick or die .... The background levels of nitrogen in New Zealand lowland rivers that are not surrounded in intensive farming catchments is around one fifth of the trigger levels for nuisance growth (0.01mg/l), and according to the report just out from Niwa (commissioned by Irrigation New Zealand), around 10 per cent of waterways in some regions exceed the 0.8 mg/l and are likely to be suffering from nuisance algae. stuff.co.nz/timaru-herald/sport/opinion/peter-shutt/10130554/Why-rivers-need-low-nitrogen-trigger-levels Excessive nutrients in runoff from land used for intensive agriculture will alter the natural composition of algae in streams and rivers. If the natural balance is disturbed algal blooms may occur, causing undesirable discolouration, scum and odours and even toxic effect doc.govt.nz/conservation/native-plants/freshwater-algae/ The first local dog death was reported in 2005. Back then it was sourced to a single spot in the Hutt River. Now its not uncommon for 20 to 30 kilometres of the river to have huge problems. In the past 10 years the algae has increased across the country. stuff.co.nz/dominion-post/news/local-papers/hutt-news/8350691/French-scientists-join-river-algae-probe Factors that affect cyanobacterial bloom formation and persistence include light intensity and total sunlight duration, nutrient availability (especially phosphorus), water temperature, pH, an increase in precipitation events, water flow (whether water is calm or fast-flowing), and water column stability. water.epa.gov/scitech/swguidance/standards/criteria/nutrients/upload/cyanobacteria_factsheet.pdf Maybe it is naturally occuring, but to be honest councils should also state why cyanobacteria is becoming an increasing problem in NZ waterways.
Posted on: Tue, 06 Jan 2015 22:54:42 +0000
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