When we first move to Knutsford in 1986 there was no generally recognised problem of blue green algae or cyanobacteria. There was a small sandy beach by the lake in Tatton Park, where people would go to picnic and bathe in the lakewater. Dogs swam in the lake without problem; even daughter’s Westie put his toes in.
Then, in the early nineties, notices began to appear about blooms of blue green algae in the water; dogs should not go in and people should definitely not bathe. They appeared with increasing frequency, and are now a permanent feature. The sandy beach is long gone.
Almost everywhere you go in Britain these algae seem to have got a hold, with a detrimental effect on other wildlife. Last year we witnessed dead Canada geese being removed from Shakerley Mere because of poisoning, suspected to be the very evident blue green algae.
Close up the resulting scum can appear ugly, but can sometimes give almost beautiful effects, as in the following picture.
So what causes these algal blooms and what changed?
According to the Centre for Earth and Environmental Science, Indiana University the combination of factors that trigger and sustain an algal bloom is not well understood, but these are the main factors:
- Nutrients – over-enrichment due to mainly phosphorus and nitrogen, arising from runoff from fertilised agricultural areas, lawns, land clearance, and sewage
- Temperature – Water temperatures above 25°C. Thus in temperate regions such as UK, blue–green algal blooms generally do not persist through the winter months
- Light – blue–green algae populations are diminished when exposed to long periods of high light intensity but have optimal growth when intermittently exposed to high light intensities.
- Stable Water Conditions – with low flows, long retention times, light winds, minimal turbulence. Drought, water extraction, weirs and dams all contribute to to this.
- Turbidity caused by suspended particles following rain.
If I might suggest a quick summary, modern industrial farming, badly managed waste water, global warming and over-exploitation of our rivers are the prime reasons.
As pointed out by George Monbiot, Britain’s rivers are dying due to similar factors.
There’s no quick fix. Moving to organic farming to maintain soil fertility is a no-brainer. As is reducing carbon emissions. This needs political change.
I can't believe it! 
‘Like’ isn’t really the most appropriate response to this topic. So much to atone for. So much to put right. 😥
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Organic farming is not the panacea many people presume. As an industry, it uses way more added resources per unit of food produced (especially pesticides). What does address all of the concerns you quite rightly raise is genetically modified foods – yet GMOs is the primary ‘target’ of widespread disinformation heavily vilified by the organic food industry and by their lobbyists!
It seems to me we can’t have it both ways here. At the very least, going ‘organic’ is hardly the ‘no-brainer’ you assume!
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The essential point about organic farming is its emphasis on retaining health of the soil and nature. The evidence suggests that industrial farming does not do so. Yes, I have maybe over-simplified to make a point.
GMOs is a different discussion, too big to have here…
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As someone who (once upon a time) studied hydrology, I understand how water is deeply affected by land use – both ‘natural’ (think salmon and forests) and designed (think storm drains and sewers). Specifically, I studied ground water movement, which does not necessarily reflect topography, meaning that what goes on here does not necessarily cause what goes on there, so to speak. In my local field work, the amount of chemical soup from the runoff of urban lawns and ‘organic’ gardens in particular was horrendous (not to downplay the toxic mess from highways and roads). So I know it’s very easy to point at farms the use added nitrogen on a large scale and place blame framed as ‘worse’ for the environment than a massively smaller scale organic acre or two that has the luxury of keeping loam fertilized by low production of food.
The issue I have is that the problem isn’t the type of farming or even how intensive or large scale it may be; this is pure ideology being peddled by ‘natural’ businesses (and I say that term ‘by’ because of massive amount of money spent on advertising and political lobbying by various ‘organic-meaning-natural-meaning-better’ organizations to peddle this framing for their own bottom line… vilify the opposition).
The REAL issue for blooms is runoff and groundwater that has too much nitrogen.
And this most certainly INCLUDES ‘organic’ farming if nitrogen rich sources are allowed to contaminate runoff and water sources. It’s just that simple. Most small scale organic farmers I talked to didn’t have the first clue why their chicken coops and manure piles – situated as they were – were far, far worse a source to contaminate a local waterway or reservoir or stream or ground water than large scale industrial farms down the road that managed their fertilizers responsibly and captured the nitrogen properly (it’s a cost benefit thing at this scale). But the truly egregious polluters were smaller scale farmers who spread liquid pig manure and left it on the surface until the rest of the fields were sprayed. A rain event in the meantime would wash up to 2/3rds of this concentrated mixture straight into local waterways while these farmers went to local markets every week making money as ‘organic’ farmers rather than understood as the main toxic polluters they were in fact. The term ‘organic’ has successfully been sold to a gullible public as label that hides what’s true about the environmental cost of their products.
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Thanks. Interesting observations from someone who knows a lot more about the subject than I do. Suggests it’s not about scale, but about understanding the full effects of the chosen approach to farming, including soil health, biodiversity and runoff. Intuition suggests that organic approaches working with nature have a better chance of success in all these areas, but maybe you don’t agree?
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