We tend to take the natural composition of rainfall that fills our rivers and streams as a constant but, like a lot of things today, that is no longer the case.
A healthy stream should be slightly alkaline and have a pH level in a range of between 7.2 and 8.0 (7 is neutral) but water that falls as rain has washed CO2 out of the atmosphere and is slightly acidic at 5.7. This acidic rainwater is made more alkaline and moved to 7.2+ by washing minerals out of the rocks and soil and the addition of organic matter from trees and grasses.
A healthy stream should be slightly alkaline and have a pH level in a range of between 7.2 and 8.0 (7 is neutral) but water that falls as rain has washed CO2 out of the atmosphere and is slightly acidic at 5.7. This acidic rainwater is made more alkaline and moved to 7.2+ by washing minerals out of the rocks and soil and the addition of organic matter from trees and grasses.
Organisms living in the streams are comfortable in alkaline water at pH levels above 7.2 and at that level will thrive. The smaller invertebrate of mayfly, caddisfly larvae and stonefly are the key here as they form the base of the fresh water fish food chain and also are sensitive to water quality. They could be called the canary in the coal mine, if the canary dies the miner is likely to die as well.
The current level of CO2 in the atmosphere has just reached 400 ppm compared to its natural high of 280 ppm, 150 years ago before we started burning coal. This has raised the acidity of fresh water from the atmosphere by 33%.
Rivers and streams are hugely variable but never the less this big change in acidity must be affecting the natural habitat of our freshwater aquatic life in much the same way that ocean acidity is affecting our mussels and corals and anything else with a calcium carbonate shell like plankton.
The current level of CO2 in the atmosphere has just reached 400 ppm compared to its natural high of 280 ppm, 150 years ago before we started burning coal. This has raised the acidity of fresh water from the atmosphere by 33%.
Rivers and streams are hugely variable but never the less this big change in acidity must be affecting the natural habitat of our freshwater aquatic life in much the same way that ocean acidity is affecting our mussels and corals and anything else with a calcium carbonate shell like plankton.
This chart from NOAA illustrates how not all fresh water aquatic life can survive a change to more acidic water and as with the oceans if the smallest creatures can not survive the base of the food chain is cut off.
The big increase in the amount of nitrogen from cattle effluent is well recognised for the damage it does, but acidity increases from atmospheric CO2 are not so well reported and yet need just as much attention.
It highlights the necessity of looking after the streams we have and treating a health stream as a resource to combat increasing spells of drought caused by a warming world.
It highlights the necessity of looking after the streams we have and treating a health stream as a resource to combat increasing spells of drought caused by a warming world.
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