UPDATE: Ice cover doubles pond oxygen level. See latest.
It’s a common piece of advice that you should break the ice on your pond.
The reason usually given is to let more oxygen in or let toxic gases out. Here’s a typical example from a major conservation organisation’s wildlife pond handbook:
‘Air holes should be opened every day during long freezing spells. These allow oxygen to diffuse into the water from the air and allow gases to escape from the pond.’
My pond has had ice cover now for the last 8 days, so I thought it was time to measure the dissolved oxygen concentration, to see if I needed to ‘allow oxygen to diffuse into the water from the air’.
The dissolved oxygen concentration this afternoon was 17.9 milligrammes of oxygen in each litre of water – this is in fact considerably more than 100% saturated – actually, its the second highest value I’ve ever measured in the pond, only slightly below the peak in summer when algae were producing oxygen like mad.
It’s considerably higher than the last time I measured the oxygen concentration a few days ago – roughly double.
I imagine that the ice is trapping the oxygen that is being produced under the water by algae and mosses.
There is no shortage of oxygen: indeed, the ice seems to have increased its concentration – the direct opposite of what standard advice tells us.
Mind you, you might want to break the ice to give the birds somewhere to drink.
Tags: Ice on the pond