No evidence? No problem!

Another unfounded suggestion about iced-up ponds comes my way, from a reputable organisation.

The authors get off to a good start, suggesting that there’s no need to make a hole in the ice.

But then they spoil it a bit. The reason they propose you don’t need to break the ice is because…

‘If there is a deep section, the pond will contain enough oxygen to keep amphibians alive over winter.’

Oops. Our recent detailed measurements in Abingdon garden ponds suggest that simply having a deep section is no guarantee that there will be oxygen in the water.

The results of the Abingdon survey – which we’re working on now – show that deeper garden ponds, when they accumulate large quantities of leaves in the bottom, often have very little, and sometimes no, oxygen.

It looks as though the standard stepped pond shape – with a sump dug down to 50 or 60 cm (sometimes more) – creates an environment where, as leaves build up, oxygen demand greatly exceeds what can be supplied by algae and plants.

So unless your pond has the right general conditions for producing oxygen – which probably means shallow, clear water, plenty of submerged plants, along with planktonic and bottom dwelling algae…

…having a deep water area is no guarantee that there will be oxygen for amphibians, or anything else.

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