Oxygen in the ponds: an update

Here are the lastest oxygen levels in my pond and, just as important, in our neighbours Sally’s.

Sally’s pond is the green line: I began measurements there part way through the freeze, just before snow covered all the ponds.

Click the graph for a better quality image.

In Sally’s pond oxygen is always much lower. This has been really important to see because at times I’ve found it hard to believe quite how high the oxygen levels have been in my ponds. Sally’s pond has been an important reality check.

Sally’s pond probably has lower oxygen levels because the pond is quite deep, and has more organic matter using up oxygen.

In both my ponds you can see the clear effect of the snow – levels were high under the ice, especially in the old pond, but dropped fast once snow covered the ponds.

Oxygen levels bounced back quickly once the snow melted. The ‘bounce’ is highest in the old pond (the red and purple lines) and a little lower in the new pond – the blue line – which has fewer plants under the water.

Sally’s pond hardly changed during the cold weather – a slight increase as the snow melted, but I think this pond will always be quite low.

With the recent icing over (with no snow) oxygen levels in my ponds have risen again – often my old pond is off the scale as my dissolved oxygen meter only goes up to 20, and its often been higher than that in the latest freeze.

I still don’t know exactly why values are so high but I think the dense moss growth, producing oxygen under the water, and the shallow water are an important part of it.


2 Responses to “Oxygen in the ponds: an update”

  1. Barbara Says:

    Can I ask where is the dense moss growth?

  2. Jeremy Biggs Says:

    Hi Barbara

    The mosses are just growing in the water – more or less anywhere in the deeper parts (but remember ‘deep’ in my pond is 10-25 cm).

    They don’t grow in the areas that regualrly dry out in summer.

    I will write a bit about them soon-ish as I’ve not really said anything very much about them so far, except that they came on their own and have grown remarkably well.


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