Update on oxygen in my ponds

Oxygen in my ponds: the graph shows the milligrammes of oxygen in each litre of water (numbers up the side). Date and time along the bottom, starting at the 27th August - with vertical lines separating the days, from midnight (oo.00) to midnight (00.00). The top line (blue) is the New Pond, out in the open; the middle line (yellow) is more-or-less permanently shaded Katy's Pond; the bottom line (purple) is the Old Pond with Lemna cover and shaded about three quarters of the day now. Click for a higher res. graph.

Measurements this afternoon and this evening have maintained the pattern of the last couple of weeks.

– New Pond highest (and in the early afternoon, really very high);

– Katy’s Pond – shaded and with mosses – in the middle;

– Old Pond lowest.

Though it’s interesting that, even with the duckweed cover, the Old Pond still had a reasonable amount of oxygen, at around 11 milligrammes in each litre of water in the middle of the afternoon.

Perhaps most striking is just how much variation there can be over the course of the day: the early morning low is around half the mid-afternoon high.

Exactly what all this means for animals in the ponds is still a good question as many pond creatures have adaptations to relatively low levels of oxygen.

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