The state of the Old Pond

The Old Pond today

My Old Pond is looking a bit overrun by Lemna so it’s with some relief that in a recent dip I found practically the same range of animals as this time last year; there were a few late staying tadpoles too.

The biggest difference between now and autumn 2009 is fewer Pond Olive mayfly larvae, and as far as I can see no Whirlpool Ram’s-horns – which is interesting because there were a lot last year. Maybe they were affected by the summer draw-down – it’s true that you don’t see Whirlpool Ram’s-horns in temporary ponds. I also wonder whether the abundance of duckweed has affected these two species.

There are many fewer Pond Olives this autumn - I think they rather like new bare ponds and are no so common where vegetation is abundant

Overall, the total number of species is down slightly from 23 to 19 – not that much of a difference really. And our Big Pond Dip score – which is based on the big groups present (dragonflies, bugs, beetles, caddis and so on) – is virtually unchanged: 47 instead of 52 (the difference is due to no water bugs).

There are still three dragonfly species, including lots of Large Red Damsel larvae, plenty of my favourite little pond snails the Smooth Ram’s-horn, and a good range of water beetles – with a dozen species they make up most of the variety of species though being in low numbers they’re not very conspicuous – you have to look around for them. One interesting arrival is a little water beetle that loves more leafy and overgrown conditions called Hydroporus memnonius – its one of the Little Brown Jobs of the pond world: a pretty little chestnut brown creature. There’s a couple of other water beetles that weren’t there last year as well.

I’ve still got caddis which is important because they’re one of the groups which should be present in natural unpolluted ponds: and I’m hoping to see more hatch and grow overwinter.

So I’m now waiting with interest to see what will happen to the duckweed this winter: will the String Moss provide some competition for it? Or do I now have a permanently duckweedy pond? And, most important of all, what difference does it make in the long run?

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One Response to “The state of the Old Pond”

  1. Damned Duckweed « The Garden Pond Blog Says:

    […] It’s harder to tell what effect the duckweed has had on animals: certainly the animals haven’t changed too much this year, and most of the species that were present this time last year are still present this year (see this recent post). […]

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