19.07.13 Torfaen. Friends of Henllys LNR and Coed Eva pond sampling
Twenty Eight volunteers from Friends of Henllys LNR and Coed Eva Primary School’s Class 4RP came along to sample macroinvertebrates from the two adjacent ponds. Year 4 were studying water quality in class and we decided it would be good idea investigate the pond water quality by recording the macroinvertebrates caught. The class learnt from the Friends that some bugs like very clean water and some live in dirty water and looking at the range and average of these bugs caught can give clues to water quality. Moreover, they could scientifically test to see if there are any differences between the two ponds which are only 40 metres apart from each other. After a quick demonstration of pond dipping and how to look at what they’d caught using sample trays, the children split into three groups which they called themselves , dragonflies, fireflies and cased caddis flies. Armed with a crib sheet and tally chart prepared beforehand by the Friends, the children set to their tasks admirably. After a suitable length of time, they cleaned their nets, but all the bugs back and headed over to the second pond. They carried on sampling in this pond noting that some of the pond was green and there was some plantlife inside this one, which was not present in the first one.
The data was summarised with loads more dragonfly larvae found in the planted up pond (Class 4WWs) compared with the top pond.

Planted PondTop Pond
Caught Sum Planted Sum top
Pondskater (BI 5) 11 12
Water boatman (BI 5) 16 14
Dragonfly nymph (BI 8) 9 2
Water beetle (BI 5) 2 2
Pond snail 6 0
Frog 1 0
Tadpole 1 0
Caddisfly larvae (BI 5) 2 0

Using the calculated BI’s and an unpaired t-test the p = 0.118. From this, they are not significantly different, but the numbers of dragonfly larvae caught were quite a bit larger than the top pond.

We were supported by equipment and experience by TCBC’s ranger Jon Howells.
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