It was drizzling as twelve members met at the entrance to Hopwood Clough.
We made our way through the woods to a site near a small bridge over Trub Brook. The brook flows through mixed woodland with Beech as the dominant species. The ground near the stream was covered in Beech leaf litter. One side of the stream was reinforced with concrete blocks. The air temperature was 10oC and the water temperature 7oC. The rain stopped and the rest of the day was fine. The water appeared clear and the substrate was gravel with some larger stones, at the edge of the brook was some finer silt. 
Field naturalists sampling the stream.
We took kick samples, drift samples and lifted some small rocks to investigate the invertebrates living in the stream and on the stones. We identified the organisms using picture keys. As well as recording the abundance we recorded the BMWP biotic index score. Organisms which can tolerate pollution have a relatively low score whereas those which need high oxygen content in the water and do not tolerate pollution have a maximum score of 10. Our results are shown in the table below. The table also shows organisms we might have expected to find but were absent, as sometimes absence of an organism reveals as much as those which are present.
The BMWP biotic index score for Trub Brook was 58 which shows reasonably good water quality for a stream close to habitation and industry. A very clean brook would score over 70 with more variety of species of Mayfly nymphs and Stonefly nymphs.
Some of the animals found in our sampling, including the mystery caddis photographed through the microscope.
After lunch most of the group continued the walk through the woods. We saw a good selection of woodland birds including bullfinch, greater spotted woodpecker, nuthatch and song and mistle thrush. Our only flowering plant was a single primrose plant near the approach road to the College. We identified a broad buckler fern, and jelly ear, turkey tail and birch bracket fungi. As always, there were grey squirrels around.
On returning from the walk we sampled a site about a 100 metres upstream with similar results. The results of both sites have been added together in the table.
It was an interesting day and hopefully we can repeat the exercise on a different stream in the future.
Results
| Species identified | Abundance
|
BMWP score
|
| Mollusca
|
None | |
| Platyhelminthes
Flatworm (Planaria sp.) |
1 |
5 |
| Annelida
True worm |
1 |
1 |
| Arachnida
Water mite |
1 |
3 |
| Crustacea
Water hog louse (Asellus sp) Freshwater shrimp (Gammarus pulex) |
few few |
3 6 |
| Hemiptera (bugs)
|
None | |
| Diptera – fly larvae
Blackfly (Simulium sp) Non-biting midge (Chorinimidae) Mosquito Larva type A Larva type B |
abundant abundant None None None |
5 2 |
| Coleoptera – beetles
|
None | |
| Trichoptera- caddis fly larva
Rhyacophila Hydropsyche sp. Cased caddis type A Cased caddis type B (in small stones case) Cased caddis type C (in twig-like case) |
None 1 None 1 1
|
5
7 7 |
| Plecoptera
Stonefly nymph |
1 |
10 |
| Odonata
|
None | |
| Megaloptera
|
None | |
| Ephemeroptera –mayfly nymphs
Ecdyonurus sp. Ephemera sp. Baetis sp. Ephemerella sp. Caenis sp. |
None None Abundant None None |
4 |
| Total BMWP
Score |
58 |
Birds Seen
great tit, long tailed tit, wood pigeon, great spotted woodpecker (2), chaffinch, robin, blue tit, magpie, song thrush, carrion crow, bullfinch(2) coal tit, jackdaw, nuthatch, mistle thrush, blackbird.