Thames21: Salmons Brook Project
Aquatic Invertebrate Survey Results
Date: 23/05/2013
Surveyors: Angela Bartlett and Giorgia Lombardi
Purpose: To record invertebrates (animals without a backbone) living in the Houndsden Stream at the Spinney and
the stream into Boxers Lake and investigate water quality by looking at the number of invertebrates found and their
species. Some species of invertebrates are much more tolerant of pollution than others.
Weather: Approximately 10°C with rain and hail at first sites.
Observations: Low flow, turbidity (cloudy water) and signs of pollution at all sites.
Method: We sieved and searched through 30cm2 of silt, gravel etc. (sediment) from the stream bed, using kick
samples (agitating the stream bed and catching creatures in a net) where there was flowing water. We looked
through the sediment at each site for 15mins and recorded the species found and numbers of invertebrates of each
species.
Site
Boxers Lake
Stream C
(downstream)
Species
Quantity Interpretation
Biting midge larvae
1
No. of species found = 5
Gammarus shrimp
1
No. of invertebrates found = 10
Hog louse
1
Pond snail
3
Tubifex worm
4
Observations: Very fine sediment and extremely turbid (cloudy) water with an oily film. Lots of leaves and sticks
etc. decaying in sediment.
Boxers Lake
Biting midge larvae
1
No. of species found = 6
Stream B (middle) Chironomid (non-biting midge
2
No. of invertebrates found = 13
larvae)
Gammarus shrimp
2
Hog louse
5
Water spider
1
Tubifex worm
2
Observations: All life seemed to be in weed and algae rather than sediment.
Boxers Lake
Hog louse (alive)
14
No. of species found = 2
Stream A
Hog louse (dead)
8
No. of invertebrates found = 23
(upstream)
Non-biting midge larvae
1
Observations: Very polluted, lots of sewage fungus. Strong unnatural smell. Litter.
Houndsden
Bivalve
1
No. of species found = 7
Stream B
Chironomid
10
No. of invertebrates found = 42
(downstream)
Cranefly larvae
1
Hog louse (alive)
9
Hog louse (dead)
3
Non biting midge larvae
5
Pond snail
1
Tubifex worm
12
Observations: Relatively clear water, flowing faster due to smaller area, overhanging vegetation. Fine/ gravel
sediment.
Houndsden
Chironomid
4
No. of species found = 6
Stream A
Non biting midge larvae
3
No. of invertebrates found = 20
(upstream)
Pond snail
1
Ramshorn snail
1
Tubifex worm
6
Worm
5
Observations: Relatively clear water, flowing faster over riffle features (stones on stream bed), overhanging
vegetation. Fine/ gravel sediment. Sewage fungus growing on submerged plants.
Midge larvae
Gammarus shrimp
Hoglouse
Pond snail
Tubifex worm
Bivalve
Cranefly larvae
Ramshorn snail
Worm
Results: Only a few different species were found at each site. The species found are generally tolerant of low oxygen
and relatively high pollution levels. The lack of species such as stoneflies, which are not tolerant of pollution and low
oxygen levels, indicates that the water quality in these sites is generally poor, and is having a subsequent impact
upon aquatic invertebrates. Boxers Lake Stream site A, had particularly bad results; low species richness but high
numbers of one species does not indicate a healthy functioning ecosystem. At this site 23 invertebrates were found
but 8 of these were dead, further evidence of poor water quality. We can conclude that water quality at all sites was
poor, especially Boxers Lake Stream site A.