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Results
Photo 4. Manor Farm.
Results
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The full species lists are presented as an appendix. The results summarised here consist of number of species, abundance and WHPT, N-taxa and ASPT for 2019, 2020 and 2021.
All the significant indices have increased this year compared with last year and compared with most of the 2019 results as well (only Manor Farm has a higher previous WHPT score from 2019). Overall abundance is generally down on previous years but this is a highly variable result and is not a significant measure of water quality or biodiversity. Overall number of species and number of contributing species (to the indices) have also increased (or remained the same in the case of Drayton Farm above settlement ponds ).
As a consequence, this years’ results are higher than the seasonal means so these have not been presented this year.
Site Date Season # species Abundance Ntaxa WHPT ASPT
Drayton Farm above settlement ponds
Manor Farm 22/8/18 Summer 46 1966 32 149.4 4.67
3/9/19 Autumn 45 1242 33 165.4 5.01 7/9/20 Autumn 43 1772 35 160.8 4.59 7/9/21 Autumn 43 1281 35 168.2 4.81 3/9/19 Autumn 53 2699 38 211.6 5.57 15/9/20 Autumn 47 4894 35 174.0 4.97 22/9/21 Autumn 54 3332 38 200.8 5.28 Values showing an increase are highlighted in blue
Table 2. Results summary
Because the increases are across all the sites, it is likely that favourable weather conditions will have contributed to the results, as well as the usual seasonal and sampling variations.
Much of the variation in species richness is contributed by single occurrences of species whereas most of the variation in abundance is due to variation of a small number of species. Gammarus counts are summarised below and show a mix of responses across the sites which would be expected as there is no overall trend to the results year on year.
Site Sept 2019 Sept 2020 Sept 2021
Bishop’s Sutton 928 1606 1708 Drayton below settlement ponds 364 440 139 Drayton above settlement ponds 159 580 127 Manor Farm 1341 3598 1560
Table 3. Gammarus counts
