Coy Pond Gdns Ecological Surveys

2001

The 2001 survey included the sampling of aquatic invertebrates in order to assess the overall water quality. Macro-invertebrates were limited in both numbers and diversity. A water beetle, several families of molluscs, midge larvae, water hoglouse and several mayfly larvae were found by the plant sampling. Gravel sampling revealed cased caddis-fly larvae, a mayfly larvae and several water shrimps.

The results indicated a poor to fair grading with the indicator species dominated by pollution tolerant organisms.

2001 Coy Pond Gardens Ecological Survey
Area	Dominated by:
Fenced boggy area close to Branksome Wood Road*	Soft Rush Juncus effuses Flote grass Glyceria fluitans
Marginal vegetation	Remote sedge Carex remota Flote grass
Bankside herbs	Water Parsnip Berula erecta Hemlock Water Dropwort Oenanthe crocata
Aquatic vegetation	Pondweed Potomogeton natens Water Parsnip Starwort Callitriche sp. Curled Pondweed Potomogeton crispus and Potomogeton pectinatus
Wildlife	Minnows 5-spined stickleback Azure damselfly Large Red damselfly A species of Hawker newly emerged (possibly a Brown Hawker) No signs of any Water Voles

* at that time an area of the gardens was fenced off for safety reasons

Note:

The samples taken from the inflow below the railway embankment were from the same point as the 2003 survey and, although a different sampling strategy was employed, the results can be approximately compared. The macroinvertebrate family list can be converted to BMWP scores and these are 19 and 29 giving a combined score of 35 (poor).

A second set of samples was taken at Branksome Wood Road, further downstream from the 2003 & 2005 sampling location. These gave BMWP scores of 23 and 34 and a combined score of 44. This slightly better score reflects the greater diversity due to greater habitat heterogeneity, more diverse plant life and greater distance (and less impact) from the discharge at the culvert below the railway embankment.

Coy Pond Gardens 2003 Aquilina, 2003

The 2003 survey was carried out on Tuesday 26^th August. It covered freshwater life in the stream, and a plant survey of the surrounding banks and field which were due to be affected by the works.

Results (summarised below) are presented in the full document which includes species lists (file size 100kb)

Summary

This baseline survey shows a section of stream with little variety and plenty of opportunities to increase habitat diversity. The vegetation survey shows a field of little botanical interest.

The results of the freshwater survey show a rather restricted range of invertebrates compared with other reaches of the Bourne Stream. The BMWP scores reflect the sensitivity of invertebrates (at Family level) to organic pollution, thus the presence of species with scores of up to 8 (the most sensitive species score 10) show that the stream is not unduly affected by pollution or organic enrichment.

The total BMWP score for the site is 76 which suggests a moderately clean site (values greater than 100 are associated with clean rivers and values less than 10 with heavily polluted waters).

The reasons for the paucity of species are likely to be threefold:

1.	Vertical, mostly concrete, embankments offer little in the way of shoreline for invertebrates or plants, thus habitat diversity is restricted.
2.	Lack of submerged or emergent vegetation will severely restrict habitats for invertebrates. There are only small patches of Curled Pondweed (Potamogeton crispus), Water Plantain (Alisma plantago-aquatica) and Floating Clubrush (Eleogiton fluitans) actually submerged and small patches of overhanging Creeping Bent (Agrostis stolonifera) and Hemlock Water Dropwart (Oenanthe crocata).
3.	The quality of the water emerging from the culvert. As this has been underground for some distance, there will have been no primary production and therefore will be low on food content. It also shows a red-brown deposit of iron oxides which coat the bottom and any submerged plants, thus restricting the ability of plants to grow at this point in the stream.

The proposed works will address the first issue directly and as a consequence will improve conditions for submerged and emergent vegetation (point 2 above). The siting of the pond should capture the water emerging from the culvert and filter it through reedbeds which will restrict the deposit and improve conditions further downstream. The proposed weir and rock splash pool should also increase the oxygen content of the water and improve the water quality downstream.

Comparison with previous data suggests that the stream has improved since 2001 as a result of works carried out upstream. The potential for biodiversity in the stream would appear to be limited more by physical and structural components than chemical or organic pollution. Therefore the proposed works should improve both the stream and surroundings by offering an increase in the range of habitats available.

Coy Pond Gardens August 2005 Aquilina, 2005

The 2005 survey was carried out on 11th August using exactly the same protocol and at the same time of year as the baseline survey in 2003, so results can reliably be compared.

His report (summarised below) is presented in the full document which includes species lists (file size 200kb)

Summary

Robert recorded a list of 30 macroinvertebrates and a BMWP score of 94 which indicates a good quality site with clean water; a clear improvement on the previous survey which recorded 20 species and a BMWP score of 76.

He also surveyed the vegetation beside the stream, and listed 42 species compared with 16 two years ago! At least 10 of the new species were introduced with the planting scheme that was carried out after the earthworks.

Robert confirms that the restructuring of the stream has been successful in introducing greater diversity of physical habitats which is reflected in the increased diversity of both plants and macroinvertebrates recorded in his survey.

In conclusion he writes, “The current situation is of a stream with good water quality and a diverse range of macroinvertebrates and plants”.

The table below indicates just how far we’ve come in the past four years:

Survey date	2001	2003	2005
BMWP score	35	76	94
Species richness	n/a	20	30

The original survey in 2001 recorded a poor quality site in terms of wildlife habitat; in 2005 it is transformed to a good, bordering on very good quality.

The Partnership is very proud that the Bourne Pools project already appears to have met many of its objectives.