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The Projects - Coy Pond Gardens 2002-2004

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Ecological Surveys

Peter Brett Associates, 2001

The first of three ecological surveys was carried out by Peter Brett Associates in 2001, as part of a feasibility study for the Coy Pond Gardens project.  It covered the entire length of the gardens from the railway embankment to Branksome Wood Road.

The 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.  A copy of the report is available on request.

Economics eventually dictated the extent of the final works which focused on the upper section of gardens where poor quality water discharges from the culvert.

Aquilina Environmental Quality Consultant, 2003

A second 'baseline' ecological survey was commissioned to cover the immediate working area - it was followed up two years later in order to gauge the impact of the works [more].

The Biological Monitoring Working Party (BMWP) scoring system is used to evaluate the stream and assign a quality category to it.

The 2003 survey was carried out on 26th 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 survey report which includes species lists (PDF 100kb)


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:


Vertical, mostly concrete, embankments offer little in the way of shoreline for invertebrates or plants, thus habitat diversity is restricted.


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).


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.

  • 2003 Water quality data for the gardens is available here.

Aquilina Environmental Quality Consultant, 2005

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

  • Results (summarised below) are presented in the full survey report which includes species lists (PDF 200kb)


Robert Aquilina 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.

The report 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 Robert 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




BMWP score




Species richness




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.

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