Wildlife Trust Derbyshire Wildlife Trust
East Mill, Bridge Foot, Belper, Derbyshire, DE56 1XH
Tel: 01773 881188 Fax: 01773 821826
E-mail: enquiries@derbyshirewt.co.uk

Porters Lane Pond

Porters Lane, Oakwood



Derbyshire Wildlife Trust
East Mill
Bridgefoot
Belper
Derbyshire
DE56 1XH
A report for the Wild About Ponds Project
Prepared by Trevor Taylor
Local Wildlife Sites Officer (Planning)
Derbyshire Wildlife Trust

November 2010

Protecting Wildlife for the future

Regisered charity no. 222212
DWT is a company registered in England and Wales
with the Company Number 715675

Porters Lane Pond

Background

Derbyshire Wildlife Trust was commissioned to survey the pond located off Porters Lane in Oakwood, Derby as part of the Wild About Ponds Project in order to provide management recommendations based upon the findings of the survey. It would also enable a comparison of survey results against data obtained as part of the 2004/5 Derby City Pond Survey.

Map 1 shows the location of the pond. The pond is located within a small area of open space off Porters Lane in Oakwood, although access is somewhat limited by the presence of a 1m high ornamental metal railing fence which forms the northern boundary of the site alongside the pavement. A locked gate is present within the fencing to allow access for management. The site is bounded to the south, east and west by the gardens of residential properties with a native hedgerow forming the boundary to the gardens of dwellings to the south of the site.

Habitats surrounding the pond within the site include species-poor grassland, bramble scrub and scattered trees. A stand of Japanese Knotweed persists on the southern bank.

The ownership of the site was transferred to Derby City Council from the developers, Miller Homes, in late 2009.

The pond is shown on Ordnance Survey First Edition maps dated 1882 and would therefore appear to be of some local historic interest. It was retained as a feature within the surrounding housing development which was built in the late 1990’s and, as well as contributing to the aesthetic value of the area, the pond provides a function in collecting surface water from the road and nearby properties via a number of land drains which feed into the pond.

Survey objectives

The aim of the survey was to gather ecological information using the PSYM methodology in order to determine the current overall ecological quality of the ponds.

Methodology

The survey followed the standard survey methodology known as PSYM developed by Pond Action (now Pond Conservation) and the Environment Agency. PSYM, the Predictive System for Multimetrics, (pronounced sim) was developed to provide a standard method for assessing the biological qualities of still waters in England and Wales.

The method uses a number of aquatic plant and invertebrate measures (known as metrics) which are combined together and fed into a computer model, along with basic environmental and location data, to obtain a single value which represents the waterbody’s overall quality status.

The recommended time of year for carrying out PSYM pond surveys is during June, July and August. The pond was surveyed during August 2010.

The following information was gathered for the pond:

Calculating the pond metrics

The data collected from the surveys are used to calculate three plant metrics and three invertebrate metrics.

1. Number of submerged and emergent plant species

This is simply the number of submerged plant species plus the number of emergent plant species. The calculation does not include the number of floating-leaved species present. This is because the pond data suggest that the number of floating-leaved plants occurring at a site does not decline significantly with increasing degradation. The metric is therefore improved by omitting this plant group.

2. Trophic Ranking Score (TRS)

TRS is a measure of the average trophic rank for the pond. This is calculated by assigning each plant species with a trophic score based on its affinity to waters of a particular nutrient status. The trophic scores vary between 2.5 (dystrophic, i.e. very nutrient poor conditions) and eutrophic, i.e. nutrient rich conditions).

Unfortunately, not all plants have trophic scores. This situation has arisen because the current TRS values for standing waters (Palmer et al., 1992) are based only on analysis of lake data, and many plant species which are common in ponds occurred at too low a frequency in lakes to give them a score. Also, some plant species exhibit little nutrient preference.

The TRS value for a site is calculated as follows:

  1. The trophic scores from each plant species present at the site are summed together.
  2. The summed score is divided by the total number of plant species which have a trophic ranking score to give the TRS.
3. Uncommon Species Index

Uncommon species are those which have a rarity score of 2 or more. The number of these species is simply summed to give the number of uncommon species.

Uncommon species refers to species which can be best described as "local", "nationally scarce" or "Red Data Book". The rarity status values for Scarce and Red Data Book species are based on existing definitions derived from the Red data Books and other authorities. The definition of "local" has been used to define species which are not uniformly common and widespread in Britain: with plants this refers specifically to species recorded from between 100 and 700 10 x 10 km squares in England, Wales and Scotland.

4. Average Score per Taxon (ASPT)

The ASPT is calculated by summing the BMWP scores for all taxa present at the site and dividing by the total number of BMWP taxa present.

BMWP (Biological Monitoring Working Party) scores are assigned to taxa depending on their known tolerance to organic pollution, a higher score indicating lower tolerance. The scores were defined by Maitland in 1977.

5. Number of dragonfly and alderfly families.

This metric is the sum of the number of dragonfly (Odonata) and alderfly (Megaloptera) families.

6. Number of beetle families

This metric is the sum of the number of beetle (Coleoptera) families present at the site. The metric has a relationship with bank quality as well as water quality.

Results

The pond was surveyed using the PSYM methodology enabling an assessment of its biological quality to be made together with a comparison with other ponds in the area.

The PSYM scores are placed in four categories which reflect the ecological quality of the pond:

0-25% is very poor, 26-50% is poor, 51-75% is fair, and 76-100% is good

Porters Lane Pond

Site and sample details

Grid reference: SK 37756 38924

Site Name: Porters Lane Pond

Location: Porters Lane

Owner/site access details: Derby City Council

Survey Date: 6th August 2010Surveyors: Trevor Taylor (Derbyshire Wildlife Trust)
Derek Golson
Maggie Cooper

Environmental Data

Altitude: (m)106m aslpH:7.1
Shade: % pond overhung:12% % emergent plant cover35%
Inflow (absent = 0, present = 1):0Pond area (m2)264m2
% of pond margin grazed:0

Pond base: categories into one of three groups; 1=0%-32%, 2=33%-66%, 3=67%-100%)

Clay/silt:3Sand, gravel, cobbles:1Bed rock:1
Peat1Other1

Emergent plants Rarity Score Trophic Ranking Score
 
Alisma plantago-aquqtica, Water-plantain19
Epilobium hirsutum, Great Willowherb 1 -
Glyceria maxima, Reed Sweet-grass 1 10
Iris pseudoacorus, Yellow Iris 1 -
Juncus effusus, Soft rush1-
Lysimachia vulgaris, Yellow Loostrife2-
Solanum dulcamara, Bittersweet110
Sparganium erectum, Branched Bur-reed18.5
Typha latifolia, Bulrush18.5
Veronica beccabunga, Brooklime110
 
Floating Leaved Plants
 
Lemna minor, Common Duckweed19
Potamogeton natansr, Broad-leaved Pondweed1-
Submerged plants
 
Ceratophyllum demersum, Rigid Hornwort210
Potamogeton crispus, Curled Pondweed 110

Number of emergent and submerged species – 12
Number of uncommon species (with a rarity score of 2 or more) – 2

Trophic Ranking Score – 9.44

Macroinvertebrates
Group 2 taxa (BMWP:8)
Aeshnidae (Dragonfly, Southern Hawker, (Aeshna cyanea)

Group 4 taxa (BMWP:6)
Gammaridae – Crustacean (Shrimp)
Coenagriidae – Damselfly
Group 5 taxa (BMWP:5)
Nepidae - Water bug (Water scorpion)
Corixidae - Water bug (water boatman)
Hydrophilidae - Water beetle (scavenger)
Planariidae – Flatworm
Gerridae – Water bug (Water skater)
Notonectidae – Water bug (Greater water boatman)
Dytiscidae – Water beetle (Diving) Hyphydrus ovatus
Hygrobiidae – Water beetle (Screech beetle, Hygrobia hermanii)

Group 6 taxa (BMWP:4)
Baetidae - Mayfly

Group 7 taxa (BMWP:3)
Planorbidae - Ramshorn snail
Hirundinae - Leech, Horse Leech, Haemopsis sangusiuga)
Lymnaeidae - Snail
Asellidae – Crustacean (Water slater)

Group 8 taxa (BMWP:2)
Chironomidae - Fly (non biting midge)

Group 9 taxa (BMWP:1)
Oligochaetae - True worm

Total No. Of taxa18
Total BMWP Score39
ASPT43.9
No. OM taxa2
No. Coleopt taxa3

Index of Biotic Integrity (PSYM Score %) = 67. As such the pond would be considered to be in fair ecological condition.

This represents a significant improvement in the ecological condition of the pond since 2004, when a survey undertaken as part of the Derby City Pond Survey returned a PSYM score of 50%.

A conductivity test to measure of the total quantity of chemicals dissolved in the water returned a reading of 200µS/cm. This figure indicates that the pond is reasonably clean and free from pollution. Where conductivity is 500-1000 + µS/cm this is usually a sign of some kind of pollution and a perfectly clean water pond would have a figure of 100µS/cm or less.

Survey Results

The pond supports a good range of aquatic plant, macroinvertebrate and amphibian species.

Yellow Loosestrife

Of particular note is the presence of a well-established population of Yellow Loosestrife, Lysimachia vulgaris, in the shallow water of the eastern side of the pond and the occurrence of the submerged aquatic plant Rigid Hornwort, Ceratophyllum demersum which is abundant throughout. Reed Sweet-grass, Glyceria maxima, is a frequent emergent component in the margins along with Yellow Iris, Iris pseudoacorus and Bulrush, Typha latifolia.


Left: Yellow Loosestrife

The pond is a well-established valuable amphibian breeding site and supports good numbers of Common Toad, a UK BAP priority species, Smooth Newt and Common Frog.

Common Toad

Right: Common Toad

A bottle trapping exercise undertaken on 30th April 2005 caught 11 male and 22 female Smooth Newts, while a torchlight survey conducted on 23rd March 2011 revealed a minimum of 30 common toads, 19 male and 5 female smooth newts together with a good quantity of frogspawn.

Male Smooth Newt

Male Smooth Newt

Female Smooth Newt

Female Smooth Newt

The hedgerow and areas of bramble provide suitable terrestrial foraging and hibernating habitat for amphibians.

The pond is a permanent water body which holds water throughout the year. However, concern has been expressed in recent years by pond warden and local resident Derek Golson in relation to ongoing low water levels.

Management history

Porters Lane Pond

Porters Lane Pond 2004

At the time of the 2004/5 Derby City Pond Survey the pond was covered with a thick surface layer of Common Duckweed.

It is likely that this was brought about as a result of nutrient enrichment due to a combination of the build-up of organic matter from leaves of overhanging trees and shrubs and surface water run off from the nearby roads and properties. It was also noted that the level of emergent vegetation in the form of Reed Sweet-grass was significantly reducing the amount of available open water.


Management advice was provided by Hugh Roberts from Pond Conservation which focussed largely on the removal of some areas of Reed Sweet-grass to create open bays and the removal/coppicing of the ornamental evergreen shrubs on the southern bank of the pond.

It was anticipated that the removal of the covering of Duckweed would be achieved by dragging a stout rope across the pond surface. However, the subsequent removal of the overhanging Rhododendron and Cherry Laurel bushes on the southern bank along with the coppicing of a mature willow and removal of additional mature trees on health and safety grounds created an open aspect which attracted a pair of Mallard which were instrumental in reducing the amount of Duckweed.

The clearance of selected areas of Reed Sweet-grass is carried out on an annual basis by a work party comprised of members of the local resident’s group and the control of Japanese Knotweed is undertaken by contractors.

Management recommendations

Porters Lane Pond

Porters Lane Pond 2010


Porters Lane Pond

Porters Lane Pond 2011


Porters Lane (Oakwood) Map