Protecting Wildlife for the futureRegisered charity no. 222212
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.
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.
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:
The data collected from the surveys are used to calculate three plant metrics and three invertebrate metrics.
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.
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:
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.
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.
This metric is the sum of the number of dragonfly (Odonata) and alderfly (Megaloptera) 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.
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
Grid reference: SK 37756 38924
Site Name: Porters Lane Pond
Location: Porters Lane
Owner/site access details: Derby City Council
|Survey Date: 6th August 2010||Surveyors:||Trevor Taylor (Derbyshire Wildlife Trust)|
|Altitude: (m)||106m asl||pH:||7.1|
|Shade: % pond overhung:||12%||% emergent plant cover||35%|
|Inflow (absent = 0, present = 1):||0||Pond 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:||3||Sand, gravel, cobbles:||1||Bed rock:||1|
|Emergent plants||Rarity Score||Trophic Ranking Score|
|Alisma plantago-aquqtica, Water-plantain||1||9|
|Epilobium hirsutum, Great Willowherb||1||-|
|Glyceria maxima, Reed Sweet-grass||1||10|
|Iris pseudoacorus, Yellow Iris||1||-|
|Juncus effusus, Soft rush||1||-|
|Lysimachia vulgaris, Yellow Loostrife||2||-|
|Solanum dulcamara, Bittersweet||1||10|
|Sparganium erectum, Branched Bur-reed||1||8.5|
|Typha latifolia, Bulrush||1||8.5|
|Veronica beccabunga, Brooklime||1||10|
|Floating Leaved Plants|
|Lemna minor, Common Duckweed||1||9|
|Potamogeton natansr, Broad-leaved Pondweed||1||-|
|Ceratophyllum demersum, Rigid Hornwort||2||10|
|Potamogeton crispus, Curled Pondweed||1||10|
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
|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 taxa||18|
|Total BMWP Score||39|
|No. OM taxa||2|
|No. Coleopt taxa||3|
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.
The pond supports a good range of aquatic plant, macroinvertebrate and amphibian species.
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.
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
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.
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.
Porters Lane Pond 2010
Porters Lane Pond 2011