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

The Arboretum Ponds

Derby Arboretum



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

August 2012

Protecting Wildlife for the future

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

The Arboretum Ponds

Background

Derbyshire Wildlife Trust was commissioned to survey the two ponds located within The Arboretum as part of the Wild About Ponds Project in order to provide management recommendations based upon the findings of the survey. It would also provide baseline data against which future survey information could be compared.

Map 1 shows the location of the ponds. The ponds are located within The Arboretum Park in the district of Normanton in the centre of Derby, which is considered to be England's first public park. It is well-used by the general public and comprises sports facilities, playgrounds, toilets, café and room hire and is open from 8.00am to 6pm, 7 days a week.

The ponds are situated within a "wildlife garden", enclosed by railings on the western edge of the Park. The larger of the two ponds was created in 2004 on the site of a former dilapidated rose garden as part of a Restoration Scheme for the Park funded by the Heritage Lottery Fund. The second smaller pond was created in 2011 by BTCV as part of the Wild About Ponds project.

The grassland within the "wildlife garden" supports a range of wildflowers including Lady's Bedstraw, Meadow Cranesbill, Common Bird's-foot-trefoil, Common Knapweed, Common Vetch and Perforate St John's-wort.

The Park is owned by Derby City Council and managed by the City Council Parks Department. At present one Ranger is allocated to the Park and a "Friends of" Group is in the process of being established to maintain a watchful eye over the site in association with the Ranger and the Parks Department.

Liners were used in the construction of the ponds to ensure that they held water throughout the year and a wooden dipping platform was constructed along one edge of the larger pond in order to facilitate its use for educational purposes and school visits.

During 2010 it was noted that the larger pond contained a population of fish which had been eagerly introduced by local residents. A number of non-native invasive aquatic plant species were also known to be present in the main pond including Myriophyllum aquaticum, Parrot's-feather, Crassula hemsii, New Zealand Pigmyweed and Lagarosiphon major, Curly Waterweed.

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 2012.

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 10x10 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


Arboretum Pond 1.

Site and sample details

Grid reference: SK 35503 35017

Site Name: Arboretum Pond 1

Location: The Arboretum, Normanton

Owner/site access details: Derby City Council

Survey Date: 16th August 2012Surveyors: Trevor Taylor (Derbyshire Wildlife Trust)

Environmental Data

Altitude: (m)59m aslpH:7.7
Shade: % pond overhung:0%% emergent plant cover65%
Inflow (absent = 0, present = 1):0Pond area (m2)389m2
% of pond margin grazed:0

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

Clay/silt:2Sand, gravel, cobbles:1Bed rock:1
Peat1Other2

Emergent plantsRarity ScoreTrophic Ranking Score
 
Epilobium hirsutum, Great Willowherb1-
Glyceria maxima, Reed Sweet-grass110
Iris pseudoacorus, Yellow Iris1-
Juncus articulatus, Jointed Rush1-
Lysimachia nummularia, Creeping-jenny1-
Menyanthes trifoliata, Bogbean15.3
Mentha aquatica, Water Mint17.3
Myosotis scorpioides, Water Forget-me-not19
Ranunculus flammula, Lesser Spearwort1-
Nasturtium officinale, Water-cress110
Sparganium erectum, Branched Bur-reed18.5
Typha latifolia, Bulrush18.5
 
Floating-leaved plants
 
Lemna minor, Common Duckweed19
Lemna trisulca, Ivy-leaved Duckweed110
Nymphaea spp, Water lily1-
 
Submerged plants
 
Ceratophyllum demersum, Rigid Hornwort210
Lagarosiphon major, Curly Waterweed1-
Myriophyllum aquaticum, Parrot's-feather1-

Number of emergent and submerged species - 15
Number of uncommon species (with a rarity score of 2 or more) - 1



Trophic Ranking Score - 8.62


Macroinvertebrates

Group 5 taxa (BMWP: 5)
Gerridae - Water bug (Water skater)
Notonectidae - Water bug (Greater Water boatman)

Group 7 taxa (BMWP: 3)
Lymnaeidae - Snail
Planorbidae - Ramshorn Snail
Glossiphoniidae - Leech
Erpobdellidae - Leech
Asellidae - Crustacean ( Water slater)

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

Total No. Of taxa8
Total BMWP Score27
ASPT3.4
No. OM taxa0
No. Coleopt taxa0

Index of Biotic Integrity (PSYM Score %) = 44. As such the pond would be considered to be in poor ecological condition.

A conductivity test to measure the total quantity of chemicals dissolved in the water returned a reading of 390µS/cm. This figure indicates that the pond is on the borderline with regard to contamination. 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.


Arboretum Pond 2.

Site and sample details

Grid reference: SK 35480 35022

Site Name: Arboretum Pond 2

Location: The Arboretum, Normanton

Owner/site access details: Derby City Council

Survey Date: 16th August 2012Surveyors: Trevor Taylor (Derbyshire Wildlife Trust)

Environmental Data

Altitude: (m)62m aslpH:8.16
Shade: % pond overhung:0%% emergent plant cover0%
Inflow (absent = 0, present = 1):0Pond area (m2)50m2
% of pond margin grazed:0

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

Clay/silt:1Sand, gravel, cobbles:1Bed rock:1
Peat1Other3

Floating-leaved plants
 
Lemna minor, Common Duckweed19
 
Submerged plants
 
Ceratophyllum demersum, Rigid Hornwort210

Number of emergent and submerged species - 1
Number of uncommon species (with a rarity score of 2 or more) - 1


Trophic Ranking Score - 9.50



Macroinvertebrates

Group 5 taxa (BMWP: 5)
Gerridae - Water bug (Water skater)
Notonectidae - Water bug (Greater Water boatman)
Corixidae - Water bug (Lesser Water boatman)
Dytiscidae - Diving beetle

Group 6 taxa (BMWP: 4)
Baetidae - Mayfly

Group 7 taxa (BMWP: 3)
Lymnaeidae - Snail (Greater Pond Snail, Lymnaea stagnalis)
Glossiphoniidae - Leech
Erpobdellidae - Leech
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 taxa11
Total BMWP Score39
ASPT3.5
No. OM taxa0
No. Coleopt taxa1

Index of Biotic Integrity (PSYM Score %) = 22. As such the pond would be considered to be in poor ecological condition.

A conductivity test to measure the total quantity of chemicals dissolved in the water returned a reading of 790µS/cm. This figure indicates that the pond is on the borderline with regard to contamination. 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

Pond 1

The larger and more established of the two ponds supports a reasonable range of aquatic plant species with Glyceria maxima, Reed Sweet-grass, Typha latifolia, Bulrush and Sparganium erectum, Branched Bur-reed, the dominant emergent species. Menyanthes trifoliata, Bogbean, Mentha aquatica, Water Mint, Ranunculus flammula, Lesser Spearwort and Juncus articulatus, Jointed Rush are occasional while Myosotis scorpioides, Water forget-me-not and Lysimachia nummularia, Creeping Jenny are relatively rare. The non-native invasive species Myriophyllum aquaticum, Parrot's-feather along with Lagarosiphon major, Curly Waterweed, are present. A small quantity of the highly invasive Crassula helmsii, New Zealand Pigmyweed, was observed in the margin during a Derby City Pond Warden training event on 19th June 2010. Following its immediate removal, the plant fortunately has not re-appeared.

The pond supports a well-established fish population as a result of introductions by local residents and the paucity of aquatic invertebrates within the pond is likely to be the result of predation by the fish. Although adult dragonflies and damselflies, including Southern Hawker, Common Darter and Banded Demoiselle, are regularly observed at the site, no larvae have been recorded during surveys that have been undertaken between 2010 and 2013, indicating negligible breeding success.

The pond suffers from abuse with regard to discarded litter and rubbish and bread is regularly thrown into the pond, presumably to feed the fish.

The pond is used a breeding site by common frog and smooth newt with large quantities of frogspawn observed in early spring. The breeding success of the amphibians is again likely to suffer as a result of predation by fish and occasional mallard.

Some removal of emergent plant species has been undertaken in the past to maintain a reasonable level of open water together with some removal of parrot's-feather. Unfortunately, it is likely that these previous management activities have unfortunately resulted in the accidental removal of Marsh-marigold and Fool's watercress from the site. These species were observed during a survey carried out on 19th June 2010 as part of a Derby City Pond Wardens training event but have not been recorded during subsequent survey visits.

Management Recommendations - Pond 1


Pond 2

A small pond with a surface area of approximately 50 square metres located to the west and adjacent to the larger, more established, pond. The pond was created, using a liner, by BTCV (now TCV) in early 2011 in an attempt to provide a fish-free environment for the benefit of the local amphibian population and to attract a greater diversity of aquatic invertebrates than currently occurs in the existing pond. The pond was left to colonise naturally with no deliberate introduction of plant material.

Arboretum Ponds

During the initial monitoring survey carried out in August 2012 it was noted that, considering its young age, the pond had developed a reasonable level of invertebrate activity. It had quickly been colonised by Rigid Hornwort, which was rather abundant, and covered by Common Duckweed. It is likely that the abundant Duckweed growth and the high conductivity reading is the result of high nutrient levels introduced to the pond in the soils and turf used to cover the liner. It is anticipated that these nutrient levels will subside in time, particularly with any subsequent colonisation by aquatic plant species.

It was noted during 2013 that the grasses from the surrounding area were beginning to invade the pond

Arboretum Ponds

Above: Pond 2 - 2013


Management Recommendations - Pond 2


Management Recommendations - Wildlife Garden

















Derby Arboretum Map