Macroinvertebrate Survey of Manor Farm outflow, Old Alresford , Hants
Report prepared by Robert Aquilina MSc MCIEEM
December 2016
Macroinvertebrate survey of the Manor Farm outflow, Old Alresford, Hants
Robert Aquilina MSc MCIEEM
December 2016
Robert Aquilina MSc MCIEEM is an independent consulting ecologist specialising in protected species and freshwater ecology. He is a Full member of the Institute of Ecology and Environmental Management and abides by their Code of Professional Conduct. For further details see www.cieem.net www.aquilina-environmental.co.uk
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Table of contents Summary ........................................................................................................................ 4 Introduction ................................................................................................................... 5 Methods ......................................................................................................................... 5 BMWP...............................................................................................................................................................6 Locations ..........................................................................................................................................................6
Results ............................................................................................................................ 7 Environmental parameters...........................................................................................................................7 Biological results.............................................................................................................................................7 Incidental records ..........................................................................................................................................9
Conclusions .................................................................................................................... 9 References ..................................................................................................................... 9 Appendix 1 Species recorded. ..................................................................................... 10
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Summary
A macroinvertebrate survey of outflow from the Manor Farm watercress beds site at Old Alresford were carried out using standard sampling techniques . The purpose was to assess the species present and any potential water quality issues of the outflow. The species present were typical of a chalk stream, with Good diversity and water quality scores. A complete list of species is presented together with abundance and diversity scores.
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Introduction
The purpose of this survey was to assess the discharge from the watercress beds at Manor Farm, Old Alresford and identify any impacts that they may be having on the stream. Manor Farm is situated at the head of a small chalk stream and uses borehole water for its watercress beds which then is discharged into the stream. This unnamed stream is a tributary of the River Alre which in turn joins the River Itchen, an important chalk stream for salmon and trout fishing and conservation. The site was visited by Robert Aquilina on Wednesday 23rd November 2016 and environmental data and samples were collected for analysis in the laboratory using standard techniques. The weather conditions were dry and suitable for the survey with normal water flow levels. Industry standard survey and extraction techniques for the stream (Environment Agency 2012) were used to assess the species present. Methods The methodology followed is the same as at the Alresford Salads site at Bighton Lane (Aquilina, 2016). The details are repeated below in Methods and BMWP sections in order to make this report stand alone but are otherwise identical. Aquatic macroinvertebrates were collected using a standard size FBA D-frame pond net from the major habitats along the stream (stands of different wetland plants, distinctive substrates, tree roots etc.). All the different habitats present were allocated a proportion of the overall sampling time (3 minutes) and different areas of the same mesohabitat were subsampled to ensure that as great a range as possible was sampled. Each location was also searched for an additional minute looking for surface dwelling animals such as water skaters and whirligig beetles and inspecting submerged habitats such as logs and larger stones for attached animals. The samples were preserved in 70% IMS and sorted in the laboratory, where all the invertebrates were extracted. The standard BMWP invertebrate groups were recorded : Tricladida (flatworms), Gastropoda (snails and bivalves), Crustacea (slaters, shrimps and crayfish), Hirudinea (leeches), Megaloptera (alderflies), Plecoptera (stoneflies), Ephemeroptera (mayflies), Odonata (dragonflies and damselflies), Hemiptera (water bugs), Coleoptera (water beetles), Trichoptera 5
(caddisflies) and three families of Diptera (true flies). Additionally, other families of Diptera that do not score in the BMWP system were identified where possible. Voucher specimens were retained in order to check their identity. Dead mollusc shells, and empty caddis cases were discarded and only whole animals were included in the counts. Basic environmental data (pH and conductivity) were recorded for each location using a Hach HQ40d meter. BMWP Condition assessment of running waters is based on the BMWP (Biological Monitoring Working Party) score. These BMWP scores (1-10) are industry standard and reflect the sensitivity of the families to pollution. The higher the family score, the more sensitive to oxygen depletion the family is and therefore their presence indicates a cleaner or less impacted site. The effects of pollution generally are to impose a Biological Oxygen Demand upon the receiving waters and so sensitive families are progressively excluded as the BOD increases. The score for each family present is totalled to give a site score. Because these site BMWP scores are influenced by sample size (a high score can be achieved through a large number of low scoring families as well as a small number of high scoring families) an Average Score Per Taxa (ASPT) is also calculated from the resulting BMWP scores and allows further interpretation of the results. The higher the ASPT, the greater the proportion of more sensitive families in the sample and therefore the better the site condition. It is important to interpret the results in the context of the physical characteristics of the sample site, so river samples are comparable with river samples but not with pond samples. This is because the inherent physical chemistry of the waters (especially dissolved oxygen which is the primary driver of BMWP) will be different in flowing waters and still waters.
Locations The outflow is located at SU 58532 33516. The different habitats present at the outflow were assessed and representative sections of each habitat were sampled (cobbles, small stone, gravel, coarse sand, Ranunculus beds, marginal watercress). Each was sampled for thirty seconds making a total of 3 minutes for the amalgamated sample.
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Results
Environmental parameters A single water sample was taken to indicate the general conditions pertaining in the stream. Chemical water quality analysis is beyond the remit of this survey. The environmental parameters recorded were as follows. Parameter
Result
pH
7.24 611 9.0
Conductivity S/cm Temp o C
Table 2. Environmental parameters These environmental parameters are merely indicative of the overall conditions and status of the stream at the time of the visit, as they represent a single point in time. The pH is neutral with slightly above average conductivity. Conductivity reflects the ions present but does not distinguish them chemically. The levels are typical of chalk streams as they naturally have enhanced Calcium and Magnesium and carbonate levels (hardness) compared with soft water sites.
Biological results The BMWP (Biological Monitoring Working Party) scores are used to categorise water bodies according to the sensitivity of taxa to oxygen depletion (as such it is widely used in running waters to assess water quality – the premise being that pollution increases BOD (Biological Oxygen Demand) and therefore reduces available oxygen and so eliminates the more sensitive taxa progressively). The higher the score for each family the greater its sensitivity to oxygen depletion and so the higher the site score, the ‘better’ the water quality. Average Score Per Taxon (ASPT) is calculated to overcome bias in sample size and generally reflects the water quality – the higher the score the more demanding the families present are of oxygen. The BMWP and ASPT scores are presented in table 3 below. 7
Index # contributing taxa BMWP ASPT Total # taxa Status (BMWP) Status (ASPT)
Result 30 163 5.43
51 Good Good
Table 3. Results summary The status is based on a basic interpretation of BMWP and ASPT scores. The count of Freshwater shrimp (Gammarus pulex) at 1680 is considerably higher than that found slightly downstream during the EA investigation in November 2011 (450) reported in RMA Environmental ‘Invertebrate Monitoring Spring 2012, The River Alre Catchment and Alresford Pond New Alresford, Hampshire’. The BMWP and ASPT results are comparable with those obtained by the Environment Agency during the above investigation although the BMWP score was a class lower. During the RMA investigation the results were again comparable albeit that investigation was carried out during the spring. Index # contributing taxa BMWP ASPT Status (BMWP) Status (ASPT)
Nov 2016 EA Nov 2011 RMA 15.5.12 30 163 5.43
25 132 5.28
34 182 5.33
Good Good
Moderate Good
Good Good
Table 4. Comparison with previous results
All species recorded were common, although the leech Trocheta subviridis is local in occurrence, and many species were typical of chalk streams. The sample was collected very late in the season and so a number of species were present as early instars only which prevented identification to species level in some cases.
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Incidental records A number of observations were recorded in passing that were not part of the scheduled survey but are reported here for completeness.
Species Cottus gobio Gasterosteus aculeatus
Common name Bullhead 3-spine stickleback
Table 5. Incidental records (fish).
Conclusions The outflow from Manor Farm watercress beds was assessed as Good from the point of view of invertebrate biodiversity. The range of species present (total 51) was high and individual abundance of freshwater shrimp (Gammarus pulex) was significantly higher than a previous investigation in 2011 found. BMWP and ASPT scores were comparable or better than previous investigations had found. There is no indication of adverse water quality.
References Aquilina, R. (2016). Macroinvertebrate Survey of Alresford Salads outflows, Alresford, Hants. Environment Agency. (2012). Freshwater macro-invertebrate sampling in rivers. Operational instruction 018_08. Environment Agency. Environment Agency. (2012). Freshwater macro-invertebrate analysis of riverine samples. Operational instruction 024_08. Environment Agency. RMA Environmental. (2012). Invertebrate Monitoring Spring 2012, The River Alre Catchment and Alresford Pond New Alresford, Hampshire.
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Appendix 1 Species recorded.
Group
BMWP family
Species
Common name
Tricladida
Planaridae
Flatworm
Tricladida Tricladida Tricladida Mollusca Mollusca
Planariidae Planariidae Planariidae Physidae Lymnaeidae
Dendrocoelum lacteum Polycelis felina Polycelis nigra Polycelis tenuis Physa fontinalis Radix balthica
Mollusca
Planorbidae
Anisus leucostoma
Mollusca
Planorbidae
Anisus vortex
Mollusca
Planorbidae
Mollusca Mollusca Crustacea Crustacea
Valvatidae Ancylidae Asellidae Gammaridae
Bathyomphalus contortus Valvata cristata Ancylus fluviatilis Asellus aquaticus Gammarus pulex
Hirudinea
Erpobdellidae
Erpobdella octoculata
Flatworm Flatworm Flatworm Bladder snail Wandering snail Button ramshorn Whirlpool ramshorn Twisted ramshorn Flat valve snail River limpet Water slater Freshwater shrimp Leech
Status
=Lymnaea peregra
BMWP score 5
Abundance
5 5 5 3 3
5 36 461 5 15
3
39
3
41
3
3
3 6 3 6
9 23 190 1680
3
68
48
Group
BMWP family
Species
Common name
Status
BMWP score 3 3
Abundance
Hirudinea Hirudinea
Erpobdellidae Glossiphonidae
Leech Leech
Local
Hirudinea
Glossiphonidae
Hirudinea
Glossiphonidae
Hirudinea Ephemeroptera
Piscicolidae Ephemerellidae
Trocheta subviridis Glossiphonia complanata Helobdella stagnalis Theromyzon tessulatum Piscicola geometra Serratella ignita
Leech
3
7
Duck leech
3
1
Fish leech Blue-winged Olive Large Dark Olive Mayfly
4 10
2 7
Ephemeroptera
Baetidae
Baetis rhodani
4
34
Ephemeroptera
Caenidae
Caenis sp.
7
110
Coleoptera
Haliplidae
Haliplus sp.
5
5
Coleoptera Coleoptera Coleoptera Coleoptera Trichoptera Trichoptera
Dytiscidae Elmidae Elmidae Scirtidae Hydropsychidae Rhyacophilidae
5 5 5 0 5 7
2 159 4 1 46 4
Trichoptera
Glossosomatidae
7
313
Crawling water beetle Diving beetle Elmis aenea Riffle beetle Riolus subviolaceus Riffle beetle Microcara testacea Marsh beetle Hydropsyche siltalai Caseless caddis Rhyacophila Caseless caddis dorsalis Agapetus fuscipes Saddle-case caddis
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early instars not identifiable to species larvae not identifiable to species larva larva and adults larva and adults larva
1 14
Group
BMWP family
Species
Common name
Status
Trichoptera
Hydroptilidae
Hydroptila sp.
Cased caddis
Trichoptera
Hydroptilidae
Oxyethira sp.
Cased caddis
Trichoptera
Leptoceridae
Mystacides sp.
Silverhorn
larvae not identifiable to species larvae not identifiable to species early instars not identifiable to species
Trichoptera Trichoptera
Limnephilidae Limnephilidae
Drusus annulatus Potamophylax latipennis
Trichoptera
Limnephilidae
Cased caddis Large Cinnamon Cased caddis
Trichoptera Trichoptera
Goeridae Odontoceridae
Trichoptera
Sericostomatidae
Diptera Diptera
Ceratopogonidae Chironomidae
Chironominae
Diptera
Chironomidae
Orthocladiinae
Diptera
Chironomidae
Tanypodinae
Diptera
Dixidae
Dixa nebulosa
Silo nigricornis Odontocerum albicorne Sericostoma personatum
BMWP score 6
Abundance
6
402
10
1
7 7
4 1
7
7
Black sedge Silver sedge
10 10
3 2
Welshman’s Button Biting midge Non-biting midge Non-biting midge Non-biting midge Meniscus midge
10
1
larvae larvae
2
19 39
larvae
2
30
larvae
2
6
12
early instars not identifiable to species
larvae
3
14
Group
BMWP family
Species
Common name
Diptera Diptera Diptera
Psychodidae Sciomyzidae Simulidae
Pericoma sp.
Diptera Diptera Others Others Total
Tipulidae Tipulidae(Pediciidae) Dicranota sp. Hydracarina Oligochaeta
Moth fly larvae Snail-killing flies larvae Blackflies early instars not identifiable to species cranefly larvae cranefly larvae Water mite True worms
Simulium sp.
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Status
BMWP score
5 5 5 1
Abundance 5 1 5 1 1 31 211 4120