Information and Advisory Note Number 4                                                 Back to menu

Botanical survey of Scottish freshwater lochs

1. Introduction

1.1 It has been estimated that there are at least 31,460 freshwater lochs in Scotland. These range in size from the small peaty mountain
lochans < 1 ha in area to the expanse of Loch Lomond (7110 ha) In Scotland, 1.9% of the land surface is covered by fresh waters. The distribution has a marked north-west to southeast gradient with the highest concentration of lochs occurring in the Western Isles (over 7500 lochs). In terms of volume, the water contained in Loch Ness (7,452,000,000 m3) is nearly twice that found in the standing waters of England and Wales combined.

1.2 Despite the great extent of the freshwater resource, relatively little information is available on which to base nature conservation assessments The bathymetrical survey of 562 lochs throughout Scotland by Murray and Pullar (1910) concentrated on the physical characteristics of the lochs although some floral and faunal information was collected. Spence (1964) sampled the vegetation of over 100
lochs and associated swamps and fens from Wigtownshire to Shetland. A limited nation-wide survey was earned out for A Nature Conservation Review (Ratcliffe, 1977) As a result 40 open water sites were identified as being of national conservation importance Local floras contain sporadic references to the plants occurring In freshwater lochs. In the 1960s and early 1970s, however, there was no comprehensive data set on which to base national conservation assessments.

2. Impetus for and initiation of the survey

2.1 The National Parks and Access to the Countryside Act 1949 gave the Nature Conservancy (and its successors) statutory
functions including the identification and notification of Sites of Special Scientific Interest (SSSIs) and the provision of advice and dissemination of knowledge about nature conservation. One important objective has been the comparison of natural areas and to set them in a national and local context.

2.2 With respect to freshwater lochs a 'stock take' and the development of a classification scheme was necessary before progress could be made. On this premise a comprehensive survey of British standing waters was initiated in 1975, with the major Scottish programme of work starting in South Uist in 1983. A combination of factors relating to staff expertise, availability of identification keys and simplicity of survey techniques led to the selection of aquatic plants as the major group for survey.

3. Objectives of the survey

4. Survey coverage

4 1 Since 1983, 2352 lochs have been surveyed The coverage of the loch survey between 1983 and 1995 is shown in Figure 1 Table 1 shows a breakdown of the numbers of lochs surveyed each year An ongoing programme of summer survey work should result in the completion of the survey by the year 2000.

5. Survey techniques

5.1 Site selection

Lochs are selected for survey within areas based on the SNH administrative boundaries (Areas of Search) (formerly NCC boundaries) In some areas, particularly vulnerable or interesting sites are identified and survey is limited to these In other areas, a synoptic survey approach is employed All standing water bodies appearing on the 1 50,000 Ordnance Survey maps are identified and fitted into a three-way matrix based on surface area, altitude and underlying solid geology Priority sites are selected from this matrix following liaison with regional staff and include

This site selection occurs during the winter months and the regional staff are involved with arranging site access

5.2 Field survey

Field work is carried out during the summer months (June to September). The protocol involves a complete circumnavigation of the loch at wader depth recording the shoreline and shallow water aquatic plant species. Deeper water is sampled by means of a double-headed rake thrown from the bank at frequent intervals along the shore Where possible a boat is used and grapnel samples are obtained from the bottom along transects across the loch All aquatic plants are recorded on a subjective DAFOR abundance scale (Dominant, Abundant, Frequent, Occasional, Rare) Stands of emergent vegetation are marked on a large-scale map of the site and the distribution of dominant and otherwise notable species in all three vegetation zones is indicated Emergent stands are classified according to the National Vegetation Classification (NVC) scheme for swamps and tall-herb fens (Rodwell, 1995). Voucher specimens of plants which are not readily identifiable in the field are kept for verification by experts (e g Potamogeton spp , Utricularia spp (bladderworts) and charophytes (stoneworts)).

Other observations are made on substrate, water colour and clarity, adjacent land use, wetland edges, artificial features, use of or
damage to the site, inflows and outflows and obvious fauna. Water samples are collected from the outflow and tested for pH, conductivity and alkalinity.

6. Loch classification scheme

6 1 The site classification was accomplished through the analysis of data collected between 1975 and 1988 from 1124 sites in England, Scotland and Wales These water bodies included lakes, meres, reservoirs, ponds, pools, gravel pits and canals of which over half were in Scotland.

6 2 For each site a species list of all the floating and submerged plants was drawn up and these data were subjected to TWINSPAN (Two Way Indicator Species Analysis) This analysis produced an ordered matrix of sites by species and a series of 10 end-groups of sites with similar vegetational characteristics. These groups or types show a general trend of increasing nutrient status from dystrophic type 1 sites to mesotrophic type 5 sites and eutrophic type 10 sites (see Table 2 for general description). Table 3 shows the species and the average number of aquatic plants associated with each loch type The NVC communities most common in emergent fringes of the 10 loch types are shown in Table 4

6.3 Key to loch types

A simple dichotomous key is used to assign a loch type to a new site on the basis of its floating and submerged flora. (See key at end of note)

7. Site evaluation

7 1 Once standing water sites in a particular AOS have been classified, it is possible to evaluate them by making comparisons within loch types Some of the following criteria may be taken into account (Nature Conservancy Council, 1989).

7.2 Site protection

A range of designations may be applied to freshwater lochs each conferring varying degrees of protection. These designations include SSSI, NNR, Ramsar site and (in due course) Special Area of Conservation (SAC) Rare plant species are covered by the Wildlife & Countryside Act 1981, Bern Convention and EC Habitats Directive.

8. What information is available?

8.1 The methodology and classification scheme is described by Palmer et al (1992)

8.2 For each loch, a site survey report is prepared which includes geographical information, lists of plants recorded and a map of the site. Copies of these are held in the Area Offices of SNH and in the Research and Advisory Services Directorate (RASD) in Edinburgh.

8 3 Area reports provide a synopsis of the range and quality of lochs within an AOS and provide recommendations for site notification (Table 5).

8 4 A large number of herbarium specimens of aquatic plants, including a full range of Potamogeton species, are kept at the RASD office in Edinburgh and are available for examination.

8 5 The contacts in the Aquatic Environments Branch (RASD) can offer advice with plant identification.

8.6 A database of all the lochs included in the survey is held on the SNH computer network.

8 7 It is envisaged that a synoptic volume describing the entire survey will appear by the end of the decade.

9. Uses for the information

9.1 Actual

9.2 Potential

References and further reading

Maitland, P.S., Boon, PJ. & McLusky, D.S. (eds) 1994. The fresh waters of Scotland A national resource of international significance. Chichester, John Wiley & Sons

Murray, J. & Pullar, L. 1910 Bathymetrical survey of the fresh water lochs of Scotland Edinburgh, Challenger Office

Nature Conservancy Council 1989 Guidelines for selection of biological SSSIs Peterborough, Nature Conservancy Council

Palmer, M.A., Belt, S.L & Butterfield, I.1992 A botanical classification of standing waters in Great Britain applications for conservation and monitoring Aquatic Conservation Marine and Freshwater Ecosystems. 2, 125-143

Ratcliffe, D.R. (ed ) 1977 A Nature Conservation Review Cambridge, Cambridge University Press

Rodwell, J.S.
(ed) 1995 British plant communities Volume 4 Aquatic communities. swamps and tall-herb fens Cambridge, Cambridge University Press

Spence, D.H.N. 1964. The macrophyte vegetation of lochs, swamps and associated fens In The vegetation of Scotland ed by J.H Burnett, 306-425 Edinburgh, Oliver and Boyd


Dr Olivia Lassiere

Contacts for further advice and information:

Dr Olivia Lassiere Aquatic Botanist

Dr Philip Boon
Head of Aquatic Environments Branch

Dr Willie Duncan
Freshwater Conservation Officer

All located at
Research and Advisory Services
2/5 Anderson Place
Edinburgh EH6 5NP
Tel. 0131 447 4784

Key to loch types

Start at couplet 1 and calculate the overall score for the couplet by giving a point for each species (either negative or positive) which occurs at the loch (abundance levels on the DAFOR scale) Follow the instructions in the 'Score' column until the loch type is keyed out (Adapted from Nature Conservancy Council, 1989)




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