Planet WGSW-24010 User manual

Mean Trophic Rank: A User’s Manual
R&D Technical Report E38
NTH Holmes3, JR Newman2, S Chadd4, KJ Rouen4, L Saint4and FH Dawson1
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Research contractors:
NERC Institute of Freshwater Ecology 1
with IACR Centre for Aquatic Plant Management 2
and Alconbury Environmental Consultants 3
Environment Agency 4
Rio House
Waterside Drive
Aztec West
Almondsbury
BRISTOL
BS32 4UD

R&D Technical Report E38
Publishing Organisation
Environment Agency
Rio House
Waterside Drive
Aztec West
Almondsbury
Bristol BS32 4UD
Tel: [phone] Fax: [phone]
ISBN: 1 85705 092 4
© Environment Agency 1999
All rights reserved. No parts of this document may be produced, stored in a retrieval system, or
transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or
otherwise without the prior permission of the Environment Agency.
The views expressed in this document are not necessarily those of the Environment Agency. Its
Officers, servants or agents accept no liability whatsoever for any loss or damage arising from the
interpretation or use of the information, or reliance on the views contained herein.
Dissemination status
Internal: Released to Regions
External: Public Domain
Statement of Use
This report sets out procedural guidance on how to carry out Mean Trophic Rank (MTR)
macrophyte surveys to assess the trophic status of rivers, and on the use of the method for the
purposes of the EC Urban Waste Water Treatment Directive. The methodology can also be used
for other applications. The guidance supersedes and replaces earlier, internal guidance issued to
Environment Agency staff. It is intended as ‘best practice’ standard methodology for all MTR
surveys and is applicable throughout the UK.
Research Contractor
This document was produced under R&D Project E1-i694 by:
NERC Institute of Freshwater Ecology IACR Centre for Aquatic Plant Management
The Rivers Laboratory, East Stoke Broadmoor Lane, Sonning, Reading
Wareham, Dorset, BH20 6BB Reading, Berkshire, RG4 0TH
Tel: [phone] Fax: -462180 Tel: [phone]
Institute of Freshwater Ecology - disclaimer IFE report reference RL/T4073Q7/7. In
accordance with the normal practice of the NERC Institute of Freshwater Ecology, this report was
prepared for use by the party to whom it is addressed (Environment Agency) and no responsibility
is accepted for the interpretation by any third party for the whole or any part of its contents.
Environment Agency's Project Manager
The Environment Agency's Project Manager for R&D Project E1-i694:
Karen J Rouen, North West Region

R&D Technical Report E38 i
ACKNOWLEDGEMENTS
This document is intended as a description of a standard methodology for the assessment
of the trophic status of rivers using macrophytes applicable throughout the United Kingdom.
Its production would not have been possible without the cooperation and assistance of Dr
Nigel Holmes, English Nature, Scottish Natural Heritage, The Countryside Commission
for Wales, the Industrial Research and Technology Unit (Northern Ireland) and the
Scottish and Northern Ireland Forum for Environmental Research (SNIFFER).

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R&D Technical Report E38 iii
CONTENTS
List of Figures v
List of Tables v
Glossar y vi
Executive Summary ix
Key Words ix
1Foreword 1
1.1 About this manual 1
1.2 Summary of the method 3
2Introduction to MTR 5
2.1 What is MTR? 5
2.2 Uses of MTR 8
2.3 Principal application: Urban Waste Water Treatment Directive 9
2.4 Other applications 11
3Survey Planning 15
3.1 Alternative methods to consider 15
3.2 Sampling strategy 20
3.3 Logistics of sampling 22
3.4 Ancillary data collection 29
3.5 Limitations of the method 31
4How to Carry Out an MTR Survey 33
4.1 Overview of the methodology 33
4.2 Preparation and pre-survey checks 33
4.3 Site and survey details 33
4.5 Carrying out the macrophyte survey 38
4.6 Assessing and recording physical variables 49
4.7 Laboratory Analysis 58
5MTR Data Analysis 61
5.1 Calculating Mean Trophic Ranks 61
5.2 Assigning a measure of confidence to the MTR 62
5.3 Assessment of confidence in the data 63
5.4 Data storage 64
6Interpretation of MTR Results 65
6.1 Interpretation for the purposes of the UWWTD 65

R&D Technical Report E38 iv
6.2 Interpretation for other purposes 72
6.3 Interpretation of species diversity 74
6.4 Interpretation of overall percentage cover values 76
7Quality Assurance 77
7.1 Introduction 77
7.2 Training 80
7.3 Audit surveys 82
7.4 Inter-calibration exercise 88
7.5 Database verification 89
7.6 Survey length selection 90
8MTR Best Practice Checklist 91
8.1 Uses of MTR 91
8.2 Survey planning 91
8.3 Survey methodology 92
8.4 Data analysis 92
8.5 Interpretation of results 93
8.6 Quality assurance 93
9References 95
Appendices 99
Appendix 1 Rare plants 100
Appendix 2 Foreign invasive plant species 101
Appendix 3 Identification guides and preservation manuals 102
Appendix 4 Equipment suppliers 104
Appendix 5 Standard record sheets 105
Appendix 6 Example sketch maps 121
Appendix 7 Summary of methodology, definitions and equipment checklist 125
Index 131

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R&D Technical Report E38 vi
LIST OF FIGURES
1Diagrammatic representation of survey method 38
2Illustration of shading 53
3Macrophyte survey flow chart 60
4Interpretation of MTR results, Stage I ‘decision tree’:
Is the site impacted by eutrophication? 70
5Interpretation of MTR results, Stage II ‘decision tree’:
Is there a significant downstream impact from the qualifying discharge? 71
LIST OF TABLES
1MTR scores summarised according to river community type 68
2Reasons for mismatch between audit and primary surveys, with suggested actions 87
A1 List of Mean Trophic Rank scoring taxa, with recent synonyms 111
A2 Cover (m2) for 100m Survey Lengths 119
LIST OF TEXT BOXES
1Factors to consider when deciding whether to use MTR or DQI/TDI 18
2Factors to consider when selecting MTR sites and survey lengths 24
3Conditions when surveys should not be undertaken 26
4Non-standard survey lengths 36
5Exceptions to surveying the full channel width 37
6Methods of estimating overall percentage cover 43
7Estimating percentage cover of individual species: width method 45
8Estimating percentage cover of individual species: square metre method 46
9Audit procedure 85

R&D Technical Report E38 vii
GLOSSARY
Audit survey Repeat survey undertaken for quality assurance purposes.
CCW Countryside Council for Wales.
Channel area The part of the river channel where macrophytes are seen submerged or
partly submerged at low flow levels. At the sides of the channel this
includes all macrophytes attached or rooted on parts of the substrata
which are likely to be submerged for more than 85% of the year.
Comparability A measure of confidence in the physical
comparability of a pair of sites
based upon the similarity of width, depth, substrata, habitat, shading,
water clarity and bed stability.
CVS
Cover Value Score
. The score allocated to a species resulting from the
multiplication of the Species Trophic Rank and the Species Cover Value.
DoE The Department of the Environment.
d/s Downstream.
EN English Nature.
DQI The Diatom Quality Index. A transformation of the
Trophic Diatom Index
for use when comparing TDI and MTR results.
Highlighted species Refers to a plant species within MTR which is believed to be a particularly
reliable indicator of trophic status.
IFE The Institute of Freshwater Ecology.
IRTU Industrial Research & Technology Unit, Northern Ireland.
LEAP Local Environment Agency Plan.
Macrophyte Larger alga or higher aquatic plant (including bryophytes), observable to
the naked eye and nearly always identifiable when observed.
MTR Mean Trophic Rank. A numerical score assigned to a survey length based
on its macrophyte presence and abundance characteristics.
Nitrate Dissolved or soluble or non-particulate nitrate.
Non-QD Non-qualifying discharge under the UWWTD, with a population
equivalent of less than 10,000.

R&D Technical Report E38 viii
NRA The National Rivers Authority. A predecessor to
the Environment
Agency.
pe Population equivalent.
Phosphate Dissolved or non-particulate phosphate, normally analysed as soluble
reactive (SRP) or by the molybdenum-blue method.
Pool Either a discrete area of slow flowing water, usually relatively deeper than
surrounding water, or between faster flowing stretches, as in a sequence
of riffle-pool-riffle. Pools are deep and often turbulent, and scoured
during spate flows.
Primary survey
When a survey is repeated for quality assurance purposes, the initial survey
is termed the ‘primary survey’ and the repeat survey the ‘audit survey’.
PSP
Potential source of pollution. A term describing potential, non-QD-derived
sources of eutrophication in riverine habitats.
QD Qualifying discharge (usually from a WWTW) under the UWWTD, with
a population equivalent of greater than 10,000.
RHS River Habitat Survey. A method for assessing the physical character and
quality of river habitats and impacts upon them.
Riffle Fast flowing, shallow water whose surface is distinctly disturbed. This
does not include water whose surface is disturbed by macrophyte
growth only.
Run Fast or moderate flowing, often deeper water whose surface is rarely
broken or disturbed except for occasional swirls and eddies.
SA(E) Sensitive Area (Eutrophic). An area of water which is considered to be
eutrophic or which in the near future may become eutrophic if protective
action is not taken, and recognised as such by designation under the
Urban Waste Water Treatment Directive.
SCV Species Cover Value. A value assigned to a species according to the
percentage of the survey area it covers.
Site This is the broad location where the survey is to take place, eg xkm
downstream of a waste water treatment works.
Slack Deep, slow flowing water, uniform in character.
SNH Scottish Natural Heritage.
SNIFFER Scottish and Northern Ireland Forum for Environmental Research.

R&D Technical Report E38 ix
STR Species Trophic Rank. A value assigned to a species on a scale of 1 to 10,
designed to reflect the tolerance of that species to eutrophication. Low
scores indicate tolerance or cosmopolitan distribution (ie no preference).
High scores indicate preference for less enriched conditions or intolerance
of eutrophic conditions.
Survey The collection of data at one site according to the prescribed methodology.
Survey length
This is the sample area — the actual river channel area surveyed, between
two fixed points on the bank. The survey length is 100m long for
standard MTR surveys.
Survey season The MTR survey season is mid-June to mid-September inclusive.
TDI The Trophic Diatom Index. A method for assessing the trophic status of
rivers using benthic diatoms.
u/s Upstream.
UWWTD The European Community Urban Waste Water Treatment Directive
(UWWTD, 91/271/EEC).
WWTW Waste water treatment works.

R&D Technical Report E38 x
EXECUTIVE SUMMARY
1The principal purpose of this manual is to provide comprehensive procedural guidance
on
how to carry out Mean Trophic Rank (MTR) macrophyte surveys to assess the
trophic status of rivers, and on the use of the method for the designation of sensitive
areas (eutrophic) (SA(E)) under the requirements of the EC Urban Waste Water
Treatment Directive (UWWTD).
2The guidance is a practical output from R&D project E1-i694 ‘Assessment of the Trophic
Status of Rivers Using Macrophytes’. The project assessed the MTR for the purposes
required of it under the UWWTD, made recommendations for improvements in the
system and compared the MTR with other methods for the biological assessment of
trophic status in rivers.
3The manual describes what the MTR system is, for what purposes it can be used and how
to use it. It gives guidance on where and when to undertake MTR surveys, how to carry
out the macrophyte survey in the field, how use the information gained to calculate an
MTR, how to interpret results for the purposes of the UWWTD and how to maximise that
the quality of the information gathered. Uses of the method for purposes other than the
requirements of the UWWTD are also considered.
4
The procedures described are intended as the standard method for undertaking MTR
surveys, and as the standard macrophyte survey method to be used by the Environment
Agency for the purposes of the UWWTD. The methodology is applicable throughout the
UK and so the manual will be of use not only to Environment Agency staff but also to
regulatory agencies in Scotland and Northern Ireland, statutory and non-statutory
conservation bodies, and others interested in the trophic status of rivers.
KEY WORDS
Macrophyte survey, Urban Waste Water Treatment Directive, UWWTD, Sensitive Areas,
phosphorus, nutrient, eutrophication, monitoring.

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R&D Technical Report E38 1
1FOREWORD
1.1 About this manual
1.1.1 Pur pose of the manual
The principal purpose of this manual is to provide procedural guidance on how to carry out
Mean Trophic Rank (MTR) macrophyte surveys to assess the trophic status of rivers, and
on the use of the method for the designation of Sensitive Areas (Eutrophic) (SA(E)) under
the requirements of the EC Urban Waste Water Treatment Directive (UWWTD,
91/271/EEC).
The manual describes what the MTR system is, for what purposes it can be used and how to use
it. It gives guidance on where and when to undertake MTR surveys, how to carry out the
macrophyte survey in the field, how to use the information gained to calculate an MTR, how to
interpret results for the purposes of the UWWTD and how to maximise the quality of the
information gathered. Uses of the method for purposes other than the requirements of the
UWWTD are also considered. The manual provides a standard methodology and hence allows
data to be collected in the same manner by all surveyors, eliminating differing interpretations of
the method.
The method described is based on the survey methodology produced by the National Rivers
Authority (NRA 1994a). It incorporates subsequent developments in the survey methodology and
calculation of Mean Trophic Rank values (Holmes 1995, 1996), and takes account of
recommendations made at a national R&D workshop to discuss methods used to assess trophic
status (Newman et al 1997a, b – also in Dawson et al 1999a). Furthermore, it is based on a
comprehensive evaluation of the MTR which used a dataset of more than 5000 surveys (Dawson
et al 1999b). It is thus based on considerable experience and represents the best current practice.
1.1.2 Statement of use
The procedures described are intended as the standard method for undertaking MTR surveys, and
as the standard macrophyte survey method to be used by the Environment Agency for the
purposes of the UWWTD. The guidelines provided should be followed in all MTR surveys, to
ensure that the data produced are of acceptable quality and are comparable on a national basis.
The methodology is applicable throughout the UK. This manual is therefore of use not only to
Environment Agency staff but also to regulatory agencies in Scotland and Northern Ireland,
statutory and non-statutory conservation bodies, and others interested in the trophic status of
rivers.
The protocol and guidance given in this document supersede and replace those previously
published in relation to macrophyte surveys for UWWTD monitoring purposes and to the MTR
system (NRA 1994a; Holmes 1995, 1996; Newman & Dawson 1996; Environment Agency
1996a).

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1.1.3 Format of the manual
A tabulated summary of the MTR method is provided below to give a broad overview of the
methodology (1.2). This is then followed in Chapters 2–8 by detailed guidance on all the sections
listed in the summary. The guidance is organised so that it progresses from general introductory
information on the MTR system and its uses, to detailed survey procedures, interpretation of the
results and quality assurance. Quality assurance measures which are integral to the survey
method itself are shown in shaded boxes throughout. Key words are underlined in the tabulated
summary and listed in an index at the back of the manual, to assist cross-referencing.
The manual should be read in full to gain a comprehensive understanding of the method and its
application. Surveyors should familiarise themselves with the definitions given in the glossary,
particularly the terms ‘site’ (the broad location of the survey), ‘survey length’ (the sample area)
and ‘survey’ (the collection of data at one site according to the prescribed methodology).
1.1.4 Other outputs from this project
This is one of four outputs from the Agency’s national R&D Project E1-i694 Assessment of the
trophic status of rivers using macrophytes. The other three outputs are:
·
R&D Technical Summary ES35 —
Assessment of the trophic status of rivers using
macrophytes: evaluation of the Mean Trophic Rank. This summarises the project findings.
·R&D Technical Report E39 — Assessment of the trophic status of rivers using macrophytes:
evaluation of the Mean Trophic Rank (Dawson et al 1999b). This presents the main research
findings and will be of interest to those involved with the development, management or
implementation of biological methods to assess trophic status.
·
R&D Project Record E1/i694/01 —
Assessment of the trophic status of rivers using
macrophytes: supporting documentation for the evaluation of the Mean Trophic Rank
(Dawson et al 1999a). This presents supporting information and is intended for use by those
involved with future development of the MTR and related methodologies.

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1.2 Summary of the method
A summary of the MTR method is given below (cf DoE Standing Committee of Analysts 1987).
Key words are underlined and are included in the index at the back of this manual.
WHAT IS MTR?
1. Purpose Assessment of trophic status and eutrophication impact.
2. Biota sampled Macrophytes (plants identifiable with the naked eye).
3. Watercourses
sampled
Rivers and streams. The method is not suitable for standing waters, canals
(unless water flow is constant in one direction) or tidal rivers.
4. Underlying
principles
Within the aquatic macrophyte flora there is a spectrum of tolerances to
nutrient enrichment which can be expressed by assigning scores to species
on a scale of 1–10: the higher the score (the Species Trophic Rank or
STR), the lower the tolerance to nutrient enrichment. The response of the
macrophyte community to nutrient status can be expressed by integrating
the scores of the species present as a mean value, weighted according to
the relative percentage cover of the individual species. The resulting value
(the Mean Trophic Rank or MTR) increases with decreasing eutrophy.
5. Basis of
operation
The macrophyte flora and physical character of defined lengths (100m) of
watercourse are surveyed using a standard checklist. The presence,
absence and % area covered by each macrophyte are recorded and used to
calculate the MTR score. Physical parameters are recorded to aid
interpretation.
FOR WHAT PURPOSES CAN THE MTR SYSTEM BE USED?
6. Uses The method can be used to give a qualitative assessment of whether a site
is impacted by eutrophication and (for physically similar sites) downstream
changes in trophic status. The method should not be used to compare the
trophic status of physically dissimilar sites, nor should it be used to make
comparisons between the trophic status of different rivers unless the rivers
are the same type.
7. Applications The principal application for which the method has been developed and
tested is to assist in the designation of identified reaches as ‘Sensitive
Areas (Eutrophic)’ under the EC Urban Waste Water Treatment Directive.
The method should be equally applicable to the assessment of other point-
sources of nutrients, but is not yet proven for other applications.
SURVEY PLANNING
8. Alternative
methods
A Diatom Quality Index (DQI) survey should be undertaken at the same
time as the MTR survey if possible.
9. Sampling
strategy
The location of survey sites varies according to the purpose of the survey.
Less impacted ‘control’ sites may help determine eutrophication impact.
10. Logistics of
sampling
A minimum of one survey per year for three years is recommended, each
being undertaken at the same time within the survey season (mid-June to
mid-September) and after several days of low or low–normal flow.

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Operator safety, shade, river flow and water clarity need to be considered
when selecting a survey length. continued....
10. ....continued Survey equipment includes sampling aids, camera and protective
clothing/equipment. Surveyors should be familiar with the provisions of
the Wildlife and Countryside Act and should follow appropriate health and
safety guidance. Surveys can be undertaken by one operator, although
multiple-staffing is recommended: surveyors should allow one person-day
per survey although this may vary considerably.
11. Ancillary data
collection
Background information on site geomorphology, pollution incidents and
river management can be useful when planning and interpreting surveys.
HOW TO CARRY OUT AN MTR SURVEY
12. Pre-survey
preparation
An equipment checklist is provided. Surveyors should be familiar with the
necessary health and safety guidance.
13. Field survey The stretch to be surveyed (the survey length, 100m) is selected or located
and if suitable for survey it is measured out and marked. Standard field
sheets are used to record site and survey details. The macrophyte flora and
physical character of the survey length are then surveyed by wading, boat,
or walking along the bank. Sampling aids are used where necessary. All
macrophytes present are recorded, together with the estimated percentage
cover of each taxon (recorded as abundance classes: the species cover
value or SCV) and the estimated percentage cover of overall macrophyte
growth. Representative samples are taken for laboratory analysis if
identification is uncertain. Physical parameters of the survey length are
estimated, a sketch map drawn and a photograph taken.
13. Laboratory
analysis
Samples taken on the field survey are identified shortly afterwards and
representative specimens retained in a ‘herbarium’ for future reference.
DATA ANALYSIS AND INTERPRETATION OF RESULTS
14. Data analysis Survey data are in the form of qualitative (presence/absence) and semi-
quantitative (estimates of % cover) records of macrophytes and physical
characteristics. MTR = (SCVS/SSCV) ´10, where CVS = SCV ´STR.
MTR scores lie in the range 10–100.
15. Interpretation
of results
Results are interpreted using standard ‘decision trees’ and general
guidance on MTR scores found in a range of different rivers. Results are
expressed qualitatively in terms of nine standard descriptors relating to the
eutrophication status of the site and downstream impact.
QUALITY ASSURANCE
16. Error and
variability
Variability between surveyors in data recorded in the field can be reduced
by correct application of the method and adoption of quality assurance.
The impact of natural background variation in MTR within the survey
season and between physically dissimilar sites, can be reduced by careful
timing of surveys and selection of survey lengths. Three measures of
confidence are assigned relating to the survey, the comparability of sites
and the MTR score.

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17. Quality
assurance
procedures
Quality assurance comprises measures integral to the survey method itself
(eg on-site checks and multiple-staffing), training requirements and audit
surveys. Two alternative audit protocols are provided.
2INTRODUCTION TO MTR
This chapter describes the purpose of the MTR methodology, the biota used, the watercourses
for which the method is suitable, the principles on which the method is based and a summary of
how it operates. It then provides guidance on the applications for which the method can be used.
2.1 What is MTR?
2.1.1 Purpose
The MTR system is a biological method to assess the trophic status of rivers in the UK and the
impact of eutrophication.
The definition of eutrophication according to the UWWTD (91/271/EEC, Article 2(11)) is:
“Enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus,
causing an accelerated growth of algae and higher forms of plant life to produce an undesirable
disturbance to the balance of organisms present in the water and to the quality of the water
concerned.”
The definition of eutrophication adopted by the Agency in its proposed Eutrophication Strategy
(Environment Agency 1998a) is:
“The enrichment of waters by inorganic plant nutrients, which results in the stimulation of an
array of symptomatic changes. These include the increased production of algae and/or other
aquatic plants affecting the quality of the water and disturbing the balance of organisms within
it. Such changes may be undesirable and interfere with water uses.”
2.1.2 Biota sampled
The MTR system is based on the presence and abundance of species of aquatic macrophyte. A
macrophyte is defined as ‘any plant observable with the naked eye and nearly always identifiable
when observed’ (Holmes & Whitton 1977). This definition includes all higher aquatic plants,
vascular cryptograms and bryophytes, together with groups of algae which can be seen to be
composed predominantly of a single species.
Macrophytes were selected for this method for several reasons.
·Species composition can change with increased nutrient concentration (2.1.4) and so can be
used as a water quality monitoring tool to determine and monitor areas affected by nutrient
enrichment.
·
These changes in the macrophyte community can be highly visible and may be deemed
‘undesirable’ in terms of the definitions of eutrophication cited above (2.1.1). For example,
they may result in the loss of conservation and amenity value, in addition to problems for
abstraction licence holders and other water users (NRA 1994a).

R&D Technical Report E38 6
·The macrophyte species recorded for these surveys are large and readily identifiable with the
naked eye. There are relatively few species in a particular river area (approximately 20), so
it is normally possible to identify all to species level when the necessary seasonal attributes
are present.
·The rooted nature of many species means that absence of species is significant and this, as
well as the presence of a species, can be used in the interpretation of survey data.
2.1.3 Watercourses sampled
The MTR methodology is designed for use in rivers and streams. The method is not suitable for
assessing standing (lentic) waters, canals (unless the water flow is constant in one direction) or
rivers with a tidal influence.
2.1.4 Underlying pr inciples
The Mean Trophic Rank methodology uses a simple scoring system to derive a single index
describing the trophic status of a site. The system works by allocating a Species Trophic Rank
(STR) score to 128 aquatic plant species (Appendix 5 – Table A1). The scores range from
1to 10. High scoring plants are associated with water bodies which are low in nutrients. Low
scoring plants are either tolerant of eutrophication or are cosmopolitan in their requirements, ie
have no preference. The response of the macrophyte community to nutrient status can be
expressed by integrating the STRs of the species present at a site as a mean value, weighted
according to the relative percentage cover of the individual species. The resulting value, the
MTR, increases with decreasing eutrophy, with a theoretical maximum of 100 and a minimum
of 10 (there is no score when scoring species are absent).
In undisturbed or un-degraded ecosystems, the plant community often contains many species,
none of which tend to dominate to the detriment of any other, ie the system is in balance. Species
with high STRs should be present and a theoretical maximum MTR score should be achieved
based on the limits imposed by floristic diversity, flow regime (altitude), river size, catchment
geology and water chemistry at a particular site. In degraded or disturbed ecosystems, the plant
community may contain fewer species and one or two species with low STRs may be dominant.
In these instances, a score somewhat less than the perfect score will be achieved. There is a
scale of degradation and in between these two extremes lie the majority of riverine ecosystems
in Britain.
The change from the perfect score can be used as a measurement of the impact or damage caused
to the ecosystem by the disturbance. A predictive element to the MTR, allowing predictions of
what MTR can be expected given a certain set of physical conditions (the ‘perfect score’), is still
only in the early stages of development. Never-the-less, the MTR system can be used to make
an estimate of how degraded the ecosystem is from the expected norm (taking into account all
other factors), and give an indication of the change in the macrophyte community from that norm
using the guidance on the interpretation of MTR results given in this manual.
The development and testing of the MTR has focussed particularly on its use as a tool to assess
eutrophication impact due to phosphate enrichment. Although eutrophication may arise from
enrichment by compounds of either phosphorous and/or nitrogen, phosphorus is usually