Planet WGSW-24010 User Manual

Mean Tr ophic Rank: A User’s Manual

R&D Technical Report E38

NTH Holmes3, JR Newman2, S Chadd4, KJ Rouen4, L Saint4 and FH Dawson

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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 stat us

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
Te l: 01929 462314 Fax: -462180 Te l: 0118 969 0072

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 Manag er
The Environment Agency' s Project Manager for R&D Project E1-i694:
Karen J Rouen, North West Region

R&D Technical Report E38 i

ACKNOWLEDGEMENT S

This docum ent 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).

R&D Technical Report E38 ii

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R&D Technical Report E38 iii

CONTENTS

List of Figures v

List of Tables v

Glossary vi

Executive Summar y ix

Key Words ix

1 Foreword 1

1.1 About this manual 1

1.2 Summary of the method 3

2 Intr oduction 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

3 Survey 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

4 How to Car ry 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

5 MTR 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

6 Interpretation 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

7 Quality Assur ance 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

8 MTR 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

9 References 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

R&D Technical Report E38 v

R&D Technical Report E38 vi

LIST OF FIGURES

1 Diagram matic representation of survey method 38

2 Illustration of shading 53

3 Macrophyte survey flow chart 60

4 Interpretation of MTR results, Stage I ‘decision tree’:

Is the site impacted by eutrophication? 70

5 Interpretation of MTR results, Stage II ‘decision tree’:

Is there a significant downstream impact from the qualifying discharge? 71

LIST OF TABLES

1 MTR scores summarised according to river community type 68

2 Reasons 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

1 Factors to consider when deciding whether to use MTR or DQI/TDI 18

2 Factors to consider when selecting MTR sites and survey lengths 24

3 Conditions when surveys should not be undertaken 26

4 Non-standard survey lengths 36

5 Exceptions to surveying the full channel width 37

6 Methods of estimating overall percentage cover 43

7 Estimating percentage cover of individual species: width method 45

8 Estimating percentage cover of individual species: square metre method 46

9 Audit 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

1 The principal purpose of this manual is to provide comprehensive procedural guidance

on

how to carry out Mean Trophic Rank (MTR) ma crophyte 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).

2 The 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.

3 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 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.

R&D Technical Report E38 xi

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R&D Technical Report E38 1

1 FOREWORD

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 desig nation 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 macr ophytes:

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.

R&D Technical Report E38 3

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 point­sources 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.

R&D Technical Report E38 4

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 INTERPR ETATION 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.

R&D Technical Report E38 5

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.

2 INTRODUCTION 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 accelera ted growth of algae and higher forms of plant life to produce an undesira ble
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 inorga nic plant nutrients, which results in the stimulation of an
array of symptomatic changes. These include the increased production of algae a nd/or other
aqua tic plants affecting the quality of the water and disturbing the balance of orga nisms within
it. Such changes may be undesirable a nd 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 Water cour ses 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 principles

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
1 to 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

R&D Technical Report E38 7

considered to be the element which limits aquatic plant growth in fresh waters because of its low
availability in relation to plant requirements. Where it is limiting, an increase in the level of
phosphate in the water should cause accelerated growth of those plants present or a change in the
species composition of the plant community to reflect the change in phosphate concentration.
At very high concentrations of phosphate, the plant community is usually species poor because
of the excessive growth of filamentous and unicellular algae and some high phosphate tolerant
macrophytes. In these cases where the biological symptoms of nutrient enrichment are manifest,
eutrophication as defined in the UWWTD and the Agency’s proposed Eutrophication Strategy
can be deemed to be taking place. In contrast, where the availability of a nutrient is sufficient so
as not to limit plant growth, such as is usually considered to be the case for compounds of
nitrogen, any increase in the concentration of that nutrient will not lead to changes in the plant
community and thus eutrophication cannot be deemed to be taking place.

Evidence suggests that the MTR is particularly responsive to change in nutrient status at
concentrations less than 1.0 mg l-1 P or 10 mg l-1 N, and even more so at less than 0.5 mg l-1 P or
5 mg l

-1

N (Dawson et al 1999b). This implies that the MTR system may be most useful at

detecting eutrophication impacts when the nutrient concentration upstream of (or prior to) the

nutrient input, is less than 1.0 mg l-1 or 10 mg l-1 N, particularly when supported by other

biological and/or chemical evidence. The level of eutrophication attributable to nitrate rather
than phosphate at any one site cannot be established using MTR at this stage of method
development. In many cases, however, the nitrate concentration is unlikely by itself to be limiting
to plant growth, and phosphate is likely to be the limiting factor (Dawson et al 1999b).

2.1.5 Basis of operation

The method involves the survey of the macrophyte flora and physical character of defined lengths
(100m) of watercourse using a standard checklist. The presence, absence and percentage area
covered by each macrophyte are recorded and the data relating to scoring species (those assigned
an STR) are then used to calculate the MTR score. Physical parameters are recorded to aid
interpretation of results. Detailed procedural guidance is given in Chapters 3–8.

R&D Technical Report E38 8

2.2 Uses of MTR

The MTR method can be used to give a qualitative assessment of whether a river site is impacted
by eutrophication and (for physically similar sites) downstream changes in trophic status. It
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.

The principal application for which the method has been developed and tested is to assist in the
designation of identified reaches as SA(E)s under the UWWTD (2.3). The methodology has
been used extensively by the Environment Agency for this purpose.

The method should be equally applicable to the assessment of other point-sources of nutrients,
but is not yet fully proven for other applications (2.4). Use of the system to date, however, is
encouraging. For example, macrophyte surveys using MTR and the method of Haslam (DoE
Standing Committee of Analysts 1987) have been used in Northern Ireland to indicate the
location of eutrophication problems and to monitor trends in the trophic status of rivers (Oliver
& Hale 1996). A combined approach using macrophyte, invertebrate and ecotoxicological work
upstream and downstream of key discharges has been found to be useful, with the potential
addition of the Trophic Diatom Index (TDI, 3.1.2). English Nature have used the MTR together
with the Nature Conservancy Council macrophyte classification to examine the impact of
discharges from small- and moderate-sized sewage works on small rivers (eg Southey 1995).
Although there was no clear relationship between the two sets of results and percentage
reductions in MTR score downstream of discharges were not great, possibly due to high
phosphate-loading upstream, it is felt that the MTR shows much potential and that it is useful to
use both systems when analysing changes of macrophyte floras over time.

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2.3 Principal application: Urban Waste Water Treatment Directive

This is the principal application for which the Mean Trophic Rank has been developed and
tested. The survey methodology and calculation of MTR are described in detail in Chapters 3–5
of this procedural manual and guidance given in Chapter 6 on interpretation of results. Before
commencing surveys, Environment Agency staff should also refer to current internal guidance
on information gathering for future reviews of SA(E)s for the rationale behind UWWTD
monitoring (Environment Agency 1998b: supersedes NRA 1994b).

In brief, the MTR is used to provide evidence of eutrophication impact on riverine macrophyte
communities, in order to support designation of identified reaches as SA(E)s under the Directive
and to provide evidence of the specific impact of ‘qualifying’ discharges on such reaches.

2.3.1 Designation of Sensitive Ar eas

Sensitive Areas (Eutrophic) (SA(E)s) are water bodies which are considered eutrophic, or

which in the near future may become eutrophic if protective action is not taken. They are
identified using the criteria listed in Annex II of the Directive, with the definition of
eutrophication as given in Article 2(11) (see 2.1.1 above). The size of discharges and type of

receiving water are taken into account. Once SA(E)s are designated, discharge requirements can
be set for ‘qualifying discharges’ (QDs) in terms of nutrient levels or a percentage reduction in
nutrients. ‘Qualifying discharges’ are those with a loading of greater than 10,000 population

equivalent (pe): they

may discharge either directly into the SA(E), or indirectly into the
relevant upstream catchm ent areas of SA(E)s, contributing to the pollution/eutrophication
of these areas. However, no action needs to be taken (ie consents do not need to be
determined) if it can be demonstrated that nutrient-removal will have no significant effect
upon the level of eutrophication. In the case of most freshwaters, nutrient removal would
usually be of phosphorus, the principal limiting nutrient in freshwaters.

A Government consultative paper was published in Ma rch 1992 (DoE et al 1992), proposing
criteria for identifying SA(E)s and subsequent procedures. This guidance was finalised in

March 1993, in Annex B of the paper published on the methodology for identifying SA(E)s

(DoE et al 1993). Under this methodology, waters are only identified if affected by QDs. For
rivers, the upstream limit of a SA(E) is either a QD or the point at which the symptoms of
eutrophication become manifest. The downstream limit is where the effects are reduced to
‘typical’. For riverine environments, the criteria relate to orthophosphate, chlorophyll a

, algal

biomass, water retention time, dissolved oxygen, fauna (fish/invertebrates), macroflora and
microflora. The MTR provides information on the macroflora by providing an estimate of the
degradation to aquatic macrophyte communities in these areas.

2.3.2 Assessment of eutrophication and the impact of qualifying dischar ges

The main pollutant causing eutrophication arising from QDs will usually be phosphorus. This
phosphorus will usually be in the form of soluble reactive phosphate (SRP) and therefore be
available immediately to submerged macrophytes downstream of the discharge. Given the
relationship between MTR and phosphate concentration (Dawson et al 1999b), the MTR can be
used to answer the two key questions required for evidence in support of SA(E) designation:

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· is the river eutrophic, or shortly at risk of becoming eutrophic?

· what is the impact of the QD?

Guidance on sampling strategy and interpretation of MTR results to answer these questions is
given in Sections 3.2.1 and 6.1. The latter includes flow-charts to enable decisions to be made
in a consistent and structured manner. Results are expressed qualitatively in terms of two
standard descriptors, one for trophic status and one for the downstream impacts of the QD.

2.3.3 Post phosphate-removal monitoring

It is anticipated that macrophyte communities previously affected by phosphate eutrophication
will attain higher MTR scores after phosphate removal (phosphate-stripping) is installed at QDs.
Although this response, or the speed at which it occurs, has yet to be demonstrated due to the
early stage of method development, the MTR system should be used to monitor improvements
in the macrophyte community after phosphate-removal has commenced. The information gained
from this monitoring will not only provide direct operational information on the impact of the
P

-removal, but will also provide much needed information for the further refinement of the

method. The latter includes information on the speed at which macrophyte communities respond
to a reduction in P concentration; how recovery takes place (which species come back first); and
the effect of P in sediments (how long it takes for phosphate-enriched sediments to cease to have
an effect on the macrophyte community).

The success of biological methods at demonstrating an improvement in the trophic status
of a system is dependent on the availability of a reliable and consistent historical data set.
Lack of such a data set may limit the application of the methods to demonstrate an

improvement in a historical context. For those SA(E)s desig nated under the 1997 review,

however, post-phosphate-removal monitoring may be able to show measured improvements
using data from the 1996 MT R surveys as the baseline for improvement.

In order to separate the effects of phosphate-removal from natural background variation in
the MTR it may be necessary to carry out an examination of the time series of chang e to
establish baseline variation in MTR scores. These data may be available by comparison with
MTR scores from previous seasons, but care should be taken to ensure that all factors
relating to the accuracy and comparability of MTR surveys prior to 1996 are satisfactory
before undertaking such comparisons. If you are sure that any change in MTR score prior
to phosphate-removal cannot be accounted for by chang es in nutrient concentrations or
other conditions then this variability can be used as a measure of natural background
variation. It is anticipated that any changes due to phosphate-reductions will be
superimposed on this natural chang e.

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2.4 Other applications

2.4.1 Non-qualifying point-source discharges

In many river systems in the UK, a significant proportion of the phosphate-loading comes from
WWTWs of less than 10,000 pe although surface water run-off and storm sewer overflow may
also be significant sources of phosphorus in urban areas. These discharges do not qualify under
the UWWTD for statutory improvement works to remove P from the effluent discharge. This
means that eutrophication can be primarily caused by phosphate-loading from sources other than
QDs and hence outside the legislative framework of the UWWTD. It also means that rivers are
frequently degraded upstream of the QD, making the demonstration of an impact of a QD
difficult to achieve in absolute terms. The MTR can be used to identify non-QDs which are
having a significant impact on the macrophyte community in order to target these for future
nutrient control measures where possible. Sampling protocol and interpretation of results is as
for assessment of QDs (3.2.1 and 6.2.1).

2.4.2 Non-point source discharges

The phosphate-loading of many agricultural catchments may arise mainly from non-point
sources, such as soil run-off and diluted slurry effluent. The use of the MTR is these
circumstances is largely untried, but provisional guidance on sampling strategy and interpretation
of result is given in 3.2.2 and 6.2.2. The information gained from such studies will help
determine if the MTR system is capable of detecting the effects of non-point source discharges.

2.4.3 Catchment studies

Studies of the MTR over a whole catchment or sub-catchment may be considered for three
purposes.

To improve the interpretation of MTR values, by placing them in a catchment context

The main inherent limitation of the MTR is that it is influenced to some extent by factors other
than nutrient levels; in particular, by the substrate, underlying geology of the river and to some
extent the flow regime. This means that to interpret the MTR in terms of trophic status it is
necessary to compare results with values expected in a relatively un-impacted reach of a similar
type. Such reaches, or at least similar reaches with less nutrient enrichment, may be found
elsewhere in the catchment being surveyed.

A second limitation relates to the sensitivity of the MTR in detecting the impact of individual
nutrient sources. In a complex environment, the impact of a nutrient discharge may not be
manifest by the MTR for some distance downstream due to impact by other polluting factor(s)
in the same discharge or by another discharge close by. In either case, interpretation of MTR
results may be improved if the sampling programme includes surveys at regular intervals down
the catchment to assess the varying influences on the macrophyte community (3.2.3).

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To undertake a ‘eutrophication audit’ of an individual catchment to determine where
nutr ient control measur es would be targeted most effectively

The MTR is recommended for this purpose provided its inherent limitations in terms of other
influencing factors, as outlined above, are taken into account in the sampling regime and
interpretation of data. Best practice will be to undertake surveys at intervals over the whole
catchment (3.2.3). Reference should also be considered to the requirements of the Nitrates
Directive (91/676/EEC).

To provide an overview of the tr ophic status of a catchment to compare with other
catchments on an area, regional or national basis

The cross-comparison of actual MTR values between catchments is NOT recommended at the
current time, except where catchments are of the same physical type. Even then, the validity of
comparing MTR scores from similar sites in different river catchments has not yet been
confirmed and so comparisons should be interpreted with caution.

Broad comparisons can be made between physically dissimilar catchments by interpreting the
results on a site-by-site basis, taking into account all the potential influencing factors and using
very broad standard descriptors of trophic status. In addition, where demonstrable and significant
downstream changes in MTR can be observed, catchments may be compared on the basis of the
relative degree of downstream degradation as demonstrated by changes in the MTR. This may
help to prioritise those catchments which would benefit most by nutrient control measures.
Specific guidance is given in 3.2.3 and 6.2.3.

2.4.4 Eutr ophication management strategies

The MTR can assist delivery of eutrophication management strategies (eg Environment Agency
1998a) and of catchment or river-basin management plans in two ways.

Assessment and pr ioritisation of problems

The MTR can make a valuable contribution to the assessment of the nature and extent of
eutrophication problems, which can then be prioritised and managed via action plans. The
efficiency of these plans will be enhanced if they are formulated and progressed under the
umbrella of either catchment or wider environmental management plans such as the Agency’s
Local Environment Agency Plans (LEAPs).

Data from all MTR surveys, whatever the primary application, will be useful for this purpose,
although to a greater or lesser degree depending on the sampling strategy (3.2.4). Guidance on
the interpretation of data is as for catchment studies (6.2.3). Emphasis should be placed on the
balance of information available, including evidence from MTR, diatom (3.1.2) and chemical
monitoring.

Whereas LEAPs will require only local collation of MTR data to identify problems within the

catchment, national collation of data is required for eutrophication management strategy
purposes.

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Compliance monitoring

The MTR may potentially be used to assess the efficacy of eutrophication control measures and
hence monitor compliance with targets. The capacity of the macrophyte community to respond
to nutrient reduction measures, however, is poorly understood (2.3.3). Until such time as this
understanding is increased, best practice will be to continue MTR surveys after nutrient control
measures are in place. Guidance on sampling strategy is given in 3.2.4. All such post-nutrient
reduction survey data should be collated nationally to allow further method development.

2.4.5 Tempora l changes in trophic status

The MTR methodology is recommended for use to monitor temporal change in trophic status at
a site over a number of years. Temporal change may be either a deterioration due to a nutrient
input or an improvement in response to nutrient control measures. Although this application is
largely untried, due to insufficient data, it is assumed for the interim that the MTR will respond
to temporal changes in nutrient status in a similar fashion to changes on a spatial scale. The
timescale of response can only be established once sufficient adequate data are available.

The general principles of post phosphorus-removal monitoring, as outlined in 2.3.3, apply to
applications beyond the UWWTD.

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3 SURVEY PLANNING

This chapter describes the steps which should be taken when planning MTR surveys and should
be read before the surveys are undertaken. The first step is to check that the MTR method is
appropriate for the use required (see 2.3 and 2.4). The next steps are to consider alternative
methods, devise a suitable sampling strategy, plan the logistics of the surveys (when and where
to survey and what resources are required) and collect ancillary data. These steps are described
below.

3.1 Alternative methods to consider

When planning biological surveys to assess river trophic status, it is important to choose the most
appropriate methodology. Method selection requires recognition of the various options available
and an understanding of their comparative strengths and deficiencies under a range of
circumstances. This section outlines the available options and lists criteria to consider when
choosing which option(s) to adopt.

3.1.1 Options

There are two biological methods recommended for the assessment of the trophic status of rivers:
the macrophyte-based Mean Trophic Rank and the diatom-based Diatom Quality Index (a
transformation of the Trophic Diatom Index). An introduction to the MTR is given in Section

2.1 and an outline of the DQI/TDI is given below. Although experienced biologists may also
glean information on trophic status from other riverine biota, for example the benthic macro­invertebrate community, there is no validated standard method to do this. Use of such
information should thus be used with caution and only to support evidence gained from one or
both of the recommended methods below.

3.1.2 Trophic Diatom Index (TDI) & Diatom Quality Index (DQI)

The Trophic Diatom Index (TDI) was developed by Kelly and Whitton (1995a & b) for the NRA
as part of an investigation into the use of plants to monitor rivers and in response to the needs of
the UWWTD. It was further refined by Kelly (1996a, b & c), following testing by practitioners
in Agency regions.

The method is designed for monitoring the trophic status of rivers and streams, and uses benthic
diatom communities rather than the macrophyte assemblages used in the MTR system. Diatoms
are widely used for monitoring water quality on the continent (Whitton & Kelly 1995), for
palaeoecological studies of lake acidification in the UK (Battarbee 1984) and, more recently, lake
eutrophication. In one instance (Anderson & Rippey 1994), a change from eutrophic to
mesotrophic conditions following diversion of a nutrient input from a lake in N. Ireland was
observed in a single season. As diatoms derive their nutrients directly from the water column and
have generation times measured in days rather than months or years, it was thought that these
might constitute a reliable tool for assessment of eutrophication in rivers.

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Comprehensive procedural guidance on the TDI methodology is given in the TDI User’s Manual
(Kelly 1996b). Briefly, the method involves the collection of benthic diatom films from natural
or artificial substrates within a 10m reach of river. Sampling of natural substrates is quick and
easy, although sampling of artificial substrates requires two visits to a site. Permanent slides of
the material collected are prepared and analysed in the laboratory. Taxa present on the slide are
identified and the relative proportion of each taxon estimated. These data are then used to
calculate an index showing the degree of eutrophication (the ‘trophic diatom index’ or TDI) and
a second value indicating the contribution of organic pollution at a site. When used together,
these enable nutrient-rich waters to be separated from those which are organically polluted.
Organic pollution is frequently associated with high nutrients, but these nutrients are not

necessarily the only factor determining success of a txaon in organically polluted water (Kelly

et al 1996).

The index is based on 86 taxa and is derived from the weighted average equation of Zelinka and
Marvan (1961), using taxon sensitivity to nutrient status, indicator value (spread around the
mean) and abundance. Taxon sensitivity values assigned to individual taxa range from 1
(favoured by very low nutrient conecntrations) to 5 (favoured by very high concentrations of
nutrients). TDI values can range from 0 (indicating very low low nutrient concentrations) to 100
(indicating very high nutrient concentrations). To facilitate comparisons with MTR assessment,
the scale of the TDI is inverted so that low scores correspond to high nutrients and high scores
to low nutrients (Kelly 1996b). Rather than run the risk of confusion by having two quite
different versions of the TDI working in opposite directions, the ‘new’ diatom index (ie 100 ­TDI) is referred to as the ‘Diatom Quality Index’ or DQI.

For the purposes of assessing trophic status, the applications of the MTR described in 2.3 and 2.4
apply equally to TDI/DQI. Macrophyte surveys have been traditionally used for conservation
assessments of rivers, while diatoms have been linked with water quality assessments: both can
now be used for trophic status assessment. Further information on the applications of the
TDI/DQI is available in Kelly (1996a & b).

3.1.3 Criteria for deciding which method to use - MTR or DQI/TDI?

Given the two recommended methods for biological assessment of the trophic status of rivers,

the next step is to consider their comparative merits and decide; (a) whether either method is
suitable, (b) if so, which is the most appropriate or (c) whether both methods are required.
Factors influencing this decision may include: the specific purpose and objectives of the survey;
the survey/site conditions; the resources; and/or, expertise available.

It is recommended that for comparison with MTR results, diatom data is presented as the DQI
rather than the TDI. This allows maximum compatibility between the data presented and thus
assists communication of results to non-biologists.

Wherever possible when assessing the trophic status of rivers, both the MTR and DQI should
be used. This includes monitoring both for UWWTD purposes and for other applications,
guidance for which is given in Section 2.3 and 2.4. The two methods complement each other and
produce results which are broadly in agreement in terms of relative values. Where results differ,
this can often be related to poor site/sampling conditions affecting one of the indices (Dawson