Water Res Vol 17 No 3 pp 333-347, 1983 0043-1354/83/030333-1550300/0 Printed m Great BrUam All rights reserved Copyright 1983 Pergamon Press Lid

THE PERFORMANCE OF A NEW BIOLOGICAL WATER QUALITY SCORE SYSTEM BASED ON

MACROINVERTEBRATES OVER A WIDE RANGE OF UNPOLLUTED RUNNING-WATER SITES

P D ARM1TAGE 1, D Moss 2, J F WRIGHT 1 and M T FURSE l

1Freshwater Bmloglcal Assoc,ation, River Laboratory, East Stoke Wareham, Dorset BH20 6BB England and

2Institute of Terrestrial Ecology, Bangor Research Station Penrhos Road, Bangor, Gwynedd LL57 2LQ Wales

(Re~elted January, 1982)

Abstract--The occurrence of famdles of macrolnvertebrates has recently been used as the basis for the BMWP (Biological Monitoring Working Party) system of assigning scores to lotic sites In this study the performance of the system across 268 sites on 41 rivers providing a wide range of physical and chemical features has been appraised Changes in score and ASPT (average score per taxon) with respect to season and sampling effort have been examined Seasonal variations were relatively shght and it is concluded that samples taken in any of the three seasons, spring, summer or autumn, were hkely to provide consistent estimates of score and particularly ASPT Sample replication led to substantial accretion of scores but had little effect on ASPT and therefore more information was obtained for less effort when ASPT was used Data are presented on score and ASPT values for 8 groups of sites derived by multwartate classificatory techniques Considerable vartaNhty in achievable score and ASPT was observed m the different groups of unpolluted sites In general, scores were highest in the group at the middle of the range of environmental features and lowest m groups at the bottom of the range (lowland areas) ASPT in contrast showed a relatwely steady decline in values between groups at the top (mainly upland rivers) and bottom of the range of environmental features Attempts were made to predict score and ASPT from physical and chemical data, or physical data alone using multiple regression Equations used to predict ASPT explained on average a higher proportion of the varmnce (659) than those predicting scores (220'o) It is suggested that predictive equations for ASPT will enable theoretical ASPT to be calculated, thus providing target values against which observed values can be compared Rec- ommendations to facthtate use and interpretation of the BMWP score system are presented

INTRODUCTION

Score systems using macrolnvertebrates have been de- veloped to facilitate the interpretation of large quanti- ties of data resulting from the biological monitoring of water quahty Such monitoring exercises are car- ned out to detect changes in communities and results take the form of lists of taxa with or without abun- dances which are analysed to produce a score, class or Index This data processing reduces ecological infor- mation but makes the results more accessible to non- biologists who need the data before making decisions lnvolwng the management of water bodies

In Great Britain the blOtlC indices and classification systems which have been used most frequently to assess water quality Include Trent Biotic Index (Woodlwlss, 1964), Chandler Biotic Score (Chandler. 1970), diversity indices, and the Department of the Environment (DOE) classification (Department of the Environment and Welsh Office, 1971) Rewews of the merits of these different systems (excluding DoE classification) are provided in Mackay et al (1973), Cook (1976), Balloch et al (1976), Hellawell (1977) and Murphy (1978) The general consensus from these reviews appears to be that no single index will satisfy all requirements, often because an index has been de-

veloped for a Iocallsed area of the country and will not have apphcatlon nationwide The DoE Nologlcal classification used in the national River Pollution Survey of 1970 (Department of the Environment and Welsh Office, 1971) was developed in consultation with certain of the River Authorities and was comJ pared with a classification based on chemical criteria One of the major hmltatlons of this DoE biological class system was Its lnablhty to represent satisfactor- ily the Nologlcal condition of all the raver types covered m national surveys In an effort to ~mprove this system the Biological Monitoring Working Party (BMWP) was set up in 1976 Its terms of reference were to recommend a system which could be used to assess the biological condmon of a river, and which was suitable for presenting a broad picture of one aspect of the biological condition of rivers in the U K (Chesters, 1980)

In 1978 the Working Party produced the first ver- sion of a new score system, which was developed through questionnaires, surveys and discussion (Bio- logical Momtorlng Working Party, 1978) In the same year a national testing exercise was orgamsed to assess the smtablhty of the score system for national surveys (Chesters, 1980) Further testing in 1979

333 WR 17/3-~o

~14 I' D ~RMI IAt , t ~'~" al

resulted in some minor changes in the st.ore sybtem and it p., this later ~erslon x~h~ch is used m the present st tidy

Examination of the results lrom the mltml 1q78 stlr- ~ey indicated considerable variation m the score both within and between certain t>pes of rl~er even when no chemical pollution was demonstrated It is the ob- ject of this present stud> to atd the interpretation and assess the performance of the score and a~erage score per taxon in relation to physical and chemical leatures of s~tes

This work forms part of a project which ts attempt- mg to tdentlf) natural communmes of river orgamsms and thmr relationships to en~lronmental factors, and to use this reformation to produce a biological classl- hcat~on ol running-water s~tes m Great Britain, IWrlght et al 1982 Furse et al 1982)

STUDS &RE,~ AND METHODS

Two hundred and slxt)-mght sites on 41 mer s~ ,It.m,, were selected for study, incorporating bctween them a v, ldt. range of physical and chemical featurt.s Details ol ri~.r and site selection are given m Wright ,t a/ (1982) On tht. basis of the Department of the EnYzronment and Welsh Office report (1971J and more recent reformation trom Water Authority biologists all 268 sites were regarded is being of good or fairly good quaht,' Each site ~a,, sampled 3 times a )ear m spring summer and autumn Analyses were carried out on both single season data and the more comprehensive hMlng of lamdms obtained b~ amalgamating the single season listings The method used to sample the sites consisted of a ~ mm kick sweep with a pond-net of 900#m mesh in all major types ol habitat present the object being to obtain a comprehensl~.c list ol taxa with the minimum ot sampling effort This procedure described and tested in Furse et al (1981} was rec- ommended to the Water ~uthorlty and River Purdicatlon Board blologist~ who took all the samples for this stud\

Table I The BMWP score system

Families Score

Slphlonundae Heptagemidae Leptophlebudae Ephemerelhdae Potamanthidae Ephemendae Taemopterygidae Leucmdae (apm,dae Perlod,dae Perhdae Chloroperhdae Aphelochemdae Phryganeidae Molanmdae Beraeldae Odontocendae Leptoceridae Goendae Lepidostomatldae Brachvcenmdae Sencostomatidae

Astac~dae LesUdae Agrndae Gomphldae Cordulegasterldae Aeshmdae Corduhldae Llbellulldae Ps)chomyndae Phllopotamldae

(. aemdae Nemoundae Rhyacophllldae Polycentropodldae Llmnephlhdae

Nermdae Vlvipandae Anc)hdae H vdroptlhdae Umonldae (_ orophndae GammarFdae Platvcnemidldae Coenagrndae

Mesovehldae Hydrometrldae Gerrldae Nepldae Naucondae Notonecudae Plmdae Cormdae Hahphdae Hygrobndae Dytlscldae Gynmdae Hydrophlhdae Clambldae Helodldae Dryoptdae Elmlnthldae Chrysomelldae Curcullomdae Hydropsychldae Tlpulldae Slmullldae Planarlldae Dendrocoehdae

10

Baetldae Stahdae 4 Plsclcohdae

Valvatidae Hydroblldae Lvmnaeldae Physidae PlanorNdae Sphaerndae GlosslphOnlldae Hlrudldae Erpobdelhdae 3 Aselhdae

Chironomldae 2

Ohgochaeta (whole class) 1

Performance of a new biological water quality score system 335

Twelve of the 268 sites included samples from deeper areas where the kick/sweep method was not feasible, and alterna- tive methods such as grabs, corers and air-lifts were used (Wright et al, 1982) Physical features of the sites were recorded on standard forms at the time of biological sam- phng Water chemistry data were provided by Water Auth- ority and Rwer Purification Board chemists

All samples were sorted and the ammals identified to species where possible (Wright et al, 1982) However, for calculation of the BMWP score tdentlfication to famdy ~s sufficient A site score was obtained by summing the lndt- vldual scores of all families present (Table 1) Score values for m&wdual families reflect their pollution tolerance based on current knowledge of distribution and abun- dance Pollution intolerant families have high scores and pollution tolerant famdles have low scores The average score per taxon (ASPT) was calculated by &wdmg the score by the total number of scoring taxa A high ASPT value usually charactenses clean upland s~tes containing relatively large numbers of high scoring taxa Lowland sites which do not support many h~gh scormg taxa gener- ally have lower ASPT values

Computations were carried out using a PDP 11/34 com- puter at the Institute of Terrestrial Ecology, Bangor, and the GENSTAT statistical package on an IBM 370/165 computer at the Umvers~ty of Cambridge

RESULTS

The frequency distributions of score and ASPT values are shown m Table 2 The majority of single- season score and ASPT values fall between 100-150 and 501~500 respectively However, a number of sites do not attain values within these ranges even though they are apparently unpolluted This could be due to insufficiently intensive sampling, or regional variations m attainable scores and ASPT, and the lm- phcatlons of this are examined below Spring, summer and autumn samples all show similar distribution pat- terns but the combined seasons' data-set shows in- creases m the modal values of score and ASPT as a result of the increased sample effort

Factors affec tmq score and ASPT values

Seawnal vartatton Each single season was com- pared with each other smgle season using the paired t-test applied to the whole data-set of 268 samples Similarly each pair of seasons was compared with each other paw of seasons The significance of the differences m score and ASPT values between seasons and between pairs of seasons ~s presented m Fig 1

Both spring and autumn samples produced scores which were significantly higher than those of summer samples The difference between spring and autumn score values was not significant Paired seasons' data showed that spring + summer and spring + autumn produced significantly higher scores than did sum- mer + autumn samples For ASPT, spring samples gave values which exceeded those of both summer and autumn and this may have been a result of the preponderance of high scoring Plecoptera in this season Paired seasons' data indicated that spring + summer gave the highest ASPT Three seasons com- bined gave slgnlficantl'~ higher values of score and

ASPT than single or paired seasons A 49 6~0 increase was observed when the lowest single season mean score was compared w~th the mean score of the three seasons combined For ASPT the eqmvalent value was 7 0~

Changes m score and ASPT wtth sample rephcatton The effect of taking 6 samples per site m one season on score and ASPT accretion was investigated using data from 4 sites on the River Axe (Devon) and 3 sites on the Avonwater (Hampshire) Scores and ASPT were calculated for single rephcates and for all poss- ible combmatlons of 2, 3, , 6 rephcates, corre- spondmg to 6, 9, , 18 mm samphng Mean scores and ASPT were calculated over all possible combi- nations corresponding to each of these samphng periods, and the highest and lowest such scores and ASPT were also recorded Scores always increased with samphng effort ASPT generally increased although at one site there was a shght decrease ASPT will increase if the new taxa added by repeated sam- phng are higher scoring than the existing mean Simi- larly a decrease m ASPT will occur if ad&tlonal taxa are lower scoring Changes m ASPT with increasing sample effort were, however, very shght Figure 2 presents a summary of score and ASPT accretion based on data from all 7 sites It is clear that BMWP score is more dependent than ASPT on the number of samples taken

The change in score and ASPT due to repeated samphng m one season was compared with change due to single samples taken m 3 seasons Table 3 shows the variations m score and ASPT at 7 sites resulting from change m samphng effort Paired t-tests showed that score values from 3 seasons com- bined were significantly lower (t = 2 892, d f = 6, P < 005) than those obtained from 6 replicate samples combined m one season ASPT showed no s~gmficant difference between 3 seasons combined and 6 rephcates combined Scores and ASPT expressed as the mean of all possible combinations of 3 replicates

Table 2 The frequency distribution of BMWP scores and ASPT in 268 samples, for spring (Sp), summer (Su), autumn

(Au) and combined seasons (Co)

Sp Su Au Co

BMWP Score 150 60 44 55 173

Total 268 268 268 268 ASPT

200-300 1 0 0 0 301-400 I1 18 19 4 4 01-5 00 60 74 72 51 5 01-6 00 91 103 105 90 601-700 96 71 68 117

>700 9 2 4 6 Total 268 268 268 268

SC

OR

E

Sp

S

p*

Su

15

0 8

/"\

/ \

t =

2 7

2

t=0

50

t=

O I0

t=

20

8

P