a proposal for modification of the belgian biotic index method

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Hydrobiologia 179: 223-228, 1989. 0 1989 Kluwer Academic Publishers. Printed in Belgium. 223 A proposal for modification of the Belgian biotic index method L. Bervoets, B. Bruylants, P. Marquet, A. Vandelannoote & R. Verheyen University of Antwerp, Department of Biology, Universiteitsplein 1, 2610 Wilrijk, Belgium Received 17 September 1987; in revised form 20 April 1988; accepted 21 July 1988 Key words: water quality, biological assessment methods, biotic index, macroinvertebrates, rivers, brooks Abstract Modifications to a standard biological water quality assessment method, used in Belgium since 1979, were studied. As a result, we recommend the following: - samples should be processed live - samples should not be washed through a series of sieves - systematic units represented by only one individual should be included in the calculation of the biotic index. Using this modification, the biotic index can be calculated more rapidly and shows a higher correlation with a chemical water quality assessment index. Introduction In the assessment of water quality, the trent biotic index (Woodiwiss, 1964) and the biotic index of Tuffery & Verneaux (1968), are most commony used. In Belgium, a method combining the latter two indices was developed (De Pauw et al., 1979; De Pauw & Vanhooren, 1983; Belgisch Instituut voor Normalisatie, 1984). In this paper, we examine some modification of this method from the point of view of reliability, time-consumption and correlation with chemical water quality assessment. We also briefly consider the problem of sampling standardization. Materials and methods Study area Samples were taken from 14 brooks in the province of Antwerp, Belgium (Table 1 and Fig. 1). Sampling points were chosen to ensure a range of pollution levels. Methods for biological quality assessment of water- courses Belgian method (Bel.) This method is as follows: - samples are collected with a standard handnet with a mesh size between 300 and 500 pm.

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Hydrobiologia 179: 223-228, 1989. 0 1989 Kluwer Academic Publishers. Printed in Belgium. 223

A proposal for modification of the Belgian biotic index method

L. Bervoets, B. Bruylants, P. Marquet, A. Vandelannoote & R. Verheyen University of Antwerp, Department of Biology, Universiteitsplein 1, 2610 Wilrijk, Belgium

Received 17 September 1987; in revised form 20 April 1988; accepted 21 July 1988

Key words: water quality, biological assessment methods, biotic index, macroinvertebrates, rivers, brooks

Abstract

Modifications to a standard biological water quality assessment method, used in Belgium since 1979, were studied.

As a result, we recommend the following: - samples should be processed live - samples should not be washed through a series of sieves - systematic units represented by only one individual should be included in the calculation of the biotic

index.

Using this modification, the biotic index can be calculated more rapidly and shows a higher correlation with a chemical water quality assessment index.

Introduction

In the assessment of water quality, the trent biotic index (Woodiwiss, 1964) and the biotic index of Tuffery & Verneaux (1968), are most commony used. In Belgium, a method combining the latter two indices was developed (De Pauw et al., 1979; De Pauw & Vanhooren, 1983; Belgisch Instituut voor Normalisatie, 1984).

In this paper, we examine some modification of this method from the point of view of reliability, time-consumption and correlation with chemical water quality assessment. We also briefly consider the problem of sampling standardization.

Materials and methods

Study area

Samples were taken from 14 brooks in the province of Antwerp, Belgium (Table 1 and Fig. 1). Sampling points were chosen to ensure a range of pollution levels.

Methods for biological quality assessment of water- courses

Belgian method (Bel.) This method is as follows: - samples are collected with a standard handnet

with a mesh size between 300 and 500 pm.

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Table 1. The average chemical in- dex of the sampled stations (Van- delannoote et al., 1986).

Brook C.I.

1 15.0 2 10.0 3 11.5 4 11.0 5 12.5 6 11.0 I 9.6 8 8.3 9 8.5

10 6.0 11 7.3 12 7.5 13 7.5 14 7.5

- sampling effort is standardized: all aquatic habitats are sampled within three to five minutes.

- samples are preserved in 4% fo~~dehyde. - in the laboratory, samples are washed through

a series of sieves of varying mesh size (2 mm; 1 mm; 0.71 mm and 0.30 mm) to separate the organisms.

- organisms are sorted visually with the aid of a magnifying glass.

- the taxonomic level of the systematic units are: * families of Trichoptera, Coleoptera, Crus-

taceae, Diptera and Oligochaeta * genera of Plecoptera, Ephemeroptera, Odon-

ata, Mollusca, Megaloptera, Hemiptera, Planaridae and Hirudinae

* Hydrocarina

Fig. 1. Map of the sampled brooks in the province of Antwerp.

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* thummi-plumosus group and non-thummi- plumosus group of Chironomidae

- systematic units consisting of only one in- dividual are not considered in the calculation of the biotic index.

- the standard table of Tuffery and Verneaux (1968) is used in calculating the biotic index.

See Vanhooren & Dehavay (1979), Vanhooren & De Brabander (1982), De Pauw & Vanhooren (1983) and Belgisch Instituut voor Normalisatie (1984) for further details.

Modifications of the Belgian standard method Modification 1. The sample fraction retained on the sieve with the smallest mesh-size was exarn- ined for organims with a stereomicrocsope. Sub- samples were taken when necessary.

ModiJcation 2. Samples were not washed through a series of sieves, but sorted live. Systematic units (S.U.‘s) consisting of two or more individuals were used in the calculation of the biotic index (B.I.).

Modification 3. Same as Mod. 2 except that S.U.‘s consisting of one or more individuals were used in the calculation.

For each method, the number of S.U.‘s (Sys- tematic Units) and the B.I. (Biotic Index) were determined. Comparison between each pair of methods was made with a paired t-test.

Chemical index and required time

The different B.I.‘s were compared with the C.I. (Chemical Index) (Vercruysse, 1979) using Spearmans rank correlation (Siegel, 1956). The average C.I. per brook or river per annum was calculated from a minimum of five samples.

The times required to car-y-out the Belgium method and each modification were measured and compared with a paired t-test.

To examine the relevance of a standard sampl- ing effort or a standard number OS subsamples (or standard sampling time), ten subsamples were

taken one every 30 seconds, at each sampling station. The subsample distances were then com- pared with an analysis of variance (Hollander & Wolfe, 1973).

Results

Correlation with the C.I.

The average C.I.‘s of each sample station are shown in Table 1. The results of the Spearmans rank correlation between the B.I.‘s and the C.I. are shown in Table 2. All correlations are highly significant, with Mod. 3 giving the highest value.

B.I. and the number of S.U,‘s obtained

The results of the paired t-test comparisons of B.I. and S.U. number between the methods are shown in Table 3. A significant difference was found only once; the B.I.‘s of Mod. 3 were higher

Table 2. Spearman rank correlations between the different B.I.‘s and the C.I. with df = 12 and *p < 0.001

Modification rs t

Mod. 3 - 0.88 - 6.323 * Mod. 2 - 0.86 - 5.196 * Be1 - 0.85 - 5.561 *

Mod. 1 - 0.86 - 5.934 *

Table 3. Comparison of the Belgian method and the modifi- cations for the calculation on the B.I. and number KU. using a paired t-test (Sokal & Rohlf, 1969). Abbreviations in text.

B.I. S.U.

Mod. 2-Mod. 3 : (2.11) NS Mod. 2-Be1 : (0.85) NS Mod. 2-Be1 : (2.11) NS Mod. 3-Be1 : (0.21) NS Mod. 2-Mod. 1 : (1.74) NS Mod. 2-Mod. 1 : (1.95) NS Mod. 3-Be1 : (2.64) * Mod. 3-Mod. 1 : (1.33) NS Mod. 3-Mod. 1 : (1.33) NS

* p < 0.05 t = 2.16 ** p < 0.01 t = 3.01 *** p<O.Ol t=4.22 df= 13

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than those of the Belgian standard method in seven of the 14 brooks.

The percentage of S.U.‘s found in the first one or two subsamples was high (up to 78%) for all sampled stations. Also high was the number of S.U.‘s with one to a few individuals.

Figure 2 shows the relationship between sub- sample number and the number of S.U.‘s repre- sented by single individuals in the strongly pol- luted brook, Grote Struisbeek, and the slightly polluted brook, Scherpenbergloop. The latter showed a gradual decrease in number of single individual S.U.‘s with increasing subsample num- ber, while, in the former, there was no decrease after two sub-samples were examined. In this brook, as in all the polluted brooks, the total number of S.U.‘s was low. In the healthy brooks, the number was high and new S.U.‘s were often found even in the last sub-samples.

Table 5. Comparison of the modifications and the Belgian method in time required for the calculation on the B.I. and number S.U. using a paired t-test (Sokal & Rohlf, 1969). Abbreviations in text.

B.I. KU.

Mod. 2-Be1 (11.26): *** Mod. 2-Be1 (9.64): *** Mod. 3-Be1 (12.32): *** Mod. 3-Be1 1 (13.83): *** Mod. 2-Mod. 1 (12.75): *** Mod. 2-Mod. 1 (12.61):*** Bel-Mod 1 (5.52): *** Mod. 3-Mod. 1 (13.86):*** Mod. 2-Mod. 3 (2.34) :*

* p < 0.05 t = 2.16 ** p < 0.01 t = 3.01 *** p < 0.001 t = 4.22 df= 13

sampling time at each station was the same, sampling distance was always different.

Discussion Time required

There were significant differences in the amount of time required to obtain the B.I. and the number of S.U.‘s between the four methods (Table 4 and 5). Mod. 3 was the most rapid, followed by Mod. 2, then the Belgian method, with Mod. 1 being the slowest.

Sampling effort

The analysis of variance performed on the sub- sampling distances showed significant differences between the various sampling stations (F = 16,04, P < 0,001). This means that although

Table 4. Mean time required (in minutes) for obtaining the B.I. and the number of S.U.

S.U. B.I.

Mod. 3 116 91 Mod. 2 197 129 Be1 692 692 Mod. 1 806 806

De Wit et al. (1984) have stated that one of the requirements of an indicator system is that it must be singular i.e. related to only one factor. A report of the A.W.P. (Ministerie van de Vlaamse Gemeenschap) in 1983 stated that comparison of the water quality of different sites is only valid when they belong to the same type of watercourse. This is because the B.I. is affected not only by water quality but by such factors as substrate nature, current speed, and food availability (Vanhooren et al., 1979). If one takes into account S.U.‘s represented by single individuals (Mod. 2 and 3 here) one reduces the effect on the B.I. of site-specific differences in faunal density. Thus, this can explain why Mod. 3 was better correlated to the C.I. than was the Belgian method. The latter was especially less well correlated to the C.I. in the oligotrophic brooks.

Connected with the latter point is the question of using a standard sampling time. As found here, within a fixed time interval, sampling distance varied between the brooks because of their dif- fering natures. The B.I. of oligotrophic water- courses could therefore be underestimated in comparison to more eutrophic watercourses due

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Grote Struisbeek

2 3 4 5 8 7 5 9 10

eampL number

Scherpenbergloop

40

35

30

25

20

15

10

:i 1 2 3 4 5 6 7 8 9 10

aomple number

Fig. 2. The decrease of the number of S.U.‘s represented by one individual, with increasing sample number.

228

to lack of time in the former to find rarer individuals. Thus, it would be more desirable to standardize sample size than sampling time or effort.

With regard to hand-sorting the organisms, it is advantageous to use a stereomicroscope (Mod. 1) or to sort the organisms before killing them (Mod. 2 and 3). In this way, there is a greater chance of finding the smallest individuals. This can explain why the Belgian method gave a lower B.I. than the modifications in a few cases.

Mod. 3 was the most rapid method for obtain- ing the B.I. and number of S.U.‘s. This was because of the length of time needed for sieving and sorting of dead animals, especially when the latter was carried out using a stereomicroscope. Another advantage of not using formaldehyde (as in Mod. 2 and 3) is that some organisms lose certain identification properties when presented.

General conclusion

Compared to the Belgian standard method, modification 3 requires less time to perform and its B.I. is slightly better correlated with a chemical index. Using this modification, more water quality assessment investigations can be carried out in the same amount of time.

References

Belgisch Instituut voor Normalisatie, 1984. Biologische kwaliteit van de waterlopen. Bepaling van de Biotische Index steunende op aquatische makro-invertebraten. Bel- gische Norm. NBN T92-402.

De Pauw, N. & G. Vanhooren, 1983. Method for biological quality assessment of watercourses in Belgium. Hydro- biologia 100: 153-168.

De Pauw, N., J. Verreth & M. Talloen, 1979. Biological water assessment methods applied on the rivers Torrente Parma,

Torrente Stirone and Fiume PO, 33-93. In: Ghetti P. F., (Ed.) 3rd technical seminar, biological water assessment methods, Parma, October 1978, vol. 1. Published for the Commission of the European Communities.

De Wit, A., P. Spring & P. Van Boheemen, 1984. Sloot- planten als indicatoren, een onderzoek naar indicatoren en hun bruikbaarheid in een biologische meetnet. Land- schap 3: 218-227.

Hollander, M. & D. Wolfe, 1973. Nonparametric Statistical Methods. John Wiley & Sons. N.Y., Londen, Sydney Toronto.

Ministerie van de Vlaamse Gemeenschap, 1983. A.W.P. niveau 1. Overzichtskaart voor het Vlaamse Gewest: 36 pp + 1 kaart.

Siegel, S., 1956. Nonparametric statistics for the behavioral sciences. MC Graw-Hill Kogakusha Ltd. London: 312 pp.

Sokal, R. & F. Rohlf, 1969. Biometry. The principles and practice of statistics in biological research. W. H. Freedman and company. San Francisco: 776 pp.

Tuffery, G. & J. Verneaux, 1968. Mtthode de determination de la qualitt biologique des eaux courantes. Exploitation coditite des inventaires de la faune du fond. Minist‘ere de 1’Agriculture (France), Centre National d’Etudes techni- ques et de recherches technologiques pour l’agriculture, les forets et l’equipement rural ,,C.E.R.A.F.E.R.“, Section Peche et Pisciculture, 23 pp.

Vandelannoote, A.,B. Bruylants & R. F. Verheyen, 1986. De relatie van de visfauna tot de vervuiling in de Grote en de Kleine Nete. Water 28: 73-82.

Vanhooren, G. & K. De Brabander, 1982. Methode ter beoordeling van de biologische waterkwaliteit van de waterlopen. Bepaling van de biotechnische index (Bel- gische variante) steunende op aquatische macroinverte- braten. Water 6: 199-203.

Vanhooren, G. & P. Dehavay, 1979. Biological water assess- ment methods. 3” technical seminar I.H.E. ENV.395/ 78EN: 34 pp.

Vanhooren, G., N. De Pauw, J. Verreth en T. Vercauteren, 1979. Kaart van de biologische kwaliteit van de waterlopen in Belgie. Leefmilieu. Ministerie van Volksgezondheid en van het Gezin.

Vercruysse, M., 1979. Studie van de oppervlaktewaters van het hydrogratische bekken van de Grote en de Kleine Nete. BECEWA. Centrum voor Studie van Water Bodem en Lucht. 128 pp.

Woodiwiss, F., 1964. The biological system ofstream classiti- cation used by the Trent River Board. Chemistry and Industry 14: 443-447.