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BZ1 413 INSTITUT FÜR HOCHGEBiRGSfORSCl|jNG

. v ■ FQRSCHUNGSitöTITUT DER UNWEÄSITÄT INNSBRUCK

A-6020 INNSßRlJCK,'UniversitätS5trat3o 4

Vcrh. Inccrmt Vrmn Limno!

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THe influence of organic pollution of the macroinvertebrate

communities of mountain streams

Marta Margrejter-Kownacka

With 1 figure in the text

As was already pointed out by Starmach (1956), Slädecek (1973), and Starmach et al. (1978), a

detaiicd quantitative investigation of the macrofauna communities may lead to the answer to the

questvon: To what extent do these communities change, due to envtronmental conditions and due

to the influence of human activity, as well as what is the direction of the changes?

Studies of macrofauna communities in the mountain streams and rivers in different environ-

mental conditions were initiated and supponed by Prof. Dr. Karol Starmach in the Polish Tatra

Mountains in the year 196C. Comparative studies of macrofauna were condueted in the Balkans and

the Caucasus (Kownacka & Kovnacki 1972).

In 1972 comparative studies (Scholarship of Polish Academy of Sciences) of streams in the

Octztal Alps were begun in the region of Obergurgl (Austria, Tyrol) where examination of the in¬

fluence of organic pollution from this tourist centre on the macrofauna of the Gurgler stream was

the objective. Since the year 1975, in parallel with the Obergurgl investigations, observations of

many other Alpine streams and rivers were condueted by the Zoological Institute of the Limnology

Department at Innsbruck University.

It was found that the method, used since 1950 by Polish hydrobiologists, of taking quantitative

samples of the river benthos by means of a hand netpW« SuRBER-sampler (the net used by the au- Siwic{or

thor measured 20 x 20cm - 4 dm 2 with 47um»««tis well-suited to the analvsis of the macrofaunaj^ij/ i. J .

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communities. At the beginning ot our investigations the total volume collected as one sample was

determined and the number of individuals found was related to 2 dm 3 of substratum (Kotnacila

1971; Kotnacki 1971). The statistical analysis done in 1975—76 (Kovnacka & Marcreiter 1978)

showed that the same ränge of statistical error is involved if the calculation in volume terms is left

out (when samples are taken from the surface of the bottom with the entire surface area of the net,

i.e. 4 dm 2 ). It is much easier to compare such samples, calculate the error and the precision of the

observations, as well as the number of samples needed for achieving that precision.

Using always the same method one may compare different streams, although the "individuality

principle" of each stream and river must always be taken into consideration. According to Star¬

mach, each river should be treated individually with all its complexity, as an indivisible dynamic

entity inseparable from its environment, physiography, geological and substratum strueture, phy-

sico-chemical conditions, geographical Situation, climatic zone etc., but there exist certain similar-

ities, especially within the same Zone.

A combination of both these principles seems to be a good solution for investigating rivers. It is

difficult to take as a basis only the generally known, so-called coefficient organisms, it we knovv/' (—(

thai the differences in the macrofauna Content are considerable and that a vanety of factors at'fect

their Contents and development in time. Not knowing the original fauna struetare characteristics

for a jjiven river or Zone, not knowing the Community characteristics of the nver and what changes

they undergo throughout the year, is likely to lead to sweeping and erroneous generalizations.

It was also stated (Margrejter-Kowtjacra in prep.) that Chironomidae (Diptera), a group that

plays a dominant role in the macrobenthos of flowing waters, is in most cases omitted, or eise pre-

sented in a superfivial way. Changes in the dominance of individual subfamilies, groups of species.

or species, as well as in the number of specimens reflect very clearly the changes taking place in the

whole Community. Clear-cut differences ia the taxa were observed depending on the degree of

pollution.

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