ALO docView - Distribution Pattern of epilithic Macrozoobenthos in a small meromictic Lake (Piburger See, Tyrol, Austria) (1995)

Limnologica 25 (2)

(1995)129-140

LIMNOLOGICA

Institut für Zoologie und Limnologie

Universität Innsbruck, Österreich

Distribution Pattern of epilithic Macrozoobenthos in a small

meromictic Lake (Piburger See, Tyrol, Austria)*)

Leopold Füreder

With 6 Figures and 4 Tables

Key words: Lake benthos, hard Substrate, epilithic zoobenthos, epilithic algae, depth distribution,

littoral fauna, Oligochaeta, Crustacea, Chironomidae.

Abstract

For several years Piburger See, a mesotrophic meromictic Tyro-

lean lake, has been the subject of a comprehensive ecosystem

study, designed to produce a holistic picture of the structure and

function of the lake. In earlier investigations of the benthic

Community structure of Piburger See the hard Substrates, which

comprise about 16% of the whole lake bottom, were excluded

because of methodological difficulties. Here a modification of a

sampling method is described which enabled sampling the hard

Substrate quantitatively in a proper way. Zoobenthos was sampled

at six different depths from March to September 1990 by SCUBA

diving. 79 taxa of aquatic invertebrates were found to the hard

Substrates, however, only a few species dominated the benthic

Community. The benthic Community structure was charaterised

by three major taxonomic groups: benthic crustaceans, oligo-

chaetes and chironomid larvae. Canthocamptus staphylinus show-

ed the highest densities, Vejdovskyella comata and Corynoneura

arctica were important taxa within the Oligochaeta and the

Chironomidae. A comparison with earlier studies carried out in

the soft Sediments demonstrates the pecularity and characteristic

of the hard Substrate fauna.

Introduction

Since 1960, Piburger See has been the site of numerous

scientific investigations. Several projects have examined

the Community structure and production of invertebrate

meio- and macrozoobenthos: Chironomidae (Schlott

1976), benthic Crustacea, especially Ostracoda and Cope-

poda (Thaler 1977), Nematoda (Pehofer 1977 & 1989),

Oligochaeta (Girtler 1987), and the benthic Rotatoria

(Buhmann 1981; Gabriel 1981; Pinter 1981).

With the exception of the Rotatoria, which were sampled

from different Substrates of shallow areas in the littoral

zone, all of these investigations were restricted to soft

Sediments. The benthic communities populating hard sub-

strates (i.e. rocks, boulders, stones), which comprise about

16% of the lake area, have not been studied to date.

The surfaces of large rock faces and fields of boulders,

stones, and cobble are probably the most difficult of all

Substrates to sample (Downing 1984). Rock faces must be

cleared of living material in situ, therefore, a diver is required,

especially in deeper water. A hydraulic sampler is probably

the best method for sampling the hard Substrates.

Table 1. Piburger See (Tyrol, Austria): (A) Morphometric para-

meters, according to Girtler (1987), and (B) water budget (values

in mm water column per year, means from 1975 — 1980, according

to Girtler 1987).

(A)

(B)

Surface area (m 2 )

133690

Evaporation

466

Volume (m 3 )

1835000

Surface outflow

3666

Length (m)

800

Oslzewsjy tube

2116

Width (m)

250

Precipitation

751

Shoreline (m)

1900

Surface inflow

3487

Maximum depth (m)

24.6

Groundwater inflow

2102

Mean depht (m)

13.7

Relative depth (%)

5.96

Dedicated to Professor Roland Pechlaner on the occasion of

his 60th birthday

Limnologica 25 (1995) 2

129