9 research outputs found
Investigations on planktonic crustacea in Lake Balaton VI.: Quantitative changes in the Eudiaptomus gracilis population at variorus regions of Lake Balaton
In the periods of 1965-67 and 1972-73 the authors investigated the
variation of Eudiaptomus gracilis populations on the basis of samples taken
monthly at water areas of different trophic level of Lake Balaton.
In the course of the investigation the following could be stated:
1. The development of the population of the species differs in space and
in seasons. At the south-western end of the lake (section M) where the water
quality is hypertrophic a spring peak of 36-40 per cent frequency was found,
while in the other basin (sections A-E) summer peaks dominated (25—40 p er
cent). In th e middle of the lake mostly spring-autumn peaks were obseved
(20-28 per cent).
2. Adapting the formula of Marczewski-Steinhaus the patterns of
the highest similarity were found at the mesotrophic areas (sections G-A),
while those of the less similarity at sections K-G.
3. In the population the relative quantity of forms of large body size
(females and egg-bearing females) gradually decreases from section A (mesotrophy)
to section M (hypertrophy). Regarding the mean values of the period
1966-67 and 1972, it is seen that the total number of the species is the highest at the south-west end of the lake (11 individuals/litre) gradually decreasing
to the north-east basin (7.2 individuals/litre).
4. The egg-number/egg-sac was found to be the highest in the hypertrophic
south-west basin (14.3) decreasing to 6.2 at the other end of the lake