|
|
Zooplankton response to a change of water chemistry and amount of food during the recovery of lakes from acidification
Bartošíková, Martina ; Stuchlík, Evžen (advisor) ; Šorf, Michal (referee)
Anthropogenic acidification has affected assemblages in thousands of lakes in North America and Europe. It turned out that, during the acidification, the number of zooplankton changed and also the species composition of their assemblages, at some sites there was also the total disappearance. The main reason was a decrease of pH, wash out toxic aluminium and a change of trophic status. The rate and extent of biological recovery after restoring the pH in acidified lakes varies considerably across regions. Recovery of aquatic communities is significantly lagging behind the recovery in chemistry. Some zooplankton species are nonetheless able to quickly colonize recuperating ecosystems and in many acidified lakes again started to appear native species that have disappeared during acidification. The return of indigenous species, however, can be blocked acid-tolerant occurrence of species after species extinct occupied empty niches. Zooplankton can be affected by water chemistry directly, but also indirectly by the quality and quantity of food. An important factor is the possible spread of colonizing species. However, the relative roles of these factors in regulating recovery may be difficult to determine. Key words: zooplankton, acidification, water chemistry, aluminium toxicity, phytoplankton
|
|
|
Biodiversity of chironomid fauna in mountain lakes and streams influenced by acidification and recovery from acidification.
Černocká, Veronika ; Stuchlík, Evžen (advisor) ; Frouz, Jan (referee)
This thesis examines the influence of acidification on the largest group of macroinvertebrates in mountain lakes and running waters - chironomids. The diversity of chironomids has been associated with temperature, the concentration of dissolved oxygen in the water, the amount of nutrients, and also with the ability to survive in conditions (e.g. extreme pH) that are not suitable for other taxa. Because of this the family Chironomidae has become a dominant group of macrozoobentos in many assemblages affected by acidification. The Bohemian Forest lakes and the Tatra Mountain lakes belong to the most frequently studied locations, which were affected by acidification. The peak of acidification was in the 1980s. It turned out that, during the acidification, the number of chironomids changed and also the species composition of their assemblages. The main reason was a change of trophic status, which chironomids reflected more than a change of pH. A decrease in the number of species occurred after the pH dropped below 5. Until then, only their relative abundance had been affected. Chironomids are also influenced by the toxic effect of Al. The most important factor affecting chironomids fauna is not the value of pH, but the change of food supply. Acid stream food webs are often viewed as being...
|
|
|
Mravenci Formica foreli a konkurenční prostředí v superkolonii na lokalitě Štěměchy
Ošlejšková, Kateřina
In this diploma thesis, the results of Formica foreli Bondroit, 1918, and other ant species in the area of Štěměchy, interspecies relations study are presented. The ant Formica foreli, belonging to subgenus Coptoformica, is a species occured only at stabil and biologicaly valuable sites. Nowadays it occures only in the six locations on the territory of the Czech Republic. Investigated complex of nests, located in Vysočina region, contains 654 nests and at present it is the largest polycalic complex of the nests of this type in the Czech Republic. Collection by ground traps results, confrontation of two worker ants in an artificial arena experiments and competitive interactions on the bait observation, demonstrated, that there is wide spectrum of other ant species in the area, which indicates of good trophy of the site. Further, the results promoted a hypothesis, that thanks to the polycalic nest character, Formica foreli species ocupies the supreme position in hierarchic organization of the whole area.
|
guest ::
