Asellus and Gammarus spp. (Crustacea) in changing environments: effects of acid stress and habitat permanence.

摘要

The research underlying this thesis included laboratory and field studies on how acid stress affects the benthic crustaceans Asellus aquaticus L. and Gammarus pulex (L.). A laboratory chamber was constructed to study growth and survival of G. pulex during acid stress. Low pH (6.0) caused 64-92% mortality within three weeks and reduced growth rate and food conversion efficiency in surviving animals. In a field experiment along a pH gradient, the mortality of G. pulex increased below pH 6. The whole-body content of sodium and potassium was reduced in surviving individuals, indicating osmoregulatory disturbance. In Asellus aquaticus, mortality was not affected by pH within the tested range (4.3-7.5). Laboratory experiments showed that interspecific interactions between A. aquaticus and G. pulex can include both exploitative competition and predation by G. pulex on A. aquaticus. Effects of seasonal habitat alterations was studied in a lake by comparing invertebrate assemblages associated with two species of submerged macroalgae (Characea), one perennial and one senescent during autumn. (28 refs.).