engleski

Size-structure of aquatic insect larvae during colonization

Colonization of aquatic insect larvae was investigated in a second order woodland stream by using trays filled with natural substrate. Patterns of colonization differed significantly between seasons. Highest number of taxa was recorded during the winter (64), and lowest during the summer colonization experiment (38). Density fluctuated strongly during each seasonal experiment, with synchronized first peak after 2 weeks of colonization during spring, summer and autumn. Other observed peaks were consequences of mass colonization of first-instar larvae, especially in late spring. During the winter there were two mass colorizations by simuliid prepupal larvae, probably due to downstream drift. Biomass fluctuated mostly during the winter. During the summer experiment biomass was on average 11 times lower compared to the winter experiment. Abundance-biomass curves suggested seasonal differences in size structure, which was confirmed by seasonal patterns of size classis. Larvae of first (out of five) size class made up 35, 5 % of all colonizers during the spring, highest share of 54, 1 % during the summer, 40, 8% and 17, 5% during the autumn and winter. The percentages of first size class had significant positive correlation with temperature. Seasonal colonization patterns reflected life history attributes of aquatic insects.

colonization; seasons; abundance; biomass; life-cycles

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