. Animal Ecology. Animal ecology. and can be expressed only at night (Parker 1902). An alternative explanation is that zooplankton ac- tively orient to a band of optimum light intensity and move up and down at different times to avoid light of too great or too little intensity (Gushing 1951, Hardy and Bainbridge 1954). These diel movements are most widespread among Cladocera and Copepoda, but other species are also involved. One of the most interesting cases is the dipteran larva Chaobonis pnnctipennis that rests on the lake bottom during the daylight hours but is often teeming in the surface
. Animal Ecology. Animal ecology. and can be expressed only at night (Parker 1902). An alternative explanation is that zooplankton ac- tively orient to a band of optimum light intensity and move up and down at different times to avoid light of too great or too little intensity (Gushing 1951, Hardy and Bainbridge 1954). These diel movements are most widespread among Cladocera and Copepoda, but other species are also involved. One of the most interesting cases is the dipteran larva Chaobonis pnnctipennis that rests on the lake bottom during the daylight hours but is often teeming in the surface waters at night. It appears that the buoyancy of this larva varies with the size of its two pairs of air-sacs (Damant 1924). There are a few rotifers, Mysis among the Mala- costraca, and Ceratiinn among the Mastigophora, in which vertical day and night movements have been demonstrated (Pennak 1944). Seasonal distribution The different species of plankton vary in their response to seasonal changes in the physical and chem- ical nature of the water, in number of generations per year, and in time of occurrence. Accordingly there is a marked seasonal variation in total numbers dur- ZOOPLANKTON PER LITER 25 50 75. 5000 4000 3000 2000 1000 0 0 1000 2000 ALGAE PER LITER 3000 4000 5000 6000 FIG. 6-6 Vert oligotrophlc I Note that the horizontal distribution of net plankton (left) in an and (right) in a eutrophic lake, Wisconsin. different for the two lakes, and for the algae as compared with the looplankton. The cross- hatched horizontal belts show the region of the thermocline (from Birge and Juday 191 I). 68 Habitats, communities, succession. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kendeigh, S. Charles (Samuel Charles), 1904-. Englewood Cliffs, N. J. , Prentice-Hall
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
