. Animal Ecology. Animal ecology. I SEP I OCT I NOV I DEC | JAN | FEB | MAR | APR | MAY | JUN | JUL Seasonal plankton populations In western Lake Erie through a year (after Char I AUG I dier 1940). ing of waves is most effective, and the sublittoral zone, which extends from the lower Hmit of wave action to the lower limit of rooted vegetation. Where such vegetation is absent, the sublittoral zone may be considered the bottom of the epilimnion down to the thermocline. The projundal zone is the entire bottom below the rooted vegetation, or commonly the bottom of the hypolimnion. The boundary lin
. Animal Ecology. Animal ecology. I SEP I OCT I NOV I DEC | JAN | FEB | MAR | APR | MAY | JUN | JUL Seasonal plankton populations In western Lake Erie through a year (after Char I AUG I dier 1940). ing of waves is most effective, and the sublittoral zone, which extends from the lower Hmit of wave action to the lower limit of rooted vegetation. Where such vegetation is absent, the sublittoral zone may be considered the bottom of the epilimnion down to the thermocline. The projundal zone is the entire bottom below the rooted vegetation, or commonly the bottom of the hypolimnion. The boundary lines between the zones are variable and change with the depth of the thermo- cline. The open water of the lake above the bottom is known as the limnetic zone. Littoral zone The bottom of the littoral zone may be rock, cobble, gravel, sand, or mud. The muddy shallows of protected bays may have considerable rooted vege- tation ; they are essentially pond habitats. Differen- tiation of species distribution is primarily between the hard bottom and mud bottom habitats; sand bot- tom habitats are transitional (Table 6-2). Sand bot- toms ordinarily have the lowest population of most species clams because they are unstable habi- tats at best; indeed, they are often destructive by reason of the action of sand grains grinding on each other (Rawson 1930, Krecker and Lancaster 1933, Lyman 1956). A lake-bottom and a streambed of similar composition will contain many of the same kinds of organisms because of the similarity in the physical conditions of existence. The respective spe- cies compositions, however, are often different. Oneida Lake in New York has an unusually high mollusk population. Baker (1918) recorded 59 spe- cies and varieties. It is interesting that most of them occurred on mud and sand bottoms. The highest populations were 1890 individuals per m- on mud at depths less than two meters, and 1573 individuals per m- on sand. On rocks and gravels there were only 656 indiv
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
