The seasonal and spatial distribution of some benthic ciliated Protozoa in Esthwaite Water

Abstract

oxygen concentrations and other physical and chemical parameters were determined in the bottom water at five sites (depths 14, 12, 8, 5 and 3 m) in Esthwaite Water in the English Lake District. In winter the bottom water at all five sites was oxygenated; while in summer, conditions at the deeper sites became anaerobic and concentrations of sulphide, ammonia and carbon dioxide increased.During the same period, some benthic ciliated Protozoa were counted at the same five sites. The species considered were Loxodes magnus, L. striatus, Frontonia leucas, Spirostomum minus, S. teres, Stentor coeruleus, S. polymorphus and Caenomorpha medusula and populations were assessed as number of individuals per 01 ml of sediment. It was found that: (1) the most dense populations tended to be at the deeper sites; (2) population maxima generally occurred when the bottom water was oxygenated (except for C. medusula) and; (3) there was, over the 21 months, considerable irregularity in the size and timing of population maxima.In March-April 1970, population densities of benthic ciliates, at the five sites, were measured in terms of individuals per cm^ of lake bottom. Population densities decreased with decrease in site depth. The availability of food organisms, turbulence and sediment texture were considered as factors which might control this distribution.

The hypolimnetic protozoan plankton of a eutrophic lake

“…and Frontonia leucas were typically found when oxygen was available. A later investigation of benthic ciliates in 1969-70 at a range of depths between 15-2 metres confirmed much of Webb's data, and also provided a quantitative dimension (Goulder, 1974). Goulder found, as we did, that Loxodes magnus was the dominant member of the genus, and although he found it at shallow sites, it was always most abundant at sites below the thermocline.…”

“…In such lakes the benthic protozoan community undergoes a gradual change in species composition as anoxia becomes established (Webb, 1961;Goulder, 1974;Bark, 1981;Finlay, 1981). While some benthic species disappear completely during anoxia, and presumably encyst, others undergo migration into the water column (Bark, 1981;Finlay, 1981), where they effectively become an element of the planktonic community grazing on planktonic bacteria and elements of the phytoand microzooplankton.…”

“…Moreover, in one case (Finlay,198 1) the investigation concentrated specifically on large ciliates including Loxodes spp. There is evidence that the benthic community of Esthwaite shows differences in its composition and the densities of constituent species at different depths (Goulder, 1974). A significant portion of the bottom of most lakes is above the thermocline during stratification and is therefore not subject to anoxia.…”

Seasonal development of hypolimnetic ciliate communities in a eutrophic pond

“…The hypolimnia of productive lakes harbour diverse protozoan communities with a characteristic species composition [1][2][3][4]. If anoxic conditions develop, protozoa become the principal or 294 obic metabolism leads to short food chains [5].…”

Water column anoxia: vertical zonation of planktonic protozoa

“…When stratification is seasonal, the development of an anoxic hypolimnion is accompanied by an exodus of otherwise benthic ciliates which find their preferred oxygen tension in the water column and even the obligatory anaerobes become planktonic. The eukaryote plankton of hypoxic waters is almost, a n d in the case of anoxic water exclusively, composed by protozoa (Goulder 1972, 1974, Finlay 1980, Bark 1981.…”