Ref ID : 1631
Judith I. Elliott; Seasonal changes in the abundance and distribution of planktonic rotifers in Grasmere (English Lake District). Freshwater Biology 7:147-166, 1977
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The planktonic rotifers of Grasmere, a small lake in the English Lake District, were studied from August 1969 to December 1972. Twenty-four species were recorded but five were very rare. The remaining species were divided into three groups according to their seasonal occurrence: spring to autumn species (Keratella quadrata, K. cochlearis, Gastropus stylifer, Asplanchna priodonta, Kellicottia longispina, Conochilus hippocrepis), spring to early summer species (Polyarthra dolichoptera, Synchaeta tremula, S. pectinata, S. stylata, S. oblonga, C. unicornis), summer to autumn species (Polyarthra vulgaris, P. major, Filinia terminalis, S. grandis, Ploesoma hudsoni, Trichocerca capucina, T. similis). The months in which each species was abundant are given. Keratella quadrata and Filinia terminalis were most abundant in the deepest stratum, Kellicottia longispina and Conochilus spp. were most abundant in the upper and middle strata, Trichocerca spp. showed no pronounced vertical distribution, and all the remaining species were most abundant in the upper stratum. Keratella cochlearis and Kellicottia longispina attained their highest densities over a wide range of temperature and oxygen concentration. Filinia terminalis, Conochilus spp., Asplanchna priodonta, K. quadrata, and Polyarthra spp., attained their highest densities within a narrow range of temperature and oxygen concentration. Optimum ranges are given for each species. Major changes occurred between 1971 and 1972 when Asplanchna priodonta, Kellicottia longispina, Conochilus unicornis and Filinia termanilis increased in abundance, whilst Keratella quadrata, Gastropus stylifer, C. hippocrepis, Polyarthra spp., Synchaeta spp. and Ploesoma hudsoni decreased in abundance. These changes are discussed in relation to the temperature and oxygen requirements of each species and also to the probable enrichment of the lake after the opening of a new sewage works in June 1971.