Diel changes in plankton and water chemistry in Wicken brickpit

Abstract

In a flooded Fenland brickpit 3 metres deep a 24-hr study (supplemented by other observations in the field and in the laboratory) revealed marked changes with depth and time in oxygen concentration, pH, total carbon dioxide, ammonium, oxidised nitrogen, phosphate and silica; as well as changes in the rate of cell-division and the vertical distribution of phytoplankton (Dinobryon and Peridinium), and the feeding and vertical movement of zooplankton (copepods, Bosmina, Ceriodaphnia, Polyarthra and Keratella) . Directional trapping of zooplankton revealed relationships between population density and the intensity of locomotory activity (a relationship subsequently supported by laboratory experiments), and between the rate of change of light intensity and the direction of swimming . Significant temporal segregation of the occupancy of a given level by zooplankters implies interspecific competition . Transient peaks in the concentrations of some nutrients near the surface are tentatively attributed to nutrient release by zooplankters that have fed at depth . Small-scale temporal and spatial heterogeneity of the type described here may help to explain the `paradox of the plankton' .These marked diel changes in water chemistry suggest that conclusions based on the analysis of single water samples should be viewed with caution .

Environmental factors associated with biodiversity and the occurrence of rare, threatened, thermophilous species of aquatic beetles in the anthropogenic ponds of the Masurian Lake District

“…The highest statistically significant differences between the two types of anthropogenic ponds were attributed to electrolytic conductivity, which is an approximate indicator of the amount of dissolved minerals. The EC was much higher in clay than in gravel pits; this difference was supported by higher anion concentration (HCO 3 -, SO 4 2-and Cl -) in agreement with other clay pits (Corbet et al 1980;Jenkin 1982;Lewin and Smolinski 2006).…”

Temperature, hydrochemistry and plankton in Wicken Brickpits, 1930?1931

“…No such measurements have been reported ; but it has been shown recently, in a Canadian Lake, that temperature changes at the surface of the substratum, under only 0 .5 m water, were `closely related' to available energy measured above the water surface (Dale et al 1977) . Light intensity measurements over 24 h near Br were, unfortunately, not related to heating (Corbet et al 1980) . Varying temperature gradients, rather similar to those at Wicken, were reported in the much deeper epilimnion of Windermere, in August 1936 .…”

“…) ; but, until very recently (Corbet et al 1980), the only reference to the hydrochemistry of the Fen waters was a short note by the late J . T .…”

“…Ass . 1966)l was told that one of the Wicken Brickpits (Br) was being used for ecology classes (later published as Corbet et al 1980) and for some new research (Polunin, in press a, b) . I then realised the historical value of this old survey and began to prepare it for publication, with only a few quotations from Saunders' original report (given here in inverted commas) ; but regretfully without his critical collaboration .…”

Seasonal variation in seston and organic matter accumulation in a sheltered fenland pond

“…), is usually brown and somewhat turbid: Secchi-disc transparency is as a rule approximately 1 m. In spite of its shallowness, the water column normally shows a marked gradient in oxygen concentration, pH and in certain ions such as silicate. Further hydrological details of the site can be found in Corbet et al (1980) and Jenkin (in press).…”