116 research outputs found
Experiments with lake phytoplankton in large enclosures
The use of large plastic enclosures, or 'Lund tubes', in lakes as a semi-natural basin for experiments, approximating to lakes within lakes, is discussed. The advantages and disadvantages of the tubes were studied, and the results of investigations into the validity of studies using such tubes and the effects of fertilisers on phytoplankton are presented
The phytoplankton of an enriched, soft-water lakel subject to intermittent hydraulic flushing (Grasmere, English Lake District)
This paper describes some characteristic features of the phytoplankton of Grasmere, one of the smaller of the principal lakes of the English Lake District, and attempts to relate these to distinctive physical and chemical properties of the lake. Quantitative data presented herein are derived from 5-m vertical column samples, collected with a flexible polyethylene hose close to the deepest point of Grasmere, generally at intervals of 14 days ( 7 days from 1972 to 1978, inclusive). The study concludes that although Grasmere has been subject to increased phosphorus-loading and has quickly developed many features associated with eutrophication, the composition of its plankton has retained the characteristics of a mesotrophic, soft-water lake: a vernal diatom maximum, generally dominated by Asterionella, is followed by summer growths of nanoplanktonic species, of various colonial Chlorophyceae, before a substantial return to Asterionella-dominance in the autumn
Investigations on phytoplankton with special reference to water usage
Experiments and observations on the phytoplankton of certain lakes in the English Lake District were made from early 1973 to the end of March, 1974. They included laboratory and lake bioassays and observations on the quantity and quality of the phytoplankton in six lakes. The introductory sections of the report are about algae, the ecology of phytoplankton and the scope of the contracted work. Laboratory bioassays on water from one lake, Blelham Tarn, showed that phosphorus, silicon (for diatoms) and organic substances forming complexes with iron were the major substances limiting the growth of the algae tested. The growth of the test algae was limited to different degrees by those substances and, to some extent, to a greater or lesser degree at different times of year. It is suggested that a relatively simple form of bioassay could give valuable information to water undertakings. Lake bioassays and other experiments were carried out by using large in situ tubular plastic enclosures. Two such investigations are described. The effects of a change in sewerage in two drainage basins on the phytoplankton of three lakes is described and some data given about changes since 1945 in three other lakes in the same overall drainage basin. These latter lakes have been affected too by changes in sewerage and by increasing inputs of domestic and agricultural wastes. Throughout, the relevance of the work done to practical problems of water usage is kept in mind and discussed. In the last section special reference is made to the largely unpredictable results of water transfers. The report ends with a note on river phytoplankton
Algal nutrient competition in continuous culture
Natural phytoplankton from Lake Constance was exposed to competition experiments in continuous culture at 6 different molar rations of PratioSi as potentially limiting nutrients. As predicted by theory there was competitive exclusion of all species but one at single nutrient limitation, and coexistence of two species in steady state when P was limiting for one and Si for the other species. In one case coexistence of three species occurred. Equilibrium species composition, which stabilized after 3 to 6 weeks of cultivation, was independent of the species composition of the inoculum and only controlled by the nutrient regime. Comparability of experimental results and field observations is discussed
Phenotypic plasticity as a clue for the invasion success of the submerged aquatic plant Elodea nuttallii
Two closely related alien submerged aquatic plants were introduced into Europe. The
new invader (Elodea nuttallii) gradually displaced E. canadensis even at sites where the
latter was well established. The aim of the study was to evaluate the combined effects
of environmental factors on several phenotypic characteristics of the two Elodea species, and to relate these phenotypic characteristics to the invasion success of E. nuttallii
over E. canadensis. In a factorial design, Elodea plants were grown in aquaria containing five different nitrogen concentrations and incubated at five different light intensities. We used six functional traits (apical shoot RGR), total shoot RGR, relative elongation, root length, lateral
spread, branching degree) to measure the environmental response of the species. We
calculated plasticity indices to express the phenotypic differences between species. Light and nitrogen jointly triggered the development of phenotypic characteristics that
make E. nuttallii a more successful invader in eutrophic waters than E. canadensis. The
stronger invader showed a wider range of phenotypic plasticity. The apical elongation
was the main difference between the two species, with E. nuttallii being more than two
times longer than E. canadensis. E. canadensis formed dense side shoots even under
high shade and low nitrogen levels, whereas E. nuttallii required higher light and
nitrogen levels. We found that under more eutrophic conditions, E. nuttallii reach the water surface
sooner than E. canadensis and through intensive branching outcompetes all other
plants including E. canadensis. Our findings support the theory that more successful
invaders have wider phenotypic plasticit
Feed of Siamese fighting fish, Betta splendens, (Regan, 1910) in open pond: live and formulated diets
Factors regulating recruitment from the sediment to the water column in the bloom-forming cyanobacterium Gloeotrichia echinulata
Structure and dynamics of the community of periphytic algae in a subtropical reservoir (state of São Paulo, Brazil)
Rivers affect the biovolume and functional traits of phytoplankton in floodplain lakes
- …