Changes in phytoplankton over various time scales in a shallow, eutrophic: the Loch Leven experience with special reference to the influence of flushing rate

1. The pattern of fluctuations in the total biomass and species composition of phytoplankton in the shallow, eutrophic Loch Leven exhibits considerable inter-annual and within-year variability. Nevertheless, studies over the 18-year period reviewed here (1968–85) show that many of the observed changes can be explained in -terms of light regimes and the concentrations and fluxes of nutrients. On occasion, the incidence of fungal parasitism and of protozoan, rotiferan and crustacean grazing is also important. 2. Changes in annual mean algal biomass from very high levels in the late 1960s and early 1970s to somewhat lower levels in the late 1970s, followed by occasional high peaks in the present decade, are attributed to shifts in phosphorus loading-particularly from a P-rich industrial source. 3. In spite of complex and erratic sequences of algal species, seasonal patterns in the size distribution of the phytoplankton assemblage have been identified. However, these also changed. During the 4 years prior to 1971, Daphnia hyalina was not recorded in the plankton, and small algae have been abundant only in late winter or early spring. 4. The potential importance of the weather is highlighted as one of the possible causes of the irregular appearance of algal species. The effect of the characteristically variable, oceanicclimate of Northern Britain on this large (13.3 km2), shallow (= 3.9 m) loch is thought to be of particular importance. 5. The influence of the weather on phytoplankton sequences is explored by comparing records of monthly flushing rate values with time-series data on aspects of the aquatic environment and plankton populations. The preliminary assessment suggests that variation in flushing rate (p) has a considerable effect on temperature regimes and the supplies and in-loch dynamics of nutrients; through such changes, p controls major features of phytoplankton succession such as the temporal abundance of diatoms, as well as detailed sequences of events relating to the development and collapse of particular algal species - and. as a consequence, in some cases, of the animals preying on them. 6. Concluding remarks emphasize how little would have been understood about the functioning of shallow lakes, had the long-term commitment to Loch Leven research been abandoned. The view is also expressed that the findings are of considerably greater relevance to research on 'classic' stratifying lake systems, than the focus on the shallow waterbody might hitherto have suggested

Determination and validation of Henry's constant for ozone in phosphate buffers using different analytical methodologies

Different procedures for measuring the concentration of ozone in aqueous buffered solutions have been reviewed for the determination of Henry s constant at different temperatures and pH. Iodometry, indigo trisulfonate and iron (II) chemical methods were compared with the direct UV absorbance measurement of ozone at 258 nm. From these data a new value for the molar extinction coefficient of ozone is proposed as 3840 ± 109 M^(-)1 cm^(-1). After the verification of the ozone analysis methods, the solubility of ozone in phosphate buffer medium was studied with in-situ absorbance direct measurements in a device with high gas-liquid transference rate, minimizing the gas desorption process on sample manipulation. The decomposition of ozone was not detected at the experimental conditions tested and, consequently, the observed solubility of ozone is constant, with the pH ranging from 2 to 7.6. The solubility of ozone was measured between 5 and 35ºC, resulting in a dimensionless solubility ratio of HB0 = 1.797 exp[0.0277·t(ºC)].J.F. acknowledges the support of the doctoral fellowship from the Universitat Politecnica de Valencia (UPV-PAID-FPI-2010-04).Ferre Aracil, J.; Cardona, SC.; Navarro-Laboulais, J. (2015). Determination and validation of Henry's constant for ozone in phosphate buffers using different analytical methodologies. Ozone: Science and Engineering. 37(2):106-118. https://doi.org/10.1080/01919512.2014.927323S10611837