Cyanobacterial blooms: statistical models describing risk factors for national-scale lake assessment and lake management

Cyanobacterial toxins constitute one of the most high risk categories of waterborne toxic biological substances. For this reason there is a clear need to know which freshwater environments are most susceptible to the development of large populations of cyanobacteria. Phytoplankton data from 134 UK lakes were used to develop a series of Generalised Additive Models and Generalised Additive Mixed Models to describe which kinds of lakes may be susceptible to cyanobacterial blooms using widely available explanatory variables. Models were developed for log cyanobacterial biovolume. Water colour and alkalinity are significant explanatory variables and retention time and TP borderline significant (R2adj = 21.9 %). Surprisingly, the models developed reveal that nutrient concentrations are not the primary explanatory variable; water colour and alkalinity were more important. However, given suitable environments (low colour, neutral-alkaline waters), cyanobacteria do increase with both increasing retention time and increasing TP concentrations, supporting the observations that cyanobacteria are one of the most visible symptoms of eutrophication, particularly in warm, dry summers. The models can contribute to the assessment of risks to public health, at a regional- to national level, helping target lake monitoring and management more cost-effectively at those lakes at highest risk of breaching World Health Organisation guideline levels for cyanobacteria in recreational waters. The models also inform restoration options available for reducing cyanobacterial blooms, indicating that, in the highest risk lakes (alkaline, low colour lakes), risks can generally be lessened through management aimed at reducing nutrient loads and increasing flushing during summer

The Scientific Mission and the Freedom of Research

This chapter takes at its starting point that an academic scientist or scholar, regardless of discipline, must be to produce knowledge, rather than mere opinion. By virtue of his fulfilling this mission, he also supports and contributes to a form of deliberative dialog, the sine qua non for citizenship in liberal democracies, in which argument on the basis of fact and coherence, rather than rhetorical tricks and powers of persuasion, is decisive. Demands for social relevance and usefulness ought to be seen in light of this mission, rather than in terms of political utility or commercial gain. In this sense, the requirement that the university produce useful knowledge is entirely commensurable with academic freedom, provided that politicians, administrators, and business leaders recognize that they cannot determine what questions ought to be asked or how best to answer them, but leave that matter to scientists and scholars to decide.</p

Nutrient ratios and phytoplankton community structure in the large, shallow, eutrophic, subtropical Lakes Okeechobee (Florida, USA) and Taihu (China)

Analysis of ten- and four-year datasets for the large, shallow, subtropical, and eutrophic Lakes Okeechobee (USA) and Taihu (China), respectively, suggest that resource-ratio explanations for cyanobacteria dominance may not apply to these two lakes. Datasets were examined to identify relationships between nutrient ratios [total nitrogen (TN):total phosphorus (TP) and ammonium (NH4+):oxidized N (NOx)] and phytoplankton community structure (as proportions of cyanobacteria and diatoms to total phytoplankton biomass). Datasets were pooled by sampling month, averaged lake-wide, and analyzed with linear regression. In Okeechobee, the cyanobacteria proportion increased and the diatom proportion decreased with increasing TN:TP. In Taihu, cyanobacteria decreased with increasing TN:TP, but the opposite trend observed for diatoms was marginally significant. Okeechobee cyanobacteria increased and diatoms decreased with increasing NH4+:NOx, but no significant relationships between phytoplankton and NH4+:NOx were observed in Taihu. Both lakes had significant relationships between phytoplankton community structure and total nutrients, but these relationships were the opposite of those expected. Relationships between phytoplankton community structure and water quality parameters from the previous month resulted in improved relationships, suggesting a predictive capability. Statistical analysis of the entire datasets (not pooled) supported these and additional relationships with other parameters, including temperature and water clarity

Seasonal variation in effects of urea and phosphorus on phytoplankton abundance and community composition in a hypereutrophic hardwater lake

© 2020 The Authors. Freshwater Biology published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.1. Urea accounts for half of global agricultural fertiliser applications, yet little is known of its role in eutrophication of freshwater ecosystems, nor how it interacts with phosphorus (P) in regulating phytoplankton composition, especially during spring and autumn. 2. To identify when and how urea and P inputs interact across the ice-free period, we conducted seven monthly fertilisation experiments in 3,240-L mesocosms from ice-off to ice-formation in a hypereutrophic lake. In addition, we ran bioassays with ammonium (NH 4 +) to compare the effects of urea with those of NH 4 +, the immediate product of chemical decomposition of urea. 3. Analysis of water-column chlorophyll a and biomarker pigments by high-perfor- mance liquid chromatography revealed that addition of inorganic P alone (100 μg P L–1 week–1) had no significant impact on either algal abundance or community composition in hypereutrophic Wascana Lake. Instead, fertilisation with urea (4 mg N L−1 week–1) alone, or in concert with P, significantly (p < 0.05) increased algal abundance in spring and much of summer, but not prior to ice formation in October. In particular, urea amendment enhanced abundance of cryptophytes, chlorophytes, and non-diazotrophic cyanobacteria during April and May, while fertilisation in summer and early autumn (September) increased only chlorophytes and non-diazotrophic cyanobacteria. 4. Comparison of urea mesocosms with NH 4 + bioassays demonstrated that urea lacked the inherent toxicity of NH 4 + in cool waters, but that both compounds stimulated production during summer experiments. 5. This study showed that urea pollution can degrade water quality in P-rich lakes across a variety of seasonal conditions, including spring, and underscores the im- portance of quantifying the timing and form of N inputs when managing P-rich freshwaters.his research was funded by grants to P.R.L. from NSERC Canada, Canada Foundation for Innovation, Canada Research Chairs, the Province of Saskatchewan, University of Regina, and Queen's University Belfast.Facultyye