No abstract

No abstract

Inland and coastal waterbodies are critical components of the global biosphere. Timely monitoring is necessary to enhance our understanding of their functions, the drivers impacting on these functions and to deliver more effective management. The ability to observe waterbodies from space has led to Earth observation (EO) becoming established as an important source of information on water quality and ecosystem condition. However, progress toward a globally valid EO approach is still largely hampered by inconsistences over temporally and spatially variable in-water optical conditions. In this study, a comprehensive dataset from more than 250 aquatic systems, representing a wide range of conditions, was analyzed in order to develop a typology of optical water types (OWTs) for inland and coastal waters. We introduce a novel approach for clustering in situ hyperspectral water reflectance measurements (n 5 4045) from multiple sources based on a functional data analysis. The resulting classification algorithm identified 13 spectrally distinct clusters of measurements in inland waters, and a further nine clusters from the marine environment. The distinction and characterization of OWTs was supported by the availability of a wide range of coincident data on biogeochemical and inherent optical properties from inland waters. Phylogenetic trees based on the shapes of cluster means were constructed to identify similarities among the derived clusters with respect to spectral diversity. This typification provides a valuable framework for a globally applicable EO scheme and the design of future EO missions.

Water temperature is critical for the ecology of lakes. However, the ability to predict its spatial and seasonal variation is constrained by the lack of a thermal classification system. Here we define lake thermal regions using objective analysis of seasonal surface temperature dynamics from satellite observations. Nine lake thermal regions are identified that mapped robustly and largely contiguously globally, even for small lakes. The regions differed from other global patterns, and so provide unique information. Using a lake model forced by 21 st century climate projections, we found that 12%, 27% and 66% of lakes will change to a lower latitude thermal region by 2080-2099 for low, medium and high greenhouse gas concentration trajectories (Representative Concentration Pathways 2.6, 6.0 and 8.5) respectively. Under the worst-case scenario, a 79% reduction in the number of lakes in the northernmost thermal region is projected. This thermal region framework can facilitate the global scaling of lake-research.

No abstract

The NERC and CEH trade marks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. . 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.

Cyanobacterial blooms are an increasing threat to water quality and global water security caused by the nutrient enrichment of freshwaters. There is also a broad consensus that blooms are increasing with global warming, but the impacts of other concomitant environmental changes, such as an increase in extreme rainfall events, may affect this response. One of the potential effects of high rainfall events on phytoplankton communities is greater loss of biomass through hydraulic flushing. Here we used a shallow lake mesocosm experiment to test the combined effects of: warming (ambient vs. +4°C increase), high rainfall (flushing) events (no events vs. seasonal events) and nutrient loading (eutrophic vs. hypertrophic) on total phytoplankton chlorophyll‐a and cyanobacterial abundance and composition. Our hypotheses were that: (a) total phytoplankton and cyanobacterial abundance would be higher in heated mesocosms; (b) the stimulatory effects of warming on cyanobacterial abundance would be enhanced in higher nutrient mesocosms, resulting in a synergistic interaction; (c) the recovery of biomass from flushing induced losses would be quicker in heated and nutrient‐enriched treatments, and during the growing season. The results supported the first and, in part, the third hypotheses: total phytoplankton and cyanobacterial abundance increased in heated mesocosms with an increase in common bloom‐forming taxa—Microcystis spp. and Dolichospermum spp. Recovery from flushing was slowest in the winter, but unaffected by warming or higher nutrient loading. Contrary to the second hypothesis, an antagonistic interaction between warming and nutrient enrichment was detected for both cyanobacteria and chlorophyll‐a demonstrating that ecological surprises can occur, dependent on the environmental context. While this study highlights the clear need to mitigate against global warming, oversimplification of global change effects on cyanobacteria should be avoided; stressor gradients and seasonal effects should be considered as important factors shaping the response.

Described below are observations which seem to account, in large part at least, for the normal resistance of the mouse's intestinal tract to infection with Salmonella enteritidis introduced by mouth, the natural route of infection. Thus inoculated, about 106 microorganisms are required to infect 50 per cent of young adult CF-1 mice (1). Their resistance, however, can be sharply reduced by the oral administration of a single, large dose of streptomycin, for during the following 24 hours, < 10 microorganisms of the same strain suffice to initiate infection (2, 3). Of the changes in the mouse's enteric microflora resulting from streptomycin treatment, the most consequential was thought to be the elimination of certain obligate anaerobes belonging to the genus Bacteroides (4,5). The experiments to be described demonstrate that multiplication of S. enteritidis was inhibited in vitro by: (a) centrifuged supernatants of heatkilled suspensions of colon content or feces of normal, i.e. untreated mice; (b) anaerobic cultures of such materials; (c) anaerobic cultures of Bacteroides isolated from them; (d) two fatty acids (acetic and butyric) recovered from bowel content and also from cultures of Bacteroides. In all these experiments, the degree of inhibitory activity was always dependent upon pH and was always greater under anaerobic conditions which simulated those within the colon content in vivo.As will be shown in the following communication inhibitory activity was never demonstrable with suspensions of colon content or feces of mice treated by mouth with streptomycin on the preceding day. The following paper (6) also describes changes in the chemical constituents and the pH of colon content which follow such treatment and are associated with enhanced susceptibility. MethodsMice were CF-1 females, approximately 9 weeks old, obtained from the same source as those used in earlier experiments. (1, 3, 5).Inoculations and treatments were per os; i.e., by stomach tube.The test microorganism was the same streptomycin-resistant strain of S. enteritidis previously used. (1) In Vitro Inhibition Tests.--(a) Plate assay: Inhibition of S. enteritidis on surface culture was determined thus: Nutrient agar containing 1 mg/ml of streptomycin 1 was buffered with phosphate to a desired pH and 15 ml pipetted into Petri dishes to insure uniform depth. Each assay was made on 3 agars of different pH, usually 5.5, 6.0, and 6.5. The surface was seeded with approximately 5000 S. enteritidis suspended in saline, and 3 or 4 paper discs 2 were placed on the agar and moistened with 0.1 ml of the material to be tested. For anaerobic assay, the plates were put immediately into a Brewer jar. All plates were then kept in a refrigerator 7 hours to permit diffusion of any inhibitory substance before incubation. After 16 hours' incubation, bacteriostatic activity was estimated by measuring the zones of inhibition. These were frequently double: an inner one of complete inhibition surrounded by an outer zone of tiny colonies just visible to the naked eye. ...