Heterogeneity in Esthwaite Water, a Small, Temperate Lake : Consequences for Phosphorus Budgets.

Eutrophication through phosphorus enrichment of lakes is potentially damaging to lake ecosystems, water quality and the ecosystem services which they provide. Traditional approaches to managing eutrophication involve quantifying phosphorus budgets. An important shortcoming of these approaches is that they take little account of the inherent heterogeneity of lakes. Furthermore, most studies of lake heterogeneity have been carried out in large lakes, a situation which reflects neither small lakes' importance in biogeochemical cycling nor their significant contribution to the global sum of lake environments. This thesis reports investigations into heterogeneity in Esthwaite Water, UK, a small, temperate, eutrophic lake. The overarching aim of the work was to improve understanding of phosphorus fluxes and budgets in this type of environment. Heterogeneity, and its governing physical mechanisms were elucidated in the lake's surface waters and bed sediments. In addition, the effects that this heterogeneity had on phosphorus supply to phytoplankton from the main stream inflow and internal sediment sources were examined. The research is presented as four studies, which address surface water heterogeneity, bed sediment heterogeneity, and phosphorus supply via inflowing streams and from internal sediment storage. Significant heterogeneity was found in the surface water, despite the lake being small and the physical forcing, relatively weak. Assumptions about the physical processes contributing to sediment heterogeneity based on models of large or shallow lakes were found not to be applicable. Taking account of bed sediment heterogeneity was found to be important for the accurate calculation of burial rates of both total phosphorus and organic carbon, as ignoring it led to discrepancies up to 110%. Soluble reactive phosphorus (SRP) dispersal in the shallow transition zone at the mouth of the main inflowing stream, and was found to be the result of not only hydrological dilution but also biological uptake. Ignoring SRP heterogeneity in this zone led to up to an 18% underestimate of lake-wide averaged concentration during the growing season. SRP pathways in the lake were both spatially and temporally heterogeneous, resulting in large seasonal and inter-annual variations in phosphorus supply. Internal and external supplies were of similar magnitude during the summer but internal anoxic sources dominated in the late summer and autumn. Inter-annual variation in the hypolimnetic build-up of phosphorus associated with differences in lake stability and mixing strongly affected the internal phosphorus supply. Overall, the thesis concludes that spatial and temporal heterogeneity is a characteristic of this lake at many scales, despite the relative weakness of the governing physical forcing, and that it affects significantly not only the nature of the lake at specific locations, but also lake-wide averaged parameter values. Specifically, different phosphorus sources have distinctly different patterns of variability, which need to be taken into account when calculating phosphorus budgets. Finally, the importance of particular physical processes for phosphorus budgets is likely to differ between large and small lakes owing to the influence of basin morphometry and therefore understanding derived about these budgets in large lakes cannot simply be assumed when considering small lakes

Editorial – A critical perspective on geo-engineering for eutrophication management in lakes

Eutrophication is the primary worldwide water quality issue. Reducing excessive external nutrient loading is the most straightforward action in mitigating eutrophication, but lakes, ponds and reservoirs often show little, if any, signs of recovery in the years following external load reduction. This is due to internal cycling of phosphorus (P). Geo-engineering, which we can here define as activities intervening with biogeochemical cycles to control eutrophication in inland waters, represents a promising approach, under appropriate conditions, to reduce P release from bed sediments and cyanobacteria accumulation in surface waters, thereby speeding up recovery. In this overview, we draw on evidence from this special issue Geoengineering in Lakes, and on supporting literature to provide a critical perspective on the approach. We demonstrate that many of the strong P sorbents in the literature will not be applicable in the field because of costs and other constraints. Aluminium and lanthanum modified compounds are among the most effective compounds for targeting P. Flocculants and ballast compounds can be used to sink cyanobacteria, in the short term. We emphasize that the first step in managing eutrophication is a system analysis that will reveal the main water and P flows and the biological structure of the waterbody. These site specific traits can be significant confounding factors dictating successful eutrophication management. Geo-engineering techniques, considered collectively, as part of a tool kit, may ensure successful management of eutrophication through a range of target effects. In addition, novel developments in modified zeolites offer simultaneous P and nitrogen control. To facilitate research and reduce the delay from concept to market a multi-national centre of excellence is required

Cumbrian lakes: community engagement. Stakeholder meeting 3rd Nov 2020

The Cumbrian Lakes Monitoring Platform provides data and knowledge that contribute to our fundamental understanding of lake ecosystem function, and responses to environmental stressors. To maximise the impact of the work done at the Platform, it is important that we engage with the wider community, including universities, Government agencies, non-governmental organisations, charities, the water industry, and the general public. To assess current levels of engagement, and to identify opportunities to build on this level of engagement, we held a virtual meeting in November 2020. This was attended by 36 delegates from a range of organisations (n=17) actively involved in the management and implementation of government policy in the Cumbrian Lakes. The meeting was hosted by the UKCEH as part of the UK-SCAPE national capability programme. The meeting included presentations from UKCEH staff and stakeholders, Q&A sessions, an online survey, and structured break out discussions. Together, these activities allowed attendees to hear about current research at the Cumbrian Lakes, consider what they need the monitoring to deliver, and make suggestions on what could be delivered by the Platform in the future. These activities revealed that the attendees agreed that the Platform has great value as a means of developing understanding of lake ecology, and responses to stressors. Currently, some of our stakeholders make use of data from the platform to contextualise and commission their own work. However, there is a desire within our community for enhanced visibility of data and knowledge from the Platform, and for the creation of materials giving “expert interpretation” of the data, in a readily accessible form. Following this consultation we propose: • To produce new content on the Cumbrian Lakes Monitoring Platform for the new UKSCaPE website, and to promote this via social media and through emails to the Research Forum community. • To produce infographics on the type of data that we collect and analyse from the lakes, and to show some simple ecosystem state indicators, which can also be hosted on the website, and shared via social media

Development and characterisation of a novel three-dimensional inter-kingdom wound biofilm model

Chronic diabetic foot ulcers are frequently colonised and infected by polymicrobial biofilms that ultimately prevent healing. This study aimed to create a novel in vitro inter-kingdom wound biofilm model on complex hydrogel-based cellulose substrata to test commonly used topical wound treatments. Inter-kingdom triadic biofilms composed of Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus were shown to be quantitatively greater in this model compared to a simple substratum when assessed by conventional culture, metabolic dye and live dead qPCR. These biofilms were both structurally complex and compositionally dynamic in response to topical therapy, so when treated with either chlorhexidine or povidone iodine, principal component analysis revealed that the 3-D cellulose model was minimally impacted compared to the simple substratum model. This study highlights the importance of biofilm substratum and inclusion of relevant polymicrobial and inter-kingdom components, as these impact penetration and efficacy of topical antiseptics

Pink Lady & Sundowner apples

This bulletin summaries for all Australian growers the present technical information concerning Pink Lady and Sundownerhttps://researchlibrary.agric.wa.gov.au/bulletins/1273/thumbnail.jp

Widespread inconsistency in estimation of lake mixed depth impacts interpretation of limnological processes

The mixed layer, or epilimnion, is a physical concept referring to an isothermal layer at the surface of a water body. This concept is ubiquitous within limnology, is fundamental to our understanding of chemical and ecological processes, and is an important metric for water body monitoring, assessment and management. Despite its importance as a metric, many different approaches to approximating mixed depth currently exist. Using data from field campaigns in a small meso-eutrophic lake in the UK in 2016 and 2017 we tested whether different definitions of mixed depth resulted in comparable estimates and whether variables other than temperature could be assumed to be mixed within the layer. Different methods resulted in very different estimates for the mixed depth and ecologically important variables were not necessarily homogenously spread through the epilimnion. Furthermore, calculation of simple ecologically relevant metrics based on mixed depth showed that these metrics were highly dependent on the definition of mixed depth used. The results demonstrate that an idealised concept of a well-defined fully mixed layer is not necessarily appropriate. The widespread use of multiple definitions for mixed depth impairs the comparability of different studies while associated uncertainty over the most appropriate definition limits the confirmability of studies utilising the mixed depths

Evaluating the use of lake sedimentary DNA in palaeolimnology:A comparison with long‐term microscopy‐based monitoring of the phytoplankton community

Palaeolimnological records provide valuable information about how phytoplankton respond to long-term drivers of environmental change. Traditional palaeolimnological tools such as microfossils and pigments are restricted to taxa that leave sub-fossil remains, and a method that can be applied to the wider community is required. Sedimentary DNA (sedDNA), extracted from lake sediment cores, shows promise in palaeolimnology, but validation against data from long-term monitoring of lake water is necessary to enable its development as a reliable record of past phytoplankton communities. To address this need, 18S rRNA gene amplicon sequencing was carried out on lake sediments from a core collected from Esthwaite Water (English Lake District) spanning ~105 years. This sedDNA record was compared with concurrent long-term microscopy-based monitoring of phytoplankton in the surface water. Broadly comparable trends were observed between the datasets, with respect to the diversity and relative abundance and occurrence of chlorophytes, dinoflagellates, ochrophytes and bacillariophytes. Up to 20% of genera were successfully captured using both methods, and sedDNA revealed a previously undetected community of phytoplankton. These results suggest that sedDNA can be used as an effective record of past phytoplankton communities, at least over timescales of <100 years. However, a substantial proportion of genera identified by microscopy were not detected using sedDNA, highlighting the current limitations of the technique that require further development such as reference database coverage. The taphonomic processes which may affect its reliability, such as the extent and rate of deposition and DNA degradation, also require further research