Regional synthesis of algal community change in the lakes and tarns of the Windermere catchment, Lake District, UK, since the 19th century

The rural Windermere catchment, English Lake District, UK comprises 11 upland and lowland lakes which feed into Windermere, England’s largest lake. Palaeolimnological algal records, alongside long-term climate and catchment land use monitoring data from all basins in the catchment were used to quantify the relative importance of regional and local-scale drivers of algal community change. Like many temperate lakes, Mann-Kendall trends showed increased concentrations of total algal production and cyanobacteria accompanied by declines in C/N ratios across the Windermere catchment over the last few centuries. Regression tree analyses suggest that nutrient enrichment has an overarching effect, with temperature playing a secondary role. Synchrony and breakpoint analyses suggested that local forcings led to catchment-wide asynchrony of algal communities after the 1950s. In the lowlands (<100 m.a.s.l), 20th century wastewater treatment installation explained the greatest changes in the algal communities, overriding agricultural intensification, but at sites without point sources, correlations to variables that indirectly explain sewage expansion such as resident catchment human populations were apparent. In contrast, algal community change in upland lakes was more responsive to atmospheric pollutants which caused acidification in the late 19th and early 20th century, alongside climatic variables notably temperature. Evidence for upland atmospheric nitrogen deposition in the 20th century was suggested by decreasing stable δ15Norg isotope values, concurrent with increased concentrations of Chlorophyll a (from all algae) but no clear response was found in algal compositional changes. Higher algal community change occurred in lakes with longer residence times overlaying sedimentary geologies typically in the lowlands. However, algal community change was also high in lowland lakes with lower residence times that had point sources, suggesting centennial-scale fertilisation had reduced the ability of local lake characteristics to attenuate environmental change. This work demonstrates that lakes within a few kilometres of one another respond uniquely to environmental change depending on physical characteristics and landscape position. Management measures should focus on reducing nutrients from waste water effluent and develop local stewardship programmes to increase environmental awareness in the region

Regional synthesis of algal community change in the lakes and tarns of the Windermere catchment, Lake District, UK, since the 19th century

The rural Windermere catchment, English Lake District, UK comprises 11 upland and lowland lakes which feed into Windermere, England’s largest lake. Palaeolimnological algal records, alongside long-term climate and catchment land use monitoring data from all basins in the catchment were used to quantify the relative importance of regional and local-scale drivers of algal community change. Like many temperate lakes, Mann-Kendall trends showed increased concentrations of total algal production and cyanobacteria accompanied by declines in C/N ratios across the Windermere catchment over the last few centuries. Regression tree analyses suggest that nutrient enrichment has an overarching effect, with temperature playing a secondary role. Synchrony and breakpoint analyses suggested that local forcings led to catchment-wide asynchrony of algal communities after the 1950s. In the lowlands (<100 m.a.s.l), 20th century wastewater treatment installation explained the greatest changes in the algal communities, overriding agricultural intensification, but at sites without point sources, correlations to variables that indirectly explain sewage expansion such as resident catchment human populations were apparent. In contrast, algal community change in upland lakes was more responsive to atmospheric pollutants which caused acidification in the late 19th and early 20th century, alongside climatic variables notably temperature. Evidence for upland atmospheric nitrogen deposition in the 20th century was suggested by decreasing stable δ15Norg isotope values, concurrent with increased concentrations of Chlorophyll a (from all algae) but no clear response was found in algal compositional changes. Higher algal community change occurred in lakes with longer residence times overlaying sedimentary geologies typically in the lowlands. However, algal community change was also high in lowland lakes with lower residence times that had point sources, suggesting centennial-scale fertilisation had reduced the ability of local lake characteristics to attenuate environmental change. This work demonstrates that lakes within a few kilometres of one another respond uniquely to environmental change depending on physical characteristics and landscape position. Management measures should focus on reducing nutrients from waste water effluent and develop local stewardship programmes to increase environmental awareness in the region

Citizen scientists filling knowledge gaps of phosphate pollution dynamics in rural areas

In situ monitoring is fundamental to manage eutrophication in rivers and streams. However, in recent decades, the frequency and spatial coverage of regulatory monitoring have often been reduced due to funding and infrastructure limitations. This reduction has made it impossible to provide adequate coverage for most water bodies. In this study, trained citizen scientists filled spatial and temporal gaps in agency monitoring across a major catchment in rural England. By integrating data from citizen scientists, regulatory agencies, and the local water company, it was possible to demonstrate the opportunities for hypothesis-based citizen scientist monitoring to identify continuous and event-driven sources of phosphate pollution. Local citizen scientists effectively covered important spatial gaps, investigating river conditions both upstream and downstream of suspected pollution point sources, improving the identification of their temporal dynamics. When combined with long-term monitoring data from regulatory agencies, it became possible to identify areas within the catchment that exhibited increased phosphate concentrations during periods of low river discharge (summer). Inter-annual trends and anomaly detection suggested that continuous pollution sources dominated over event-driven sources in many sub-basins, allowing for the prioritisation of mitigation actions. This study highlights the opportunity for citizen scientists to fill gaps in regulatory monitoring efforts and contribute to the improved management of eutrophication in rural catchments

Investigating the role of hydrological connectivity on the processing of organic carbon in tropical aquatic ecosystems

Inland waters are highways of carbon and nutrient flows between the land and ocean. Aquatic environments integrate multiple sources and processes over space and time that influence ecosystem functionality. The complexity of these systems and their multiple interactions with the surrounding environment are conceptualised, but often lack empirical scrutiny that allows further understanding of how inland waters mobilise, transport, and utilise carbon and nutrients. This is particularly evident in tropical waters. Here, we apply advanced geochemical analyses of dissolved organic matter (DOM) composition in conjunction with algal pigment biomarkers, to determine the seasonal variability of organic matter production, processing and export for a tropical, floodpulse wetland, Tasik Chini (Malaysia). We identify two phases in the hydrological cycle: Phase 1 signifying a transition from the wet season with high suspended sediment and dissolved organic carbon concentrations. DOM is composed of humic substances, building blocks and lower molecular weight compounds. Towards the end this phase then are periods of increased water clarity and algal productivity. This is followed by Phase 2, which has a greater contribution of autochthonous DOM, composed of proteinaceous material, concomitant with lower dissolved nutrient concentrations, increased mixotrophic algae and emergent vegetation. Based on this framework, we highlight the role of such tropical wetland lakes as hydrological “bottlenecks,” through a lentic/lotic switch that shifts aquatic transport of carbon and nutrients from lateral river continuum supply to flood pulses. We highlight the need to consider inherent biases of spatial and temporal scaling when examining freshwater ecosystems along the land-ocean aquatic continuum

Using lake sediments to assess the long-term impacts of anthropogenic activity in tropical river deltas

Tropical river deltas, and the social-ecological systems they sustain, are changing rapidly due to anthropogenic activity and climatic change. Baseline data to inform sustainable management options for resilient deltas is urgently needed and palaeolimnology (reconstructing past conditions from lake or wetland deposits) can provide crucial long-term perspectives needed to identify drivers and rates of change. We review how palaeolimnology can be a valuable tool for resource managers using three current issues facing tropical delta regions: hydrology and sediment supply, salinisation and nutrient pollution. The unique ability of palaeolimnological methods to untangle multiple stressors is also discussed. We demonstrate how palaeolimnology has been used to understand each of these issues, in other aquatic environments, to be incorporated into policy. Palaeolimnology is a key tool to understanding how anthropogenic influences interact with other environmental stressors, providing policymakers and resource managers with a ‘big picture’ view and possible holistic solutions that can be implemented

Deciphering long-term records of natural variability and human impact as recorded in lake sediments: a palaeolimnological puzzle

Global aquatic ecosystems are under increasing threat from anthropogenic activity, as well as being exposed to past (and projected) climate change, however, the nature of how climate and human impacts are recorded in lake sediments is often ambiguous. Natural and anthropogenic drivers can force a similar response in lake systems, yet the ability to attribute what change recorded in lake sediments is natural, from that which is anthropogenic, is increasingly important for understanding how lake systems have, and will continue to function when subjected to multiple stressors; an issue that is particularly acute when considering management options for aquatic ecosystems. The duration and timing of human impacts on lake systems varies geographically, with some regions of the world (such as Africa and South America) having a longer legacy of human impact than others (e.g., New Zealand). A wide array of techniques (biological, chemical, physical and statistical) is available to palaeolimnologists to allow the deciphering of complex sedimentary records. Lake sediments are an important archive of how drivers have changed through time, and how these impacts manifest in lake systems. With a paucity of ‘real-time’ data pre-dating human impact, palaeolimnological archives offer the only insight into both natural variability (i.e., that driven by climate and intrinsic lake processes) and the impact of people. While there is a need to acknowledge complexity, and temporal and spatial variability when deciphering change from sediment archives, a palaeolimnological approach is a powerful tool for better understanding and managing global aquatic resources

Deciphering long-term records of natural variability and human impact as recorded in lake sediments: a palaeolimnological puzzle

Global aquatic ecosystems are under increasing threat from anthropogenic activity, as well as being exposed to past (and projected) climate change, however, the nature of how climate and human impacts are recorded in lake sediments is often ambiguous. Natural and anthropogenic drivers can force a similar response in lake systems, yet the ability to attribute what change recorded in lake sediments is natural, from that which is anthropogenic, is increasingly important for understanding how lake systems have, and will continue to function when subjected to multiple stressors; an issue that is particularly acute when considering management options for aquatic ecosystems. The duration and timing of human impacts on lake systems varies geographically, with some regions of the world (such as Africa and South America) having a longer legacy of human impact than others(e.g. New Zealand). A wide array of techniques (biological, chemical, physical and statistical) is available to palaeolimnologists to allow the deciphering of complex sedimentary records. Lake sediments are an important archive of how drivers have changed through time, and how these impacts manifest in lake systems. With a paucity of ‘real‐time’ data pre‐dating human impact, palaeolimnological archives offer the only insight into both natural variability (i.e. that driven by climate and intrinsic lake processes) and the impact of people. Whilst there is a need to acknowledge complexity, and temporal and spatial variability when deciphering change from sediment archives, a palaeolimnological approach is a powerful tool for better understanding and managing global aquatic resources

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570