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Lake water quality issue related to algal blooms is a serious problem in basins with abundant agricultural lands, causing harmful effects to freshwater ecosystems and decreasing water quality for human uses. Remote sensing methods have been used to monitor water quality of large lakes and coastal areas; however, few studies have been conducted to understand spectral properties of small lakes. This research explores applicability of Sentinel-2 satellite in understanding spatiotemporal patterns of water quality of two small-sized reservoirs, Lake Bloomington and Evergreen Lake, Central Illinois. We tested the feasibility of Sentinel-2 satellite data for monitoring algal blooms by comparing and calibrating multiple satellite algorithms (e.g., Bottom-of-Atmosphere (BOA) reflectance, Maximum Chlorophyll Index (MCI), and band ratios) against lake water quality indicator variables (e.g., chlorophyll-a, turbidity, secchi depth) obtained from water sample analysis in the laboratory or field measurements. The regression models performed better for Evergreen Lake than Lake Bloomington. Comparison of chlorophyll-a and turbidity with satellite reflectance values showed that suspended sediments contribute to the turbidity in the case of Lake Bloomington, while the algae contribute to the turbidity in Evergreen Lake. Using regression models, water quality indicator maps were created, showing the spatial pattern of algae in the lakes, generally, showing heterogeneous chlorophyll-a distribution, lower in downstream and higher in upstream areas. The study confirmed suitability of Sentinel-2 data for monitoring water quality of less turbid small-sized lake.

To ensure the long-term sustainable use of African Great Lakes (AGL), and to better understand the functioning of these ecosystems, authorities, managers and scientists need regularly collected scientific data and information of key environmental indicators over multi-years to make informed decisions. Monitoring is regularly conducted at some sites across AGL; while at others sites, it is rare or conducted irregularly in response to sporadic funding or short-term projects/studies. Managers and scientists working on the AGL thus often lack critical long-term data to evaluate and gauge ongoing changes. Hence, we propose a multi-lake approach to harmonize data collection modalities for better understanding of regional and global environmental impacts on AGL. Climate variability has had strong impacts on all AGL in the recent past. Although these lakes have specific characteristics, their limnological cycles show many similarities. Because different anthropogenic pressures take place at the different AGL, harmonized multi-lake monitoring will provide comparable data to address the main drivers of concern (climate versus regional anthropogenic impact). To realize harmonized long-term multi-lake monitoring, the approach will need: (1) support of a wide community of researchers and managers; (2) political goodwill towards a common goal for such monitoring; and (3) sufficient capacity (e.g., institutional, financial, human and logistic resources) for its implementation. This paper presents an assessment of the state of monitoring the AGL and possible approaches to realize a long-term, multi-lake harmonized monitoring strategy. Key parameters are proposed. The support of national and regional authorities is necessary as each AGL crosses international boundaries. publishedVersion

Microplastics in the environment can impact feeding and physiological functions of organisms. Most studies have focused on marine systems, and studies of lacustrine organisms are less common. We examined microplastic concentration in 72 gizzard shad and 24 largemouth bass from two agricultural reservoirs in the midwestern U.S.A. with differing shoreline development. Microplastics were found in 100% of the fish, with 1–49 No. Fish−1, independent of shoreline development. Bass had higher concentrations overall than shad. For bass, microplastics were more concentrated in the guts rather than gills, but the opposite was the case for shad, suggesting that feeding guild may influence where microplastics accumulate in fishes. The prevalence and concentrations reported here are greater than reported in marine systems and higher than reported in riverine studies. Our results underscore the ubiquitous distribution of microplastics and suggest that lake ecosystems in agricultural landscapes may be particularly susceptible to microplastic contamination.

Fisheries around the world are declining due to growing anthropogenic pressures including climate change and overexploitation. Understanding how small-scale fishers respond to this unprecedented challenge is critical for developing more effective management strategies in vulnerable socio-ecological systems. While considerable research is focused on adaptation to change in marine contexts, greater attention is urgently needed on regionally important but often neglected inland fisheries. This study analyzes the adaptation intentions of littoral fishers on Lake Tanganyika, a biodiversity hotspot and one of the largest inland fisheries in Africa. Data were collected through in-person surveys of 154 littoral fishers across 11 major landing sites in Tanzania. Based on the Theory of Planned Behavior, we identified and tested 15 individual and site-level factors as potential indicators of adaptation intentions to a hypothetical 50% decline in catch. Our results show that fishers with other (non-fishing) primary livelihoods are more likely to adapt in ways that decrease fishing pressure, increase income, and are supported by family and friends. Homeowners were also more likely to adapt in ways that lessen fishing pressure. Our findings highlight the importance of fostering regional adaptation strategies that increase primary livelihood alternatives and capital outside the fishery, while discouraging investment in adaptations focused on increasing catch amount or fishing income.

Water quality degradation is one of the largest threats to freshwater ecosystems. Nutrient inputs, land use changes, and climate are expected to be the most important drivers of water quality degradation. Here, we quantify the relative influence of nutrient inputs, climate, and lake geomorphometry on primary production in freshwater lakes globally, using chlorophyll a (chla) as a proxy. We used a large lake chlorophyll database that included chla and total phosphorus, in addition to lake geomorphometric variables (mean depth, watershed area, elevation, surface area, volume, residence time) and climate (air temperature, precipitation, cloud cover, solar radiation) for 2561 freshwater lakes around the globe. Our model was able to explain 60% of the variation in chla concentrations. Of that, total phosphorus (TP) explained 42%, a combination of climate variables explained 38%, and geomorphometrics explained 20% of the variation. Although there have been increased efforts and regulations in place for land use and farming, nutrient inputs continue to be the leading cause of primary production in lakes. However, the influence of climatic variables acting synergistically (temperature, precipitation, cloud cover and solar radiation) is nearly equal to that of total phosphorus, suggesting nutrient management efforts are not sufficient alone to mitigate water quality degradation. Our findings underscore the critical need to incorporate climate factors into water quality management given current climate change.

Winter activities on ice are culturally important for many countries, yet they constitute a high safety risk depending upon the stability of the ice. Because consistently cold periods are required to form stable and thick ice, warmer winters could degrade ice conditions and increase the likelihood of falling through the ice. This study provides the first large-scale assessment of winter drowning from 10 Northern Hemisphere countries. We documented over 4000 winter drowning events. Winter drownings increased exponentially in regions with warmer winters when air temperatures neared 0 ̊C. The largest number of drownings occurred when winter air temperatures were between -5 ̊C and 0 ̊C, when ice is less stable, and also in regions where indigenous traditions and livelihood require extended time on ice. Rates of drowning were greatest late in the winter season when ice stability declines. Children and adults up to the age of 39 were at the highest risk of winter drownings. Beyond temperature, differences in cultures, regulations, and human behaviours can be important additional risk factors. Our findings indicate the potential for increased human mortality with warmer winter air temperatures. Incorporating drowning prevention plans would improve adaptation strategies to a changing climate. Funding was provided to SS by the Ontario Ministry of Research, Innovation and Science Early Researcher Award and York University Research Chair programme. Funding support for BAD was provided by Kempestiftelserna. AL was supported by Estonian Research Council Grant PSG 32. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Funding was provided to SS by the Ontario Ministry of Research, Innovation and Science Early Researcher Award and York University Research Chair programme. Funding support for BAD was provided by Kempestiftelserna. AL was supported by Estonian Research Council Grant PSG 32. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Lakes are sensitive indicators of anthropogenic climate change and also respond to direct human activities. Yet, long-term lake inventories and quantitative evaluation of the factors driving observed lake changes across China remain elusive. Here, for the first time, we examined multi-decadal lake area changes in China during 1960s–2015, using historical topographic maps and >3831 Landsat satellite images, including lakes as fine as ≥1 km2 in size. In addition, we quantified the causes of lake changes from climatic and anthropogenic factors. The total area of lakes in China has increased by 5858.06 km2 (9%) between 1960s and 2015, and with heterogeneous spatial variations. Lake area changes in the Tibetan Plateau, Xinjiang, and Northeast Plain and Mountain regions reveal significant increases of 5676.75, 1417.15, 1134.87 km2 (≥15%), respectively, but the Inner-Mongolian Plateau shows an obvious decrease of 1223.76 km2 (22%). We find that 141 new lakes have appeared predominantly in the arid western China; but 333 lakes, mainly located in the humid eastern China, have disappeared over the past five decades. We conclude that climate factors have played a dominant role in lake changes across China, coupled with noticeable anthropogenic contribution of ~35% in the Eastern Plain and Yunnan-Guizhou Plateau. This study has substantial implications to improve decision support regarding water-resource management strategies and land-use planning throughout China.

Ice provides a range of ecosystem services—including fish harvest1, cultural traditions2, transportation3, recreation4 and regulation of the hydrological cycle5—to more than half of the world’s 117 million lakes. One of the earliest observed impacts of climatic warming has been the loss of freshwater ice6, with corresponding climatic and ecological consequences7. However, while trends in ice cover phenology have been widely documented2,6,8,9, a comprehensive large-scale assessment of lake ice loss is absent. Here, using observations from 513 lakes around the Northern Hemisphere, we identify lakes vulnerable to ice-free winters. Our analyses reveal the importance of air temperature, lake depth, elevation and shoreline complexity in governing ice cover. We estimate that 14,800 lakes currently experience intermittent winter ice cover, increasing to 35,300 and 230,400 at 2 and 8 °C, respectively, and impacting up to 394 and 656 million people. Our study illustrates that an extensive loss of lake ice will occur within the next generation, stressing the importance of climate mitigation strategies to preserve ecosystem structure and function, as well as local winter cultural heritage. Up to 35,000 lakes in the Northern Hemisphere may be at risk of intermittent winter ice cover at 2 °C warming, reveals an observation-based study. This would affect 394 million people reliant on lake ice for ecosystem services.

Thermal stratification in meromictic Lake Tanganyika weakens during the cool, dry and windy season, allowing intrusions of deeper nutrient-rich waters into the upper mixed layer enhancing primary productivity. The current study examined the seasonal influence of thermal structure on the patterns of primary production in Lake Tanganyika. Two sites (Kigoma Bay and Mahale) were sampled on a monthly basis for 1 year. Water temperature and chlorophyll a fluorescence profiles (0–100 m) were measured using a multisonde. Water samples were taken every 20 m (0–100 m) to measure soluble reactive phosphorus (SRP), chlorophyll a and primary production. Pulse Amplitude Modulated Fluorometry was used for the measurements of primary production. The results show that the dry season coincided with higher wind speeds, elevated SRP and some peaks of chlorophyll a and primary production at both sites. During the wet season, high levels of chlorophyll a and primary production coincided with an increase in the euphotic depth, a deep chlorophyll maximum (DCM) and a contribution from metalimnetic areal production at both sites. Our results suggest that the vertical distribution of primary production in Lake Tanganyika is affected by the lake thermal structure, nutrient availability and the extent of the euphotic zone. In Lake Tanganyika, estimates of areal primary production were significantly affected by DCM and required estimation throughout the entire upper mixed layer and the metalimnion which extended to ~89 m.

Environmental Data-Driven Inquiry and Exploration (EDDIE) modules engage students in analysis of data collected by networks of environmental sensors, which are used to study various natural phenome...

Within the Midwest United States, agricultural fields are drained by tile drainage systems. These systems are emplaced to enhance crop production, but they serve as a direct flowpath to surface streams, delivering excess nutrients to the streams. Identifying and establishing methods to reduce excess nutrient delivery to surface streams has become a priority. Surface processes within wetlands, both natural and constructed, have been shown to abate excess nutrients. This work explores the benefit associated with the subsurface flow of seepage from a wetland. Water level monitoring and geochemical analyses were used to ascertain the reduction of nitrate occurring in the subsurface following leakage from a wetland. Receiving only tile-drainage water, the wetland waters had a mean nitrate as nitrogen (NO3-N) concentration of 19.80 mg/L, which is a magnitude larger than the measured NO3-N concentration in the upgradient groundwater of 1.53 mg/L. As water travels in subsurface away from the wetland, the NO3-N concentrations decrease to 10.99 mg/L, a 44.5% reduction. The reduction occurs over a distance of 47 m, representing a 0.16 mg/L decrease in NO3-N per meter of travel distance.

The concepts of randomness and variation are pervasive in science. The purpose of this study was to document how post-secondary life science students explain randomness and variation, infer relationships between their explanations, and ability to describe and identify appropriate and inappropriate variation, and determine if students can identify sources of variation. An instrument designed to test statistical concepts was administered to 282 college students from three universities, ranging from introductory non-science majors to science graduate students. Students readily distinguished between causes of variation. A naive no-pattern concept of randomness persisted from first-year non-science majors to senior-level science majors, contributing to incorrect responses on the variation instrument. Students’ expressions of randomness were better predictors of performance on the variation instrument than their expressions of variation. It is argued that inclusion of everyday language uses of randomness in instruction can bridge the gap between vernacular and scientific uses of this term.

Understanding interactions between nutrient cycles is essential for recognizing and remediating human impacts on water quality, yet multielemental approaches to studying nutrient cycling in streams are currently rare. Here we utilized a relatively new approach (tracer additions for spiraling curve characterization) to examine uptake dynamics for three essential nutrients across a landscape that varied in absolute and relative nutrient availability. We measured nutrient uptake for soluble reactive phosphorous, ammonium-nitrogen, and nitrate-nitrogen in 16 headwater streams in the Catskill Mountains, New York. Across the landscape, ammonium-nitrogen and soluble reactive phosphorus had shorter uptake lengths and higher uptake velocities than nitrate-nitrogen. Ammonium-nitrogen and soluble reactive phosphorus uptake velocities were tightly correlated, and the slope of the relationship did not differ from one, suggesting strong demand for both nutrients despite the high ambient water column dissolved inorganic nitrogen: soluble reactive phosphorus ratios. Ammonium-nitrogen appeared to be the preferred form of nitrogen despite much higher nitrate-nitrogen concentrations. The uptake rate of nitrate-nitrogen was positively correlated with ambient soluble reactive phosphorus concentration and soluble reactive phosphorus areal uptake rate, suggesting that higher soluble reactive phosphorus concentrations alleviate phosphorus limitation and facilitate nitrate-nitrogen uptake. In addition, these streams retained a large proportion of soluble reactive phosphorus, ammonium-nitrogen, and nitrate-nitrogen supplied by the watershed, demonstrating that these streams are important landscape filters for nutrients. Together, these results (1) indicated phosphorus limitation across the landscape but similarly high demand for ammonium-nitrogen and (2) suggested that nitrate-nitrogen uptake was influenced by variability in soluble reactive phosphorus availability and preference for ammonium-nitrogen.

Asia's high plateaus are sensitive to climate change and have been experiencing rapid warming over the past few decades. We found 99 new lakes and extensive lake expansion on the Tibetan Plateau during the last four decades, 1970–2013, due to increased precipitation and cryospheric contributions to its water balance. This contrasts with disappearing lakes and drastic shrinkage of lake areas on the adjacent Mongolian Plateau: 208 lakes disappeared, and 75% of the remaining lakes have shrunk. We detected a statistically significant coincidental timing of lake area changes in both plateaus, associated with the climate regime shift that occurred during 1997/1998. This distinct change in 1997/1998 is thought to be driven by large-scale atmospheric circulation changes in response to climate warming. Our findings reveal that these two adjacent plateaus have been changing in opposite directions in response to climate change. These findings shed light on the complex role of the regional climate and water cycles and provide useful information for ecological and water resource planning in these fragile landscapes. Publisher PDF