Urban lakes provide important recreational and aesthetic benefits but often require intensive management to restore and maintain water quality. However, if there are mismatches between measured and perceived water quality, improvements may go unnoticed. While conventional water quality indicators such as chlorophyll a and Secchi depth are routinely monitored, it remains unclear how well these biophysical metrics align with public perceptions. We conducted a survey to measure visitors’ perceptions of water quality at two highly visited urban lakes in Saint Paul, Minnesota—Como Lake, a shallow eutrophic lake undergoing intensive in-lake management, and Lake Phalen, a deeper mesotrophic lake with fewer recent interventions. Across three years (2022–2024), we recruited over 800 survey respondents via signage that encouraged volunteers to participate by exchanging text-messages with a custom chatbot. Comparing long-term open water measurements with visitors’ water quality scores showed mixed relationships with chlorophyll a levels. Visitor perception scores were lower for eutrophic Como Lake, but this difference was small relative to the four-fold difference in chlorophyll a concentrations between the lakes. Open-ended responses suggest that visitors base their evaluations on a combination of visual cues such as water clarity, trash, and aquatic vegetation. These findings underscore the complexity of human–lake interactions and suggest that perception of ecological conditions may be informed by additional factors including expectations, communication, and lake-specific context. Incorporating visitor perception into lake monitoring and management may help align restoration goals with visitor experiences in urban settings.

1. Fish play a crucial role in nutrient recycling within various aquatic ecosystems, but how their contribution varies across streams with different levels of disturbance remains poorly understood. 2. In our study, we investigated the role of fish assemblage in nutrient cycling within eight Neotropical streams characterised by varying degrees of land use. 3. We found that fish were significant nutrient recyclers, excreting nitrogen and phosphorus at rates approximately 1.8- and 1.6-fold higher, respectively, than the nutrient demand in these ecosystems. This contribution became even more pronounced in the forested, low-nutrient streams. Notably, allochthonous insectivorous fish were dominant in these well-preserved streams and played a primary role in nutrient excretion within the community. One particular, as yet undescribed species (Astyanax sp. n.) was found to excrete nitrogen and phosphorus at rates 2- and 2.9-fold greater than the demand of the stream. 4. These findings underscore the critical role of fish as regulators of nutrient cycling and highlight the significance of specific key species in facilitating the transfer of nutrients from terrestrial to aquatic ecosystems.

Road salt inputs have caused widespread salinization of urban lakes in northern temperate regions. Watershed characteristics related to road salt application rates are known to be important drivers of lake chloride concentrations, but there has been less focus on how lake morphometry and climate influence seasonal and interannual dynamics in lake chloride, and how these chloride levels may alter mixing in the water column. We analyzed chloride retention for two urban lakes in Saint Paul, Minnesota with adjacent watersheds and similar surface areas that contrast in depth and water residence time. Summer chloride concentrations were negatively related to total summer precipitation for the shallower lake (Como Lake; maximum depth 2.2 m), but the relationship was substantially weaker for the deeper lake (Lake McCarrons; maximum depth 7.6 m). We used a zero-dimensional model to simulate chloride dynamics in both lakes and tracked the fate of chloride over time. In Como Lake, the mass of chloride in the lake turns over within three years, whereas chloride inputs are retained for >10 years in Lake McCarrons. We then used a one-dimensional hydrodynamic lake model (GLM-AED) to examine how chloride loading rates alter lake mixing across a wide range of lake morphometry. Salt inputs significantly extended the duration of summer stratification for simulated lakes with depths >8 m, which may exacerbate anoxic conditions. These results underscore the importance of considering lake morphometry in understanding and managing for the effects of salt inputs on lake ecosystems.

Urban agriculture provides multiple services, but its potentially adverse impact on water quality remains poorly understood. Here we present empirical data from three coordinated studies examining nitrogen and phosphorus leaching in Minneapolis-St. Paul, Minnesota, USA, and Linköping Sweden, ranging from controlled experiments to observational studies of garden practices. Using zero-tension lysimeters at 30 cm in the soil over multiple growing seasons, we found that although plots receiving nutrient inputs tended to leach more nutrients than those that did not, annual nutrient input rates were not systematically strong predictors of growing season leaching. Legacy effects from previous soil management and cumulative inputs help explain patterns observed for phosphorus leaching, with differences among treatments becoming visible over time. While urban agriculture can support nutrient circularity through organic waste recycling, careful management is needed to balance this benefit against leaching risks. Long-term monitoring is essential for understanding and managing nutrient losses from such systems.

Metagenomes and metatranscriptomes were generated from the surface mixed layer and hypolimnion at a NOAA-Great Lakes Environmental Research Laboratory Real-Time Coastal Observation Network (ReCON) site in Lake Erie's central basin during the onset of hypolimnetic hypoxia. Here, we describe the sequencing of the samples, metagenome assembly, and binning of microbial taxa.

The ecosystem concept encompasses relationships among different species while also including non-living components. The term "ecosystem" was first used by Tansley, in 1935, but the concept was described in the late 19th Century. One major usage of the term, advanced by E.P. Odum, has been the stock-and-flow conceptualization, which explicitly analyzes the movement of material or energy through various ecosystem compartments. A structural conceptualization of the term has also become common, with the term "ecosystem" referring to a local instance of a biome. The ecosystem concept was originally developed for natural systems but can also be applied to human-dominated environments.

AbstractBiological soil health is recognized as an important component of sustainable agriculture due to microbial biomineralization of nutrients. However, soil health can be difficult to assess consistently across urban agricultural systems due to diverse land use histories, soil heterogeneity, and lack of mechanistic links to agricultural management practices (e.g., recycled compost addition) and crop outcomes. In this study, we characterized soil microbial activity profiles in an urban agriculture system in Minnesota, USA, including microbial abundance, soil respiration, extracellular enzyme activity, and crop yield. Garden plots were fertilized with recycled organic compost (either manure or municipal) at high or low rates (ranging from 2.6 to 39 tons ha−1) targeted to crop N and P demands. Control plots received inorganic fertilizer or no fertilizer. We found that a high application rate of manure compost supported 6–10x higher basal respiration than municipal compost or inorganic fertilizer. Enzyme activity data demonstrated that soil microbial communities exhibited unique profiles of biochemical function that varied among fertilizers of different compositions. Microbial biochemical function predicted 50% of the variability in bell pepper (Capsicum annuum) yield, while soil microbial community size alone was a poor predictor of yield. Yield was highest in plots fertilized with municipal compost, outperforming inorganic fertilizer by threefold. High‐yield plots exhibited higher ratios of N to P enzyme activity compared to those with lower yield. Our findings demonstrate that “more is better” may not necessarily be true regarding soil microorganisms in biological soil health, and that measures of soil microbial biochemical function may be more important.

AbstractUrban vegetable gardens provide an opportunity to recycle nutrients from food waste back into the human food system through the application of compost. However, a reliance on compost for soil fertility can lead to excess phosphorus (P) inputs that can build up in garden soil and potentially be exported via leachate or runoff. We report the results of a 7‐year experiment in a campus research garden in which replicated raised‐bed garden plots received manure‐based compost or municipal compost that was applied at a higher rate targeted to meet crop nitrogen demand or a lower rate targeted to meet crop P demand. Control plots received either no soil inputs or targeted synthetic fertilizer. Higher input treatments for both types of composts showed steadily increasing concentrations of soil plant‐available P, with a corresponding increase in leachate phosphate concentration. For both higher input compost treatments, approximately 30% of P added as compost was recovered in harvested crops over the 7‐year period, compared to >88% in the lower input compost treatments. In both high‐ and low‐input manure compost treatments, export of P as leachate accounted for approximately 10% of total P input, compared to 4% for the municipal compost. Over the 7‐year study period, P exported as leachate ranged from 0.8 g P/m2 in the no‐input treatments to 6.5 g P/m2 in the higher input manure compost treatments. These results show that tradeoffs are not inevitable as targeted compost applications can lead to high yield and low leachate export.

The application of compost to urban vegetable gardens presents an opportunity to recycle nutrients from the urban waste stream back into the human food system. However, many gardeners apply phosphorus (P) in the form of compost at a rate that far exceeds what crops can take up. The fate of this P-whether stored in soil, taken up by plants, or exported through leachate, depends on the dynamics of water, carbon (C), and nitrogen (N) in this agroecosystem. We developed a model representing these four currencies (C, N, P, water) in urban garden soils, that was parameterized and validated using data from four years of data from an experiment in which high or low amounts of labile manure-based compost, or recalcitrant municipal compost, are added to garden plots annually. We used the model to simulate the effects of longer-term (10-year) additions of labile or recalcitrant compost at low, medium, or high levels (based on previously reported survey data for Minneapolis-Saint Paul, Minnesota), tracking the fate of added N and P, as well as calculating net C sequestration. The fraction of compost nutrients recovered over 10 years ranged from 3 to 47% (N) and 4-67% (P) with higher efficiencies associated with lower input rates and for recalcitrant compost. Approximately half of added C was ultimately respired by soil microbes, while C sequestration from crop growth was much lower than soil respiration. This model provides a tool for understanding how management decisions and climate control nutrient recycling and loss via leachate from compost application in urban agroecosystems.

Forest vegetation management plays an important role in maintaining soil quality and function. In highly managed urban forests, the clearing of understory vegetation has potential to cause loss of soil nutrients, resulting in stoichiometric imbalances and a decrease in soil function. Whether the presence of ornamental understory in urban forests can mitigate the negative influences on soil quality remains highly uncertain. Here, we collected soil samples from a plantation forest in Zijin Shan National Forest Park in two stands, each with three adjacent plots with different understory management practices: one with natural understory vegetation (≥10 species), a second with managed understories of ornamental groundcover [ Reineckea carnea (Andrews) Kunth or Ophiopogon bodinieri H.Lév], and a third with cleared understory. Compared with plots with natural understories, we found lower levels of soil total carbon (C), total nitrogen (N), and microbial C and N, in plots with no understories. Correspondingly, ratios of soil C:phosphorus (P) and N:P, and microbial C:N, were lower in the absence of understories in one of the two stands. The magnitude of these effects differed between the two stands, with greater effects observed in the stand with higher soil quality. These influences were smaller with groundcover plants in both stands, particularly O. bodinieri H.Lév. While we cannot rule out the effects of other influences on soil properties, these results offer support for the hypothesis that clearing of understories is potentially detrimental to soil quality, and that maintaining ornamental groundcover can alleviate these adverse influences in urban forest.

Urban gardens and farms typically use compost as a source of nutrients, often at levels that exceed crop nutrient demands. Although land dedicated to agriculture is a small fraction of urban land use, high input rates coupled with low nutrient use efficiencies suggest that export of nitrogen (N) and phosphorus (P) from this land could be potentially important contributors to urban nutrient budgets. We used the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Nutrient Delivery Ratio model to examine the potential impact of garden density, compost input rates, and nutrient retention efficiency on N and P export from stormwater runoff for a 737-ha urban residential area in Saint Paul, Minnesota. Although gardens and farms accounted for 0.1-0.5% of land area in our scenarios, compost inputs accounted for as much as 33% of N inputs and 85% of P inputs to the urban landscape. The contribution of gardens to urban nutrient export through stormwater runoff is highly dependent on modeled maximum retention efficiency values. If retention efficiency is high, gardens with low compost inputs are similar to other vegetated land uses in contributions to nutrient export, but gardens become significant contributors to watershed P export if compost inputs are high, or if retention efficiency drops to 75% or lower. These results underscore mass-balance constraints inherent in urban nutrient recycling and highlight the importance of understanding the long-term fate of excess nutrients applied to urban landscapes.

Soil acidification induced by reactive nitrogen (N) inputs can alter the structure and function of terrestrial ecosystems. Because different N-transformation processes contribute to the production and consumption of H+ , the magnitude of acidification likely depends on the relative amounts of organic N (ON) and inorganic N (IN) inputs. However, few studies have explicitly measured the effects of N composition on soil acidification. In this study, we first conducted a meta-analysis to test the effects of ON or IN inputs on soil acidification across 53 studies in grasslands. We then compared soil acidification across five different ON:IN ratios and two input rates based on long-term field N addition experiments. The meta-analysis showed that ON had weaker effects on soil acidification than IN when the N addition rate was above 20 g N m-2  year-1 . The field experiment confirmed the findings from meta-analysis: N addition with proportions of ON ≥ 20% caused less soil acidification, especially at a high input rate (30 g N m-2  year-1 ). Structural equation model analysis showed that this result was largely due to a relatively low rate of H+ production from ON as NH3 volatilization and uptake of ON and NH4 + by the dominant grass species Leymus chinensis (which are both lower net contributors to H+ production) result in less NH4 + available for nitrification (which is a higher net contributor to H+ production). These results indicate that the evaluation of soil acidification induced by N inputs should consider N forms and manipulations of relative composition of N inputs may provide an effective approach to alleviate the N-induced soil acidification.

Active learning in STEM education is essential for engaging the diverse pool of scholars needed to address pressing environmental and social challenges. However, active learning formats are difficult to scale and their incorporation into STEM teaching at U.S. universities varies widely. Here, we argue that urban agriculture as a theme can significantly increase active learning in undergraduate biology education by facilitating outdoor fieldwork and community-engaged education. We begin by reviewing benefits of field courses and community engagement activities for undergraduate biology and discuss constraints to their broader implementation. We then describe how urban agriculture can connect biology concepts to pressing global changes, provide field research opportunities, and connect students to communities. Next, we assess the extent to which urban agriculture and related themes have already been incorporated into biology-related programs in the United States using a review of major programs, reports on how campus gardens are used, and case studies from five higher education institutions (HEIs) engaging with this issue. We found that while field experiences are fairly common in major biology programs, community engagement opportunities are rare, and urban agriculture is almost nonexistent in course descriptions. We also found that many U.S. HEIs have campus gardens, but evidence suggests that they are rarely used in biology courses. Finally, case studies of five HEIs highlight innovative programming but also significant opportunities for further implementation. Together, our results suggest that urban agriculture is rarely incorporated into undergraduate biology in the United States, but there are significant prospects for doing so. We end with recommendations for integrating urban agriculture into undergraduate biology, including the development of campus gardens, research programs, community engagement partnerships, and collaborative networks. If done with care, this integration could help students make community contributions within required coursework, and help instructors feel a greater sense of accomplishment in an era of uncertainty.

Forest vegetation management plays an important role in maintaining soil health and function. In highly-managed urban forests, the clearing of understory vegetation has potential to cause loss of soil nutrients, resulting in stoichiometric imbalances and a decrease in soil function. Therefore, studying how to effectively manage understory to improve soil quality is critical for stability and function of urban forest. Here, we collected soil samples from a plantation forest in Zijin Shan National Forest Park in two stands, each with three adjacent plots with different understory management practices: one with high diversity natural understory vegetation, another with low diversity managed understories of ornamental groundcover (Reineckia carnea (Andr.) Kunth or Ophiopogon bodinieri Levl.), and a third with cleared understory. Compared to plots with natural understories, we found lower levels of soil total carbon (C), total nitrogen (N), and some their fractions especially microbial C and N, in plots with no understories. Correspondingly, ratios of soil C: phosphorus (P) and N:P, and microbial C:N, were lower in the absence of understories in one of the two stands. These influences were smaller with ground-cover plants in both stands, particularly O. bodinieri. The magnitude of these effects differed between the two stands, with greater effects observed in the stand with higher soil C. While we cannot rule out the effects of other influences on soil properties, these results offer support for the hypothesis that human management practices affect urban forest soil properties and microorganisms, and that appropriate understory managements can alleviate these adverse influences.

The role of streams and rivers in the global carbon (C) cycle remains unconstrained, especially in headwater streams where CO2 evasion (FCO2) to the atmosphere is high. Stream C cycling is understudied in the tropics compared to temperate streams, and tropical streams may have among the highest FCO2 due to higher temperatures, continuous organic matter inputs, and high respiration rates both in-stream and in surrounding soils. In this paper, we present paired in-stream O2 and CO2 sensor data from a headwater stream in a lowland rainforest in Costa Rica to explore temporal variability in gas concentrations and ecosystem processes. Further, we estimate groundwater CO2 inputs (GWCO2) from riparian well CO2 measurements. Paired O2–CO2 data reveal stream CO2 supersaturation driven by groundwater CO2 inputs and large in-stream production of CO2. At short time scales, CO2 was diluted during storm events, but increased at longer seasonal scales. Areal fluxes in our study reach show that FCO2 is supported by greater in-stream metabolism compared to GWCO2. Our results underscore the importance of tropical headwater streams as large contributors of carbon dioxide to the atmosphere and show evaded C can be derived from both in-stream and terrestrial sources.

Among the ecosystem services provided by urban greenspace are the retention and infiltration of stormwater, which decreases urban flooding, and enhanced evapotranspiration, which helps mitigate urban heat island effects. Some types of urban greenspace, such as rain gardens and green roofs, are intentionally designed to enhance these hydrologic functions. Urban gardens, while primarily designed for food production and aesthetic benefits, may have similar hydrologic function, due to high levels of soil organic matter that promote infiltration and water holding capacity. We quantified leachate and soil moisture from experimental urban garden plots receiving various soil amendments (high and low levels of manure and municipal compost, synthetic fertilizer, and no inputs) over three years. Soil moisture varied across treatments, with highest mean levels observed in plots receiving manure compost, and lowest in plots receiving synthetic fertilizer. Soil amendment treatments explained little of the variation in weekly leachate volume, but among treatments, high municipal compost and synthetic fertilizer had lowest leachate volumes, and high and low manure compost had slightly higher mean leachate volumes. We used these data to parameterize a simple mass balance hydrologic model, focusing on high input municipal compost and no compost garden plots, as well as reference turfgrass plots. We ran the model for three growing seasons under ambient precipitation and three elevated precipitation scenarios. Garden plots received 12–16% greater total water inputs compared to turfgrass plots because of irrigation, but leachate totals were 20–30% lower for garden plots across climate scenarios, due to elevated evapotranspiration, which was 50–60% higher in garden plots. Within each climate scenario, difference between garden plots which received high levels of municipal compost and garden plots which received no additional compost were small relative to differences between garden plots and turfgrass. Taken together, these results indicate that garden soil amendments can influence water retention, and the high-water retention, infiltration, and evapotranspiration potential of garden soils relative to turfgrass indicates that hydrologic ecosystem services may be an underappreciated benefit of urban gardens.

Excessive use of sloping soil in agriculture can result in loss of soil carbon (C) and stoichiometric imbalances, leading to soil degradation and a reduction in ecosystem services. Therefore, studying the effects of different utilization patterns on soil C stocks and stoichiometry is critical for the sustainable development of agriculture on uneven terrain. Here, we conducted a 7-year field study of cropland with a 10% slope, comparing soil C, nitrogen (N), and phosphorus (P) stocks and ratios between experimental plots of naturally abandoned land and different planting patterns (peanuts, daylily, oil tea planting with bare floor or inter-row coverage of straw, white clover or peanuts). We found that oil tea planting without inter-row coverage significantly lessened soil total C, microbial C and N, soil organic C, dissolved organic C, readily oxidizable C and available N compared with natural abandonment, whereas peanuts showed smaller differences, and daylily planting was most similar to natural abandonment. We also found that most planting patterns exacerbated soil C and P imbalance through the combination of C loss and P addition from fertilization. Our results show that inter-row coverage of straw or white clover can significantly alleviate these adverse influences. The atomic C:N and C:P ratios across all experimental plots were 5.10 ~ 30.5- and 0.675 ~ 8.13-fold lower, respectively, than the median values for Chinese soils, indicating that soil restoration or reasonable utilization has a high C sequestration potential, but it may be limited by P. These results suggest that perennial crops, such as oil tea with intercropping, can be nearly as effective as natural forest succession to reduce soil degradation on sloped farmland.

Among the ecosystem services provided by urban greenspace are the retention and infiltration of stormwater, which decreases urban flooding, and enhanced evapotranspiration, which helps mitigate urban heat island effects. Some types of urban greenspace, such as rain gardens and green roofs, are intentionally designed to enhance these hydrologic functions. Urban gardens, while primarily designed for food production and aesthetic benefits, may have similar hydrologic function, due to high levels of soil organic matter that promote infiltration and water holding capacity. We quantified leachate and soil moisture from experimental urban garden plots receiving various soil amendments (high and low levels of manure and municipal compost, synthetic fertilizer, and no inputs) over three years. Soil moisture varied across treatments, with highest mean levels observed in plots receiving manure compost, and lowest in plots receiving synthetic fertilizer. Soil amendment treatments explained little of the variation in weekly leachate volume, but among treatments, high municipal compost and synthetic fertilizer had lowest leachate volumes, and high and low manure compost had slightly higher mean leachate volumes. We used these data to parameterize a simple mass balance hydrologic model, focusing on high input municipal compost and no compost garden plots, as well as reference turfgrass plots. We ran the model for three growing seasons under ambient precipitation and three elevated precipitation scenarios. Garden plots received 12–16% greater total water inputs compared to turfgrass plots because of irrigation, but leachate totals were 20–30% lower for garden plots across climate scenarios, due to elevated evapotranspiration, which was 50–60% higher in garden plots. Within each climate scenario, difference between garden plots which received high levels of municipal compost and garden plots which received no additional compost were small relative to differences between garden plots and turfgrass. Taken together, these results indicate that garden soil amendments can influence water retention, and the high water retention, infiltration, and evapotranspiration potential of garden soils relative to turfgrass indicates that hydrologic ecosystem services may be an underappreciated benefit of urban gardens.

As a result of extensive urban development coupled with warming temperatures, urban heat islands (UHI) have become an important factor affecting energy consumption and human health in cities. Prior research has shown that evapotranspiration (ET) from urban vegetation can have a significant cooling effect, but there are relatively few direct measurements from urban vegetable gardens.We compared hourly temperature measurements during two summers (2017 and 2018) in a 750 m 2 research garden at the University of St. Thomas (Saint Paul, Minnesota, USA) to hourly temperatures at the nearby Minneapolis-Saint Paul (MSP) International Airport, located 6 km to the south.We also quantified seasonal ET (June-October) in 132 garden plots and five reference turfgrass plots during the summers of 2017 and 2018.For both years, an increase in temperature of 1.00°C at the MSP airport resulted in an average increase of 0.55°C in the research garden.At temperatures greater than 22°C, the garden was cooler on average compared to MSP airport.ET in the garden plots was significantly higher than in the grass reference plots both years, with means of 46 cm for garden plots compared to 19 cm for grass plots in 2017, and 51 cm for garden plots compared to 33 cm for grass plots in 2018.These results are consistent with other research showing potentially large benefits of cooling through ET from urban gardens that are primarily aimed at crop production.

The use of compost in urban agriculture offers an opportunity to increase nutrient recycling in urban ecosystems, but recent studies have shown that compost application often results in phosphorus (P) being applied far in excess of crop nutrient demand, creating the potential for P loss through leachate and runoff. Management goals such as maximizing crop yields or maximizing the mass of nutrients recycled from compost may inadvertently result in P loss, creating a potential ecosystem disservice. Here, we report the results from the first two years of an experimental study in which four different crops grown in raised-bed garden plots with high background P and organic matter received one of two types of compost (municipal compost made from urban organics waste, or manure-based compost) at two different levels (applied based on crop N or P demand), while additional treatments received synthetic N and P fertilizer or no soil amendments. Because of the low N:P ratio of compost relative to crop nutrient uptake, compost application based on crop N demand resulted in overapplication of P. Crop yield did not differ among treatments receiving compost inputs, and the mass of P recovered in crops relative to P inputs decreased for treatments with higher compost application rates. Treatments receiving compost targeted to crop N demand had P leachate rates approximately twice as high as other treatments. These results highlight tradeoffs inherent in recycling nutrients through UA, but they also show that targeted compost application rates have the capacity to maintain crop yields while minimizing nutrient loss. UA has the potential to help close the urban nutrient loop, but if UA is to be scaled up in order to maximize potential social, economic, and environmental benefits, it is especially important to carefully manage nutrients to avoid ecosystem disservices from nutrient pollution.