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Abstract Many ecosystems can abruptly shift between states, and shallow lakes are a classic example. Biomanipulation via the removal of benthivores can shift a shallow lake from a turbid to a clear-water macrophyte-dominated state, but the limited number of long-term studies indicates that persistence in this state rarely lasts beyond 5–10 years. We analyzed 12 years of pre-removal (1996–2007) and 17 years of post-removal (2008–2024) data to assess the ecological impacts of a common carp (Cyprinus carpio) removal from Lake Wingra, a shallow eutrophic lake in Madison, Wisconsin, USA. Summer water clarity abruptly increased following the winter 2008 carp removal, resulting in a 64% increase in mean Secchi depth in post-removal summers and a major expansion of the littoral zone. Fast growing submerged macrophytes (for example,Ceratophyllum demersumand invasiveMyriophyllum spicatum) rapidly expanded into deeper zones, reaching the maximum colonization depth of 3.96 m within four summers. Post-removal nutrient concentrations declined by 24–34% and became more correlated with precipitation, suggesting a shift from internal to external regulation of nutrient loading. Three likely interacting mechanisms for maintaining water clarity include predation by centrarchids maintaining low carp populations, the high and stable coverage of submerged macrophytes, and abundant filamentous algae that provide an additional nutrient sink. However, high biomass of invasive species and filamentous algae can degrade ecosystem services and function, and increased variability of precipitation-driven nutrient inputs may destabilize the macrophyte-dominated state in the future. We demonstrate with long-term data the sustained shift of a shallow eutrophic lake out of the turbid state with a single biomanipulation. 

{"Abstract":["This data product contains physical, chemical, and biological data ranging from the minute to daily to weekly scale in six artificial ponds (400 square meter surface area, 2m depth) in central Iowa (USA) 2020. Ponds were paired into three sets of treatment and reference with treatment ponds receiving two nutrient pulses designed to increase ambient phosphorus concentrations ~ 3 - 5%. Nitrogen and phosphorus were added as NH4NO3 and H3PO4, respectively, at a 24:1 molar ratio. The first nutrient pulse occurred on Julian day of year (DOY) 176 corresponding to a 3% increase and the second nutrient pulse occurred on DOY 211 to a 5% increase. Each treatment-reference set had a different food web structure established ranging between low, intermediate, and high complexity based on trophic connectivity and food chain length. \n \n Added to this data package is a document titled "2020 Iowa State University Horticultural Farm Experimental Ponds Nutrient Addition Experiment". For experimental set up, context, and a summary table of the data tables archived herein with available variables please review this document. It is added to aid in successful interpretation and to increase ease-of-use. Please email Tyler Butts (tyler.james.butts@gmail.com) for any and all questions regarding context or use of this dataset!"]} 

Abstract Aquatic heatwaves are increasing in frequency, intensity, and duration worldwide. While increases in mean water temperatures are linked to enhanced phytoplankton biomass, it is unclear how heatwaves alter phytoplankton dynamics in lakes at an ecosystem scale. We investigated changes in surface chlorophyll during 29 summer heatwaves between 2008 and 2019 in 3 north temperate lakes. These lakes vary in staining and were either references or manipulated with nutrients and top predator additions. The manipulations provided a variety of nutrient, grazing, and light conditions during heatwave and non‐heatwave conditions. Surface chlorophyll concentrations increased during 24 out of 29 heatwaves. In the low‐nutrient reference lake the mean increase in chlorophyll was 57% while in the two experimental lakes the mean increases were 127% and 183%. Overall, the effects of the whole‐lake experiments were variable but still provided context for possible patterns amid a diverse set of food web and nutrient conditions. 

{"Abstract":["Temperature and chlorophyll data were collated from multiple datasets to identify the effects of aquatic heatwaves on phytoplankton in three north temperate lakes, Peter Lake, Paul Lake, and Tuesday Lake between 2008 and 2019. Heatwaves were identified using a water temperature model constructed from temperature data from Sparkling Lake and Woodruff Airport between 1989 and 2022. Heatwave characteristics, water color, nutrients, grazing, and lake stability data are included to relate chlorophyll response to heatwaves to other conditions associated with a set of whole-lake experiments. The food web of Peter Lake was manipulated with largemouth bass additions between 2008 and 2011. Nutrient additions were made to Peter Lake and Tuesday Lake between 2013 and 2015, and again in Peter Lake in 2019. Paul Lake was always maintained as an unmanipulated reference lake. Full descriptions of the experiments can be found in Szydlowski et al., "Aquatic heatwaves increase surface chlorophyll concentrations in experimental and reference lakes.""]} 

Abstract In aquatic ecosystems, greater food web complexity is theorized to increase persistence and resilience of primary production to pulse disturbances, yet experimental evidence is limited. We simulated two storm‐induced pulse disturbances by adding nutrients (~ 3%–5% increase in ambient concentrations) to three ponds with low, intermediate, and high food web complexity and compared to reference ponds. We evaluated the ecological stability of primary production by quantifying persistence as the number of days it took chlorophyll‐aor ecosystem metabolism to deviate significantly from reference conditions and resilience as the time to recover to reference conditions following each disturbance. We also evaluated if a critical transition occurred following the disturbance. The high complexity pond did not significantly deviate from reference conditions following either nutrient pulse, suggesting high ecological stability. The intermediate complexity pond had lower stability, with persistence relatively consistent at 18 and 24 d after each nutrient pulse, and resilience trending toward a substantial increase from 23 d to less than a week before the experiment concluded. Stability was lowest in the low complexity pond where persistence decreased from 24 d to just 8 d and resilience decreased from 5 to 22 d. There was also evidence of a critical transition after the first pulse in the low complexity pond, but not for higher complexity ponds. This experiment provides strong support that food web connectivity and food chain length can aid in buffering aquatic ecosystems against increasing and intensifying by influencing persistence and resilience to repeated nutrient pulses. 

Abstract Stormwater ponds are common features in urbanized landscapes because they enhance flood reduction and nutrient retention. With shallow depths and high inputs of organic matter, these systems can be highly productive with rapid oxygen depletion when thermally stratified or ice‐covered. However, most of our understanding of the biogeochemistry of stormwater ponds comes from the open water period. We explored under‐ice oxygen dynamics in 20 stormwater ponds in Madison, WI (USA) that were ice covered from late December to early March to investigate the drivers of bottom water oxygen saturation and the impact on the accumulation of carbon dioxide (CO₂) and methane (CH₄). Winter anoxia was driven by ice transmissivity, winter nutrient concentrations, and precedent summer productivity. Oxygen depletion led to overall higher concentrations of greenhouse gases in pond surface waters. This research enhances our understanding of winter pond biogeochemistry and its links to summer productivity. 

Abstract Particles are a key component of aquatic light climate due to their attenuation of light. Near the water surface, waves and sheared currents can induce a preferential orientation of nonspherical particles that alters their inherent optical properties and the associated light attenuation. This modeling study focuses on how particle shape, and the corresponding preferential orientation, impacts the light climate in an aquatic environment. We assume aquatic particles, such as bacteria, algae, and microplastic pollutants, are optically homogeneous spheroids that move with the flow. The model computes their preferential orientations within the upper water column in flow driven by linear water waves and sheared currents. This is combined with the anomalous diffraction optical approximation to examine the effect of particle orientation on the beam attenuation coefficient. We find that the preferential orientation by waves and shear tends to increase the projected area of the spheroid compared to random (isotropic) orientation. This has particle size‐dependent effects on light attenuation: for particles comparable in size and shape to algae or microplastics, the preferential orientation corresponds to an increase of 10–25% in the beam attenuation coefficient, whereas there is a decrease of 10–20% in the beam attenuation coefficient for smaller particles comparable in size to bacteria. Overall, our results reveal how preferential orientation of nonspherical particles by waves and currents can impact light climate in the upper water column.