Ecosystem respiration: Drivers of daily variability and background respiration in lakes around the globe

We assembled data from a global network of automated lake observatories to test hypotheses regarding the drivers of ecosystem metabolism. We estimated daily rates of respiration and gross primary production (GPP) for up to a full year in each lake, via maximum likelihood fits of a free‐water metabolism model to continuous high‐frequency measurements of dissolved oxygen concentrations. Uncertainties were determined by a bootstrap analysis, allowing lake‐days with poorly constrained rate estimates to be down‐weighted in subsequent analyses. GPP and respiration varied considerably among lakes and at seasonal and daily timescales. Mean annual GPP and respiration ranged from 0.1 to 5.0 mg O2 L−1 d−1 and were positively related to total phosphorus but not dissolved organic carbon concentration. Within lakes, significant day‐to‐day differences in respiration were common despite large uncertainties in estimated rates on some lake‐days. Daily variation in GPP explained 5% to 85% of the daily variation in respiration after temperature correction. Respiration was tightly coupled to GPP at a daily scale in oligotrophic and dystrophic lakes, and more weakly coupled in mesotrophic and eutrophic lakes. Background respiration ranged from 0.017 to 2.1 mg O2 L−1 d−1 and was positively related to indicators of recalcitrant allochthonous and autochthonous organic matter loads, but was not clearly related to an indicator of the quality of allochthonous organic matter inputs

Therapeutic Use of Self: The Impact on the Health and Wellness of Older Adults Involved in a Creative Dance Program

This study was part of a larger mixed methods design exploring the effects of a dance program on elders. The purpose of this research was to examine the impact of a creative arts- based program on the health, wellness, and overall quality of life of older adults. Another aspect of the study involved determining how the staff’s “therapeutic use of self” contributed to the positive outcomes of the creative music and dance program called “The Dancing Heart TM ”. The research questions were, “What is the importance of a creative dance program for long term care residents?” and “What is happening in the group that contributes to its outcomes?”. This study involved both an analysis of behaviors recorded in observation notes by program staff and an analysis of field notes taken by this researcher. Results indicated that participation in the sessions encouraged increased physicality, mood, creativity, cognitive engagement, musical involvement, reminiscence/memory involvement, interpersonal interactions, and overall had positive impact on quality of life. In regard to the second research question, results suggest that the staff utilized therapeutic use of self and many tools to maximize the level of engagement and participation for the participants. The results of this study suggest that participation in a creative-arts program for seniors has the potential to positively impact quality of life for seniors

The Enabler: Design and Fabrication of an Assistive Walking Device with Wheels

The enabler is a device that provides a person in need of walking assistance the ability to walk fluidly and independently without having to lift the device off of the ground. The use of carbon fiber/epoxy 42 composite allows the device to maintain a high strength to weight ratio. It can adjust to a range of heights with an ergonomic handle and braking system. CAD modeling including SolidWorks and Fusion 360, aided in the 3D modeling of parts and in the development of CNC tool paths. Three wheels attached to the base plate provide fluid mobility and stability. The composite handle is designed with comfort in mind and allows the user to handle the device with ease. The sleek design is meant to portray a low profile to not draw attention to the user while maintaining an aesthetic appeal. Relevant mechanical and weather testing were performed to ensure strength requirements were met in a wide variety of environmental conditions.https://openriver.winona.edu/urc2019/1047/thumbnail.jp

Factors influencing the hooking mortality of walleyes caught by recreational anglers on Mille Lacs,

Abstract.-Recent implementation of size-based regulations in recreational fisheries for walleye Sander vitreus have led to more released walleyes and presumably to more losses of released fish. We conducted this study to estimate hooking mortality in Mille Lacs, Minnesota, and to determine factors that influence the survival of released walleyes. Volunteers and Minnesota Department of Natural Resources employees sampled walleyes with common angling methods in 2003 and 2004 on Mille Lacs (n ¼ 1,246). Simple hooking mortality rates ranged from 0% (95% confidence interval ¼ 0-1.8%; n ¼ 204) in May, when lake water temperatures were less than 208C, to 12.2% (9.2-15.9%; n ¼ 392) in the July-August period, when lake water temperatures were at least 208C. We used logistic regression within generalized linear or additive models to determine influential variables. Hooking mortality was most associated with water temperature, bleeding, fish length, hook location, and fish floating upon release. Mortality increased as the water warmed above 188C and was higher for fish that bled at temperatures less than 248C but similar for both bleeding and nonbleeding fishes at temperatures of 248C or more. Fish hooked in the throat or stomach died at higher rates than fish hooked in the jaw, inner mouth, or gills and those that were externally foul-hooked, especially when they were smaller. Although fish of medium length (300-600 mm) were more likely to be deep hooked, they died less frequently than walleyes of other lengths. Cutting the line did not significantly improve survival in deeply hooked fish. Mortality was similar between live bait jigs and live bait regular hooks. Most observed hooking mortality was caused by damage to major internal organs. Hooking mortality is minimized when anglers fish in cool water, use active fishing methods, and catch medium-length walleyes

Sedimentary Environment Influences the Effect of an Infaunal Suspension Feeding Bivalve on Estuarine Ecosystem Function

The suspension feeding bivalve Austrovenus stutchburyi is a key species on intertidal sandflats in New Zealand, affecting the appearance and functioning of these systems, but is susceptible to several environmental stressors including sedimentation. Previous studies into the effect of this species on ecosystem function have been restricted in space and time, limiting our ability to infer the effect of habitat change on functioning. We examined the effect of Austrovenus on benthic primary production and nutrient dynamics at two sites, one sandy, the other composed of muddy-sand to determine whether sedimentary environment alters this key species' role. At each site we established large (16 m2) plots of two types, Austrovenus addition and removal. In winter and summer we deployed light and dark benthic chambers to quantify oxygen and nutrient fluxes and measured sediment denitrification enzyme activity to assess denitrification potential. Rates of gross primary production (GPP) and ammonium uptake were significantly increased when Austrovenus was added, relative to removed, at the sandy site (GPP, 1.5 times greater in winter and summer; ammonium uptake, 8 times greater in summer; 3-factor analysis of variance (ANOVA), p<0.05). Denitrification potential was also elevated in Austrovenus addition plots at the sandy site in summer (by 1.6 times, p<0.1). In contrast, there was no effect of Austrovenus treatment on any of these variables at the muddy-sand site, and overall rates tended to be lower at the muddy-sand site, relative to the sandy site (e.g. GPP was 2.1 to 3.4 times lower in winter and summer, respectively, p<0.001). Our results suggest that the positive effects of Austrovenus on system productivity and denitrification potential is limited at a muddy-sand site compared to a sandy site, and reveal the importance of considering sedimentary environment when examining the effect of key species on ecosystem function

Response of lake metabolism to catchment inputs inferred using high-frequency lake and stream data from across the northern hemisphere

In lakes, the rates of gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NEP) are often controlled by resource availability. Herein, we explore how catchment vs. within lake predictors of metabolism compare using data from 16 lakes spanning 39°N to 64°N, a range of inflowing streams, and trophic status. For each lake, we combined stream loads of dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP) with lake DOC, TN, and TP concentrations and high frequency in situ monitoring of dissolved oxygen. We found that stream load stoichiometry indicated lake stoichiometry for C : N and C : P (r2 = 0.74 and r2 = 0.84, respectively), but not for N : P (r2 = 0.04). As we found a strong positive correlation between TN and TP, we only used TP in our statistical models. For the catchment model, GPP and R were best predicted by DOC load, TP load, and load N : P (R2 = 0.85 and R2 = 0.82, respectively). For the lake model, GPP and R were best predicted by TP concentrations (R2 = 0.86 and R2 = 0.67, respectively). The inclusion of N : P in the catchment model, but not the lake model, suggests that both N and P regulate metabolism and that organisms may be responding more strongly to catchment inputs than lake resources. Our models predicted NEP poorly, though it is unclear why. Overall, our work stresses the importance of characterizing lake catchment loads to predict metabolic rates, a result that may be particularly important in catchments experiencing changing hydrologic regimes related to global environmental change.publishedVersio

Community Biological Ammonium Demand: A Conceptual Model for Cyanobacteria Blooms in Eutrophic Lakes

Cyanobacterial harmful algal blooms (CyanoHABs) are enhanced by anthropogenic pressures, including excessive nutrient (nitrogen, N, and phosphorus, P) inputs and a warming climate. Severe eutrophication in aquatic systems is often manifested as non-N2-fixing CyanoHABs (e.g., Microcystis spp.), but the biogeochemical relationship between N inputs/dynamics and CyanoHABs needs definition. Community biological ammonium (NH4 +) demand (CBAD) relates N dynamics to total microbial productivity and NH4 + deprivation in aquatic systems. A mechanistic conceptual model was constructed by combining nutrient cycling and CBAD observations from a spectrum of lakes to assess N cycling interactions with CyanoHABs. Model predictions were supported with CBAD data from a Microcystis bloom in Maumee Bay, Lake Erie, during summer 2015. Nitrogen compounds are transformed to reduced, more bioavailable forms (e.g., NH4 + and urea) favored by CyanoHABs. During blooms, algal biomass increases faster than internal NH4 + regeneration rates, causing high CBAD values. High turnover rates from cell death and remineralization of labile organic matter consume oxygen and enhance denitrification. These processes drive eutrophic systems to NH4 + limitation or colimitation under warm, shallow conditions and support the need for dual nutrient (N and P) control

Pelagic phytoplankton community change‐points across nutrient gradients and in response to invasive mussels

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/136002/1/fwb12873_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/136002/2/fwb12873.pd

Reservoir Fish Escapement in North America: A Historical Review and Future Directions

Downstream escapement of fishes from reservoirs via release structures can represent a loss to populations that is comparable to natural and harvest mortality. Consequently, quantifying and managing fish escapement constitute a critical component of sustainable reservoir fish management. We reviewed existing literature to assess the state of knowledge of reservoir fish escapement and found 57 unique papers published from 1942 through 2021. Early studies sought to evaluate escapement by directly capturing fish below release structures. More recently, advances in technology have enabled more detailed studies on factors influencing escapement and the influence it has on regulating reservoir fisheries. Evaluations have occurred throughout North America, assessing escapement of 49 species through a number of different outlet structures. Annual escapement estimates ranged from 0% to 100%, and escapement tended to be higher from spillways and surface release outlets compared to other outlets. Further, smaller-bodied individuals tended to escape at higher rates than larger fish and escapement was generally positively related to reservoir discharge metrics. Sixteen papers assessed benefits of physical and nonphysical barriers for reducing reservoir fish escapement and determined that the barriers were effective for retaining fish in reservoirs. We conclude by describing management options to address escapement as well as three pressing research needs that will broaden the existing knowledge base regarding fish escapement. In light of predicted changes in precipitation events and subsequent adaptations to reservoir management, quantifying and mitigating fish escapement will be a critical component of sustainable reservoir fish management in the future.This article is published as Lewis, Madeline C., W. Robert Cope, Thomas P. Miles, Claire Rude, Richard E. Bruesewitz, Benjamin J. Dodd, Mark K. Flammang et al. "Reservoir fish escapement in North America: a historical review and future directions." North American Journal of Fisheries Management 43, no. 2 (2023): 352-368. doi:10.1002/nafm.10790

Nutrient function over form: Organic and inorganic nitrogen additions have similar effects on lake phytoplankton nutrient limitation

The concentration of dissolved organic nitrogen (DON) is increasing in many northern hemisphere lakes, yet its use by phytoplankton and fate in the environment seldom have been quantified. We conducted 1 week, in situ, microcosm incubations across 25 lakes in northeastern North America to understand how DON, dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus (P) affected phytoplankton biomass. In addition, we tested whether lakes were limited by single macronutrients (N or P) or colimited by both. Phytoplankton biomass in 80% of lakes responded similarly to DON and DIN additions. Of the lakes where N form produced differential responses, the majority of phytoplankton communities exhibited greater biomass accumulation with DON than DIN. Colimitation was the most common type of nutrient limitation among the study lakes, followed by P limitation. Limitation type shifted with N form in 40% of the study lakes, but without consistent patterns explaining how shifts occurred. Regardless of N form, lakes with watersheds more dominated by agriculture and higher total dissolved nitrogen (TDN) tended to show P-limited phytoplankton responses, while lakes with less agricultural watersheds and lower TDN tended to show colimited phytoplankton responses. Finally, ambient TDN and total phosphorus (TP) nutrient concentrations were stronger predictors of limitation type than ambient TDN : TP ratios. The different contributions of DON and DIN to phytoplankton biomass in some of our study lakes suggest that DON loading from surrounding watersheds may be an overlooked component in predicting phytoplankton productivity and nutrient limitation dynamics in freshwater ecosystems