Tracing nutrient inputs into a eutrophic lake using nitrogen isotopes, Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake is a dammed lake that has been classified as nutrient-impaired (303d list) by the EPA and State of Kentucky. The lake is moderately-sized covering 169 acres (0.7 km2), and drains a watershed with residential developments, cattle pasture, modified woodlands, and some industrial/urban usage in the city of Richmond. The principal tributaries are Taylor Fork and Old Town Branch that meet to form the trunk of the lake approximately one mile in length. The upper reaches of Taylor Fork are adjacent to a densely-packed (quarter-acre lots) housing development with septic systems. Old Town Branch drains cattle pasture and residential areas. Residences within these developments, while also served by septic systems, are more sparsely distributed than residences within developments adjacent to those of Taylor Fork. An ancillary tributary flowing into Pond Cove is intermittent, and drains cattle pasture and one small housing development. Recognizing and quantifying potential nutrient sources is critical to any remediation efforts in decreasing nutrient input to the lake. We hypothesize that significant nutrient input occurs from the septic systems adjacent to the shallow lake waters of Taylor Fork. We use stable nitrogen isotopes (14N and 15N) as a tracer in characterizing organic sources of nitrogen entering lake waters, and in characterizing organic sinks of nitrogen residing in the lake system. We measure the carbon-to-nitrogen ratio, carbon isotopic composition (d13C), and nitrogen isotopic composition (d15N) of organic matter held within potential nutrient sources and sinks within the Wilgreen Lake system. Potential sources include fertilizers, bovine fecal matter, human effluent from septic systems, and “natural” organic material. Sinks include plankton, macroalgae, macrophyta, and organic matter within sediments. Our samples are being measured at press time. The fundamental assumption of the test of our hypothesis is that d15N values of nitrogen sinks should reflect that of their source. With knowledge of the nitrogen isotopic composition of nitrogen sources, we may be able to recognize gradients within the nitrogen sinks of the system. Consequently, our samples of plankton, macroalgae, macrophyta, and sedimentary organic matter are taken over the entire expanse of lake

Fecal microbe distribution and abundance used as a possible proxy for nutrient source identification in eutrophic Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake is a eutrophic lake that has been listed on the EPA’s 303d list as nutrient impaired. Potential sources of this impairment are from humans, cattle manure and fertilizers. We suspect that the majority of nutrients originate from human sources. As a possible proxy for nutrient input, we test our hypothesis by examining fecal microbe distribution and abundance in the lake. We took water samples at 19 sampling locations on 4 occasions. Sampling spanned 26 June to 15 August with the last 3 sampling events occurring at roughly two-week intervals. These samples were then processed using IDEXX methods, which count total coliform and Escherichia coli colonies. For sampling localities with microbial abundance that exceeded maximum sensitivity (\u3e2419 cfu/100ml), we performed dilutions of 1:4 or 1:10. Both total coliform and E. coli levels are elevated at sites adjacent to septic tank clusters. There is a gradual decline in microbial abundance distal to these populated areas and microbe levels are low in the third lake tributary that drains only cattle pasture. This strongly suggests that the source of microbial input is from septic systems; however, we cannot eliminate the possibility that fecal microbes are introduced into the lake via inflows, because of high microbial abundance in their waters. We plan on using Reverse-Transcription Polymer Chain Reaction (RT-PCR) techniques to distinguish between human and cattle sources of Bacteroides to potentially eliminate the inflows as a microbial source

Using E. coli and Bacteroides distribution and abundance in a eutrophic lake as a tracer for nutrient inputs, Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake is a eutrophic lake that has been listed on the EPA’s 303d list as nutrient impaired. Potential sources of this impairment are likely from humans, cattle manure, and fertilizers. We suspect that the majority of nutrients originate from human sources, namely from septic tank effluent emanating from key housing developments ringing the lakeshore. We test our hypothesis with conventional microbial assays (Escherichia coli) and RT-PCR techniques (Bacteroides). We took water samples at 19 sampling locations on 4 occasions, and measured the abundance of Escherichia coli using IDEXX methods. Corresponding sub-samples slated for potential PCR analysis were stored at -40oC. We chose PCR assay candidates on the basis of elevated E. coli levels, and the probability of differing source contributions. There is a systematic decline in E. coli microbial abundance distal to developments with closely-spaced septic units. This suggests that the principal source of microbial input is from septic systems; however, we cannot eliminate the possibility that fecal microbes are introduced into the lake via inflows. We used quantitative PCR analysis to measure Bacteroides abundance, and to distinguish between human and cattle sources. We measured 14 samples and found total fecal microbe concentrations in all samples targeting all Bacteroides species ranged from 45 mg/L to 142 mg/L. Unlike other studies, there was no apparent relationship between the concentration of all Bacteroides species and that of E. coli. We also attempted to quantitatively determine the proportion of Bacteroides contributions from specific sources, namely human and bovine fecal matter. Although fecal contamination was measured in all 14 samples, only 1 sample had significant amounts of human fecal contamination (21%) as measured by the human-associated Bacteroides assay. None of the samples had significant amounts bovine fecal concentration as measured by the bovine-associated Bacteroides assay. These inconclusive results suggest that either there are other unidentified sources of fecal contamination by Bacteroides and/or E. coli, or that the prevailing drought conditions skewed our results by not capturing fecal transport effects due to lack of surface and/or groundwater flow

Nutrient and fecal microbe sources for a eutrophic lake and recommended remediation steps, Wilgreen Lake, Madison County, Kentucky

Wilgreen Lake is a man-made lake, classified as nutrient-impaired (303d list) by the EPA and State of Kentucky. The lake drains a watershed with residential developments, cattle pasture, modified woodlands, and some industrial/urban usage in the city of Richmond. The principal tributaries are Taylor Fork and Old Town Branch that meet to form the trunk of the lake approximately one mile in length. The upper reaches of Taylor Fork are adjacent to a densely-packed (quarter-acre lots) housing development with septic systems, and its watershed drains some portions of southern Richmond. Old Town Branch drains cattle pasture and residential areas of moderate to large lot size. An intermittent tributary flowing into Pond Cove drains cattle pasture and one small housing development. Fecal material contributes both nutrients and microbes to Wilgreen Lake. Both cattle and human fecal material enter the lake as documented by high fecal microbes counts and DNA tracing techniques. DNA tracing methods are limited by our sampling frequency but show that bovine Bacteroides microbes dominate water samples even at loci where suspected septic effluent enters the lake. The nitrogen isotopic composition (d15N) of lake plankton and algae are broadly consistent with nitrogen input from human fecal material, but results are equivocal. We suspect that large amounts of nutrients do enter the lake through septic groundwater input, however, the strong bovine signal clearly suggests deployment of remediation methods that would limit runoff from pastures adjacent to Wilgreen Lake and within its watershed. Such methods include fencing cattle off from drainages and the lake, and planting vegetative buffers around stream and lake margins. Our data alone cannot justify elimination of septic systems by costly implementation of a sewage treatment system

Rate-Induced Transitions in Networked Complex Adaptive Systems: Exploring Dynamics and Management Implications Across Ecological, Social, and Socioecological Systems

Complex adaptive systems (CASs), from ecosystems to economies, are open systems and inherently dependent on external conditions. While a system can transition from one state to another based on the magnitude of change in external conditions, the rate of change -- irrespective of magnitude -- may also lead to system state changes due to a phenomenon known as a rate-induced transition (RIT). This study presents a novel framework that captures RITs in CASs through a local model and a network extension where each node contributes to the structural adaptability of others. Our findings reveal how RITs occur at a critical environmental change rate, with lower-degree nodes tipping first due to fewer connections and reduced adaptive capacity. High-degree nodes tip later as their adaptability sources (lower-degree nodes) collapse. This pattern persists across various network structures. Our study calls for an extended perspective when managing CASs, emphasizing the need to focus not only on thresholds of external conditions but also the rate at which those conditions change, particularly in the context of the collapse of surrounding systems that contribute to the focal system's resilience. Our analytical method opens a path to designing management policies that mitigate RIT impacts and enhance resilience in ecological, social, and socioecological systems. These policies could include controlling environmental change rates, fostering system adaptability, implementing adaptive management strategies, and building capacity and knowledge exchange. Our study contributes to the understanding of RIT dynamics and informs effective management strategies for complex adaptive systems in the face of rapid environmental change.Comment: 25 pages, 4 figures, 1 box, supplementary informatio

Increase in pediatric recurrent fever evaluations during the first year of the COVID-19 pandemic in North America

The impact of the COVID-19 pandemic on new diagnoses of recurrent fevers and autoinflammatory diseases is largely unknown. The Childhood Arthritis and Rheumatology Research Alliance (CARRA) PFAPA/AID Working Group aimed to investigate the impact of the COVID-19 pandemic on the number of pediatric patients evaluated for recurrent fevers and autoinflammatory diseases in North America. The absolute number of new outpatient visits and the proportion of these visits attributed to recurrent fever diagnoses during the pre-pandemic period (1 March 2019–29 February 2020) and the first year of the COVID-19 pandemic (1 March 2020–28 February 2021) were examined. Data were collected from 27 sites in the United States and Canada. Our results showed an increase in the absolute number of new visits for recurrent fever evaluations in 21 of 27 sites during the COVID-19 pandemic compared to the pre-pandemic period. The increase was observed across different geographic regions in North America. Additionally, the proportion of new visits to these centers for recurrent fever in relation to all new patient evaluations was significantly higher during the first year of the pandemic, increasing from 7.8% before the pandemic to 10.9% during the pandemic year (p < 0.001). Our findings showed that the first year of the COVID-19 pandemic was associated with a higher number of evaluations by pediatric subspecialists for recurrent fevers. Further research is needed to understand the reasons behind these findings and to explore non-infectious triggers for recurrent fevers in children