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1. Diet alters rodent fecal pellet size: implications for paleoecological and demographic studies using fecal dimensions

   https://doi.org/10.1093/jmammal/gyab098  

   Maurer, Maya; Peralta Martínez, Karen; Trevelline, Brian K.; Tripoli, Domenique; Dearing, M. Denise; Derting, Terry; Martinez Mota, Rodolfo; Pasch, Bret; Kohl, Kevin D.; Zollner, ed., Patrick (September 2021, Journal of Mammalogy)

   Abstract Measurements of fecal pellet size can provide important information about wild mammals, such as body size and demographic information. Previous studies have not rigorously tested whether diet can confound these measurements. Furthermore, it is unknown whether diet might alter fecal dimensions directly or through changes in animal physiology. Here, we studied three closely related rodent species that differ in natural feeding strategies. Individuals were fed diets that varied in protein and fiber content for 5 weeks. We then measured body size, fecal widths and lengths, and the radius of the large intestine. Diet composition significantly changed fecal widths in all species. High-fiber content significantly increased fecal widths and would cause overestimations of body size if applied to wild feces. Using path analysis, we found that fiber can increase fecal widths both directly and indirectly through increasing the large intestine radius. Protein affected each species differently, suggesting that protein effects vary by species feeding strategy and existing physiology. Overall, diet and large intestine morphology can alter fecal pellet measurements. Studies using fecal measurements therefore must consider these effects in their conclusions. 

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2. Fecal Composition and its Relation to Diet

   Gilbert, H; Reitsema, LJ (April 2017, Center for Undergraduate Research Opportunities, UGA)
3. Removal of Fecal Indicator Bacteria by River Networks

   https://doi.org/10.3390/w14040617  

   Huang, Tao; Wollheim, Wilfred M.; Jones, Stephen H. (February 2022, Water)

   Fecal contamination is a significant source of water quality impairment globally. Aquatic ecosystems can provide an important ecosystem service of fecal contamination removal. Understanding the processes that regulate the removal of fecal contamination among river networks across flow conditions is critical. We applied a river network model, the Framework for Aquatic Modeling in the Earth System (FrAMES-Ecoli), to quantify removal of fecal indicator bacteria by river networks across flow conditions during summers in a series of New England watersheds of different characteristics. FrAMES-Ecoli simulates sources, transport, and riverine removal of Escherichia coli (E. coli). Aquatic E. coli removal was simulated in both the water column and the hyporheic zone, and is a function of hydraulic conditions, flow exchange rates with the hyporheic zone, and die-off in each compartment. We found that, at the river network scale during summers, removal by river networks can be high (19–99%) with variability controlled by hydrologic conditions, watershed size, and distribution of sources in the watershed. Hydrology controls much of the variability, with 68–99% of network scale inputs removed under base flow conditions and 19–85% removed during storm events. Removal by the water column alone could not explain the observed pattern in E. coli, suggesting that processes such as hyporheic removal must be considered. These results suggest that river network removal of fecal indicator bacteria should be taken into consideration in managing fecal contamination at critical downstream receiving waters. 

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4. Body size–fecal nutrient patterns of mammalian herbivores

   https://doi.org/10.1073/pnas.2020137118  

   Sitters, Judith; Olde Venterink, Harry (February 2021, Proceedings of the National Academy of Sciences)

   null (Ed.)
5. Detection of human fecal pollution in environmental waters using human mitochondrial DNA and correlation with general and human-associated fecal genetic markers

   https://doi.org/10.2166/wh.2019.197  

   Tanvir Pasha, A. B.; Hinojosa, Jessica; Phan, Duc; Lopez, Adrianne; Kapoor, Vikram (December 2019, Journal of Water and Health)

   Abstract Human mitochondrial DNA (mtDNA) genetic markers are abundant in sewage and highly human-specific, suggesting a great potential for the environmental application as human fecal pollution indicators. Limited data are available on the occurrence and co-occurrence of human mtDNA with fecal bacterial markers in surface waters, and how the abundance of these markers is influenced by rain events. A 1-year sampling study was conducted in a suburban watershed impacted by human sewage contamination to evaluate the performance of a human mtDNA-based marker along with the bacterial genetic markers for human-associated Bacteroidales (BacHum and HF183) and Escherichia coli. Additionally, the human mtDNA-based assay was correlated with rain events and other markers. The mtDNA marker was detected in 92% of samples (n = 140) with a mean concentration of 2.96 log10 copies/100 ml throughout the study period. Human mtDNA was detected with greater abundance than human-associated Bacteroidales that could be attributed to differences in the decay of these markers in the environment. The abundance of all markers was positively correlated with rain events, and human mtDNA abundance was significantly correlated with various bacterial markers. In general, these results should support future risk assessment for impacted watersheds, particularly those affected by human fecal pollution, by evaluating the performance of these markers during rain events. 

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