Spatial And Temporal Variation In Water Chemistry And Littoral Benthic Macroinvertebrate Communities Of Precambrian Shield Lakes

Author : Luke Clifton Loken
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (18 download)

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Download or read book Spatial Heterogeneity of Water Chemistry Within Lakes and Rivers written by Luke Clifton Loken and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overarching goal of this dissertation is to improve our understanding of spatial heterogeneity of water chemistry in aquatic ecosystems. Lakes and rivers are fluid ecosystems, and thus spatial variation in physical, chemical, and biological properties are strongly tied to water movements, which can both create and annihilate heterogeneity. However, spatial patterns are evident and common in inland waters indicating that processes creating heterogeneity are powerful enough to resist complete dispersion. There is much to learn about the processes that create heterogeneity and the consequences it has on many aspects of ecosystems. In Chapter 1, I assessed spatial patterns of nitrate in the Mississippi River and evaluated nitrogen cycling at multiple scales. The broad scale (~1000 km) pattern was primarily driven by the arrangement of water sources and the water residence times among river habitats. Although one river segment had notable retention, at the river-scale most of the nitrate entering the river was shunted downriver. At a finer scale (~40 km), heterogeneity was driven by water exchange between the river's main channel and lateral habitats. At both scales water residence times were too short to allow substantive processing. Thus, any nutrient mitigation strategies to reduce nitrogen loading to the Gulf of Mexico would require massive changes to the hydrology of the Mississippi River. In Chapter 2, I evaluated greenhouse gas spatial heterogeneity in a medium-sized eutrophic lake and the consequences of heterogeneity on fluxes to the atmosphere. Variation across the lake reflected the arrangement and chemistry of inflowing rivers and carbon cycling rates within the lake, leading to substantial variation in both space and time. Despite the existence of spatial heterogeneity, at the annual scale estimates from the lake center reasonably well-approximated the lake surface. However, it is unclear if this pattern is consistent among years or would apply to other lakes. Because of its elevated nutrient status, rates of metabolic processes (metabolism, methane production, etc.) were likely elevated, which may have allowed these biological drivers to shape heterogeneity. In Chapter 3, I consider drivers of heterogeneity among lakes and the structure of variation within lakes. The arrangement of river inlets, lake morphometry, and biology were all important for within lake heterogeneity. The relative scale for the physical drivers tended to be at or near the scale of the lake, while drivers of biology more frequently occurred at finer scales. We expand upon the landscape limnology framework (Soranno et al. 2010) by describing drivers of variation at scales finer than whole lake. We consider the consequences of within-lake patchiness on lake ecosystem functions. In Chapters 4 and 5, I summarize findings from this dissertation and the collaborative works pertaining to spatial patterns in aquatic ecosystems. I have had great joy working collaboratively and believe that the success of our group symbolizes our general attitude towards each other. In each of these papers, I provided substantial time, thought, and/or guidance. While our understanding of spatial heterogeneity in aquatic ecosystems has improved since this dissertation began, there is still much to learn.