Physical Sciences and Mathematics Commons^™

Phytoplankton Mortality In An Urban Pond: Understanding The Roles Of Abiotic Factors, Grazing Pressure And Allelopathy, Lauren J. Simmons

Theses and Dissertations

Phytoplankton are found in dynamic aquatic environments, subjected to variations in abiotic (i.e., light, temperature, nutrients) and biotic (i.e., grazing, species interactions) conditions. Phytoplankton responses to these environmental variations are typically observed as changes in chlorophyll a (a surrogate for biomass), but such measurements do not provide information about individual taxa and cannot provide information about cell condition, for example, whether phytoplankton are living or dead. Furthermore, in examining the dynamics of phytoplankton, emphasis is placed on growth, but consideration of loss processes is usually limited to grazing and sedimentation, and not cell death The present study examined cell death …

Mathematical Modeling And Analysis Of A Phytoplankton Competition Model Incorporating Preferential Nutrient Uptake, Thomas George Stojsavljevic Jr

Theses and Dissertations

Phytoplankton live in a complex environment with two essential resources forming various gradients. Light supplied from above is never homogeneously distributed in a body of water due to refraction and absorption from biomass present in the

ecosystem and from other sources. Nutrients in turn are typically supplied from below. In poorly mixed water columns, phytoplankton can be heterogeneously distributed forming various layering patterns. We present a new reaction-diffusion-taxis model describing the vertical distribution of two phytoplankton species competing for two nutrients, one of which is assumed to be preferred. The parameter space of the model is analyzed for parameter identifiability …

Spatial And Temporal Variation Of Phytoplankton Production In Lake Michigan, Katelyn Alexis Bockwoldt

Theses and Dissertations

Although many studies have documented decreases in phytoplankton production since the quagga mussel invasion, we currently have a limited understanding of the spatial variation and temporal dynamics of phytoplankton production in Lake Michigan. In this study, phytoplankton production and seston stoichiometry were measured bi-weekly near Milwaukee, three times at two northern basin sites, and along three nearshore-offshore transects from May to November 2017, as well as at 5-6 sites on three whole-lake surveys in 2016 and 2017. Estimates of growth rates were calculated from phytoplankton production and carbon measurements. In spring 2016 and 2017, growth estimates were similar across the …

Modelling Of Dreissenid Mussel Impacts On Lake Michigan, Chunqi Shen

Theses and Dissertations

Invasive dreissenid mussel appear to have profoundly altered Great Lakes food webs and nutrient cycles during the past several decades. Recent declines of phytoplankton were supposed to be highly related with the increase of mussel population. These phytoplankton declines were further found to be coincident with declines in the abundance of planktivorous fish. In addition, the resurgence of Cladophora in Great lakes was estimated to be associated with the high density colonization of mussels. More light is available at lake bottom due to the mussels’ graze effect. The mussels further promote Cladophora growth by fertilizing it with nutrient-rich excrement. And …

Mathematical Modeling Of Competition For Light And Nutrients Between Phytoplankton Species In A Poorly Mixed Water Column, Thomas George Stojsavljevic

Theses and Dissertations

Phytoplankton live in a complex environment with two essential resources forming various gradients. Light supplied from above is never homogeneously distributed in a body of water due to refraction and absorption from biomass present in the ecosystem and from other sources. Nutrients in turn are typically supplied from below. In poorly mixed water columns phytoplankton can be heterogeneously distributed forming various layering patterns. The relationship between the location and the thickness of the layers is an open problem of interest. Here we present three models which study how competition for light and resources can form common layering patterns seen in …

Phytoplankton Life History Events: Resting Stages And Physiological Cell Death, Christine R. Kozik

Theses and Dissertations

Understanding and predicting changes in phytoplankton populations requires knowledge of key life history processes such as recruitment from benthic resting stages and losses due to sedimentation and cell death. Currently, these processes are poorly understood in freshwater systems. Phytoplankton resting stage and cell death life history events were separately examined in two freshwater systems in Wisconsin, four northern lakes and an urban pond. In the norther lakes, sedimentation and benthic recruitment were examined using sediment and recruitment traps that were sampled weekly over two summers. Sedimentation and benthic recruitment contributed little to changes in standing crop chl a, but rather …

Freshwater Phytoplankton Populations Detected Using High Pressure Liquid Chromatography (Hplc) Of Taxon-Specific Pigments, Lauren Jeanne Simmons

Theses and Dissertations

Phytoplankton are key primary producers in aquatic ecosystems, and the principle food source for primary consumers. Individual phytoplankton species respond to different physical, chemical and biological parameters, so monitoring taxonomic composition of the phytoplankton community is a means to monitor changes in environmental conditions. Phytoplankton community changes have frequently been monitored by estimating biomass (using chlorophyll a, measured fluorometrically), and taxonomic data obtained from cell counts. While such methods are useful, they are time-consuming. I hypothesized that high pressure liquid chromatography (HPLC) methods, which have been frequently used in marine systems, would allow separation and identification of key pigments. …