Novel approaches for modelling changes in phytoplankton diversity and lake ecosystem function
type: CreativeWork
description: Ecosystem function represents the collective outcome of many different processes. Function may be interrupted by events that originate from outside a system, influencing biological diversity dynamics. Difficulties in expressing how a system is functioning originate firstly from being able to define a normative status for a dynamic system and secondly from the accuracy of common metrics of biodiversity changes. In this thesis, I used a numerical model and high-frequency ecological observations to express functioning of a system. Chapter 2 used biogeochemical parameter perturbations in a lake ecological model to identify seasonal parameter sensitivity variabilities. A set of internal process parameters of calibrated shallow eutrophic Lake Waahi DYRESM-CAEDYM ecological model was used to apply Monte-Carlo perturbation. Analysis was conducted by examining the collective results variability, a “spread” of the ensemble results from the iteration. The results showed that the spreads were small when lake inflows had high discharge, suggesting that lake internal dynamics had lesser effect on water quality and inflows dominated the system dynamics. Due to the simplicity of the methods, regular use of perturbation methods is suggested to assess model uncertainty and to better understand the model. Chapter 3 used interdisciplinary methods to identify changes in dissolved oxygen (DO) observations caused by biological processes. DO in lakes is a key indicator of ecosystem function. Methods used in this chapter included expert panel decision making, Symbolic Aggregate approXimation (SAX) analysis, and text classification. The use of an expert panel was motivated by the common practice of DO data visual assessment. Variability in experts’ boundaries for data quality were observed by data survey, reinforcing the necessity of robust and reproducible methods for unbiased analysis. Surface DO sensor data from 18 global lakes were used to create day-long data segments. The modelling fra…
abstract: Ecosystem function represents the collective outcome of many different processes. Function may be interrupted by events that originate from outside a system, influencing biological diversity dynamics. Difficulties in expressing how a system is functioning originate firstly from being able to define a normative status for a dynamic system and secondly from the accuracy of common metrics of biodiversity changes. In this thesis, I used a numerical model and high-frequency ecological observations to express functioning of a system. Chapter 2 used biogeochemical parameter perturbations in a lake ecological model to identify seasonal parameter sensitivity variabilities. A set of internal process parameters of calibrated shallow eutrophic Lake Waahi DYRESM-CAEDYM ecological model was used to apply Monte-Carlo perturbation. Analysis was conducted by examining the collective results variability, a “spread” of the ensemble results from the iteration. The results showed that the spreads were small when lake inflows had high discharge, suggesting that lake internal dynamics had lesser effect on water quality and inflows dominated the system dynamics. Due to the simplicity of the methods, regular use of perturbation methods is suggested to assess model uncertainty and to better understand the model. Chapter 3 used interdisciplinary methods to identify changes in dissolved oxygen (DO) observations caused by biological processes. DO in lakes is a key indicator of ecosystem function. Methods used in this chapter included expert panel decision making, Symbolic Aggregate approXimation (SAX) analysis, and text classification. The use of an expert panel was motivated by the common practice of DO data visual assessment. Variability in experts’ boundaries for data quality were observed by data survey, reinforcing the necessity of robust and reproducible methods for unbiased analysis. Surface DO sensor data from 18 global lakes were used to create day-long data segments. The modelling fra…
author: Muraoka, Kohji
license: https://researchcommons.waikato.ac.nz/bitstreams/3a544949-8542-4395-8d0a-b135a76e2e10/download
date published: 2019
date modified: 2026-07-24T05:57:55Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Waikato