Seasonal and spatial patterns in nitrogen cycling and food web interactions in Lake Taupō New Zealand
type: CreativeWork
description: Lakes with high water quality and low productivity, commonly referred to as ‘oligotrophic’, are often viewed as relatively pristine and highly aesthetic ecosystems, but may still require management of nutrient inputs and fisheries. The ecosystem processes that determine functions in oligotrophic lakes are often distinct from those in eutrophic lakes, which are traditionally more actively managed. This is particularly true for nitrogen cycling which, in oligotrophic lakes, is closely coupled with food web dynamics. Strong nitrogen cycling-food web coupling in oligotrophic systems is partly related to greater significance of consumer nutrient recycling. Given that processes affecting nutrient cycles and food web dynamics can be actively managed (e.g., through catchment nutrient load regulation and fisheries management, respectively), understanding the interactions between these two processes is key to management of oligotrophic lakes globally. This thesis examines interactions between nitrogen cycling and food web dynamics in oligotrophic Lake Taupō. Lake Taupō is a large (616 km² in area), deep (92 m mean depth), warm monomictic lake in the North Island of New Zealand. It shares many of the characteristics typical of large, deep oligotrophic lakes globally and can be viewed as a model system to examine nutrient cycling-food web interactions. Since 2008, nitrogen loads to the lake have been restricted by local government regulation with the objective to maintain high standards of water quality. Lake Taupō is the only example globally of exclusively N management for water quality purposes. Abundance of rainbow trout (Oncorhynchus mykiss: Salmonidae), the top predator in the Taupō system, is managed through a regulated recreational fishery. Coincident with a period of declining water quality between 1995 and 2005, the trout in Lake Taupō underwent a drastic decline in abundance and individual size. However, connection between the changes in water quality and trout abund…
abstract: Lakes with high water quality and low productivity, commonly referred to as ‘oligotrophic’, are often viewed as relatively pristine and highly aesthetic ecosystems, but may still require management of nutrient inputs and fisheries. The ecosystem processes that determine functions in oligotrophic lakes are often distinct from those in eutrophic lakes, which are traditionally more actively managed. This is particularly true for nitrogen cycling which, in oligotrophic lakes, is closely coupled with food web dynamics. Strong nitrogen cycling-food web coupling in oligotrophic systems is partly related to greater significance of consumer nutrient recycling. Given that processes affecting nutrient cycles and food web dynamics can be actively managed (e.g., through catchment nutrient load regulation and fisheries management, respectively), understanding the interactions between these two processes is key to management of oligotrophic lakes globally. This thesis examines interactions between nitrogen cycling and food web dynamics in oligotrophic Lake Taupō. Lake Taupō is a large (616 km² in area), deep (92 m mean depth), warm monomictic lake in the North Island of New Zealand. It shares many of the characteristics typical of large, deep oligotrophic lakes globally and can be viewed as a model system to examine nutrient cycling-food web interactions. Since 2008, nitrogen loads to the lake have been restricted by local government regulation with the objective to maintain high standards of water quality. Lake Taupō is the only example globally of exclusively N management for water quality purposes. Abundance of rainbow trout (Oncorhynchus mykiss: Salmonidae), the top predator in the Taupō system, is managed through a regulated recreational fishery. Coincident with a period of declining water quality between 1995 and 2005, the trout in Lake Taupō underwent a drastic decline in abundance and individual size. However, connection between the changes in water quality and trout abund…
author: Stewart, Simon Donald
keywords: Nitrogen cycling, Lake Taupō, Limnology, Hydrodynamic model, Stable isotope biogeochemistry, Food web, Trout fishery
license: https://researchcommons.waikato.ac.nz/bitstreams/d44fdc25-e100-4665-ada4-4310cb969c05/download
date published: 2018
date modified: 2026-07-24T05:57:46Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Waikato