Simon, KevinPerry, GeorgeGregersen, Rose Georgina2021-05-162021-05-162020https://hdl.handle.net/2292/55092Studies of anthropogenic impacts on lake ecosystems are limited by the scarcity of long-term records. Furthermore, paleolimnological approaches utilised to address missing records are restricted by various important epistemological issues and theoretical assumptions. In this thesis I aimed to address some of the limitations to our understanding, and thus management, of long-term lake change in the face of anthropogenic impacts. I used diatoms, single celled photosynthetic organisms, as models for lake response to impacts. Using paleolimnological records of lake diatoms, I investigated the influence of prior human impacts on lake response and resilience to recent land use change. I found evidence for impacts of both prehistoric and contemporary human land use; however, the effects of current land use practices far exceed the effects of prehistoric humans in both pace and magnitude. I assessed the applicability of trait-based methods in expanding our understanding of lake response to anthropogenic stress, finding evidence that trajectories of diatom cell size add important information to paleo-diatom analyses, and may help to elucidate the effects of land use impacts on lake structure and function. Using a nutrient amendment experiment, I investigated diatom species specific responses to nutrient impacts, in a New Zealand context. The experimental results highlight that diatom response to environmental stressors is highly context dependent and should not be considered fixed either among lakes or environmental conditions. The experimental results also have implications for lake nutrient management in New Zealand, reinforcing that reductions in both nitrogen and phosphorous are required. Finally, I assessed novel metabarcoding methods to overcome the methodological limitations of morphological diatom identification in paleolimnology. DNA metabarcoding performed significantly worse than morphological techniques. However, metabarcoding did expand taxonomy for some taxa, and thus this method warrants further investigation. Overall, my research both addresses and highlights several limitations to our understanding of long-term lake ecosystem change. Most importantly, for us to halt the decline of lake environments, an approach from both short-term fine grain studies and long term paleolimnological perspectives is required.Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htmhttp://creativecommons.org/licenses/by-nc-sa/3.0/nz/Thesis2021-05-10Copyright: The authorhttp://purl.org/eprint/accessRights/OpenAccessQ112952178