{"id":{"repo_id":"cape-town","oai_identifier":"oai:open.uct.ac.za:11427/37014"},"canonical_url":"https://search.dev.ndltd.org/etd/cape-town/oai:open.uct.ac.za:11427/37014","repository":{"repo_id":"cape-town","name":"University of Cape Town","base_url":"https://open.uct.ac.za/oai/request"},"display":{"title":"The diatom record: Reconstructing historically recent environmental change in the Knysna estuary","abstract":"Estuaries are highly productive systems responsible for many vital ecosystem goods and services. Therefore, it is not surprising that the diversity and abundance of exploitable estuarine resources have attracted human settlers for centuries. Increased anthropogenic pressures have placed much stress on estuarine and coastal ecosystems. This is the case of the Knysna Estuary, which is South Africa's highestrated estuary in terms of biodiversity and conservation importance. This study represents the first highresolution diatom record from the Knysna Estuary encompassing the last ∼680 years. Diatom analysis was employed to reconstruct salinity, nutrients, and saprobity variables in addition to inferring community structure and trophic status over time by creating an age-depth model based on a combination of ²¹⁰Pb and radiocarbon dates. The record is divided into three distinctive phases, namely the Pre-Colonial (∼610 to ∼200 cal BP), Colonial (∼200 cal BP to ∼1900 CE), and Anthropogenically Impacted Lagoon Phase (∼1900 CE to Present). These phases correspond with the Little Ice Age (LIA), the arrival of colonialists, and anthropogenic impacts linked to rapid population growth and land use change. More specifically, the dominance of marine species illustrate that the first phase of the LIA is associated with drier conditions, whereas a growing dilute and eutrophic assemblage reveals a wetter second phase of the LIA coinciding with the arrival of colonialists in the 1700s. Consequently, it is challenging to disentangle natural climate change with the effects of deforestation and agriculture during the Colonial Phase. A shift towards an increasingly fresh, hypertrophic, and polysaprobic diatom assemblage is indicative of the intensification of agricultural practices in the catchment from ∼1900 CE to present, stormwater inflow, the inefficiency of the Knysna Waste Water Treatment Works (WWTW), and sewage entering the estuary via streams during the final phase of the estuary's development. This high-resolution record is of vital importance, as it is one of a few palaeoestuarine studies in the Southern Hemisphere to illuminate the effects of natural climate change and human-induced impacts on an estuarine system. Despite the limitations, this study illustrates that diatoms are a useful tool for tracking environmental change in estuaries.","abstract_html":"Estuaries are highly productive systems responsible for many vital ecosystem goods and services. Therefore, it is not surprising that the diversity and abundance of exploitable estuarine resources have attracted human settlers for centuries. Increased anthropogenic pressures have placed much stress on estuarine and coastal ecosystems. This is the case of the Knysna Estuary, which is South Africa's highestrated estuary in terms of biodiversity and conservation importance. This study represents the first highresolution diatom record from the Knysna Estuary encompassing the last ∼680 years. Diatom analysis was employed to reconstruct salinity, nutrients, and saprobity variables in addition to inferring community structure and trophic status over time by creating an age-depth model based on a combination of ²¹⁰Pb and radiocarbon dates. The record is divided into three distinctive phases, namely the Pre-Colonial (∼610 to ∼200 cal BP), Colonial (∼200 cal BP to ∼1900 CE), and Anthropogenically Impacted Lagoon Phase (∼1900 CE to Present). These phases correspond with the Little Ice Age (LIA), the arrival of colonialists, and anthropogenic impacts linked to rapid population growth and land use change. More specifically, the dominance of marine species illustrate that the first phase of the LIA is associated with drier conditions, whereas a growing dilute and eutrophic assemblage reveals a wetter second phase of the LIA coinciding with the arrival of colonialists in the 1700s. Consequently, it is challenging to disentangle natural climate change with the effects of deforestation and agriculture during the Colonial Phase. A shift towards an increasingly fresh, hypertrophic, and polysaprobic diatom assemblage is indicative of the intensification of agricultural practices in the catchment from ∼1900 CE to present, stormwater inflow, the inefficiency of the Knysna Waste Water Treatment Works (WWTW), and sewage entering the estuary via streams during the final phase of the estuary's development. This high-resolution record is of vital importance, as it is one of a few palaeoestuarine studies in the Southern Hemisphere to illuminate the effects of natural climate change and human-induced impacts on an estuarine system. Despite the limitations, this study illustrates that diatoms are a useful tool for tracking environmental change in estuaries.","abstract_has_math":false,"creators":["Antonopoulos, Helen Grace"],"institution":"Department of Environmental and Geographical Science","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Meadows, Michael Edward","Kirsten, Kelly L"],"committee_chairs":[],"committee_members":[],"year":2022,"date_issued":"2022","date_published":"2022","updated_at":"2026-07-22T22:23:13Z","subjects":["Diatoms","estuaries","historically recent change","Little Ice Age","land use change","anthropogenic impact"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11427/37014","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Meadows, Michael Edward","Kirsten, Kelly L"]},{"key":"dc:creator","label":"Author","values":["Antonopoulos, Helen Grace"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2023-02-23T10:10:44Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2023-02-23T10:10:44Z"]},{"key":"dc:date.issued","label":"Date","values":["2022"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Department of Environmental and Geographical Science"]},{"key":"dc:type","label":"Dc Type","values":["Master Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Masters","MSc"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Diatoms","estuaries","historically recent change","Little Ice Age","land use change","anthropogenic impact"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/11427/37014"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Estuaries are highly productive systems responsible for many vital ecosystem goods and services. Therefore, it is not surprising that the diversity and abundance of exploitable estuarine resources have attracted human settlers for centuries. Increased anthropogenic pressures have placed much stress on estuarine and coastal ecosystems. This is the case of the Knysna Estuary, which is South Africa's highestrated estuary in terms of biodiversity and conservation importance. This study represents the first highresolution diatom record from the Knysna Estuary encompassing the last ∼680 years. Diatom analysis was employed to reconstruct salinity, nutrients, and saprobity variables in addition to inferring community structure and trophic status over time by creating an age-depth model based on a combination of ²¹⁰Pb and radiocarbon dates. The record is divided into three distinctive phases, namely the Pre-Colonial (∼610 to ∼200 cal BP), Colonial (∼200 cal BP to ∼1900 CE), and Anthropogenically Impacted Lagoon Phase (∼1900 CE to Present). These phases correspond with the Little Ice Age (LIA), the arrival of colonialists, and anthropogenic impacts linked to rapid population growth and land use change. More specifically, the dominance of marine species illustrate that the first phase of the LIA is associated with drier conditions, whereas a growing dilute and eutrophic assemblage reveals a wetter second phase of the LIA coinciding with the arrival of colonialists in the 1700s. Consequently, it is challenging to disentangle natural climate change with the effects of deforestation and agriculture during the Colonial Phase. A shift towards an increasingly fresh, hypertrophic, and polysaprobic diatom assemblage is indicative of the intensification of agricultural practices in the catchment from ∼1900 CE to present, stormwater inflow, the inefficiency of the Knysna Waste Water Treatment Works (WWTW), and sewage entering the estuary via streams during the final phase of the estuary's development. This high-resolution record is of vital importance, as it is one of a few palaeoestuarine studies in the Southern Hemisphere to illuminate the effects of natural climate change and human-induced impacts on an estuarine system. Despite the limitations, this study illustrates that diatoms are a useful tool for tracking environmental change in estuaries."]},{"key":"dc:title","label":"Title","values":["The diatom record: Reconstructing historically recent environmental change in the Knysna estuary"]}]}],"canonical_facts":{"dc:contributor.advisor":["Meadows, Michael Edward","Kirsten, Kelly L"],"dc:creator":["Antonopoulos, Helen Grace"],"dc:date.accessioned":["2023-02-23T10:10:44Z"],"dc:date.available":["2023-02-23T10:10:44Z"],"dc:date.issued":["2022"],"dc:description.abstract":["Estuaries are highly productive systems responsible for many vital ecosystem goods and services. Therefore, it is not surprising that the diversity and abundance of exploitable estuarine resources have attracted human settlers for centuries. Increased anthropogenic pressures have placed much stress on estuarine and coastal ecosystems. This is the case of the Knysna Estuary, which is South Africa's highestrated estuary in terms of biodiversity and conservation importance. This study represents the first highresolution diatom record from the Knysna Estuary encompassing the last ∼680 years. Diatom analysis was employed to reconstruct salinity, nutrients, and saprobity variables in addition to inferring community structure and trophic status over time by creating an age-depth model based on a combination of ²¹⁰Pb and radiocarbon dates. The record is divided into three distinctive phases, namely the Pre-Colonial (∼610 to ∼200 cal BP), Colonial (∼200 cal BP to ∼1900 CE), and Anthropogenically Impacted Lagoon Phase (∼1900 CE to Present). These phases correspond with the Little Ice Age (LIA), the arrival of colonialists, and anthropogenic impacts linked to rapid population growth and land use change. More specifically, the dominance of marine species illustrate that the first phase of the LIA is associated with drier conditions, whereas a growing dilute and eutrophic assemblage reveals a wetter second phase of the LIA coinciding with the arrival of colonialists in the 1700s. Consequently, it is challenging to disentangle natural climate change with the effects of deforestation and agriculture during the Colonial Phase. A shift towards an increasingly fresh, hypertrophic, and polysaprobic diatom assemblage is indicative of the intensification of agricultural practices in the catchment from ∼1900 CE to present, stormwater inflow, the inefficiency of the Knysna Waste Water Treatment Works (WWTW), and sewage entering the estuary via streams during the final phase of the estuary's development. This high-resolution record is of vital importance, as it is one of a few palaeoestuarine studies in the Southern Hemisphere to illuminate the effects of natural climate change and human-induced impacts on an estuarine system. Despite the limitations, this study illustrates that diatoms are a useful tool for tracking environmental change in estuaries."],"dc:identifier.uri":["http://hdl.handle.net/11427/37014"],"dc:publisher.department":["Department of Environmental and Geographical Science"],"dc:subject":["Diatoms","estuaries","historically recent change","Little Ice Age","land use change","anthropogenic impact"],"dc:title":["The diatom record: Reconstructing historically recent environmental change in the Knysna estuary"],"dc:type":["Master Thesis"],"dc:type.qualificationlevel":["Masters","MSc"]},"updated_at":"2026-07-22T22:23:13Z"}