The depositional history of the Knysna estuary since European colonization in the context of sea level and human impacts

Kelly Kirsten, Lauren Pretorius, Michael E. Meadows, Rieneke Weij, Marco Aquino-López, Helen G. Antonopoulos, Yakhuluntu Dubazana, Abdul Qadeer, Jemma Finch, Kunshan Bao

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1 Citation (Scopus)
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Abstract

Introduction: Estuaries are highly vulnerable systems and increasingly exposed to a number of environmental, climatic and human-induced stressors. The Knysna estuary and lagoon complex, on the south coast of South Africa, is regarded as environmentally and economically important, yet faces regional impacts resulting from ongoing urbanisation and land use change as well as the significant global threats of rising sea levels and changing climate. Although the estuary has been reasonably well studied in terms of modern ecological processes, little is known of how the system has responded to changes in the longer term, not least the impact of European colonization and subsequent population growth and economic development. Methods: In order to address this shortcoming, a series of shallow (<1 m) cores was extracted from a range of representative habitats and marine influences in the estuary and three of these (namely KNY-19A, KNY-19B, KNY-19G) selected for detailed analysis, including organic matter content, magnetic susceptibility, selected elemental analysis and particle size. Results and Discussion: Notwithstanding the challenges of dating estuarine sediments due to the possibility of erosion and resuspension, combined modelling of 210Pb and 14C ages is successfully deployed to develop an age-depth relationship for each core, providing a chronological framework for late Holocene environmental changes. Sedimentary characteristics of the three cores, taken in contrasting estuarine conditions, yield insights as to how different parts of the estuary responded to changes in sea level and anthropogenic activities in and around the Knysna basin, as well as in the wider catchment.

Original languageEnglish
Article number1120460
Number of pages13
JournalFrontiers in Ecology and Evolution
Volume11
DOIs
Publication statusPublished - 15 May 2023
Externally publishedYes

Bibliographical note

© 2023 Kirsten, Pretorius, Meadows, Weij, Aquino-López, Antonopoulos, Dubazana, Qadeer, Finch and Bao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Funder

This study was funded by the National Natural Science Foundation of China (41761144062, 41730646, 41725002, and 41771506) and by the National Research Foundation of South Africa (Grant no: 110776) under SANParks Permit Number: MEAD-ME/2018–007. KK acknowledges the DSI-NRF Centre of Excellence in Palaeosciences (Grant Ref#: COE2021NGP-KD), the NRF CPRR (Grant Ref#: 120806), the UCT #AdvancingWomxn funding for HERI and the UCT VC2030 Leadership grant scheme. LP acknowledges the support from the NRF (Grant ID: 129531). RW was funded by the Oppenheimer Memorial Trust and VC2030 Scholar Postdoctoral Fellowship awards. Publisher Copyright: Copyright © 2023 Kirsten, Pretorius, Meadows, Weij, Aquino-López, Antonopoulos, Dubazana, Qadeer, Finch and Bao.

Keywords

  • C
  • estuarine sediments
  • grain size
  • human impact
  • loss-on-ignition
  • magnetic susceptibility
  • pb
  • sedimentation rate

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology

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