Reviewing evidence of marine ecosystem change off South Africa

  • CL Moloney
  • ST Fennessy
  • MJ Gibbons
  • A Roychoudhury
  • FA Shillington
  • BP von der Heyden
  • K Watermeyer

Abstract

Recent changes have been observed in South African marine ecosystems. The main pressures on these ecosystems are fishing, climate change, pollution, ocean acidification and mining. The best long-term datasets are for trends in fishing pressures but there are many gaps, especially for non-commercial species. Fishing pressures have varied over time, depending on the species being caught. Little information exists for trends in other anthropogenic pressures. Field observations of environmental variables are limited in time and space. Remotely sensed satellite data have improved spatial and temporal coverage but the time-series are still too short to distinguish long-term trends from interannual and decadal variability. There are indications of recent cooling on the West and South coasts and warming on the East Coast over a period of 20–30 years. Oxygen concentrations on the West Coast have decreased over this period. Observed changes in offshore marine communities include southward and eastward changes in species distributions, changes in abundance of species, and probable alterations in foodweb dynamics. Causes of observed changes are difficult to attribute. Full understanding of marine ecosystem change requires ongoing and effective data collection, management and archiving, and coordination in carrying out ecosystem research.

Keywords: climate change, fishing, global change, marine ecosystems, ocean acidification, offshore mining, pollution

African Journal of Marine Science 2013, 35(3): 427–448

Author Biographies

CL Moloney
Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
ST Fennessy
Oceanographic Research Institute, PO Box 10712, Marine Parade, Durban 4056, South Africa
MJ Gibbons
Department of Biodiversity and Conservation Biology, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
A Roychoudhury
Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
FA Shillington
Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Department of Oceanography, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
BP von der Heyden
Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
K Watermeyer
Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
Published
2013-10-24
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X