A5058849224- Marine and coastal ecosystems
- Heavy metals in environment
- Geochemistry and Elemental Analysis
- Marine Biology and Ecology Research
- Geology and Paleoclimatology Research
- Mine drainage and remediation techniques
- Geochemistry and Geologic Mapping
- Isotope Analysis in Ecology
- Oceanographic and Atmospheric Processes
- Arctic and Antarctic ice dynamics
- Groundwater and Isotope Geochemistry
- Geological formations and processes
- Mercury impact and mitigation studies
- Marine animal studies overview
- Groundwater flow and contamination studies
- Aquatic Ecosystems and Phytoplankton Dynamics
- Coastal wetland ecosystem dynamics
- Microbial Community Ecology and Physiology
- Paleontology and Stratigraphy of Fossils
- Polar Research and Ecology
- Iron oxide chemistry and applications
- Marine and environmental studies
- Aquatic Ecosystems and Biodiversity
- Methane Hydrates and Related Phenomena
- Chromium effects and bioremediation
Stellenbosch University
2016-2025
Wageningen University & Research
2024
Engineers India (India)
2019
Central Inland Fisheries Research Institute
2015
University of Cape Town
2003-2008
Georgia Institute of Technology
1998-2004
Northwestern University
2001
Abstract. Due to its importance as a limiting nutrient for phytoplankton growth in large regions of the world's oceans, ocean water column observations concentration trace-metal iron (Fe) have increased markedly over recent decades. Here we compile >13 000 global measurements dissolved Fe (dFe) and make this available community. We then conduct synthesis study focussed on Southern Ocean, where dFe plays fundamental role governing carbon cycle, using four regions, six basins five depth...
Chemical distributions and microbial culture data are combined to identify the biogeochemical pathways that control cycles of manganese iron at oxic−anoxic transition Orca Basin. The redox coincides with an increase in salinity from 35 260‰; hence, mixing diagrams used constrain ranges over which consumption or production solute species takes place. Analysis shows very high dissolved Mn(II) levels (>400 μM) intermediate salinities (60−180‰) result dissimilatory (microbial) reduction oxides,...
Iron is a limiting nutrient in many parts of the oceans, including unproductive regions Southern Ocean. Although dominant fraction marine iron pool occurs form solid-phase particles, its chemical speciation and mineralogy are challenging to characterize on regional scale. We describe diverse array ranging from 20 700 nanometers diameter, waters Ocean euphotic zone. Distinct variations oxidation state composition these particles exist between coasts South Africa Antarctica, with different...
Abstract The Southern Ocean is a major sink of anthropogenic CO 2 and an important foraging area for top trophic level consumers. However, iron limitation sets upper limit to primary productivity. Here we report on considerably dense late summer phytoplankton bloom spanning 9000 km in the open ocean eastern Weddell Gyre. Over its 2.5 months duration, accumulated up 20 g C m −2 organic matter, which unusually high waters. We show that, over 1997–2019, this was likely driven by anomalies...
Abstract We present the first nitrogen isotope (δ 15 N) measurements of planktic foraminifera, paleoceanographically important zooplankton, from nutrient‐rich waters modern Southern Ocean. Foraminifera were collected net tows in Subantarctic and Polar Frontal Zones (SAZ PFZ, respectively) south Africa during winter 2015 late summer 2016. In summer, consistent with preferential uptake 14 N‐nitrate progressive, northward depletion nitrate by phytoplankton across Ocean, foraminifer tissue...
Zinc (Zn) is vital to marine organisms. Its active uptake by phytoplankton results in a substantial depletion of dissolved Zn, and Zn bound particulate organic matter replenishes the ocean through remineralization. However, we found that changes from phosphoryls cells recalcitrant inorganic pools include biogenic silica, clays, iron, manganese, aluminum oxides Southern Ocean water column. The abundances increase with depth are only phases preserved sediments. Changes particulate-Zn...
The quantification of dissolved metals in seawater requires pre-treatment before the measurement can be done, posing a risk contamination, and requiring time-consuming procedure. Despite development automated preconcentration units sophisticated instruments, entire process often introduces inaccuracies quantification, especially for low-metal seawaters. This study presents robust method measuring from accurately precisely using seaFAST quadrupole Inductively Coupled Plasma Mass Spectrometer...
In early May 2012, South Africa will take delivery of a new polar research ship, the SA Agulhas II, representing significant investment R1.6 billion in infrastructure to further strengthen Africa’s presence region, particularly support its stewardship Southern Ocean and Antarctic Treaty obligations. This follows closely on recent DST–CSIR investments Centre for High Performance Computing, used run global ocean–climate models, an ocean robotics observational capability five other facilities....
AbstractRecent changes have been observed in South African marine ecosystems. The main pressures on these ecosystems are fishing, climate change, pollution, ocean acidification and mining. best long-term datasets for trends fishing but there many gaps, especially non-commercial species. Fishing varied over time, depending the species being caught. Little information exists other anthropogenic pressures. Field observations of environmental variables limited time space. Remotely sensed...
Despite being thermodynamically less stable, small ferrous colloids (60 nm to 3 μm in diameter) remain an important component of the biogeochemical cycle at Earth's surface, yet their composition and structure reasons for persistence are still poorly understood. Here we use X-ray-based Fe L-edge carbon K-edge spectromicroscopy address speciation organic–mineral associations ferrous, ferric, Fe-poor particles collected from sampling sites both marine freshwater environments. We show that...
Abstract Seasonal progression of dissolved iron (DFe) concentrations in the upper water column was examined during four occupations Atlantic sector Southern Ocean. DFe inventories from euphotic and aphotic reservoirs decreased progressively July to February, while inorganic nitrogen January with no significant change between February. Results suggest that January, loss both predominantly support phytoplankton growth (iron‐to‐carbon uptake ratio 16 ± 3 μmol/mol), highlighting importance...
DATA REPORT article Front. Mar. Sci., 14 July 2020 | https://doi.org/10.3389/fmars.2020.00468