Research
Recently funded projects:
- Roychoudhury AN (2023-2026) Humpback whales in changing climate, Phase II Donor funding.
- Roychoudhury AN (2018-2022) Humpback whales in changing climate, Donor funding AUD 1,250,797
- Roychoudhury AN (2018-2020) Distribution and Speciation of Bioactive Trace Elements in Southern Ocean, SANAP, R 1,820,000
- Roychoudhury AN (2017-2019) Nanoparticles at Air-Sea interface. NRF Competitive Rated Researcher Grant, R 1,550,000
- Roychoudhury AN (2016-2019) TraceEx: Establishment of Center of excellence in Trace and Experimental Biogeochemistry, Donor funding, R 17 Million
- Roychoudhury AN (2015) ICP-MS mass spectrometer for ultra-trace metal analysis. National Equipment Program, NRF, R 2,699,000
- Roychoudhury AN (2015-2017) Speciation and interaction of iron nanoparticles in Southern Ocean, SANAP, R 1,353,500
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Humpback Whales in Changing Climate |
South African (SA), South American (SAm), and Australian (Au) coastal areas are home to the longest and largest annual whale migration. Migratory linked whale watching is a major global tourism industryand a major source of income for many countries. Humpback whales’ migratory pattern between Southern Ocean feeding grounds to coastal breeding regions of SA, AU and SAm (Fig. 1) is integrally linked to ocean ecosystem functioning. Climate shifts(e.g. El Niño-Southern Oscillation, Sea-surface temperature, Antarctic krill abundance, glacial melt linked nutrient supply) and anthropogenic impacts(e.g. excess nutrients and pollutants in breeding areas) are starting to affect whale migration behavior, mortality and reproductive output. I intend to investigate that despite international protection schemes (since 1935) aided whale population increase, what is causing declining patterns in abundance of coastal breeding whales and a shift to longer reproductive cycles (less calves). In a concerted effort from scientists from three continents, the research will involve global ocean circulation modeling, ocean observation and whale sighting data to link climate and ocean productivity changes in feeding and breeding areas to the prevalence of whales in coastal waters of SA, AU, and SAm. New insights will help future governance, regulation and management of marine ecosystem services, and protection of Antarctic whale feeding sanctuaries (e.g. Krill resource exploitation).
Keywords: Whales, climate change, productivity, migration, tourism, assessment, prediction, service
Keywords: Whales, climate change, productivity, migration, tourism, assessment, prediction, service
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Speciation and distribution of bioactive trace metals in Southern Ocean |
The biologically important trace metals Fe, Mn, Co, Ni, Cu, Zn and Cd are essential for phytoplankton growth and therefore also play an important role in atmospheric CO2 regulation and climate change (Martin et al., 1990; Morel et al.,1994; Boyd et al., 2000; Boye and van den Berg, 2000; Boyd et al., 2007). Looking at our current situation of rising atmospheric CO2 levels, with the prediction of increasing seawater acidity, resulting in changes in ocean chemistry and the dependent biology (Millero et al, 2009), it is vital to have more knowledge on these interdependent systems. In order to understand the bioavailability of these trace elements and how they increase or limit phytoplankton production, information is required not only on their concentration profiles within the water column, but also on their chemical speciation as well as physical form. Through this project we aim to test the following hypotheses:
- The distribution of bioactive trace metals in the waters of Southern Ocean below South Africa varies as a function of frontal zones (Subtropical, Subantarctic, Polar), season (summer, winter), their source and biological community structure. Size fractionation within the dissolved phase affect their speciation and bioavailability thereby exerting a control over Southern Ocean primary productivity.
- The size, structure, crystallinity, and speciation of pTM (particulate trace metals) varies in surface waters and with water column depth in the Southern Ocean.
- Complexing organic ligands (e.g., carboxylates, phenolates) and organic coatings protect speciation of particles and dissolved species in the surface and sub-surface waters
- Larger (micron-sized) and crystalline pTM species are rendered bioavailable by biogeochemical transformation into amorphous, nanoparticulate pTM and dissolved species
Nano-particles in the ocean environment
A great deal of research activity has focused on addition of material to the ocean across the air – sea interface since the realizations that iron (Fe) plays a key role as a limiting nutrient for primary productivity or biological nitrogen fixation in large areas of the global ocean (Martin, 1990; Martin, & Fitzwater, 1988; Falkowski, 1997) and that the deposition of mineral dust from the atmosphere was a major source of Fe to the remote ocean (Jickells, et al., 2005). That research has led to huge advances in the understanding of the impact of Fe biogeochemistry on the marine carbon cycle (Boyd, et al. 2007), the sources and composition of Fe-bearing material to the atmosphere (Nickovic, et al. 2012; Luo, et al., 2008) and the chemical and physical processing of that material during transportation through the atmosphere (Baker, & Croot, 2010). In this project we posit that it is the properties of dust colloids and nanoparticles, by virtue of their speciation, dissolution kinetics and uptake pathways by biota, that play a major role in controlling ocean productivity.
In our previous study focused on nano- and colloidal-iron (pFe) in natural environments we show their ubiquitous presence in the Southern Ocean waters. Interestingly, we find their speciation quite varied along a transect between Cape Town and Antarctica (von der Heyden et al., 2012). We also noticed a clear relationship between biological productivity and particulate iron speciation. This finding is of great significance as iron is considered a limiting nutrient in the oceans and largely controls the carbon cycle (atmospheric carbon drawdown) in major parts of the Southern Ocean.
A great deal of research activity has focused on addition of material to the ocean across the air – sea interface since the realizations that iron (Fe) plays a key role as a limiting nutrient for primary productivity or biological nitrogen fixation in large areas of the global ocean (Martin, 1990; Martin, & Fitzwater, 1988; Falkowski, 1997) and that the deposition of mineral dust from the atmosphere was a major source of Fe to the remote ocean (Jickells, et al., 2005). That research has led to huge advances in the understanding of the impact of Fe biogeochemistry on the marine carbon cycle (Boyd, et al. 2007), the sources and composition of Fe-bearing material to the atmosphere (Nickovic, et al. 2012; Luo, et al., 2008) and the chemical and physical processing of that material during transportation through the atmosphere (Baker, & Croot, 2010). In this project we posit that it is the properties of dust colloids and nanoparticles, by virtue of their speciation, dissolution kinetics and uptake pathways by biota, that play a major role in controlling ocean productivity.
In our previous study focused on nano- and colloidal-iron (pFe) in natural environments we show their ubiquitous presence in the Southern Ocean waters. Interestingly, we find their speciation quite varied along a transect between Cape Town and Antarctica (von der Heyden et al., 2012). We also noticed a clear relationship between biological productivity and particulate iron speciation. This finding is of great significance as iron is considered a limiting nutrient in the oceans and largely controls the carbon cycle (atmospheric carbon drawdown) in major parts of the Southern Ocean.