Thomas M Holmes

University of Tasmania · Institute for Marine and Antarctic Studies (IMAS)

Australia contributes a significant amount of dust-borne nutrients (including iron) to the Southern Ocean, which can stimulate marine primary productivity. A quantitative assessment of the variability of dust fluxes from Australia to the surrounding ocean is therefore important for investigating the impact of atmospheric deposition on the Southern...

While modeling efforts have furthered our understanding of marine iron biogeochemistry and its influence on carbon sequestration, observations of dissolved iron (dFe) and its relationship to physical, chemical and biological processes in the ocean are needed to both validate and inform model parameterization. Where iron comes from, how it is transp...

Low bioavailability of the vital element iron (Fe) limits primary production in large regions of the Southern Ocean, thus impacting phytoplankton community structures. Primary productivity seems to be particularly sensitive to the reduced form of iron (Fe(II)), which is thought to be the most readily bioavailable redox form of Fe in the ocean. Here...

Manganese (Mn) is an essential element involved in photosynthesis, yet its concentrations in Southern Ocean open waters are very low, arising from biological uptake and limited external inputs. At southern latitudes, waters overlying the Antarctic shelf are expected to have much higher Mn concentrations due to their proximity to external sources. I...

The availability of iron (Fe) to marine microbial communities is enhanced through complexation by ligands. In Fe limited environments, measuring the distribution and identifying the likely sources of ligands is therefore central to understanding the drivers of marine productivity. Antarctic coastal marine environments support highly productive ecos...

Hydrothermal iron supply contributes to the Southern Ocean carbon cycle via the regulation of regional export production. However, as hydrothermal iron input estimates are coupled to helium, which are uncertain depending on whether helium inputs are based on ridge spreading rates or inverse modelling, questions remain regarding the magnitude of the...

Despite widespread iron (Fe) limitation in the Southern Ocean, intense phytoplankton blooms are observed around productive coastal regions such as the Mertz Polynya (off George V Land and Adelie Land, East Antarctica; 140–155°E). Sources of Fe across coastal East Antarctica vary, with limited data available for late summer months. We investigated t...

Manganese (Mn) is an abundant element in the Earth's crust. However, its concentrations in open ocean seawater are low, where external inputs are scarce. In this study, we report the dissolved Mn and particulate Mn distributions in the Southern Ocean, measured along the GEOTRACES—SR3 transect, from Tasmania (Australia) to Antarctica in the Southern...

The Southern Ocean is the largest region in which iron limits the growth of phytoplankton. However, a phytoplankton bloom thousands of square kilometers in area forms each spring–summer in the Indian sector of the Southern Ocean, both above and to the east of the Kerguelen Plateau. The central region of the Kerguelen Plateau hosts the volcanically...

Hydrothermal vents are a recognized source of trace elements to the ocean inventory. Nevertheless, the contribution of slow-spreading ridges remains poorly resolved. To address this, high-resolution dissolved (<0.45 μm) iron (dFe) and manganese (dMn) samples were collected during the GEOTRACES HERMINE GApr07 process study at the Mid Atlantic Ridge....

Iron (Fe) is an essential micronutrient that controls phytoplankton growth in the Southern Ocean. Dissolved Fe (<0.4 μm) has been extensively studied due to its relatively high bioavailability. However, particulate Fe (>0.4 μm) is far more abundant and may also become bioavailable through biogeochemical processing. To assess natural Fe fertilisatio...

At the southern part of the northern Kerguelen Plateau (Southern Ocean) is an active volcanic hotspot, hosting volcanically active Heard Island and McDonald Islands (HIMI), the former of which is largely covered by glaciers. While offshore waters are persistently Fe limited, typical of the broader Southern Ocean, near shore waters over the Kerguele...

A seawater preconcentration system (seaFAST) with offline sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) detection was critically evaluated for ultra-low trace elemental analysis of Southern Ocean samples over a four-year period (2015-2018). The commercially available system employs two Nobias PA1 resin columns for buffer cle...

This review aims to bring into focus the current understanding of hydrothermal systems and plume dynamics, tracers of hydrothermalism and the contribution of iron from hydrothermal vents to the global oceanic iron budget. The review then explores hydrothermal effect on surface ocean productivity. It is now well documented that scarcity of iron limi...

Low iron (Fe) concentrations limit biological productivity in over a third of the world’s oceans. The Southern Ocean (SO) is the largest of these regions of Fe deficiency. However, within the Indian sector of the SO lays an oasis of relatively Fe rich waters overlaying the Kerguelen Plateau. At the southern part of the central Kerguelen plateau is...