Potential sources of particulate iron in surface and deep waters of the terra nova bay (Ross sea, antarctica)

The distribution of particulate Fe (pFe), suspended particulate matter (SPM), and other particulate trace metals were investigated in Terra Nova Bay as part of CDW Effects on glaciaL mElting and on Bulk of Fe in the Western Ross sea (CELEBeR) and Plankton biodiversity and functioning of the Ross Sea ecosystems in a changing Southern Ocean (P-ROSE) projects. Variable concentrations of SPM (0.09–97 mg L−1 ), pFe (0.51–8.70 nM) and other trace metals were found in the Antarctic Surface waters (AASW) layer, where the addition of meltwater contributed to the pool with both lithogenic and biogenic forms. The deeper layer of the water column was occupied by High Salinity Shelf Water (HSSW) and Terra Nova Bay Ice Shelf Water (TISW) encompassing glacial water as confirmed by the lightest δ18 O measured values. The concentration of pFe in TISW (11.7 ± 9.2 nM) was higher than in HSSW samples (5.55 ± 4.43 nM), suggesting that the drainage of material released from glaciers surrounding the area is relevant in terms of pFe contribution. Particulate Fe/Al and Mn/Al ratios were substantially in excess compared with the mean crustal ratios. Microscopic analyses confirmed that more labile Fe oxyhydroxides and authigenic MnO2 phases were present together with biogenic sinking material. Future expected increasing melt rates of these glaciers enlarge Fe input, thus having a greater role in supplying iron and counteracting the reductions in sea ice cover around Terra Nova Bay

HPLC-DAD purification and characterization of meta-cresol-purple for spectrophotometric seawater pH measurements

High-quality pH measurements are essential for observing ocean acidification and interpreting its chemical and ecological effects. Spectrophotometric measure is the preferred method for pH analysis of seawater because of its high reproducibility and excellent precision. Meta-cresol purple (mCP) is one of the most used indicator dyes for spectrophotometric pH determination. Impurities in indicator salts can significantly bias spectrophotometric pH determinations, and there-fore the use of purified mCP is recommended. This work describes the use of a fast, simple, and green-friendly High-Performance-Liquid Chromatography (HPLC) procedure for purification of mCP dye solution. A C18 reversed phase column was used, and different compositions of the mobile phase were considered. The selected mobile phase was 85% Milli-Q water and 15% CH3 CN pH 8.0 that allowed reasonable run time and a suitable purified mCP retention time (4.65 \ub1 0.005 min). Aliquots of purified mCP were mixed and evaporated by rotary evaporator that resulted in the fastest preconcentration procedure among those considered in this study. Purified mCP was used for measuring the pH in seawater samples collected in the Ross Sea (Antarctica) and the values ranged between 8.202 and 7.983, with the highest values at the surface

Carbonate system data tracing freshwater inflow into the Ross Sea through the eastern gate and along the Ross Ice Shelf (Antarctica)

The eastern Ross Sea is a key area to understand the role of the Amundsen Sea inflow of freshwater that can influence the Ross Sea water properties and salt budget. A survey was carried out in the eastern Ross Sea during the austral summer 2019-20 to evaluate the contribution of the Amundsen Sea Water (ASW) to the salinity variability. A total of 248 seawater samples were collected f\or the analysis of total alkalinity (A(T)) and pH. The data collected were used together with temperature and salinity to obtain a full description of the carbonate system properties including total inorganic carbon (C-T), CO2 partial pressure (pCO(2)), calcium carbonate saturation state of aragonite and calcite (ohm), and Revelle factor. Moreover, we estimated the anthropogenic carbon (C-ant) throughout the TrOCA method to better understand the carbon cycle, also considering the effect of atmospheric CO2 uptake on ocean acidification. We used principal component analysis (PCA) to investigate the major controls on the carbonate system parameters with the aim of defining their sensitivity as chemical tracers. The changes in carbonate chemistry in surface waters were mainly due to the physical properties. A(T) and pH traced the entry of the ASW showing limited mixing between water masses on the shelf area. Shelf waters were enriched in C-ant, which resulted lower than the estimated value for shelf waters produced in western Ross Sea

Carbonate system data tracing freshwater inflow into the Ross Sea through the eastern gate and along the Ross Ice Shelf (Antarctica)

The eastern Ross Sea is a key area to understand the role of the Amundsen Sea inflow of freshwater that can influence the Ross Sea water properties and salt budget. A survey was carried out in the eastern Ross Sea during the austral summer 2019-20 to evaluate the contribution of the Amundsen Sea Water (ASW) to the salinity variability. A total of 248 seawater samples were collected f\or the analysis of total alkalinity (A(T)) and pH. The data collected were used together with temperature and salinity to obtain a full description of the carbonate system properties including total inorganic carbon (C-T), CO2 partial pressure (pCO(2)), calcium carbonate saturation state of aragonite and calcite (ohm), and Revelle factor. Moreover, we estimated the anthropogenic carbon (C-ant) throughout the TrOCA method to better understand the carbon cycle, also considering the effect of atmospheric CO2 uptake on ocean acidification. We used principal component analysis (PCA) to investigate the major controls on the carbonate system parameters with the aim of defining their sensitivity as chemical tracers. The changes in carbonate chemistry in surface waters were mainly due to the physical properties. A(T) and pH traced the entry of the ASW showing limited mixing between water masses on the shelf area. Shelf waters were enriched in C-ant, which resulted lower than the estimated value for shelf waters produced in western Ross Sea