Assessment of Annual Physico-Chemical Variability via High-Temporal Resolution Monitoring in an Antarctic Shallow Coastal Site (Terra Nova Bay, Ross Sea)

• Published in: Minerals
• Main Authors: Chiara Lombardi, Piotr Kuklinski, Andrea Bordone, Edoardo Spirandelli, Giancarlo Raiteri
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2021
• Subjects: Antarctica; environmental variability; pH measurement; underwater observatory; conductivity–temperature–depth (CTD) probe; autonomous; Mineralogy; QE351-399.2; Antarctic; Southern Ocean; Ross Sea; Terra Nova Bay; Antarc*; ice pack; Sea ice
• Online Access: https://doi.org/10.3390/min11040374; https://doaj.org/article/8d55d61e4c78420eb88bf3f6213898cd

The Southern Ocean is an important atmospheric carbon sink, and potential changes in the carbon flux in this region will affect the ocean as a whole. Thus, to monitor the variability of its physico-chemical parameters is becoming a priority. This study provides the first high-resolution all-year-round record of observed and computed physico-chemical data from a shallow coastal site in Terra Nova Bay (Ross Sea). From November 2018 to November 2019, an underwater observatory deployed at a 25 m depth under an ice pack recorded pressure ( p ), temperature ( t ), electrical conductivity ( C ), dissolved oxygen ( DO ), pH in total scale (pH T ), and illuminance ( E v ). Practical salinity ( S P ), density (ρ), tidal constituents, carbonate system parameters (total alkalinity (TA), carbon dioxide partial pressure ( p CO 2 ), calcite, and aragonite (Ω Ca , Ω Ar )), together with sea ice concentration ( SIC ) and chlorophyll-a ( Chl -a), were derived from measured and satellite data. t , DO , and pH T displayed the lowest values between July and November (–1.95 °C, 6.61 mL L −1 , 7.97) whereas the highest in January (+1.08 °C, 10.61 mL L −1 , 8.35). S P had the lowest values (33.72 PSU) in February and the highest (34.87 PSU) in September. E v peaked in March (201 lux), with the highest values (>50 lux) in correspondence to the lowest values of SIC and a delayed trend, between December and March, with respect to Chl -a values (0.2–1.1 mg m −3 ). Ω Ca and Ω Ar showed their highest average monthly values (±s.d.) in January (Ω Ca : 3.41 ± 0.27; Ω Ar : 2.14 ± 0.17), when DO had maximum values. The lowest Ω occurred in September (Ω Ca : 2.11 ± 0.02; Ω Ar : 1.32 ± 0.02), at the end of phytoplankton activity. No undersaturation for both calcite and aragonite was recorded during the study period. This study highlights that biological activities and physico-chemical variables of the investigated shallow coastal site are coupled and, in many cases, influence each other.