Frontal dynamics and water mass variability on the Campbell Plateau

Forcén-Vázquez, Aitana; Williams, Michael; Bowen, Melissa; Carter, Lionel; Bostock, Helen C.

doi:10.1080/00288330.2021.1875490

Cited by 12 publications

(9 citation statements)

References 63 publications

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“…Subantarctic Mode Water and Antarctic Intermediate Water are present over the Campbell Plateau and Bounty Trough, respectively (Forcén-Vázquez et al, 2021). The steep slope of the Campbell Plateau directs the flow of the full depth SAF around its south-eastern flank (Chiswell et al, 2015;Forcén-Vázquez et al, 2021). Previous work also found a similar pattern of radiolarian distribution in the Southwest Pacific region using factor analysis to show links to water mass associations in this region (Cortese and Prebble, 2015).…”

Section: Sw Pacific Sectormentioning

confidence: 57%

Ecoregionalisation of the Southern Ocean Using Radiolarians

et al. 2022

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The Southern Ocean is an important region for identifying ecoregions, both to assist in conservation efforts as well as for paleoecological studies. In this paper we use the Southern Ocean Radiolarian Dataset (SORAD), a compilation of surface sediment radiolarian census data, to determine radiolarian ecoregions throughout the Southern Ocean within the Atlantic, Indian and Southwest Pacific Sectors. The distribution of radiolarian species is explored using the unconstrained non-Metric Multidimensional Scaling to identify gradients in species assemblage variability, as well as distinct and sharp changes in assemblage composition. Ecoregions are assigned to groups of sites using Multivariate Regression Tree analysis, and environmental variables are assessed for their explanatory power. Radiolarian distribution was found to be heterogeneous throughout the Southern Ocean, with each Sector hosting a unique group of radiolarian ecoregions. A total of 6 ecoregions were identified for the Atlantic Sector, 8 for the Indian Sector and 6 for the Southwest Pacific Sector. Ecoregions were generally latitudinally distributed, but also appear to be influenced by significant oceanographic features, such as plateaux and islands, large eddy fields, hydrological fronts and sea ice. This study highlights the need for further exploration of radiolarian ecology, and for caution when using radiolarian assemblage variability in paleo-environmental studies.

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Section: Sw Pacific Sectormentioning

confidence: 57%

Ecoregionalisation of the Southern Ocean Using Radiolarians

et al. 2022

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“…In the S-STF, Chloropicon sieburthii made a substantial contribution in addition to the more dominant Chloroparvula pacifica (Figure S10). Whether this regional preference was linked to the bathymetric and hydrographic characteristics of the plateau (Forcén-Vázquez et al 2021; Neil et al 2004), the natural iron fertilization hypothesized for the region (Banse and English 1997; Gutiérrez-Rodríguez et al 2020) or a combination of these and other aspects cannot be concluded from our study. Moreover, an ASV belonging to this genus was also found to contribute substantially to protistan communities in coastal waters of the California Current Ecosystem (Gutierrez-Rodriguez et al 2019), highlighting the need of further studies to better understand the ecological drivers beyond coastal-oceanic trophic gradients responsible for the water mass preferences of such phytoplankton groups and species.…”

Section: Discussionmentioning

confidence: 79%

Planktonic protist diversity across contrasting Subtropical and Subantarctic waters of the southwest Pacific

Gutiérrez‐Rodríguez

Santos

Safi

et al. 2021

Preprint

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Planktonic protists are an essential component of marine pelagic ecosystems where they mediate important trophic and biogeochemical functions. Although these functions are largely influenced by their taxonomic affiliation, the composition and spatial variability of planktonic protist communities remain poorly characterized in vast areas of the ocean. Here, we investigated the diversity of these communities in contrasting oceanographic conditions of the southwest Pacific sector (33-58 S) using DNA metabarcoding of the 18S rRNA. Seawater samples collected during twelve cruises (n = 482, 0-2000 m) conducted east of New Zealand were used to characterize protist communities in subtropical (STW) and subantarctic (SAW) water masses and the subtropical front (STF) that separates them. Diversity decreased with latitude and temperature but tended to be lowest in the STF. Sample ordination resulting from the abundance of amplicon single variants (ASVs) corresponded to the different water masses. Overall, Dinophyceae (34% of standardized total reads) and Chlorophyta (27%) co-dominated the euphotic zone, but their relative abundance and composition at class and lower taxonomic levels varied consistently between water masses. Among Chlorophyta, several picoplanktonic algae species of the Mamiellophyceae class including Ostreococcus lucimarinus dominated in STW, while the Chloropicophyceae species Chloroparvula pacifica was most abundant in SAW. Bacillariophyta (7%), Prymnesiophyceae (5%), and Pelagophyceae (3%) classes were less abundant but showed analogous water mass specificity at class and finer taxonomic levels. Protist community composition in the STFZ had mixed characteristics and showed regional differences with the southern STF (50 S) having more resemblance with subantarctic communities than the STF over the Chatham Rise region (42-44 S). Below the euphotic zone, Radiolaria sequences dominated the dataset (52%) followed by Dinophyceae (27%) and other heterotrophic groups like Marine Stramenopiles and ciliates (3%). Among Radiolaria, several unidentified ASVs assigned to Spumellarida were most abundant, but showed significantly different distribution between STW and SAW highlighting the need to further.

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“…The oceanic water mass that enters this Sub-Antarctic zone is the Sub-Antarctic water mass (SAAW), which is modified within the Strait of Magellan by mixing with continental freshwater (runoff from glaciers and rivers), forming MSAAW and is found from the surface to 150 m depth. The properties of the MSAAW were established based on reported information (Sarmiento et al, 2004;Sievers and Silva, 2008;Silva et al, 2009;Llanillo et al, 2012;Torres et al, 2014;Forceń-Vaźquez et al, 2021). The strong salinity and alkalinity relationship reported for the Patagonian archipelago interior sea (41-56°S: Torres et al, 2011a;Torres et al, 2020) makes it possible to calculate alkalinity of the MSAAW using the equation: A Tsal (mmol kg -1 ) = 66.4 × Salinity + 1.1, (R 2 = 0.93, n=81; Figure 2; Supplementary Table 1).…”

Section: Water Mass Distribution Analysismentioning

confidence: 99%

Understanding the Implications of Hydrographic Processes on the Dynamics of the Carbonate System in a Sub-Antarctic Marine-Terminating Glacier-Fjord (53°S)

et al. 2022

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The biogeochemical dynamics of fjords in the southeastern Pacific Ocean are strongly influenced by hydrological and oceanographic processes occurring at a seasonal scale. In this study, we describe the role of hydrographic forcing on the seasonal variability of the carbonate system of the Sub-Antarctic glacial fjord, Seno Ballena, in the Strait of Magellan (53°S). Biogeochemical variables were measured in 2018 during three seasonal hydrographic cruises (fall, winter and spring) and from a high-frequency pCO2-pH mooring for 10 months at 10 ± 1 m depth in the fjord. The hydrographic data showed that freshwater input from the glacier influenced the adjacent surface layer of the fjord and forced the development of undersaturated CO2 (< 400 μatm) and low aragonite saturation state (ΩAr < 1) water. During spring, the surface water had relatively low pCO2 (mean = 365, range: 167 - 471 μatm), high pH (mean = 8.1 on the total proton concentration scale, range: 8.0 - 8.3), and high ΩAr (mean = 1.6, range: 1.3 - 4.0). Concurrent measurements of phytoplankton biomass and nutrient conditions during spring indicated that the periods of lower pCO2 values corresponded to higher phytoplankton photosynthesis rates, resulting from autochthonous nutrient input and vertical mixing. In contrast, higher values of pCO2 (range: 365 – 433 μatm) and relatively lower values of pHT (range: 8.0 – 8.1) and ΩAr (range: 0.9 – 2.0) were recorded in cold surface waters during winter and fall. The naturally low freshwater carbonate ion concentrations diluted the carbonate ion concentrations in seawater and decreased the calcium carbonate saturation of the fjord. In spring, at 10 m depth, higher primary productivity caused a relative increase in ΩAr and pHT. Assuming global climate change will bring further glacier retreat and ocean acidification, this study represents important advances in our understanding of glacier meltwater processes on CO2 dynamics in glacier–fjord systems.

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Frontal dynamics and water mass variability on the Campbell Plateau

Cited by 12 publications

References 63 publications

Ecoregionalisation of the Southern Ocean Using Radiolarians

Ecoregionalisation of the Southern Ocean Using Radiolarians

Planktonic protist diversity across contrasting Subtropical and Subantarctic waters of the southwest Pacific

Understanding the Implications of Hydrographic Processes on the Dynamics of the Carbonate System in a Sub-Antarctic Marine-Terminating Glacier-Fjord (53°S)

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