Exploring the roles of iron and irradiance in dynamics of diatoms and Phaeocystis in the Amundsen Sea continental shelf water

2021 ◽  
Author(s):  
Young Shin Kwon ◽  
Hyoung Sul La ◽  
Jin Young Jung ◽  
Sang Heon Lee ◽  
Tae‐Wan Kim ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Shelf Water ◽  
Amundsen Sea ◽  
Continental Shelf Water

scholarly journals TEMPERATURE, SALINITY AND OXYGEN CLIMATOLOGY OF AFRICAN CONTINENTAL SHELF WATER, SOUTH OF THE EQUATOR, AND CHANGES SINCE 1945

2021 ◽  
Author(s):  
Stephanie de Villiers
Keyword(s):  
Continental Shelf ◽  
Environmental Variability ◽  
Marine Ecosystem ◽  
Ecosystem Approach ◽  
Shelf Water ◽  
Classification Schemes ◽  
Continental Shelf Water ◽  
Large Marine Ecosystem ◽  
Oceanographic Data ◽  
Spatial Grid

The first temperature, salinity and oxygen climatologies for waters of the continuous southern African continental shelf is presented. It is based on oceanographic data collected since 1945, sub-sampled at depths of 5, 50 and 100 m on a mixed-spatial grid with 0.25° to 0.5° resolution. The climatologies capture spatial heterogeneities and seasonal variability in key ocean variables for the southern African shelf in unique detail. The results correspond relatively well with biogeographic boundaries informed by classification schemes grounded in taxonomy, but questions the value of the Large Marine Ecosystem approach. Analysis of decadal trends demonstrates the inherent complexity and spatial heterogeneity associated with environmental variability, and suggest the possibility that decadal periodicities are in the process of being disrupted by a longer-term trend. The overall pattern is that southern African West and South coast shelf waters are becoming warmer, except for some upwelling areas, where cooling is evident. Benguela and Agulhas Bank shelf water are also becoming more oxygen depleted.

scholarly journals Sex-specific variation in the use of vertical habitat by a resident Antarctic top predator

2020 ◽  
Vol 287 (1937) ◽  
pp. 20201447
Author(s):  
Theoni Photopoulou ◽  
Karine Heerah ◽  
Jennifer Pohle ◽  
Lars Boehme
Keyword(s):  
Habitat Use ◽  
Continental Shelf ◽  
Weddell Sea ◽  
Water Masses ◽  
Shelf Water ◽  
Top Predator ◽  
Marine Animals ◽  
Deep Diving ◽  
Continental Shelf Water ◽  
Oceanographic Conditions

Patterns of habitat use are commonly studied in horizontal space, but this does not capture the four-dimensional nature of ocean habitats (space, depth, and time). Deep-diving marine animals encounter varying oceanographic conditions, particularly at the poles, where there is strong seasonal variation in vertical ocean structuring. This dimension of space use is hidden if we only consider horizontal movement. To identify different diving behaviours and usage patterns of vertically distributed habitat, we use hidden Markov models fitted to telemetry data from an air-breathing top predator, the Weddell seal, in the Weddell Sea, Antarctica. We present evidence of overlapping use of high-density, continental shelf water masses by both sexes, as well as important differences in their preferences for oceanographic conditions. Males spend more time in the unique high-salinity shelf water masses found at depth, while females also venture off the continental shelf and visit warmer, shallower water masses. Both sexes exhibit a diurnal pattern in diving behaviour (deep in the day, shallow at night) that persists from austral autumn into winter. The differences in habitat use in this resident, sexually monomorphic Antarctic top predator suggest a different set of needs and constraints operating at the intraspecific level, not driven by body size.

scholarly journals Sex-specific variation in the use of vertical habitat by a resident Antarctic top predator

2020 ◽  
Author(s):  
Theoni Photopoulou ◽  
Karine Heerah ◽  
Jennifer Pohle ◽  
Lars Boehme
Keyword(s):  
Habitat Use ◽  
Continental Shelf ◽  
Weddell Sea ◽  
Water Masses ◽  
Shelf Water ◽  
Top Predator ◽  
Marine Animals ◽  
Deep Diving ◽  
Continental Shelf Water ◽  
Oceanographic Conditions

1AbstractPatterns of habitat use are commonly studied in horizontal space, but this does not capture the four-dimensional nature of ocean habitats. There is strong seasonal variation in vertical ocean structuring, particularly at the poles, and deep-diving marine animals encounter a range of oceanographic conditions. We use hidden Markov models fitted to telemetry data from an air-breathing top predator to identify different diving behaviours and understand usage patterns of vertically distributed habitat. We show that preference for oceanographic conditions in the Weddell Sea, Antarctica, varies by sex in Weddell seals, and present the first evidence that both sexes use high-density, continental shelf water masses. Males spend more time in the colder, unique high-salinity shelf water masses found at depth, while females also venture off the continental shelf and visit warmer, shallower pelagic water masses. Both sexes exhibit a diurnal pattern in diving behaviour that persists from austral autumn into winter. These findings provide insights into the Weddell Sea shelf and open ocean ecosystem from a top predator perspective. The differences in habitat use in a resident, sexually monomorphic Antarctic top predator suggest a different set of needs and constraints operating at the intraspecific level, which are not driven by body size.

scholarly journals Impact of seasonal oxygen deficiency on the phosphorous geochemistry of surface sediments along the Western Continental Shelf of India

2010 ◽  
Vol 7 (4) ◽  
pp. 6089-6119 ◽  
Author(s):  
◽  
K. K. Balchandran ◽  
◽  
Keyword(s):  
Continental Shelf ◽  
Surface Sediments ◽  
Oxygen Deficiency ◽  
Late Summer ◽  
Subsurface Water ◽  
Shelf Water ◽  
Inner Shelf ◽  
Overlying Water ◽  
Labile Organic Matter ◽  
Phosphorus Species

Abstract. The intensification of the natural coastal hypoxic zone over the western Indian shelf in the recent years and its impact on the biogeochemistry and marine life is a matter of concern. This study examines the influence of the seasonal oxygen deficiency on the phosphorus geochemistry of the surface sediments along the western continental shelf of India (WCSI). Speciation of phosphorus along with the geochemical characteristics (total organic carbon – TOC, total nitrogen – TN, and total phosphorus – TP) of the surface sediments and the hydrography of the western continental shelf of India (WCSI) were studied, during late summer monsoon (LSM) and spring intermonsoon (SIM). The hydrography of the WCSI revealed upwelling and associated seasonal oxygen deficiency with denitrifying suboxic conditions along the inner shelf and hypoxic conditions along the outer shelf. High concentrations of dissolved phosphate (PO4) and dissolved Iron (Fe) were also observed in the subsurface water of the inner shelf during LSM. The shelf water of the WCSI was oligotrophic and oxygen rich during SIM. A latitudinal enrichment of TOC, TN and TP in the surface sediments was observed at 13–17° N, along the WCSI during LSM, where seasonal suboxia was intense. Authigenic apatite bound phosphorus (Paut) was the major phosphorus species along the WCSI during LSM whereas detrital flourapatite bound phosphorus (Pdet) was the major species during SIM. Substantial depletion of reactive iron(III)-bound phosphorus (ΔPFe) was observed in the surface sediments of the WCSI during LSM which showed significant correlation with the enrichment of PO4 (ΔPO4) in the overlying water during LSM compared to SIM. PO4 diffusing into the water column from the sediments by reductive dissolution of PPFe probably leads to high dissolved PO4 along the inner shelf water during LSM which agrees with the existing hypothesis. Hence, phosphorus geochemistry of the surface sediments plays a major role in the biogeochemical cycling of phosphorus during periods of seasonal oxygen deficiency along the WCSI. Similar studies carried out along the eastern continental shelf of India (ECSI), where any kind of seasonal oxygen deficiency has not been reported yet, showed an abundance of Pdet (~50% of TP) and Porg (~32% of TP) in the surface sediments. The characteristic hydrographical features of the region such as high terrigeneous input, low production in the surface euphotic layers and greater preservation of labile organic matter in the sediments is also reflected in the phosphorus geochemistry of the surface sediments along ECSI.

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