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 Functional redundancy in polychaete assemblages from a tropical Large Marine Ecosystem (LME)

Zoosymposia ◽  
2020 ◽  
Vol 19 (1) ◽  
pp. 72-90
Author(s):  
BARBARA C.G. GIMENEZ ◽  
PAULO LANA
Keyword(s):  
Continental Shelf ◽  
Marine Ecosystem ◽  
Functional Redundancy ◽  
Estuarine Environment ◽  
Environmental Drivers ◽  
Unique Combination ◽  
Marine Life ◽  
Low Level ◽  
Large Marine Ecosystem ◽  
South Brazil

Functional redundancy assumes a critical relevance nowadays due to the serious threats that affect marine life worldwide. We assessed and compared levels of functional redundancy in polychaete assemblages from the continental shelf and from estuarine environments along the South Brazil Shelf Large Marine Ecosystem (SBSLME). To quantify functional redundancy, we used functional originality (FOri) and functional uniqueness (FUni). We found 57 and 47 polychaete taxa distributed in 48 and 41 functional entities (i.e., a unique combination of trait values) in continental shelf and estuarine environments, respectively. Results suggest a low level of functional redundancy in both environments. However, FOri was higher in the estuarine environment, whereas FUni was higher in the continental shelf. As expected, estuarine polychaetes have fewer unique combinations of trait values, but these combinations are more original and adequate to the varying conditions imposed by estuarine environmental drivers.

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