scholarly journals Tracing latitudinal gradient, river discharge and water masses along the subtropical South American coast using benthic Foraminifera assemblages

2012 ◽  
Vol 72 (3 suppl) ◽  
pp. 723-759 ◽  
Author(s):  
PPB Eichler ◽  
AR Rodrigues ◽  
BB Eichler ◽  
ES Braga ◽  
EJD Campos
Keyword(s):  
Benthic Foraminifera ◽  
River Discharge ◽  
Latitudinal Gradient ◽  
South American ◽  
Shelf Water ◽  
Silicate Concentration ◽  
Tropical Water ◽  
Freshwater Influence ◽  
Antarctic Shelf ◽  
High Silicate

More than 30% of Buccella peruviana (D'Orbigny), Globocassidulina crassa porrecta (Earland & Heron-Allen), Cibicides mackannai (Galloway & Wissler) and C. refulgens (Montfort) indicate the presence of cold Sub Antarctic Shelf Water in winter, from 33.5 to 38.3º S, deeper than 100 m, in the southern part of the study area. In summer, the abundance of this association decreases to less than 15% around 37.5-38.9º S where two species (Globocassidulina subglobosa (Brady), Uvigerina peregrina (Cushman) take over. G. subglobosa, U. peregrina, and Hanzawaia boueana (D'Orbigny) are found at 27-33º S in both seasons in less than 55 m deep in the northern part, and are linked with warm Subtropical Shelf Water and Tropical Water. Freshwater influence was signalized by high silicate concentration and by the presence of Pseudononion atlanticum (Cushman), Bolivina striatula (Cushman), Buliminella elegantissima (D'Orbigny), Bulimina elongata (D'Orbigny), Elphidium excavatum (Terquem), E. poeyanum (D'Orbigny), Ammobaculites exiguus (Cushman & Brönnimann), Arenoparrella mexicana (Kornfeld), Gaudryina exillis (Cushman & Brönnimann), Textularia earlandi (Parker) and thecamoebians in four sectors of the shelf. The presence of Bulimina marginata (D'Orbigny) between 34.1-32.8º S in the winter and 34.2-32.7º S in the summer indicates that the influence of the Subtropical Shelf Front on the sediment does not change seasonally, otherwise, the presence of Angulogerina angulosa (Williamson) in the winter, only in Mar del Plata (38.9º S), show that Malvinas currents are not influencing the sediment in the summer.

scholarly journals Distribution and annual occurrence of Chaetognatha off Cananeia and Santos coast (São Paulo, Brazil)

1968 ◽  
Vol 17 (1) ◽  
pp. 33-55 ◽  
Author(s):  
M. S. de Almeida Prado
Keyword(s):  
Coastal Water ◽  
Annual Variation ◽  
Abundant Species ◽  
Breeding Period ◽  
Shelf Water ◽  
Vertical Movements ◽  
Tropical Water ◽  
The Vertical Distribution ◽  
Water Species ◽  
Different Levels

Plankton samples were fortnightly taken at three fixed stations off Cananéia (1958, 1959, 1960) and off Santos (1960, 1961) by vertical hauling. They contained the following species: Sagitta enflata, S. friderici, S. hispida, S. minima, S. serratodentata, Krohnitta pacifica and Pterosagitta draco. S. frideriei is a typical coastal water species. S. enflata is a typical shelf water species. S. hispida and K. pacifica were present more frequently in shelf water but they were sometimes very abundant in coastal water. S. serratodentata, S. minima and P. draco occurred sparingly in tropical water, however, very few samples were taken in this water mass. Three different maturity stages were established (juvenile, intermediate and adult) in order to study the annual variation of the Chaetognatha. A special breeding period throughout the year was not observed as great swarms of juveniles and intermediates were found in spite of the very small number of adults. Two series of samples taken off Santos at a fixed station (Pt. III) during a period of 24 hours in three different levels were also counted to study the vertical distribution of the Chaetognatha in this area. The three most abundant species were: S. enflata, S. hispida and K. pacifica. S. enflata was more frequent at mid-water. S. hispida and K. pacifica seemed to prefer the surface layer. The thermocline did not affect their vertical migration except for S. hispida. There is indication that S. serratodentata performs vertical movements. S. minima seems to live below 25 m depth. K. subtilis occurred exceptionally in this vertical series of samples.

scholarly journals Mg/Ca-Temperature Calibration of Polar Benthic foraminifera species for reconstruction of bottom water temperatures on the Antarctic shelf

2020 ◽  
Vol 283 ◽  
pp. 54-66
Author(s):  
Elaine M. Mawbey ◽  
Katharine R. Hendry ◽  
Mervyn J. Greaves ◽  
Claus-Dieter Hillenbrand ◽  
Gerhard Kuhn ◽  
...  
Keyword(s):  
Benthic Foraminifera ◽  
Bottom Water ◽  
Temperature Calibration ◽  
Antarctic Shelf ◽  
The Antarctic

scholarly journals A numerical study of the Plata River plume along the southeastern South American continental shelf

2005 ◽  
Vol 53 (3-4) ◽  
pp. 129-146 ◽  
Author(s):  
Felipe M. Pimenta ◽  
Edmo José Dias Campos ◽  
Jerry L. Miller ◽  
Alberto R. Piola
Keyword(s):  
South America ◽  
River Discharge ◽  
Numerical Study ◽  
South American ◽  
Southern Brazil ◽  
Large Area ◽  
Plume Dynamics ◽  
Low Salinity ◽  
River Outflow ◽  
Low Latitudes

The Rio de la Plata, one of the largest rivers on Earth, discharges into the ocean waters from basin that covers a large area of South America. Its plume extends along northern Argentina, Uruguay, and southern Brazil shelves strongly influencing the ecosystems. In spite of this, little is known about the mechanisms that control it. Here we report results of simulations with POM carried out to investigate the roles of wind and river discharge in Plata plume dynamics. Different outflows were explored, including an average climatological value and magnitudes representative of La Niña and El Niño. Forcing the model with river discharge the average plume speed was directly related to the outflow intensity. The Plata northward extension varied from 850 to 1550 km and for average discharge a band of low salinity waters formed from the estuary up to 30ºN of South Brazilian Shelf. Upwelling and downwelling winds were applied after 130 days. The distribution of low salinity waters over the shelf was more sensitive to the wind direction than to the river outflow variability. Downwelling winds were very capable of advecting the low salinity signal downshelf. Upwelling winds were efficient in eroding the plume, which was basically detached from the coast by Ekman drift. Abnormal plume intrusions toward low latitudes may be a result of the original plume position coupled with events of persistent strong downwelling favorable winds.

scholarly journals Distribution and abundance of the Lesser electric ray Narcine brasiliensis (Olfers, 1831) (Elasmobranchii: Narcinidae) in southern Brazil in relation to environmental factors

2009 ◽  
Vol 57 (2) ◽  
pp. 105-112 ◽  
Author(s):  
Gabriel Maciel de Souza Vianna ◽  
Carolus Maria Vooren
Keyword(s):  
Coastal Water ◽  
Latitudinal Gradient ◽  
Seasonal Pattern ◽  
Rio Grande ◽  
Bottom Trawl ◽  
Trawl Survey ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Patos Lagoon ◽  
Tropical Water

The distribution and abundance of the lesser electric ray, Narcine brasiliensis, was assessed based on bottom-trawl survey data collected off the coast of Rio Grande do Sul, southern Brazil. Between 1980 and 1984 and in 2005, 416 bottom trawl hauls were carried out at depths of 10-100 m. Narcine brasiliensis occurred mainly in waters with bottom temperature between 20 and 25ºC. Density of the species was higher between the depths of 10 and 20 m, during the summer and autumn. The seasonal pattern of N. brasiliensis in the shallow coastal water of Rio Grande do Sul reflects a southward migration in summer. This is conditioned by the southward advance of warmer and high-salinity Tropical Water of the Brazil Current In winter, the return or northward migration is a response to seasonal cooling of the coastal waters and to the northward advance of cold Coastal Water of lower salinity. The latitudinal gradient in density of N. brasiliensis was related to the latitudinal gradient in salinity of the bottom waters. This was caused by the freshwater runoff from the Patos Lagoon establishing a physical barrier to the occurrence of the species farther south than the city of Rio Grande.

ANÁLISE POPULACIONAL DO PEIXE–ESPADA, Trichirus lepturus (PERCIFORMES;TRICHIURIDAE), NO ESTUÁRIO DO RIO CAETÉ, COSTA NORTE DO BRASIL

2008 ◽  
Vol 3 (1) ◽  
pp. 104-108
Author(s):  
Gleydson Cordovil ◽  
Mauricio Camargo
Keyword(s):  
Environmental Factors ◽  
Frequency Distribution ◽  
Food Availability ◽  
Latitudinal Gradient ◽  
Northeastern Brazil ◽  
South American ◽  
Population Parameters ◽  
Estuarine Area ◽  
Total Length ◽  
Trichiurus Lepturus

This study describes frequency distribution of the total length and estimates the weight-length relation of Trichiurus lepturus in the estuary of the Caeté River, northeastern Brazil. These population parameters were compared among four areas along the latitudinal gradient of the South American coast. Samples were gathered in the estuarine area of the Caeté River from October 1996 to August 1997. The total length of T. lepturus at the River varied between 27-81 cm, with a mode at 57 cm. No significant differences were detected among the four stocks. Different stock responses to environmental factors such as food availability, local seasonality and variations among years might probably explain these findings.

scholarly journals External forcings, oceanographic processes and particle flux dynamics in Cap de Creus submarine canyon, NW Mediterranean Sea

2013 ◽  
Vol 10 (6) ◽  
pp. 3493-3505 ◽  
Author(s):  
A. Rumín-Caparrós ◽  
A. Sanchez-Vidal ◽  
A. Calafat ◽  
M. Canals ◽  
J. Martín ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
River Discharge ◽  
Submarine Canyon ◽  
Heat Losses ◽  
Shelf Water ◽  
Surface Cooling ◽  
Bottom Water Temperature ◽  
Mass Fluxes ◽  
Nw Mediterranean ◽  
Nw Mediterranean Sea

Abstract. Particle fluxes (including major components and grain size), and oceanographic parameters (near-bottom water temperature, current speed and suspended sediment concentration) were measured along the Cap de Creus submarine canyon in the Gulf of Lions (GoL; NW Mediterranean Sea) during two consecutive winter-spring periods (2009–2010 and 2010–2011). The comparison of data obtained with the measurements of meteorological and hydrological parameters (wind speed, turbulent heat flux, river discharge) have shown the important role of atmospheric forcings in transporting particulate matter through the submarine canyon and towards the deep sea. Indeed, atmospheric forcing during 2009–2010 and 2010–2011 winter months showed differences in both intensity and persistence that led to distinct oceanographic responses. Persistent dry northern winds caused strong heat losses (14.2 × 103 W m−2) in winter 2009–2010 that triggered a pronounced sea surface cooling compared to winter 2010–2011 (1.6 × 103 W m−2 lower). As a consequence, a large volume of dense shelf water formed in winter 2009–2010, which cascaded at high speed (up to ∼1 m s−1) down Cap de Creus Canyon as measured by a current-meter in the head of the canyon. The lower heat losses recorded in winter 2010–2011, together with an increased river discharge, resulted in lowered density waters over the shelf, thus preventing the formation and downslope transport of dense shelf water. High total mass fluxes (up to 84.9 g m−2 d−1) recorded in winter-spring 2009–2010 indicate that dense shelf water cascading resuspended and transported sediments at least down to the middle canyon. Sediment fluxes were lower (28.9 g m−2 d−1) under the quieter conditions of winter 2010–2011. The dominance of the lithogenic fraction in mass fluxes during the two winter-spring periods points to a resuspension origin for most of the particles transported down canyon. The variability in organic matter and opal contents relates to seasonally controlled inputs associated with the plankton spring bloom during March and April of both years.

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