scholarly journals Assemblages of certain benthic molluscs along the southwestern Atlantic: from subtidal to deep sea

BMC Ecology ◽  
2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Valeria Teso ◽  
Diego Urteaga ◽  
Guido Pastorino
Keyword(s):  
Continental Shelf ◽  
Continental Slope ◽  
Large Scale ◽  
Geographic Location ◽  
Southwestern Atlantic ◽  
Biogeographic Patterns ◽  
Southwestern Atlantic Ocean ◽  
Sw Atlantic ◽  
Marine Currents ◽  
Main Factor

Abstract Background We analyse the distribution of Gastropods and Chitons from shallow to deep waters along the southwestern Atlantic Ocean off Argentina and discuss possible factors determining the observed biogeographic patterns. Results Three major biogeographic groups are defined on the basis of Gastropod and Chiton species associations, i.e., continental shelf (< 350 m), upper continental slope (> 350–2000 m) and lower continental slope (2000–3000 m). Bathymetry appears as the main factor modifying large-scale distribution of the fauna at a. In this scenario, species associations are determined by marine currents that clearly occur at a particular and well defined depth. No arrangement of species by geographic location was found in assemblages from the continental shelf and upper continental slope. Conclusions We hypothesize that depth and marine currents are the main factor affecting the distribution of Gastropods and Chitons along the SW Atlantic between 200 and 3000 m depth.

scholarly journals Size and sex composition of two species of the genus Atlantoraja (Elasmobranchii, Rajidae) caught by the bottom trawl fisheries operating on the Uruguayan continental shelf (southwestern Atlantic Ocean)

2011 ◽  
Vol 59 (4) ◽  
pp. 357-364 ◽  
Author(s):  
Luis Orlando ◽  
Ines Pereyra ◽  
Laura Paesch ◽  
Walter Norbis
Keyword(s):  
Continental Shelf ◽  
Significant Variation ◽  
Length Distribution ◽  
Seasonal Distribution ◽  
Size At Maturity ◽  
Southwestern Atlantic ◽  
Spatial And Seasonal Variation ◽  
Southwestern Atlantic Ocean ◽  
Trawl Fisheries ◽  
Size And Sex Composition

In this work we analyzed the spatial and seasonal variation of length distribution, sexual proportion and mature dominance for Atlantoraja cyclophora and A. castelnaui, at the Uruguayan continental shelf. There were significant differences in total length (TL) composition between sexes, being females bigger than males for both species. Atlantoraja cyclophora showed a relatively uniform length distribution between inner and outer shelf. There were no major variations in the sex compositions and in the mature dominance between seasons, suggesting no temporal variation. Atlantoraja castelnaui showed a significant variation in its spatial and seasonal distribution. Individuals were smaller in inner shelf, pointing out the existence of juvenile zone in areas up to 50 m depth. A tendency to capture smaller individuals towards the end of the year was observed. In all seasons over 50% of females were caught below the estimated size at maturity, suggesting that this species is highly susceptible to exploitation.

Description of three new species of Ampelisca (Crustacea: Amphipoda: Ampeliscidae) from Southwestern Atlantic, with a key of the genus for Brazilian species

Zootaxa ◽  
2007 ◽  
Vol 1626 (1) ◽  
pp. 25-37 ◽  
Author(s):  
MARIA TERESA VALÉRIO-BERARDO
Keyword(s):  
New Species ◽  
Atlantic Ocean ◽  
Continental Shelf ◽  
Benthic Communities ◽  
Brazilian Coast ◽  
Southwestern Atlantic ◽  
Soft Bottom ◽  
Brazilian Species ◽  
Southwestern Atlantic Ocean ◽  
Three New Species

Ampelisca species are inhabitant of soft bottom marine benthic communities of tropical to cold – temperate zones. Prior to this paper, 11 species of the genus were recognized from Brazilian coast. Three new species of Ampelisca are herein described: Ampelisca longipropoda, Ampelisca meridionalis and Ampelisca youngi. The specimens were dredged from the continental shelf of Southwestern Atlantic Ocean between the latitudes 22°06’S and 34°32’S. A key to the Ampelisca species of the Brazilian coast is provided.

Hydromedusae (Cnidaria: Hydrozoa) from the temperate southwestern Atlantic Ocean: a review

Zootaxa ◽  
2008 ◽  
Vol 1750 (1) ◽  
pp. 1 ◽  
Author(s):  
GENZANO GABRIEL ◽  
HERMES MIANZAN ◽  
JEAN BOUILLON
Keyword(s):  
Species Richness ◽  
Atlantic Ocean ◽  
Continental Shelf ◽  
New Records ◽  
South Atlantic Ocean ◽  
Valid Species ◽  
Southwestern Atlantic ◽  
Southwest Atlantic ◽  
Number Of Species ◽  
Southwestern Atlantic Ocean

Hydromedusae are one of the best-represented planktonic groups in waters of the South Atlantic Ocean in terms of species richness. Nevertheless, medusae of the region are inadequately known because earlier studies have been limited and restricted to few areas. During the last two decades, almost 2000 samples from 54 research cruises have been collected, mostly within the continental shelf of Argentina and Uruguay (33 – 55º S). These samples provide an opportunity to significantly augment knowledge of the richness of the medusa fauna in the southwest Atlantic. Forty species of hydromedusae (six of them new records for the area), including 15 of Anthomedusae, 14 of Leptomedusae, three of Limnomedusae, four of Narcomedusae, and four of Trachymedusae, were identified. Our results indicate that previous lists overestimated species richness of hydromedusae in the area. When misidentifications, updated species synonymies, and doubtful records are taken into account, 71 valid species are recognized here from the study area. Based upon this corrected inventory list, the data suggest that the number of species of hydromedusae decreases markedly with increasing latitude, corresponding with that observed in other planktonic groups of invertebrates.

scholarly journals Remarks on the morphology and distribution of some rare centric diatoms in southern Brazilian continental shelf and slope waters

2012 ◽  
Vol 60 (4) ◽  
pp. 415-427 ◽  
Author(s):  
Marinês Garcia ◽  
Clarisse Odebrecht
Keyword(s):  
Atlantic Ocean ◽  
Continental Shelf ◽  
Southwestern Atlantic ◽  
Patos Lagoon ◽  
La Plata ◽  
Centric Diatoms ◽  
Southwestern Atlantic Ocean ◽  
The Family ◽  
Scanning Electron Microcopy ◽  
First Time

This paper provides information on the morphology and occurrence of extant diatoms of the family Asterolampraceae and Azpeitia species of the southernmost Brazilian continental shelf and slope waters in the Southwestern Atlantic Ocean (28 -34ºS), under the influence of Tropical, Subtropical, Subantarctic Waters, terrestrial discharges from La Plata River and Lagoa dos Patos lagoon. Plankton was sampled (20 µm net; vertical hauls) at the same 27 stations in winter 2005 and summer 2007. Among Asterolampraceae, Asteromphalus flabellatus was the most frequent species (57% of samples) observed mainly in winter samples (92%) in Subtropical Shelf Water but also under the influence of La Plata River plume (salinity <35). Lower frequencies were observed for Asterolampra marylandica, Asteromphalus elegans, Asteromphalus heptactis and Spatangidium arachne. Four species of Azpeitia were observed: A. barronii and A. neocrenulata for the first time in the South Atlantic Ocean while A. africana and A. nodulifer had already been registered in equatorial and southern areas of Brazil. All Azpeitia species were rare (19%) in offshore samples (100-200 m depth. Remarks on the morphology based on light and scanning electron microcopy observations are provided along with their distribution in the study area.

scholarly journals Internal Tides in the Southwestern Atlantic off Brazil: Observations and Numerical Modeling

2007 ◽  
Vol 37 (6) ◽  
pp. 1512-1526 ◽  
Author(s):  
Adriene F. Pereira ◽  
Belmiro M. Castro
Keyword(s):  
Continental Shelf ◽  
Three Dimensional ◽  
Internal Tide ◽  
Equation Model ◽  
Shelf Break ◽  
Internal Tides ◽  
Southwestern Atlantic ◽  
Model Response ◽  
Southwestern Atlantic Ocean ◽  
Vertical Displacements

Abstract Data collected from moored instruments, deployed over the southeastern Brazilian continental shelf during the summer and winter months of 2001, show internal tide activity near the shelf break. To help to elucidate the observations, a fully three-dimensional nonlinear primitive equation model is applied to simulate the regional barotropic and baroclinic tides. Two semidiurnal (M2 and S2) and two diurnal (K1 and O1) tidal frequencies are considered. Tidal surface elevations are relatively small over the whole modeled area, reaching maximum values of about 0.40 m for M2 and 0.11 m for O1. Comparison between observed and computed tide elevation and Greenwich phase shows reasonable agreement. When the baroclinic response of the model is investigated, stratification is prescribed using summer and winter climatology data of potential density. In this case, the model response to summer and winter stratifications is very similar and internal tides are generated over the shelf break and slope, with vertical displacements up to 25 m, and seaward propagation. Modeled semidiurnal tidal ellipses agree well with winter and summer observations. Observed diurnal tidal ellipses in the middle of the continental shelf and close to the shelf break during summer show an intensification through the water column that could not be represented by the model. Estimates of the total baroclinic M2 offshore energy flux are about 3.5 and 0.5 MW considering winter and summer stratifications, respectively. Although these quantities are three orders of magnitude less than that estimated for regions known for intense internal tides, they refer to offshore fluxes computed for a very small section of the southeastern Brazilian shelf. This is the first published investigation into internal tides in the southwestern Atlantic Ocean off Brazil.

A new species of Ligiarctus (Tardigrada, Arthrotardigrada) from the Brazilian continental shelf, Southwestern Atlantic Ocean

2017 ◽  
Vol 48 (1) ◽  
pp. 5-12 ◽  
Author(s):  
Edivaldo Gomes-Júnior ◽  
Érika Santos ◽  
Clélia M. C. da Rocha ◽  
Paulo J. P. Santos ◽  
Paulo Fontoura
Keyword(s):  
New Species ◽  
Atlantic Ocean ◽  
Continental Shelf ◽  
Southwestern Atlantic ◽  
Southwestern Atlantic Ocean ◽  
A New Species
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