Pesquisadores dos GTs 2.1 (Geodiversidade, Biodiversidade e Recursos Vivos da Plataforma Continental) e 3.0 (Variabilidade climática, ciclos biogeoquímicos e fluxo de CO2 no oceano Atlântico tropical) do inct AmbTropic II publicaram no Journal of Marine Sciences (IF: 2.542) um interessante trabalho que investiga as interações entre a topografia submarina e a circulação na região nordeste do Brasil. Esta interação pode ser considerada como um conjunto de processos que resultam da interação entre as correntes e gradientes topográficos especialmente aqueles associados com canyons submarinos, que apresentam um potencial para produzir ressurgência e transporte "cross-isobath" em margens continentais. O trabalho intitulado "Flow-topography interactions in the western tropical Atlantic boundary off Northeast Brazil" tem como autores Marcos V.B. Silva, Beatrice Ferreira, Mauro Maida, Syumara Queiroz, Marcus Silva, Humberto L. Varona, Tereza C.M. Araújo e Moacyr Araújo.
Resumo Gráfico
ABSTRACT
Flow-Topography Interaction can be considered as a particular set of processes resulting of the currents inter- action with a topographic gradient, specially associated with submarine canyon areas, which are important morphological features with potential to upwelling and cross-isobath transport on the continental margins. The South Pernambuco Continental Shelf (SPCS) and Pernambuco Plateau located on the Southwestern Tropical Atlantic (SWTA), present incised morphological features, highlighting the shelf valleys and blind canyons, which do not have a connection to the shelf or an onshore river system. They are likely features for interactions between the dominant along-shelf flow represented by the strong western boundary North Brazil Undercurrent. We investigated potential canyon induced upwelling and the respective mechanisms at the late spring/early fall context. CTD and reanalysis data from GLORYS12V1, and in situ bathymetric measurements were used to characterise the hydrodynamics and canyon morphology, respectively. Then, we combined both to obtain dimensionless numbers from dynamical scale analysis to infer possible imbalances of the acting forces. Rean- alysis data evidenced uplift at the slope not related to the blind canyons. CTD data indicated a seasonal variation of the intrusion of water masses, especially at the shelf-break for the Middle shelf valley and Campas shelf valley. A temperature difference of 2.5 ◦ C (2.0 ◦ C) between surface and deep waters was observed during the late spring. A stepwise temperature structure was present in both seasons, indicating instability below the mixed layer depth, the uplifting of isotherms, and the corrosion of the lower portion of the surface mixed layer. The dimensionless parameters analysis reveals highest Rossby values during the fall, mainly in Zieta shelf valley (R0=130.87) and Csv (R0=111.71), and lower values for the canyons of the Pernambuco Plateau. Our hypothesis is that the shelf valleys might play a role in conducting the uplifted slope water coast-ward. For the blind canyons, although no related upwelling was observed, reanalysis revealed the presence of a deep anti-cyclonic eddy at one of the blind canyon’s mouth. Rossby and Burger numbers indicate a weak geostrophic balance at the canyon rim, and instability of the horizontal length scale of the pressure gradient force, with tendency to vorticity control. While the paradigm that shelf and coastal waters off north-eastern Brazil are mostly oligotrophic in the surface is true, our observation of shallow (<60 m) subsurface uplift should be considered in future works in the SWTA.
O trabalho completo pode ser acessado em: https://doi.org/10.1016/j.jmarsys.2021.103690
O GT2.2 (Variabilidade Espaço-Temporal da Diversidade e Estrutura Trófica do Ambiente Pelágico na Plataforma Continental) tem uma novo artigo publicado no Journal of the Marine Biological Association of the United Kingdom (FI: 1.181) intitulado "Factors affecting the seasonal variability of planktonic shrimps (Dendrobranchiata) along an estuary–ocean gradient on the Amazon continental shelf" de autoria de Leiliane Souza da Silva, Danielle Viveiros Cavalcante-Braga, Caio Brito Lourenço, Ralf Schwamborn e Jussara Moretto Martinelli-Lemos.
ABSTRACT
Dendrobranchiata shrimp taxonomic composition and spatial and temporal distribution on the Amazon continental shelf (ACS) were investigated along a transect between the sources of the Amazon and Pará Rivers, encompassing an extension of !250 km towards the contin- ental slope. Plankton was collected with oblique trawls (200 !m mesh size), and nine taxa were found; 59.4% were larvae (mysis or decapodid stages) and 40.6% were juveniles or adults. Acetes was negatively related to chlorophyll-a and temperature, and Luciferidae were posi- tively correlated with months. This study provides novel information on the density distribu- tion of dendrobranchiate shrimps, thus helping to pave the way to characterize a large-scale, hugely relevant area that is poorly studied. As in other tropical coastal areas, there is here an increase in number of taxa with increased distance from the coast. Luciferidae, Solenoceridae and Penaeidae were the most frequent families whereas Sicyoniidae and Sergestidae had the lowest frequency of occurrence nearer the slope. Despite the low larval density of penaeid shrimps, their presence in all months and at all sampling sites along the ACS proves the importance of this area for shrimps with socioeconomic relevance, as well as its importance as a nursery and growth habitat for dendrobranchiate shrimps.
O trabalho completo pode ser acessado em:
https://doi.org/10.1017/S0025315421.000308
ou solicitando diretamente a autora correspondente: Jussara Moretto Martinelli-Lemos, e-mail: jussara@ufpa.br
Atualizado: 21 de jul. de 2020
A primeira larva de uma espécie rara de camarão fantasma Naushonia foi descrita a partir de amostras de plâncton retiradas do Arquipélago de Fernando de Noronha, por um grupo de pesquisadores da Universidade Federal de Pernambuco. Foi o primeiro registro de ocorrência do gênero nas ilhas oceânicas do Atlântico Equatorial. Existem muito poucos registros para adultos e larvas desse gênero em todo o mundo e essa pode ser uma nova espécie.
As espécies raras apresentam baixa abundância de espécies e baixa frequência de ocorrência, fatores que aumentam seu risco de extinção e, portanto, as regiões de maior ocorrência são amplamente reconhecidas como áreas prioritárias para conservação.
As ilhas oceânicas são consideradas oásis no meio de um oceano geralmente pobre em nutrientes e desempenham um papel importante, contribuindo para a dispersão e permanência desses organismos e de muitas outras espécies importantes.
Para saber mais sobre esse estudo acesse o artigo científico completo.