Diel Vertical Dynamics of Gelatinous Zooplankton (Cnidaria, Ctenophora and Thaliacea) in a Subtropical Stratified Ecosystem (South Brazilian Bight)

Author(s)

Nogueira Junior, Miodeli ^[1] ; Brandini, Frederico Pereira ^[2] ; Ugaz Codina, Juan Carlos ^[3]

Affiliation

^[1] Univ Fed Paraiba, Dept Sistemat & Ecol, BR-58059900 Joao Pessoa, Paraiba - Brazil

^[2] Univ Sao Paulo, Inst Oceanog, Dept Oceanog Biol, Sao Paulo - Brazil

^[3] Univ Fed Paraiba, Dept Zool, Programa Pos Grad Zool, Curitiba, Parana - Brazil

• Document type: Journal article
• Source: PLoS One; v. 10, n. 12 DEC 4 2015.
• Web of Science Citations: 8

Abstract

The diel vertical dynamics of gelatinous zooplankton in physically stratified conditions over the 100-m isobath (similar to 110 km offshore) in the South Brazilian Bight (26 degrees 45'S; 47 degrees 33'W) and the relationship to hydrography and food availability were analyzed by sampling every six hours over two consecutive days. Zooplankton samples were taken in three depth strata, following the vertical structure of the water column, with cold waters between 17 and 13.1 degrees C, influenced by the South Atlantic Central Water (SACW) in the lower layer (>70m); warm (>20 degrees C) Tropical Water in the upper 40 m; and an intermediate thermocline with a deep chlorophyll-a maximum layer (0.3-0.6 mg m(-3)). Two distinct general patterns were observed, emphasizing the role of (i) physical and (ii) biological processes: (i) a strong influence of the vertical stratification, with most zooplankton absent or little abundant in the lower layer. The influence of the cold SACW on the bottom layer apparently restricted the vertical occupation of most species, which typically inhabit epipelagic warm waters. Even among migratory species, only a few (Aglaura hemistoma, Abylopsis tetragona eudoxids, Beroe sp., Thalia democratica, Salpa fusiformis) crossed the thermocline and reached the bottom layer. (ii) A general tendency of partial migrations, with variable intensity depending on the different species and developmental stages; populations tended to be more widely distributed through the water column during daylight, and to become more aggregated in the upper layer during the night, which can be explained based on the idea of the ``hungersatiation hypothesis{''}, maximizing feeding and minimizing the chances of being predated. (AU)

• FAPESP's process: 11/21290-1 - Long term (1969-2003) fluctuations on structure and abundance of gelatinous zooplankton (Cnidaria and Thaliacea) on South Brazilian Bight
• Grantee: Frederico Pereira Brandini
• Support type: Regular Research Grants
• FAPESP's process: 11/09880-8 - Long-term flutuations (1963-2003) on the structure and abundance of gelatinous zooplankton (Cnidaria and Thaliacea) on South Brazilian Bight
• Grantee: Miodeli Nogueira Junior
• Support type: Scholarships in Brazil - Post-Doctorate