Distribution of planktonic cnidarians in response to South Atlantic Central Water intrusion in the South Brazilian Bight

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

“…triplicate hauls over two consecutive days), we consider that the assemblage structure and the daily dynamics of vertical occupation are well represented for the study site. Our data are limited to a single cruise and therefore do not address possible seasonal variations; however, large seasonal variations in the oceanographic configuration and in the zooplankton abundance and assemblage structure are not expected in offshore areas of the South Brazilian Bight [ 23 – 25 , 39 ]. The depth levels of the layers sampled were chosen according to the oceanographic structure of the water column, and do not allow the depiction of possible smaller-scale patterns such as DVM within the same water mass [ 2 , 19 , 40 ].…”

“…tetraphylla , and M . kochii [ 24 , 25 , 39 , 41 ], also suggest the influence of this water mass. This probably results from wind-driven offshore advection of Coastal Water, which forms a surface haline front over the shelf that separates Tropical Water from Coastal Water and may reach over 100 km offshore [ 23 – 25 , 39 ].…”

“…kochii [ 24 , 25 , 39 , 41 ], also suggest the influence of this water mass. This probably results from wind-driven offshore advection of Coastal Water, which forms a surface haline front over the shelf that separates Tropical Water from Coastal Water and may reach over 100 km offshore [ 23 – 25 , 39 ]. In this study we sampled at a single station and therefore cannot precisely locate the position of the front; however, the salinities lower than 36 in the upper 20 m indicate that our station was probably close to it.…”

“…These observations suggest that the cold SACW restricted the vertical occupation of most species, which typically inhabit epipelagic warm waters [ 7 , 8 , 26 , 39 , 40 ], emphasizing the role of the physical vertical stratification of the water column in shaping the assemblages of gelatinous zooplankton. A previous investigation of the vertical distribution of gelatinous zooplankton in the South Brazilian Bight showed the seasonal influence of the SACW, with overall low species richness and abundance in the BL when it is influenced by this water mass [ 39 ]. The present data agree with this observation and offer additional details on vertical patterns of the gelatinous zooplankton, owing to the finer scale of temporal sampling and to the analysis of other gelatinous taxa whose distributional patterns are largely understudied and therefore unknown in the southwestern Atlantic (i.e.…”

Are free-floating planktonic hydroids (Cnidaria, Hydrozoa) common components of the pelagic fauna from the South Brazilian Bight?

“…Nevertheless, occurrences of hydroids in the pelagic environment are mostly anecdotal, with records of Obelia longissima (Pallas, 1766) and Amphisbetia operculata (Linnaeus, 1758) from Argentina (Genzano et al , 2008), several species from north-eastern and south-eastern Brazil (Vannucci, 1957, 1958, 1963), including ‘polyps of Hydrozoa’ (Resgalla, 2001; Veado & Resgalla, 2005; Resgalla et al , 2008) and Clytia spp. (Nagata et al , 2014; Nogueira Júnior et al , 2014) from southern Brazil. Although these records are anecdotal, they suggest that hydroids may be both common and widespread in the plankton of the region.…”