Vertical distribution of mesozooplankton and ichthyoplankton communities in the South-western Atlantic Ocean (23°14′1″S 40°42′19″W)

Abstract

A study was conducted over eight consecutive days in February 2010 in which daily variations in the vertical distributions of heterotrophic bacteria, mesozooplankton and ichthyoplankton at 1–1200 m in the South-western Atlantic Ocean were investigated. Diurnal and nocturnal samples were collected at an oceanographic station at four regional depths: Tropical Water (TW) (1 m), South Atlantic Central Water (SACW) (250 m), Antarctic Intermediate Water (AAIW) (800 m) and Upper Circumpolar Deep Water (UCDW) (1200 m). Bacterial, mesozooplankton and larval fish densities significantly differed between sample depths but not between sampling tow times. In total, 154 zooplankton species and 18 larval fish species were identified. The highest number of taxa was obtained from the night-time TW trawls. This depth zone had the highest densities of mesozooplankton, larval fish and bacterioplankton (auto and heterotrophic), associated with the highest temperature and salinity and the lowest inorganic nutrient concentrations. Two sample groups were identified based on their mesozooplankton and larval fish compositions: night-time TW and other water masses (daytime TW, SACW, AAIW and UCDW). Thirty-two indicator species were detected in night-time TW. The copepod Nullosetigera impar was, to the best of our knowledge, identified for the first time on the Brazilian coast. Our results showed significant variability in the abundance and vertical distribution of mesozooplankton, bacterioplankton and larval fish along the water column in an oceanic area. We have provided new data and insights on the composition and vertical distribution of mesozooplankton, larval fish and bacterioplankton in deep waters in the South-western Atlantic Ocean.

Seasonal variability of ichthyoneuston assemblage on the continental shelf and slope of the Southwest Atlantic Ocean, Brazil (20°–23°S)

“…Many species considered rare in the present study were very abundant in the subsurface water in Campos Basin (Bonecker et al, 2017(Bonecker et al, , 2012 and in deeper waters in other areas of the Brazilian coast (Goçalo, Katsuragawa, & Silveira, 2011;Namiki et al, 2017). Therefore, the low frequency and abundance of some species in the present study probably reflect net avoidance of fish larvae during the day, due to the visual and swimming capacity of larger larvae (Doyle, 1992;Katsuragawa & Matsuura, 1990), or because they are pseudoneuston species, which means that their center of distribution occurs at deeper layers and the surface is the edge of their vertical range of distribution (Hempel & Weikert, 1972).…”

“…These species was classified as euneuston according to other authors (Hempel & Weikert, ; Katsuragawa & Matsuura, ; Vilchis, Balance, & Watson, ). Bonecker et al () also found Exocoetus obtusirostris Günther, 1866 and Coryphaena equiselis Linnaeus, 1758 near the surface during the day. According to Hempel and Weikert (), mullid larvae concentrated in the surface during the day and moved to the subsurface layer at night.…”

Unveiling the diversity of thaliaceans (Chordata, Thaliacea) from the the South Brazilian Bight and Southern Subtropical Shelf (22° - 33° S)

“…So far, in the Southern Subtropical Shelf, 10 species of thaliaceans have been reported (Amaral et al 1997;Daponte & Thompson 2022), 14 in the South Brazilian Bight (Nogueira- Júnior, 2011;Resgalla, 2011;Bonecker et al 2014;Bonecker et al 2019), 12 species in the eastern region (12°S-22°S) (Bonecker 2006), and 7 in the northeastern region, from the coastal area to offshore (2°S-9°S) (Tosetto et al 2022).…”

“…mainly by the large latitudinal range of samplings (22°S to 33°S), covering the entire southeast-south region of Brazil. In contrast, most other studies were limited to a considerably smaller latitudinal range and were carried out in more coastal/shelf areas (Tavarez 1967;Amaral et al 1997;Bonecker 2016ab;Resgalla 2011;Nogueira-Júnior 2011;Bonecker et al 2014;Bonecker et al 2019;Fernandes 2019;Tosetto et al 2022).…”

“…It was recorded in northeast Brazil between 2°S-9°S (Tosetto et al 2022). In southeastern Brazil (~26°S) (Bonecker et al 2014;Bonecker et al 2019) and 26°45'S (Nogueira-Júnior 2011). We have extended the species' distribution to the southern subtropical shelf (28°S-33°S).…”