Spatial and nycthemeral distribution of the zooneuston off Fernando de Noronha, Brazil

Abstract

A B S T R A C TIsland environments drastically modify the hydrodynamics of ocean currents and generate strong vertical turbulence. This leads to an upward transport of nutrient-rich waters, thus increasing the biomass of plankton in these oceanic marine environments. The objective of this study was to assess the biomass and density of the zooneuston communities in relation to the upper and lower layers (epi-/hyponeuston), the nycthemeral variation (day/night), the currents in relation to the island (downstream vs upstream), and the distance from the island, focusing on the spatial variability. Samples were taken in July and August 2010 with a David-Hempel neuston net (Hydro-Bios) with a mesh size of 500 μm. Twenty-one taxa were recorded. The most abundant taxa were Copepoda, Chaetognatha, Teleostei (eggs) and Hydrozoa. This is the first record of phoronid larvae for the waters of the Tropical Atlantic. For both layers, density and biomass were significantly higher at night. Density and biomass were always significantly higher in the upper (epineuston) layer than in the lower (hyponeuston) layer. This was probably due to a zooneuston aggregation at the surface and massive vertical migration from deep waters at night, leading to increased abundances at night in both neuston layers. R E S U M OAmbientes insulares são responsáveis pela modificação da hidrodinâmica das correntes oceânicas e por gerar turbulência vertical. Esta faz com que águas da camada inferior ricas em nutrientes sejam elevadas à região superior da coluna de água, aumentando a biomassa do plâncton local. O objetivo deste trabalho foi avaliar a biomassa e a densidade e das comunidades do zoonêuston em relação às camadas superior e inferior da coluna de água (epi/hiponêuston), à variação nictemeral (dia/noite), corrente superficial predominante (jusante/montante) e à distância da ilha, com foco na variabilidade espacial do plâncton. Amostragens foram realizadas de julho a agosto de 2010 com uma rede de nêuston David-Hempel (Hydro-Bios) com malha de 500 μm. Vinte e um táxons foram registrados, sendo os mais abundantes Copepoda, Chaetognatha, Teleostei (ovos) e Hydrozoa. Apresenta-se também o primeiro registro de larvas de Phoronida para o Atlântico Tropical. Para ambas as camadas, a densidade e a biomassa foram significativamente mais elevadas durante a noite e também significativamente maiores no epinêuston. Este fato provavelmente ocorreu devido à agregação do zoonêuston na superfície do oceano e à forte migração vertical a partir de camadas profundas durante a noite, levando a um aumento das abundâncias dos organismos nesse período, em ambas as camadas neustônicas.

Spatio-temporal variation of planktonic decapods along the leeward coast of the Fernando de Noronha archipelago, Brazil

“…A higher abundance of planktonic decapods was found at the southernmost stations of the island, however there were no great variations among stations in relation to taxonomic composition. Studies on abundance of planktonic decapods were performed in the oceanic waters off Fernando de Noronha by Lira et al (2014). However, these studies were conducted far away from the coast, and none of these previous studies investigated the distribution of decapods along the nearshore leeward area of the archipelago.…”

“…This general pattern can be related to local hydrodynamics, as the predominant surface currents of the leeward part of the island usually flow from Porto de Santo Antônio to Baía dos Golfinhos (from northeast to southwest), and the current could thus carry the larvae from the north of the island and accumulate them in the south (Lira et al, 2014;Lira, personal communication *2 ), highlighting the larval Island effect. However, there are still no published detailed data on the dynamics of currents in the nearshore leeward area of the Fernando de Noronha archipelago.…”

“…Studies on the larval ecology of Decapoda are essential to the understanding of the marine ecosystems in which they are inserted (Schwamborn et al, 1999;Anger, 2001;Brandão et al, 2012Brandão et al, , 2013. Even so, little effort has been made to assess the distribution and composition of decapod larvae in oceanic island environments in Brazil (Koettker et al, 2010;Brandão et al, 2012Brandão et al, , 2013Marafon-Almeida et al, 2016), specifically for the Fernando de Noronha archipelago (Lira et al, 2014(Lira et al, , 2017(Lira et al, , 2018.…”

Body size and stable isotope composition of zooplankton in the western tropical Atlantic

“…This region comprehends the extension from the shelf, slope and slope, seamounts and oceanic islands, all with low levels of nutrient supply and productivity and high zooplankton diversity . Numerous studies have investigated zooplankton communities in this region, most of which focusing on community structure, abundance diversity (e.g., Neumann-Leitão et al, 1999;Diaz et al, 2009;Brandão et al, 2013;Lira et al, 2014;Santana et al, 2018), and size spectra (Marcolin J o u r n a l P r e -p r o o f et al, 2013). In this region, the stable isotope composition (δ 13 C and δ 15 N) of zooplankton and particulate organic matter (POM) has been investigated in mangrove estuaries, on the shelf and at the adjacent slope, revealing that any measurable estuarine influence was limited to the line of intertidal coastal reefs, approximately 10 km from the coast (Schwamborn et al, 1999(Schwamborn et al, , 2002.…”

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

“…Nevertheless, large migratory copepods like Calanoides carinatus and Rhincalanus cornutus were observed in the deep waters (SACW, AAIW and UCDW). Copepod dominance is reported in most mesozooplankton studies and demonstrates the importance of this group in transferring energy between different trophic levels (Turner, 2004; Escribano et al ., 2009; de Lira et al ., 2014; Munk et al ., 2015).…”