Chaetognatha of the Brazil-Malvinas (Falkland) confluence: distribution and associations

Abstract

The planktonic chaetognaths from the Brazil-Malvinas (Falkland) confluence, extending between 36º 30' - 50º 5' S and 60º 33' - 41º 7' W, were studied. Ten species were found: Eukrohnia hamata (Möbius, 1875) (Eukrohniidae), Pterosagitta draco (Krohn, 1853) (Pterosagittidae), Sagitta enflata Grassi, 1881, Sagitta gazellae Ritter-Zahony, 1909, Sagitta hexaptera d´Orbigny, 1834, Sagitta lyra Krohn, 1853, Sagitta minima Grassi, 1881, Sagitta planctonis Steinhaus, 1896, Sagitta serratodentata Krohn, 1853, and Sagitta tasmanica Thomson, 1947 (Sagittidae). Sagitta gazellae was the most abundant species followed by E. hamata, S. tasmanica and S. serratodentata. The association analysis among the different species, salinity and temperature revealed two groups of species, one related to higher salinities and warmer waters (P. draco, S. hexaptera and S. serratodentata) and the other to lower salinities and colder waters (E. hamata, S. gazellae and S. tasmanica). The fact that P. draco and S. hexaptera, formerly defined as warm-water species, appeared further south than previously reported might be related to the existence of warm core eddies up to 46º S in September and October 1988

The influence of environmental conditions onParasagitta friderici(Chaetognatha) abundance in a subtropical estuary (south Brazil)

“…The influence of physical and biological environment on chaetognath populations and their spatial and temporal dynamics from shelf and oceanic ecosystems is relatively well-known, with many available studies on the South-western Atlantic (e.g. Crelier & Daponte, 2004; Araújo & Ribeiro, 2005; Souza et al ., 2014) and in most other main regions worldwide (e.g. Gibbons & Stuart, 1994; Nair et al ., 2002; Ruiz-Boijseauneau et al ., 2004; Noblezada & Campos, 2012; Wu et al ., 2014).…”

Pteropoda, Cladocera, and Chaetognatha associations as hydrological indicators in the southern Brazilian Shelf

“…S. minima, in particular, is considered an indicator of mixed waters between the neritic and oceanic region, and between Sub-Antarctic and Tropical Waters (Hida, 1957;Johnson & Brinton, 1963;Tokioka, 1979;Raymont, 1983). Therefore, this group would not be a good indicator of Tropical Water, since typical species such as Pterosagitta draco and Sagitta hexaptera (Crelier & Daponte, 2004) do not present the minimum occurrences for inclusion in the analysis. The oceanographic stations associated with this group of species probably delimit a transition zone between the cold waters of the Sub-Antarctic Shelf Water and the warm waters of the Tropical Water.…”

“…Boltovskoy (1982), classifying the study area as a southern transition zone. Crelier & Daponte (2004) presented chaetognath associations sampled during the same period off the northern coast of Argentina, whereas Coelho (1993) carried out a study based on samples obtained 10 years earlier off the south of Brazil. The similarities observed among the studies on species associations highlight the existence of past data that might be used in the future to assess the changes in fauna that are observed today and that are attributed to climate changes resulting from global warming.…”

Relationship between spatial distribution of chaetognaths and hydrographic conditions around seamounts and islands of the tropical southwestern Atlantic

“…Their highest densities are found under optimal development conditions (temperature, salinity and local productivity favoring the growth, sexual development and feeding rate), and decrease when approaching their distri bution boundary. This fl uctuation in density must be taken into account when determining the allocation range of the species (Crelier and Daponte 2004). The distribution patterns of the species detected was closely related to the hydrology of the area analyzed.…”