Meso- and bathypelagic distribution and abundance of chaetognaths in the Atlantic sector of the Southern Ocean

Abstract

We conducted multinet sampling during winter and summer in the Southern Ocean (Atlantic sector) to investigate the eVect of water mass, season and water depth on abundance and species composition of meso-and bathypelagic chaetognaths. Eukrohnia hamata (mean 115 ind. 1,000 m ) below 1,000 m. A further six species were identiWed, among them the rare bathypelagic species Heterokrohnia fragilis and the subtropical Eukrohnia macroneura that is new to the Antarctic. Water depth and season were the principal determinants of abundance and species composition patterns, indicating vertical seasonal migration and vertical segregation of species. The life cycles of E. hamata and S. marri were studied additionally. Their maturity stages were vertically segregated and prolonged reproductive periods are suggested for both species.

Species composition, seasonal abundance and population structure of chaetognaths in Admiralty Bay (Antarctic)

“…However, E. hamata was the most abundant in all areas (up to 95% of all chaetognaths), whereas the contribution of other species depended on the location and the study season. Kruse et al (2009), investigating the Lazarev Sea in summer and winter, suggested that chaetognath abundance and species composition were affected by several parameters: water mass, water depth, season and ontogenesis, with the effect of water depth considered to be the major determinant. A similar trend was observed by Alvarino (1964), Bielecka and Żmijewska (1993), Błachowiak-Samołyk et al (1995), Duro et al (1999), Duro and Gili (2001), and Kulagin (2010).…”

“…The species number varies from a few to ca. 30 in a given region, and is higher at lower latitudes (Alvarino 1964;Terazaki 1998;Ulloa et al 2000;Pierrot-Bults 2008;Kruse et al 2009). Due to their relatively low tolerance to changes in hydrological conditions, many species, including the endemic Antarctic species P. gazellae, are considered good indicators on various water masses (O'Sullivan 1982;Pierrot-Bults 2008).…”

“…Although Chaetognatha is a relatively small phylum consisting of 150 currently known species (Kapp 2004), they represent, in terms of abundance and biomass, one of the main zooplankton components (O'Sullivan 1982;Øresland 1990;Pierrot-Bults 2008;Kruse et al 2009;Kruse 2010). They occupy a wide horizontal and vertical range in the world's ocean.…”

“…Over the last decades, studies of Chaetognatha have focused mainly on their occurrence and abundance in different regions worldwide: from the Arctic (Samemoto 1987;Terazaki 1998) through the Atlantic (Pierrot-Bults 2008), the Indian Ocean (Vijayalakshmi and Gireesh 2010) and the Pacific (Alvarino 1964;Ulloa et al 2000) to the Southern Ocean (Bielecka and Żmijewska 1993;Duro and Gili 2001;Kruse et al 2009;Kulagin 2010). In addition, such important aspects as behaviour, feeding, position in the trophic chain, the role of individual taxa in the ecosystem functioning and the structure of local populations of the most common and most abundant species have been also investigated (Kramp 1939;Alvarino 1968;Zo 1973;Samemoto 1987;Øresland 1990Błachowiak-Samołyk et al 1995;Terazaki 1998;Choe and Deibel 2000;Kruse et al 2009;Kruse et al 2010;Grigor et al 2014;Grigor et al 2015).…”

“…In addition, such important aspects as behaviour, feeding, position in the trophic chain, the role of individual taxa in the ecosystem functioning and the structure of local populations of the most common and most abundant species have been also investigated (Kramp 1939;Alvarino 1968;Zo 1973;Samemoto 1987;Øresland 1990Błachowiak-Samołyk et al 1995;Terazaki 1998;Choe and Deibel 2000;Kruse et al 2009;Kruse et al 2010;Grigor et al 2014;Grigor et al 2015).…”