Interannual fluctuations in copepod abundance and contribution of small forms in the Drake Passage during austral summer

Abstract

The relative importance of small forms of copepods has been historically underestimated by the traditional use of 200-300-lm mesh nets. This work quantified the distribution and abundance of copepods, considering two size fractions (\300 lm and[300 lm), in superficial waters (9 m deep) of the Drake Passage and contributed to the knowledge of their interannual fluctuations among three summers. Four types of nauplii and eleven species of copepods at copepodite and adult stages were identified, with abundance values of up to 13 ind L -1 and 28,300 lg C m -3 . The\300-lm fraction, composed of Oithona similis, small cyclopoids and nauplii, dominated the copepod communities in the 3 years; it accounted for more than 77% of the total number and for between 40 and 63% of the total biomass. Changes in density and biomass values among the three cruises differed according to copepod size fraction and water mass; the [300-lm fraction showed no changes among the 3 years, both in Antarctic (density and biomass) and in Subantarctic waters (density), whereas the \300-lm fraction showed higher (density and biomass) values in 2001 both in Subantarctic and in Antarctic waters. Sea surface temperature and its anomaly accounted for the largest proportion of variability in copepod density and biomass, particularly for the\300-lm fraction.

Structure, abundance and biomass size spectra of copepods and other zooplankton communities in upper waters of the Southwestern Atlantic Ocean during summer

“…The predictive values of environmental variables in the spatial distribution of the ,300-mm fraction and their main components (nauplii larvae, Oithona similis, and the harpacticoid Microsetella norvegica) complemented previous results in this respect (Tables V and VI). SST accounted for the largest proportion of variability in abundance and biomass of this size fraction in the Drake Passage waters during summer (Thompson et al, 2012). Studies based on mesh sizes .330 mm showed that SST and salinity were important predictors of copepods composition in the SAO (Berasategui et al, 2005), while others have suggested that SST is more important than chlorophyll a in defining plankton assemblages in the Southern Ocean (Chiba et al, 2001;Ward et al, 2012).…”

“…Differences in copepod composition and densities have been reported north and south of the Subantarctic Front (Woodd-Walker et al, 2002;Berasategui et al, 2005) and between Continental Shelf Waters and the BMC (Berasategui et al, 2006). On the other hand, similarities in copepod composition but differences in their density and biomass were reported north and south of the Polar Front (Thompson et al, 2012). Probably as a result of the use of a 20-mm mesh net, the present study also detected differences in the body length distribution of copepods and other zooplankton among ecological domains (Fig.…”

“…López and Anadón (López and Anadón, 2008) concluded that small copepods and nauplii accounted for a higher amount of total chlorophyll ingestion than larger copepods. The use of finer mesh nets has revealed the numerical relevance of these organisms in the SAO (Thompson, 2001) and, more recently, in Argentine Continental Shelf Waters (Di Mauro et al, 2009), in Antarctic Waters of the Atlantic Sector (Ward et al, 2012) and in the Drake Passage (Thompson et al, 2012).…”

On the uncertainty beneath the name Oithona similis Claus, 1866 (Copepoda, Cyclopoida)

“…In the SW Atlantic both names have been recorded: Oithona similis has been used by, for example, Pallares (1968), Björnberg (1981), Mazzochi et al (1995), Viñas et al (2002), Fernández-Severini and Hoffmeyer (2005), Aguirre et al (2012), Cepeda et al (2012), Thompson et al (2012), and Oithona helgolandica by, for example, Ramírez (1970), Sabatini and Martos (2002), Viñas et al (2013), Antacli et al (2014), and Temperoni et al (2014).…”

Temporal distribution of zooplankton communities in coastal waters of the northern Bay of Bengal, Bangladesh

“…Acartia clause) and increasing temperature (i.e. Acartia tonsa and Acartia hudsonica) (Hirst et al, 1999;Bianchi et al 2003;Mulyadi 2004;Hooff 2006), and copepod distribution was used as indicator of salinity variation (Thompson et al, 2012;Vineetha et al, 2015;Abu Hena et al, 2016;Fontana et al, 2016). Indeed, trophic condition of secondary production and ecological succession in aquatic ecosystems are led by zooplankton (Iqbal et al, 2014: Abdullah Al et al, 2018, thanks to their ability to integrate lower with higher trophic levels.…”