Population densities, growth, and respiration of the chaetognath Parasagitta elegans in the Canadian high Arctic

Abstract

The chaetognath population at Resolute in the Canadian high Arctic (75°N) was monitored biweekly during 1993. Parasagitta elegans composed 98.9% of the population, and Eukrohnia hamata made up the remaining 1.1%. The proportion of E. hamata increased east toward Baffin Bay. Parasagitta elegans had a 700-d life-span at a mean annual temperature of about -1.5°C. The population of P. elegans at Resolute had a mean annual density of 191⋅m -2 , weighed 0.409 g dry weight⋅m -2 , respired 1.259 g O 2 ⋅m -2 ⋅yr -1 , and grew 0.566 g dry weight⋅m -2 ⋅yr -1 , with a 0.40 net growth efficiency and a P:B (production : biomass) ratio of 1.38. It made up 5.7% of the macroplankon biomass by weight, respired 1.5% of its total oxygen consumption, and consumed 1.78 g dry weight prey⋅m -2 ⋅yr -1 , a minimum of 0.1%⋅d -1 or 36% of the mean annual copepod biomass.

Seasonal ecology and life-history strategy of the high-latitude predatory zooplankter Parasagitta elegans

“…Cohort 2 had low growth rates throughout the year (total growth of 5 mm), suggesting little growth after maturation, in agreement with results from Baffin Bay (Samemoto 1987) and Resolute (Welch et al 1996). Cohort 1, however, grew considerably from around 23 mm in February to 30 mm in April.…”

“…Cohort 1, however, grew considerably from around 23 mm in February to 30 mm in April. Whilst this strong growth could be an artefact of our method of detecting size cohorts from length-frequency data, Welch et al (1996) similarly observed high winter growth rates for adolescents in the cold environment of Resolute (Canadian Arctic). Saito & Kiørboe (2001) showed that individuals >12.5 mm can feed on many prey size classes > 250 µm, suggesting that adolescents and adults are unlikely to face food shortages in winter.…”

“…Welch et al 1992). P. elegans often dominates chaetognath communities in Arctic shelf seas (Dunbar 1962, Welch et al 1996, whereas the other 2 species may be more common at mesoto bathypelagic depths offshore (Koso bo kova et al 2011). P. elegans is a heterogeneous feeder, but calanoid and cyclopoid copepods are its major prey (see review by Terazaki 2004), and it can consume relatively high portions of the daily secondary production (Samemoto 1987).…”

Role of midwater chaetognaths in Southern Ocean pelagic energy flow

“…This model was fitted using our data on Sagitta gazellae as well as data from Reeve et al (1970), Nival et al (1972), Ivleva (1976, Båmstedt (1979), Ikeda (1989), Ikeda & Kirkwood (1989), Ikeda & Skjoldal (1989), , Welch et al (1996), Ikeda & Hirakawa (1998), Coston-Clements et al (2009), andKruse et al (2010). The data published by Sameoto (1972) were not used because an a priori analysis showed that these values deviated consistently and significantly from all other sources, indicating a source-specific bias.…”

“…Several respiration measurements provided information on the chaetognath individual metabolism (e.g. Reeve et al 1970, Sameoto 1972, Båmstedt 1979, Welch et al 1996. However, we know little about the metabolism of Antarctic deep-sea chaetognaths and only a few studies have been conducted to date on individual metabolic activity in Antarctic chaetognaths (Ikeda & Kirkwood 1989, Kruse et al 2010.…”