Planktonic ciliates in different water masses in open waters near Prydz Bay (East Antarctica) during austral summer, with an emphasis on tintinnid assemblages

Abstract

Planktonic ciliates are important microzooplankton in pelagic ecosystems. Previous studies in Antarctic waters have only investigated ciliate assemblages in different habitats without considering water masses. In this article, we report the characteristics of ciliate assemblages in different water masses in open waters near Prydz Bay (East Antarctica) during austral summer. Three water masses were identified according to temperature and salinity: Summer Surface Water (SSW), Winter Water (WW), and Circumpolar Deep Water (CDW). SSW was further divided into SSW Chl a < 3 (in vivo Chlorophyll a > 3 mg m −3) and SSW Chl a < 3 (in vivo Chlorophyll a < 3 mg m −3). Ciliate abundance and biomass in water masses decreased in the order: SSW > WW > CDW. SSW Chl a > 3 had a higher proportion (38.2%) of tintinnids to the total ciliate abundance and larger aloricate ciliates (ciliates in the 10-20 µm size class were < 15% of the total aloricate ciliate abundance) than in other water masses. WW had a higher proportion (> 30%) of Southern Ocean endemic tintinnid species in total tintinnid abundance than in other water masses. Each water mass had the following indigenous tintinnid species: SSW, Salpingella sp., Codonellopsis gaussi; WW, Salpingella costata, S. faurei, Cymatocylis affinis/convallaria forma drygalskii, and C. vanhoeffeni. Laackman-niella naviculaefera and C. affinis/convallaria forma cristallina were present at high abundance in both WW and SSW Chl a > 3. Upwelling caused discontinuity of the ciliate distribution. Our results will help predict the spatial and temporal variations of ciliate assemblages and other plankton according to the dynamics of water masses in Antarctic waters.

Organization of planktonic Tintinnina assemblages in the Atlantic Ocean

“…The weak upwelling at about 5°S might account for the relative difference in position between Eutintinnus perminutus, Rhabdonella indica and E. medius in the two hemispheres (Supplementary Figure 3). This upwelling might also cause the surface occurrence of Proplectella claparedei and Acanthostomella obtusa in the southern hemisphere (Supplementary Figure 5) as in Prydz Bay, Antarctic (Liang et al, 2018).…”

The grazing of abundant microzooplankton causes ultrahigh seawater dimethylsulfide during Southern Ocean algal blooms

“…Each sample was concentrated to a final volume of about 50 mL by repeatedly settling and siphoning. The concentrated sample was then settled in an Utermöhl counting chamber for at least 24 h, and examined using an Olympus IX 71 inverted microscope (×100 or ×400) (Liang et al 2018). Note that aloricate ciliates and tintinnids were the dominating groups in the Southern Ocean, and generally, abundance and biomass of aloricate ciliate were much higher than those in tintinnid.…”

Seasonal acoustic presence of marine mammals at the South Orkney Islands, Scotia Sea

“…Despite several species of marine mammals almost being eradicated after the commercial harvest during the nineteenth and twentieth centuries and the Scotia Sea being one of the most heavily exploited areas, there have been clear signs of population recovery over recent decades [2,8–13]. Considering ongoing and future climatic changes, and with the AP and Scotia Sea being among the fastest-warming areas on Earth [14,15], there is an increasing need to gain knowledge about the cascading effect that such environmental changes may have on the distribution patterns and ethology of the major krill predators. Additionally, the operation of the commercial krill fishery in this region has the potential to affect the marine mammal consumption requirements by removing or displacing prey and thus affecting their distribution [13,16–18].…”