Microzooplankton composition under the sea ice and in the open waters in Terra Nova Bay (Antarctica)

Spatial distribution of microzooplankton in different areas of the northern Antarctic Peninsula region, with an emphasis on tintinnids

The Western Antarctic Peninsula (WAP) is experiencing rapid climate warming, resulting in affecting the marine food web. To investigate the microzooplankton spatial distribution and to assess how climate change could affect the tintinnids community, sea water samples were collected during late summer 2018 at 19 stations in three different areas: Deception Island, Elephant Island and Antarctic Sound. The microzooplankton community comprised mainly tintinnids, aloricate ciliates, heterotrophic dinoflagellates and micrometazoans. Microzooplankton abundance varied between 3 and 109 ind. L−1 and biomass ranged from 0.009 to 2.55 µg C L−1. Significant differences in terms of abundance and taxonomic composition of microzooplankton were found among the three sampling areas. Deception Island area showed 44% of tintinnids and the rest were heterotrophic dinoflagellate, aloricate ciliates and micrometazoans. In Elephant Island and Antarctic Sound areas, tintinnids reached, respectively, 73% and 83% of the microzooplankton composition, with all the other groups varying between 20 and 30%. Tintinnids were the most representative group in the area, with the species Codonellopsis balechi, Codonellopsis glacialis, Cymatocylis convallaria and Cymatocylis drygalskii. The highest amounts of tintinnids were found at the surface and 100 m depth. The above mentioned species may be considered key species for the WAP and therefore they can be used to track environmental and hydrographical changes in the area. In late summer, microzooplankton presented low abundances and biomass, nevertheless they represented an important fraction of the planktonic community in the area.

Antarctic coastal nanoplankton dynamics revealed by metabarcoding of desalination plant filters: Detection of short-term events and implications for routine monitoring

One of the main requirements of any sound biological monitoring is the availability of long term and, possibly, temporal data with a high resolution. This is often difficult to be achieved, especially in Antarctica, due to a variety of logistic constraints, which make continuous sampling and monitoring activities generally unfeasible. Here we focus on the 5 μm filters used in the desalination plant of the Italian research base "Mario Zucchelli" in the Terra Nova Bay area (Ross Sea, Antarctica) to evaluate intra-annual coastal nanoplankton dynamics. These filters, together with others of larger mesh sizes, are used to decrease the amount of organisms and debris in the input seawater before the desalination processes take place, hence automatically collect the plankton present in the water column around the desalination system intake. We have used a DNA metabarcoding approach to characterize the communities retained by filters' sets collected in January 2012 and 2013. Intra-annual dynamics were disclosed with an unprecedented detail, that would not have been possible by using standard sampling approaches, and highlighted the importance of extreme, stochastic events such as katabatic wind pulses, which triggered dramatic, short-term shifts in coastal nanoplankton composition. This method, by combining a cost-effective sampling and molecular techniques, may represent a viable solution for long-term monitoring programs focusing on Antarctic coastal communities.