Browsing by Subject "nanoflagellates"

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  • Kaikkonen, Laura; Enberg, Sara; Blomster, Jaanika; Luhtanen, Anne-Mari; Autio, Riitta; Rintala, Janne-Markus (Springer Nature, 2020)
    Polar Biology 43 9 (2020)
    Marine microbial communities undergo drastic changes during the seasonal cycle in high latitude seas. Despite the dominance of microbial biomass in the oceans, comprehensive studies on the seasonal changes of microbial plankton during the complete winter period are lacking. To study the seasonal variation in abundance of the microbial community, water samples were collected weekly in the Northern Baltic Sea from October to May. During ice cover from mid-January to April, samples from the sea ice and the underlying water were taken in addition to the water column samples. Abundances of bacteria, virus-like particles, nanoflagellates, and chlorophyll a concentrations were measured from sea ice, under-ice water, and the water column, and examined in relation to environmental conditions. All studied organisms had clear seasonal changes in abundance, and the sea-ice microbial community had an independent wintertime development compared to the water column. Bacteria were observed to have a key role in the biotic interactions in both ice and the water column, and the dormant period during the cold-water months (October–May) was limited to before ice formation. Our results provide the first insights into the temporal dynamics of bacteria and viruses during the whole cold-water season (October–May) in coastal high latitude seas, and demonstrate that changes in the environmental conditions are likely to affect bacterial dynamics and have implications on trophic interactions.
  • Brek-Laitinen, Grazyna; López Bellido, Jessica; Ojala, Anne (2012)
    The clearwater boreal Lake Vesijärvi experiences annual periods of hypolimnetic hypoxia with unknown consequences for the microbial food web. We quantified the abundance of heterotrophic bacteria, autotrophic picoplankton (APP), nanoflagellates (NF) and ciliates in Lake Vesijärvi throughout the water column and vegetation season and determined how these varied with changes in environmental conditions, including dissolved oxygen concentrations. The abundance and diversity of ciliates increased significantly throughout the water column with the development of thermal stratification and the onset of hypoxia leading to distinct ciliate communities in the oxic epilimnion and hypoxic hypolimnion. Bacterivorous taxa dominated in the hypoxic zone, while in the epilimnion, bacterivorous, algivorous and predatory taxa feeding on other protozoa were present. Seasonal changes in oxygen and temperature explained nearly 80% of variance in ciliate community composition. Changes in total ciliate numbers correlated with seasonal dynamics of bacteria, but not with the dynamics of NF. In the epilimnion, NF were abundant in early spring and their numbers were positively correlated to numbers of prostomatids and haptorids, but not to APP or bacteria. In the hypolimnion, a significant correlation was found between NF and bacteria, but not NF and ciliates. Significant positive correlations between ciliates and bacteria suggest that concentrations of food resources are important in determining the abundance of ciliates in the plankton. Moreover, we recorded close coupling between seasonal dynamics of bacteria and productivity of phytoplankton, including APP.