Abstract:

The predominant picoplankton of the Arctic is Micromonas sp., which plays a pivotal role in biogeochemical cycles and is an important link showing that the microbial loop affects organic carbon transfer to higher trophic levels and to deep-sea outputs. As one of the key ecological roles in the Arctic Ocean ecosystem, the interaction between Micromonas sp. and associated bacterioplankton has been explored. A series of inocula experiments was undertaken with isolated CCMP2099 Micromonas sp. in an axenic treatment and in one inoculated with marine bacteria. There was no significant effect on the growth of Micromonas sp., whether treated with bacteria or not. The microalgae grew healthily during the experiments and promoted bacterial growth. Bacterial abundance during the stationary phase was higher than during the exponential phase, although it fluctuated occasionally. Adding exogenous bacteria had no obvious effect on algal growth, bacterial numbers, dissolved organic carbon (DOC), transparent exopolymer particles (TEP), and dissolved free amino acids (DFAA). Based on this preliminary study, the interaction between Micromonas sp. and its associated bacteria was discussed in relation to TEP formation, DOC, and DFAA. Algae-bacterial interaction has a significant effect on the microbial loop in the Arctic ecosystem. The results of this study provide an experimental and theoretical basis for microbial loop, phytoplankton, and key microbial community coupling interactions in the Arctic ecosystem.

Key words: Arctic, Micromonas sp., bacterioplankton, algae-bacterial interaction