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4.2. Bacterial growth, production and imprints on nutrient concentrations
Our Leu- and TdR-based bacterial production estimates are convergent, pointing to the reliability of the results. Overall BP Leu and TdR in ice were low, but were comparable to those Y27632 of Kuparinen et al. (2011) obtained on predator-free batch cultures from melted 2-week-old sea ice. The bacterial abundance and ice salinities were in the same range to other studies measuring bacterial production in sea ice in the Southern Ocean (Grossmann and Dieckmann, 1994 and Helmke and Weyland, 1995), the Arctic Ocean (Kaartokallio et al., 2013 and Nguyen and Maranger, 2011) and the Baltic Sea (Kuparinen et al., 2007). Unlike many studies done in natural sea ice, algae and other typical larger sea ice organisms were absent in our experiment, which may have led to lower bacterial production, since ice algae may be a source of autochthonous DOM in ice (Thomas et al., 2001).
While cell-specific Leu showed a similar pattern in both treatments, TdR was higher in SWR (compared to SW) in both ice and parent water. This indicates symbiosis DOC addition had a positive impact on bacterial growth, which is also in agreement with the slightly higher bacterial abundance and overall higher bacterial production in SWR series (Table 3).