Abstract

Bacteria are an essential part of the microbial loops and play key roles in carbon cycling. To understand their ecological contributions in polar regions, they were measured in the northwest Weddell Sea during the 32nd Chinese National Antarctic Research Expedition in the austral summer of 2016. The results showed a range of bacterial abundance from 0.20 to 3.34 × 10⁸ cells/L with an average of 1.03 × 10⁸ cells/dm³. Bacterial production varied between 0.06 and 2.42 mg C/(m³ d) with an average of 0.44 mg C/(m³ d). Bacterial carbon budgets were unevenly distributed in the northwest Weddle Sea, and surpluses appeared in the autotrophic area such as Weddell Surface Water and Transitional Zonal Water with Weddell Sea influence (TWW), and deficits in the Weddell-Scotia Confluence (heterotrophic area). A t-test result suggested that the unbalanced bacterial carbon budgets were mainly caused by distributions of Chl a. Bacterial abundance was uncorrelated with environmental and biological factors in the autotrophic region. At the same time, production was positively correlated with temperature and Chl a. In the heterotrophic area, bacterial abundance was positively correlated with temperature. Production was significantly positively correlated with temperature, and Chl a. Bacterial production had a small contribution to the increase of bacterial abundance because of a strong top-down control in the northwest Weddell Sea.