MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps13001

Phytoplankton communities and size-fractionated chlorophyll a in newly opened summer waters of the central Arctic Ocean

Yu Wang, Jian-hua Kang, Peng Xiang, You-yin Ye, He-shan Lin, Mao Lin*

*Email: linmao@tio.org.cn

ABSTRACT: The rapid decline of sea ice extent during the Arctic summer seasons has profound implications on the pelagic ecosystem. During the fourth Chinese National Arctic Research Expedition (4th CHINARE) in August 2010, a snapshot of the spatial distribution of phytoplankton communities (>10 µm) and size-fractionated chlorophyll a (chl a) in newly opened waters in the central area of the western Arctic Ocean (80°–86° N) was studied. Potential environmental drivers were linked with community profiles to assess the influences of water masses and sea ice shrinking. Results indicate that the central Arctic Ocean exhibited a typical low-nutrients low-chlorophyll a (LNLC) environment accompanied with low phytoplankton diversity and abundance. A total of 49 taxa belonging to 25 genera from 5 classes were identified by Utermöhl method, with diatoms (Chaetoceros spp., Nitzschia spp., Thalassiosira nordenskiöldii, Nitzschia longissima) numerically dominating the community. Based on chl a contributions, picophytoplankton (<2 µm) had the highest proportion followed by nanophytoplankton (2–20 µm) and then microphytoplankton (>20 µm). Phytoplankton abundance and size-fractionated chl a differed significantly between the early ice-melting northern Canada Basin influenced by summer Bering shelf water and near the Alpha Ridge that had thicker ice coverage. Redundancy analysis (RDA) and Spearman’s correlation suggest that salinity, temperature and nitrate concentration were the major factors influencing phytoplankton abundance and size-fractionated chl a. In addition, irradiance played an important regulatory role in the vertical variation of size-fractionated chl a, where low light adapted picophytoplankton dominated. These support previous studies showing their advantage in oligotrophic and light-limited environments such as the central Arctic Ocean.