期刊
DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
卷 63, 期 -, 页码 118-132出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.dsr.2012.01.011
关键词
Photosynthesis; Phytoplankton; Turbulence; Mixing processes; Southern Ocean; Acoustic backscatter; Fast repetition rate fluorometry
类别
资金
- National Science Foundation [OPP-0127037, OPP-0127022, OPP-0125818]
- Scientific Committee for Antarctic Research
- Spanish Ministry of Education and Science
- RVIB Nathaniel B. Palmer
- Office of Polar Programs (OPP)
- Directorate For Geosciences [0839011] Funding Source: National Science Foundation
Detailed studies were made in the springtime Ross Sea Polynya of the interaction between near-surface mixing processes, inferred from Thorpe scales and acoustic backscatter, and the quantum efficiency and rate of PSII electron transport of phytoplankton photosynthesis measured at fine depth and time scales by active fluorometry. The phytoplankton assemblage was dominated by Phaeocystis antarctica. Surface conditions alternated between windy episodes producing Langmuir circulation (LC) or calm periods favoring internal waves, in both cases there was significant vertical transport of phytoplankton. During LC episodes, strong near-surface ( < 10 m) vertical gradients in quantum efficiency and inhibition of electron transport were observed despite evidence of vigorous vertical exchange. Under sunny mid-day conditions, profiles of PSII electron transport had sub-surface peaks and electron transport at PAR irradiances > 40 mu mol photons m(-2) s(-1) was generally lower compared to early morning profiles on the same day. In time-series deployments, intrinsic quantum efficiency (F-v'/F-m') was relatively constant under calm conditions at 12 m, but highly variable at 6 m under LC conditions. Simultaneously measured time-series of acoustic backscatter and F-v'/F-m' during LC conditions were negatively correlated, i.e. high backscatter arising from the downward advection of surface originating micro-bubbles coincided with low intrinsic efficiency. Transport also occurred in connection with finer-scale features, possibly arising from breaking surface waves. These results show that LC in the Ross Sea Polynya, in combination with changes in quenching driven by near surface UVR and PAR exposure, reduce photosynthetic electron transport over much of the upper mixed layer. Further observations and modeling will be needed to establish the extent to which this decreases water column productivity. Published by Elsevier Ltd.
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