Latitudinal variability (6°S–20°N) of early summer phytoplankton species compositions and size-fractioned productivity from Java Sea to South China Sea

Abstract

In order to study the effects of latitudinal change in physical and chemical environments on phytoplankton cells, we investigated the early summer phytoplankton biomass, species composition and size-fractioned productivity in surface water from the Java Sea to the South China Sea (from 6°S to 20°N) from 18 May to 27 May 2010. Chlorophyll a (Chl a) concentration decreased latitudinally from 0.18 (∼6°S) to 0.05 µg l^–1 (∼10°N). The dominant species, the cyanobacteria Trichodesmium erythraeum, dinoflagellates (e.g. Gyrodinium dominans, Amphidinium carterae and Gonyaulax spp.) and diatoms (e.g. Thalassionema nitzschioides, Rhizosolenia spp. and Chaetoceros spp.) changed to only the dinoflagellate species. Also, the Chl a biomass increased to 0.14 µg l^–1 towards the end of the survey (∼20°N) with the dinoflagellates as the most abundant group. Productivity of phytoplankton assemblages coincided with Chl a concentration, and decreased accordingly from 9.24 ± 0.71 to 2.87 ± 0.41 µg C l^–1 day^–1, then increased to 5.45±1.1 µg C l^–1 day^–1. Chl a concentration and productivity were significantly correlated (P<0.05) with microplankton cell abundance, as well as nutrient concentrations, which appeared to exert a strong influence over latitudinal variation in primary production.

Keywords:

• Carbon fixation
• latitudinal variation
• phytoplankton
• size distribution

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

We are very thankful for the comments and suggestions of two anonymous reviewers and of Subject Editor Dr David J.S. Montagnes that helped to improve our manuscript. This work was supported by Key Innovation Group Project of Chinese Academy of Sciences (KZCX2-YW-Q07), National Natural Science Foundation (41130855), Natural Science Foundation of Guangdong (S2011040000151), National Project of Sciences and Technology (2008FY110100), CAS Strategic Pilot Science and Technology (XDA05030403)”.(XDA05030403)”. and MEL Young Scientist Visiting Fellowship of State Key Laboratory of Marine Environment Science, Xiamen University (MELRS 1006). Thanks are also given to Qiuyan Lin for species analysis, to Yongqiang Chen and Dajun Qiu for experimental assistance and to captain and crews of the research ship Shiyan I for logistic support.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark