Journal
BIOGEOSCIENCES
Volume 15, Issue 12, Pages 3909-3925Publisher
COPERNICUS GESELLSCHAFT MBH
DOI: 10.5194/bg-15-3909-2018
Keywords
-
Categories
Funding
- French research national agency [ANR-14-CE01-0007-01]
- LEFE-CyBER program (CNRS-INSU)
- GOPS program (IRD)
- CNES
- National Science Foundation (NSF) [OCE-1434916]
- NSF [OCE-1458070]
- CNRS-INSU grants
- Natural Environment Research Council
- Division Of Ocean Sciences
- Directorate For Geosciences [1434916] Funding Source: National Science Foundation
Ask authors/readers for more resources
Oligotrophic regions play a central role in global biogeochemical cycles, with microbial communities in these areas representing an important term in global carbon budgets. While the general structure of microbial communities has been well documented in the global ocean, some remote regions such as the western tropical South Pacific (WTSP) remain fundamentally unexplored. Moreover, the biotic and abiotic factors constraining microbial abundances and distribution remain not well resolved. In this study, we quantified the spatial (vertical and horizontal) distribution of major microbial plankton groups along a transect through the WTSP during the austral summer of 2015, capturing important autotrophic and heterotrophic assemblages including cytometrically determined abundances of non-pigmented protists (also called flagellates). Using environmental parameters (e.g., nutrients and light availability) as well as statistical analyses, we estimated the role of bottom-up and top-down controls in constraining the structure of the WTSP microbial communities in biogeochemically distinct regions. At the most general level, we found a typical tropical structure, characterized by a shallow mixed layer, a clear deep chlorophyll maximum at all sampling sites, and a deep nitracline. Prochlorococcus was especially abundant along the transect, accounting for 68 +/- 10.6% of depth-integrated phytoplankton biomass. Despite their relatively low abundances, pico-phytoeukaryotes (PPE) accounted for up to 26 +/- 11.6% of depth-integrated phytoplankton biomass, while Synechococcus accounted for only 6 +/- 6.9 %. Our results show that the microbial community structure of the WTSP is typical of highly stratified regions, and underline the significant contribution to total biomass by PPE populations. Strong relationships between N-2 fixation rates and plankton abundances demonstrate the central role of N-2 fixation in regulating ecosystem processes in the WTSP, while comparative analyses of abundance data suggest microbial community structure to be increasingly regulated by bottom-up processes under nutrient limitation, possibly in response to shifts in abundances of high nucleic acid bacteria (HNA).
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available