KOSMOS Finland 2012 mesocosm study: Size-fractionated bacterial protein production (BPP) of free-living and particle associated bacteria and abundance of particle associated heterotrophic prokaryotes.


The oceans absorb about a quarter of the annually produced anthropogenic atmospheric carbon dioxide (CO2), resulting in a decrease in surface water pH, a process termed ocean acidification (OA). Surprisingly little is known about how OA affects the physiology of heterotrophic bacteria or the coupling of heterotrophic bacteria to phytoplankton when nutrients are limited. Previous experiments were, for the most part, undertaken during productive phases or following nutrient additions designed to stimulate algal blooms. Therefore, we performed an in situ large-volume mesocosm (ca. 55 m**3) experiment in the Baltic Sea by simulating different fugacities of CO2 (fCO2) extending from present to future conditions. The study was conducted in July?August after the nominal spring bloom, in order to maintain low-nutrient conditions throughout the experiment. This resulted in phytoplankton communities dominated by small-sized functional groups (picophytoplankton). There was no consistent fCO2-induced effect on bacterial protein production (BPP), cell-specific BPP (csBPP) or biovolumes (BVs) of either free-living (FL) or particle-associated (PA) heterotrophic bacteria, when considered as individual components (univariate analyses). Permutational Multivariate Analysis of Variance (PERMANOVA) revealed a significant effect of the fCO2 treatment on entire assemblages of dissolved and particulate nutrients, metabolic parameters and the bacteria?phytoplankton community. However, distance-based linear modelling only identified fCO2 as a factor explaining the variability observed amongst the microbial community composition, but not for explaining variability within the metabolic parameters. This suggests that fCO2 impacts on microbial metabolic parameters occurred indirectly through varying physicochemical parameters and microbial species composition. Cluster analyses examining the co-occurrence of different functional groups of bacteria and phytoplankton further revealed a separation of the four fCO2-treated mesocosms from both control mesocosms, indicating that complex trophic interactions might be altered in a future acidified ocean. Possible consequences for nutrient cycling and carbon export are still largely unknown, in particular in a nutrient-limited ocean.

Bacterial protein production was determined by measuring incorporation of 14C-Leucine.Abundance of particle associated heterotrophic prokaryotes was determined by epifluorescence microscopy.

Supplement to: Hornick, Thomas; Bach, Lennart Thomas; Crawfurd, Katharine J; Spilling, Kristian; Achterberg, Eric Pieter; Woodhouse, Jason N; Schulz, Kai Georg; Brussaard, Corina P D; Riebesell, Ulf; Grossart, Hans-Peter (2017): Ocean acidification impacts bacteria–phytoplankton coupling at low-nutrient conditions. Biogeosciences, 14(1), 1-15

DOI https://doi.org/10.1594/PANGAEA.868621
Related Identifier IsSupplementTo https://doi.org/10.5194/bg-14-1-2017
Related Identifier References https://doi.org/10.1594/PANGAEA.863032
Related Identifier References https://doi.org/10.1594/PANGAEA.863933
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.868621
Creator Hornick, Thomas ORCID logo; Bach, Lennart Thomas ORCID logo; Crawfurd, Katharine J; Spilling, Kristian ORCID logo; Achterberg, Eric Pieter; Woodhouse, Jason N; Schulz, Kai Georg ORCID logo; Brussaard, Corina P D; Riebesell, Ulf (ORCID: 0000-0002-9442-452X); Grossart, Hans-Peter ORCID logo
Publisher PANGAEA
Publication Year 2016
Rights Creative Commons Attribution 4.0 International; https://creativecommons.org/licenses/by/4.0/
OpenAccess true
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 568 data points
Discipline Earth System Research
Spatial Coverage (23.258 LON, 59.858 LAT)
Temporal Coverage Begin 2012-06-19T00:00:00Z
Temporal Coverage End 2012-08-04T00:00:00Z