Combined Carbohydrates Support Rich Communities of Particle-Associated Marine Bacterioplankton.

Martin Sperling,Jutta Niggemann,Gunnar Gerdts,Antje Wichels,Anja Engel,Judith Piontek,Karen H. Wiltshire

doi:10.3389/fmicb.2017.00065

Abstract

Carbohydrates represent an important fraction of labile and semi-labile marine organic matter that is mainly comprised of exopolymeric substances derived from phytoplankton exudation and decay. This study investigates the composition of total combined carbohydrates (tCCHO; >1 kDa) and the community development of free-living (0.2–3 μm) and particle-associated (PA) (3–10 μm) bacterioplankton during a spring phytoplankton bloom in the southern North Sea. Furthermore, rates were determined for the extracellular enzymatic hydrolysis that catalyzes the initial step in bacterial organic matter remineralization. Concentrations of tCCHO greatly increased during bloom development, while the composition showed only minor changes over time. The combined concentration of glucose, galactose, fucose, rhamnose, galactosamine, glucosamine, and glucuronic acid in tCCHO was a significant factor shaping the community composition of the PA bacteria. The richness of PA bacteria greatly increased in the post-bloom phase. At the same time, the increase in extracellular β-glucosidase activity was sufficient to explain the observed decrease in tCCHO, indicating the efficient utilization of carbohydrates by the bacterioplankton community during the post-bloom phase. Our results suggest that carbohydrate concentration and composition are important factors in the multifactorial environmental control of bacterioplankton succession and the enzymatic hydrolysis of organic matter during phytoplankton blooms.

Highlights

It is well established that marine bacterioplankton communities maintain high genetic diversity
The present study shows a correlation between the concentration of combined carbohydrates in HMW-organic matter (OM) and the diversity of PA bacteria during the development of a spring bloom, suggesting that the availability of carbohydrates contributes to the multifactorial control of marine bacterioplankton communities
This highlights the additional value of analyzing bacterioplankton community composition in size-fractionated samples

Summary

Introduction

It is well established that marine bacterioplankton communities maintain high genetic diversity. As for phytoplankton (Hutchinson, 1961), little is understood, how such high diversities are maintained or what determines the community composition in situ. Carbohydrates Sustain Rich Marine Bacterioplankton bacterioplankton communities (Pinhassi et al, 2004; RooneyVarga et al, 2005; Sapp et al, 2007; Rink et al, 2011). These two factors are not sufficient to explain the high diversity of marine bacterioplankton. The in situ structuring of bacterial communities is thought to be more complicated, involving a combination of available substrates, inorganic nutrients, physical factors and competition among bacteria (Gómez-Consarnau et al, 2012)

Methods

Results

Conclusion