Thermal discharge-created increasing temperatures alter the bacterioplankton composition and functional redundancy.

Jinbo Xiong,Demin Zhang,Yuejun Fei,Peng Qian,Lian Liu,Shangling Xiong

doi:10.1186/s13568-016-0238-4

Abstract

Elevated seawater temperature has altered the coupling between coastal primary production and heterotrophic bacterioplankton respiration. This shift, in turn, could influence the feedback of ocean ecosystem to climate warming. However, little is known about how natural bacterioplankton community responds to increasing seawater temperature. To investigate warming effects on the bacterioplankton community, we collected water samples from temperature gradients (ranged from 15.0 to 18.6 °C) created by a thermal flume of a coal power plant. The results showed that increasing temperatures significantly stimulated bacterial abundance, grazing rate, and altered bacterioplankton community compositions (BCCs). The spatial distribution of bacterioplankton community followed a distance similarity decay relationship, with a turnover of 0.005. A variance partitioning analysis showed that temperature directly constrained 2.01 % variation in BCCs, while temperature-induced changes in water geochemical and grazing rate indirectly accounted for 4.03 and 12.8 % of the community variance, respectively. Furthermore, the relative abundances of 24 bacterial families were linearly increased or decreased (P < 0.05 in all cases) with increasing temperatures. Notably, the change pattern for a given bacterial family was in concert with its known functions. In addition, community functional redundancy consistently decreased along the temperature gradient. This study demonstrates that elevated temperature, combined with substrate supply and trophic interactions, dramatically alters BCCs, concomitant with decreases in functional redundancy. The responses of sensitive assemblages are temperature dependent, which could indicate temperature departures.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0238-4) contains supplementary material, which is available to authorized users.

Highlights

Climate warming has led to an accelerating pace of elevated seawater temperature (EST) (Brown et al 2004), which is evidenced by long-term observations and prediction model (Pachauri et al 2014; Vezzulli et al 2012)
The EST, in turn, dramatically altered the geochemical variables, that is, the seawater temperatures were positively correlated with the concentrations of PO43− (r = 0.523, P < 0.001) and chemical oxygen demand (COD) (r = 0.300, P = 0.039), and negatively correlated with the levels of NO3− (r = 0.410, P = 0.003) and Dissolved oxygen (DO) (r = −0.330, P = 0.011) (Additional file 1: Table S2)
EST significantly stimulated the level of Chlorophyll a (Chl a) (r = 0.410, P = 0.003, Additional file 1: Table S2), bacterial cell density (r = 0.241, P = 0.032), DNA yield and grazing rate (r = 0.645, P = 0.001) (Additional file 1: Figure S1)

Summary

Introduction

Climate warming has led to an accelerating pace of elevated seawater temperature (EST) (Brown et al 2004), which is evidenced by long-term observations and prediction model (Pachauri et al 2014; Vezzulli et al 2012). Xiong et al AMB Expr (2016) 6:68 composition (Hoegh-Guldberg and Bruno 2010; Vezzulli et al 2012) This approach is restricted because there are few long-term data sets available. Available microcosm and/or mesocosm experiments to date only design one or two elevated temperature levels (Dziallas and Grossart 2011; Lindh et al 2013; Scheibner et al 2014) For these reasons, it is unclear whether the responses of the natural bacterioplankton community are temperature dependent, mirroring what has been observed in artificial experiments (Hoppe et al 2008). A plausible explanation for these discrepant patterns is that microbial communities exhibit functional redundancy (different microbial communities execute a functional process at the same rate)

Methods

Results

Conclusion