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

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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 material: The online version of this article (doi:10.1186/s13568-016-0238-4) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

Variation partitioning analysis of bacterioplankton community explained by grazing rate (G), geographic distance (D), and environmental factors (E). a General outline, b variation partitioning percentages. Each number represents the biological variation partitioned into the relative effects of each factor or a combination of factors. The edges of the triangle presented the variation explained by each factor alone. The sides of the triangles presented, interactions of any two factors and the middle of the triangles represented interactions of all three factors. The explained percentage of each environmental factor was shown in the rectangle
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Fig4: Variation partitioning analysis of bacterioplankton community explained by grazing rate (G), geographic distance (D), and environmental factors (E). a General outline, b variation partitioning percentages. Each number represents the biological variation partitioned into the relative effects of each factor or a combination of factors. The edges of the triangle presented the variation explained by each factor alone. The sides of the triangles presented, interactions of any two factors and the middle of the triangles represented interactions of all three factors. The explained percentage of each environmental factor was shown in the rectangle

Mentions: To minimize the autocorrelation between the biogeochemical variables, a forward selection was used to reduce the number of explanatory variables to retain only the most important ones (McArdle and Anderson 2001). As a result, temperature, grazing rate, COD, PO43− and DO were selected for a subsequent variance partitioning analysis (Table 2). These variables were empirically categorized into three groups, i.e. geographic distance, biotic factor (i.e., grazing rate) and abiotic seawater parameters. Geographic distance constrained substantially more variations (12.9 %) than seawater variables (6.4 %), whereas grazing rate independently explained 12.8 % of the observed variation (Fig. 4). In addition, approximate 10 % variation of the BCCs was constrained by the interaction of geographic distance and seawater variables (Fig. 4), which is in concert with the notion that coastal BCCs is controlled by spatially structured environmental gradient (Wang et al. 2015). However, there was still a large proportion (54.5 %) of the variation unexplained by the above selected biogeochemical variables (Fig. 4).Table 2


Thermal discharge-created increasing temperatures alter the bacterioplankton composition and functional redundancy
Variation partitioning analysis of bacterioplankton community explained by grazing rate (G), geographic distance (D), and environmental factors (E). a General outline, b variation partitioning percentages. Each number represents the biological variation partitioned into the relative effects of each factor or a combination of factors. The edges of the triangle presented the variation explained by each factor alone. The sides of the triangles presented, interactions of any two factors and the middle of the triangles represented interactions of all three factors. The explained percentage of each environmental factor was shown in the rectangle
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016491&req=5

Fig4: Variation partitioning analysis of bacterioplankton community explained by grazing rate (G), geographic distance (D), and environmental factors (E). a General outline, b variation partitioning percentages. Each number represents the biological variation partitioned into the relative effects of each factor or a combination of factors. The edges of the triangle presented the variation explained by each factor alone. The sides of the triangles presented, interactions of any two factors and the middle of the triangles represented interactions of all three factors. The explained percentage of each environmental factor was shown in the rectangle
Mentions: To minimize the autocorrelation between the biogeochemical variables, a forward selection was used to reduce the number of explanatory variables to retain only the most important ones (McArdle and Anderson 2001). As a result, temperature, grazing rate, COD, PO43− and DO were selected for a subsequent variance partitioning analysis (Table 2). These variables were empirically categorized into three groups, i.e. geographic distance, biotic factor (i.e., grazing rate) and abiotic seawater parameters. Geographic distance constrained substantially more variations (12.9 %) than seawater variables (6.4 %), whereas grazing rate independently explained 12.8 % of the observed variation (Fig. 4). In addition, approximate 10 % variation of the BCCs was constrained by the interaction of geographic distance and seawater variables (Fig. 4), which is in concert with the notion that coastal BCCs is controlled by spatially structured environmental gradient (Wang et al. 2015). However, there was still a large proportion (54.5 %) of the variation unexplained by the above selected biogeochemical variables (Fig. 4).Table 2

View Article: PubMed Central - PubMed

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 material: The online version of this article (doi:10.1186/s13568-016-0238-4) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus