Seawater desalination plants increase local coastal salinities by discharging concentrated brine back to the sea with ∼50% higher than ambient salinities. The impacts of high salinities on microbial coastal populations of the eastern Mediterranean Sea (EMS) were examined in two mesocosm experiments; first, during the mixed-spring and second, during the stratified-summer periods with average salinity of ∼39. Ambient salinities were increased by 5% and 15%. Higher salinity (15%) mesocosms induced rapid (within 2 h) declines in both primary productivity (PP) and algal biomass parallel to an increase in bacterial productivity. Subsequently, for the duration of the experiments (11–12 days), both Chlorophyll a and PP rates increased (2 to 5 and 1.5 to 2.5–fold, respectively) relative to unamended controls. The initial assemblages of the ambient microbial populations and intensity of salinity enrichments influenced the community responses. During the mixed-spring experiment, the composition of prokaryotic and eukaryotic populations shifted only slightly, suggesting high functional plasticity of the initial populations. While during the stratified-summer experiment, high salinity changed the composition and reduced the biodiversity of the microbial communities. In an ultra-oligotrophic environment such as the EMS, salinity induced declines in microbial diversity may provide a tipping point destabilizing the local aquatic food web.
Bibliographical noteFunding Information:
We acknowledge the Israel Water Authority grant number 4500445459 for partial funding to Ilana Berman-Frank (IBF). We thank Dan Miller for technical help and samplings during the experiments. This research is part of the PhD requirements for Natalia Belkin from Bar Ilan University (BIU). Natalia Belkin (NB) was supported by a President's Fellowship from BIU and The National Fellowship Graduate Program for Marine Conservation in the Mediterranean.
© 2015 Society for Applied Microbiology and John Wiley & Sons Ltd
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics