How an influx of salt may affect microbial ecosystems
As sea levels rise due to climate change, encroaching sea water will likely make freshwater environments saltier.
These microbial communities play important roles in the carbon cycle, and they also help to decompose organic matter such as algae. The MIT team found that when salt levels rise, these populations lose diversity as faster-growing strains tend to take over the community, but they maintain their overall growth rate.
“At higher salinity, you lose diversity, which is ultimately not good for an ecosystem. But what we were surprised at is that in the meantime, even though diversity decreases, the growth of the community and the production of biomass is not impacted that much,” says Jana Huisman, an MIT postdoc and the lead author of the new study.
Jeff Gore, an MIT professor of physics, is the senior author of the paper, which appears today in Nature Microbiology . Martina Dal Bello, a former MIT postdoc who is now an assistant professor of ecology and evolutionary biology at Yale University, is also an author of the study.
Microbes that live in aquatic environments are typically adapted to thrive in fresh or salt water, or somewhere in between. Microbes that live in higher salt environments have cell walls that are optimized to resist osmotic pressure, and membrane transporters that can pump sodium ions out of the cell.
Freshwater lakes and rivers have salt concentrations around 1 gram of salt per liter of water (g/L), while oceans can reach 35 g/L. As the climate warms and sea levels rise, those oceanic waters may seep into estuaries and other inland bodies of water, increasing their salinity.