Researchers have found that global warming is affecting the salinity in the intertidal zone of beaches. As temperatures rise due to climate change, pore water becomes saltier. This may make intertidal zones less hospitable for certain plant and animal species. The findings are in a paper that was just published in the journal Scientific Reports.
The intertidal zone is the part of the beach between the low tide and high tide lines. At low tide, the area is above water and exposed to the air. At high tide, the intertidal zone is completely submerged. This dynamic environment results in a unique ecosystem that includes animals such as crabs, mussels, snails, and anemones.
Researchers from the New Jersey Institute of Technology’s Center for Natural Resources Development analyzed sediment samples from a beach in Delaware. They found that the samples had very high salt concentrations, higher than the salinity of the nearby seawater. In some cases, the salt content was up to four times as high as the measured salt concentration of the ocean water. This struck the researchers as unusual since pore water (water contained in sediment) is a mix of seawater and groundwater. The groundwater should dilute the salt content of the seawater. Yet the samples showed that the pore water consistently had a higher salinity.
The team found that the salinity of pore water was more dependent on air temperature than the salt content of the seawater. This is due to evaporation. As temperatures rise, water evaporates and salt is left behind, increasing the overall salt concentration. This means that global warming will cause increases in pore water salinity throughout intertidal zones.
Higher salt concentrations in pore water will have an impact on the organisms that live in intertidal zones. Some plants and animals may be unable to adapt to high salinity, especially when combined with rising air temperatures due to climate change. The authors of the study recommend that global warming impact models take these salinity changes into account.
Xiaolong Geng, Michel C. Boufadel, and Nancy L. Jackson. Evidence of salt accumulation in beach intertidal zone due to evaporation. Scientific Reports (2016).