Groundwater and ecosystems; Previous research trend and future perspective

Abstract

This article aims to overview the previous research trends and find out the future perspective about the relationship between groundwater and ecosystems. Especially, we focused on the dynamics of microbes in groundwater which involve any material cycles and ecosystems, and seagrass/seaweed meadows and coral reefs which are categorized as Groundwater Dependent Ecosystems (GDEs) in the coastal groundwater discharge area and play important roles in the conservation of material cycles and biodiversity. Regarding the microbes, most of the studies were focused on the application of groundwater as drinking water and purification of pollutants in groundwater in the past, however, the relationship between groundwater flow and the dynamics of microbes has been studied recently. Regarding the seagrass/seaweed meadows and coral reefs, most of the research was targeted the area with a significant impact of Submarine Groundwater Discharge (SGD). Some previous studies demonstrated that SGD tends to increase the biomass of seagrass/seaweed as a nutrient source, however, it leads to a lack of their biodiversity. Some other studies reported that SGD may intensify the coral reef vulnerability due to the growth of specific algae and degradation of skeletal density and breeding potential of coral reefs if SGD-derived nutrients cause eutrophication in seawater. However, the relationship between groundwater and these ecosystems are still not fully understood in the previous research. It will be important to accumulate the results in various observation sites, apply the new techniques, and cooperate the researchers with different backgrounds (e.g. biogeochemistry, microbiology, ecology) based on groundwater hydrology for further understanding.