Submarine Groundwater Discharge Dynamics in Volcanic Island Systems

Submarine groundwater discharge (SGD) in volcanic island settings represents a critical link between terrestrial aquifers and coastal marine environments. Highly permeable volcanic substrates facilitate rapid subsurface flow of fresh groundwater into the nearshore zone, bypassing surface runoff. This flux delivers significant volumes of water, dissolved nutrients and organic compounds directly to coastal ecosystems, often exceeding riverine inputs where surface drainage is limited. The discharge varies from steady seepage under normal weather to pulsed releases during storm events or typhoons, influenced by rainfall intensity, tidal cycles and geological heterogeneity. Tracer techniques—employing naturally occurring radionuclides, salinity gradients and fluorescent dissolved organic matter—have been combined with mass-balance models to quantify seepage rates, residence times and associated biogeochemical fluxes. These investigations reveal that SGD-driven nutrient inputs can stimulate primary productivity and, in some cases, trigger algal blooms or modulate coral reef health. Understanding the spatial distribution of discharge zones, the seasonal variability in fluxes and the controls exerted by volcanic aquifer architecture is essential for assessing water budgets, coastal nutrient budgets and ecosystem resilience on sparsely gauged islands worldwide.

Research from Nature Portfolio

Recent studies have employed fluorescent dissolved organic matter–silicon mass-balance models to quantify storm-driven seepage in volcanic island bays. One investigation during a major typhoon revealed that submarine discharge rates peaked at over 0.5 m day⁻¹, with nutrient fluxes from fresh groundwater accounting for more than 90 per cent of total inputs. This work underscored the importance of episodic weather events in delivering pulses of dissolved inorganic nitrogen, phosphorus and carbon to oligotrophic coastal waters, thereby sustaining coastal biological productivity. Foundational research in similar volcanic settings has demonstrated that fresh groundwater seepage is the dominant source of dissolved inorganic nitrogen in sheltered harbours, enhancing nutrient concentrations by an order of magnitude relative to offshore waters and driving prolific algal growth. Parallel investigations have shown that humic-like fluorescent compounds transported via submarine discharge can double the inventory of coloured dissolved organic matter in surface waters, thereby altering optical properties and influencing microbial and coral community dynamics.

Submarine Groundwater Discharge Dynamics in Volcanic Island Systems publication trend

The graph below shows the total number of articles in submarine groundwater discharge dynamics in volcanic island systems across all publications each year (not limited to Nature Index journals).

Technical terms

Submarine groundwater discharge (SGD): The flow of groundwater from coastal aquifers into the sea, transporting water and dissolved substances directly into the marine environment.

Fluorescent dissolved organic matter (FDOM): Organic compounds in water that emit fluorescence under specific light wavelengths, used as tracers for groundwater inputs.

Mass-balance model: A quantitative framework that accounts for inputs, outputs and internal transformations of chemical constituents to estimate fluxes.

Seepage rate: The velocity at which groundwater moves through sediment or rock into a receiving body, typically expressed in metres per day.

222Rn tracer: The radon-222 isotope used as a natural geochemical tracer to distinguish groundwater discharge from seawater mixing.

References

1. Research on Real-Time Groundwater Quality Monitoring System Using Sensors around Livestock Burial Sites. Agriculture (2024).
2. Green tide development associated with submarine groundwater discharge in a coastal harbor, Jeju, Korea. Scientific Reports (2017).
3. Inputs of humic fluorescent dissolved organic matter via submarine groundwater discharge to coastal waters off a volcanic island (Jeju, Korea). Scientific Reports (2017).
4. Estimating submarine groundwater discharge in Jeju volcanic island (Korea) during a typhoon (Kong-rey) using humic-fluorescent dissolved organic matter-Si mass balance. Scientific Reports (2021).
5. Field Study and Numerical Modeling to Assess the Impact of On-Site Septic Systems on Groundwater Quality of Jeju Island, South Korea. Hydrology (2024).