Synthesizing the Effects of Submarine Groundwater Discharge on Marine Biota

Lecher, Alanna L; Mackey, Katherine

doi:10.3390/hydrology5040060

Cited by 77 publications

(69 citation statements)

References 122 publications

(290 reference statements)

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“…1e, g). In such locations, coastal groundwater discharge can strongly influence coastal ecosystems, as shown in local studies 19 , and could act as freshwater resource for the coastal population 20 .…”

Section: Resultsmentioning

confidence: 98%

Fresh groundwater discharge insignificant for the world’s oceans but important for coastal ecosystems

2020

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The flow of fresh groundwater may provide substantial inputs of nutrients and solutes to the oceans. However, the extent to which hydrogeological parameters control groundwater flow to the world's oceans has not been quantified systematically. Here we present a spatially resolved global model of coastal groundwater discharge to show that the contribution of fresh groundwater accounts for~0.6% (0.004%-1.3%) of the total freshwater input and~2% (0.003%-7.7%) of the solute input for carbon, nitrogen, silica and strontium. However, the coastal discharge of fresh groundwater and nutrients displays a high spatial variability and for an estimated 26% (0.4%-39%) of the world's estuaries, 17% (0.3%-31%) of the salt marshes and 14% (0.1-26%) of the coral reefs, the flux of terrestrial groundwater exceeds 25% of the river flux and poses a risk for pollution and eutrophication.

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Section: Resultsmentioning

confidence: 98%

Fresh groundwater discharge insignificant for the world’s oceans but important for coastal ecosystems

2020

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“…Although there is no doubt that SGD-derived nutrients contribute to marine organisms and ecosystem functions, evidence of the actual linkage between SGD and marine organisms is limited. Evidence seems best at some specific geological sites (e.g., karstic and volcanic regions) and intertidal sandflats where the discharge of groundwater can be directly viewed (Moosdorf and Oehler, 2017;Lecher and Mackey, 2018). In some cases, gas bubbles and excessive phenomena such as eutrophication and algal blooms are tied to SGD (Knee and Paytan, 2011).…”

Section: Bio-ecological Methodologymentioning

confidence: 99%

“…These effects are enhanced by recirculated seawater as it reacts within the aquifer sediment (see the Geochemical section). SGD can also act as a conduit of anthropogenic pollutants to coastal regions, and the lower salinity and pH associated with some types of SGD can stress local marine biota (reviewed in Lecher and Mackey, 2018).…”

Section: Bio-ecological Processesmentioning

confidence: 99%

Submarine Groundwater Discharge: Updates on Its Measurement Techniques, Geophysical Drivers, Magnitudes, and Effects

Taniguchi

Dulai

Burnett

et al. 2019

Front. Environ. Sci.

192

143

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The number of studies concerning Submarine Groundwater Discharge (SGD) grew quickly as we entered the twenty-first century. Many hydrological and oceanographic processes that drive and influence SGD were identified and characterized during this period. These processes included tidal effects on SGD, water and solute fluxes, biogeochemical transformations through the subterranean estuary, and material transport via SGD from land to sea. Here we compile and summarize the significant progress in SGD assessment methodologies, considering both the terrestrial and marine driving forces, and local as well as global evaluations of groundwater discharge with an emphasis on investigations published over the past decade. Our treatment presents the state-of-the-art progress of SGD studies from geophysical, geochemical, bio-ecological, economic, and cultural perspectives. We identify and summarize remaining research questions, make recommendations for future research directions, and discuss potential future challenges, including impacts of climate change on SGD and improved estimates of the global magnitude of SGD.

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“…Although a handful of recent SGD investigations included a biotic component, there is a relative lack of knowledge regarding the effects of SGD on marine ecosystems and humans that use them. As concluded in a recent review by Lecher and Mackey [86], there are currently few studies that focus on the impact of groundwater at an ecosystem level, yet these were found to be the most insightful.…”

Section: Management Considerations and Future Directionsmentioning

confidence: 99%

Assessment of Terrigenous Nutrient Loading to Coastal Ecosystems along a Human Land-Use Gradient, Tutuila, American Samoa

et al. 2019

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Anthropogenic nutrient loading is well recognized as a stressor to coastal ecosystem health. However, resource managers are often focused on addressing point source or surface water discharge, whereas the impact of submarine groundwater discharge (SGD) as a nutrient vector is often unappreciated. This study examines connections between land use and nutrient loading through comparison of four watersheds and embayments spanning a gradient of human use impact on Tutuila, a high tropical oceanic island in American Samoa. In each study location, coastal radon-222 measurements, dissolved nutrient concentrations, and nitrogen isotope values (δ15N) in water and in situ macroalgal tissue were used to explore SGD and baseflow derived nutrient impacts, and to determine probable nutrient sources. In addition to sampling in situ macroalgae, pre-treated macroalgal specimens were deployed throughout each embayment to uptake ambient nutrients and provide a standardized assessment of differences between locations. Results show SGD-derived nutrient flux was more significant than baseflow nutrient flux in all watersheds, and δ15N values in water and algae suggested wastewater or manure are likely sources of elevated nutrient levels. While nutrient loading correlated well with expected anthropogenic impact, other factors such as differences in hydrogeology, distribution of development, and wastewater infrastructure also likely play a role in the visibility of impacts in each watershed.

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Synthesizing the Effects of Submarine Groundwater Discharge on Marine Biota

Cited by 77 publications

References 122 publications

Fresh groundwater discharge insignificant for the world’s oceans but important for coastal ecosystems

Fresh groundwater discharge insignificant for the world’s oceans but important for coastal ecosystems

Submarine Groundwater Discharge: Updates on Its Measurement Techniques, Geophysical Drivers, Magnitudes, and Effects

Assessment of Terrigenous Nutrient Loading to Coastal Ecosystems along a Human Land-Use Gradient, Tutuila, American Samoa

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