The land-sea continuum, such as sandy beaches, mud flats, salt marshes, mangrove swamps, and estuarine intertidal zones, is a unique transition zone connecting terrestrial and marine ecosystems. Such regions provide resources and habitats to a wide variety of plants and animals, as well as serve as “reaction pools” for large amounts of chemical constituents including nutrients. Since the Industrial Revolution, anthropogenic activities have greatly increased the level of terrestrial nutrients (e.g., reactive nitrogen and organic phosphorus). Traditionally, rivers have long been regarded as a major discharge pathway of nutrients to the ocean. However, recent studies showed that Submarine Groundwater Discharge (SGD) can be a dominant pathway for terrestrial nutrient delivery to the ocean. Furthermore, the biogeochemical reactions hosted within the land-ocean transition zone have shown to be the main driver influencing the chemical composition of SGD. Thus, studies on how onshore biogeochemistry and microbiological processes influence the environment offshore through SGD are eagerly required.
To date, many nutrient studies in the land-sea continuum focus on physical interactions or geochemical reactions only with no regard for community composition within the setting. Comparatively fewer studies couple microbial processes to the geochemical reactions, even though microbial communities and their activities, influenced by environmental factors such as temperature, redox gradients, and salinity, control the transformation of nutrients and carbon delivered by SGD to coastal waters. Whether microbial processes in the land-ocean continuum act as a source or sink for terrestrial nutrients and carbons during their transportation is still not clear. Furthermore, the land-sea continuum is an environment with complex hydrodynamics, steep salinity and redox gradients, and alternatively varied oxic and anoxic conditions. Our understanding of how the linked mechanism of physical interactions, geochemical reactions and microbial processes influence the transformation of nutrients and carbon is still limited.
We invite researchers to submit original research work or comprehensive review that advances understanding of the nutrient and carbon biogeochemistry in the land-sea continuum. This Research Topic welcomes the collaboration between biogeochemical oceanographers, coastal hydrogeologists, and microbial ecologists. Potential topics include but are not limited to the following:
• The activity (nitrification/denitrification/anammox), community diversity (novel groundwater microbial taxa) and metabolic functions (C, N, P biogeochemistry) of microbes in the land-sea continuum.
• The SGD, saltwater intrusion, and related groundwater-surface water interaction via environmental isotopes (e.g., hydrogen, oxygen, carbon, nitrogen, radium and radon) and numerical simulations.
•Nutrient and carbon fluxes carried by SGD or benthic porewater exchange.
•The fluxes and processes of greenhouse gas (N2O, CH4 & CO2) emissions in coastal ecosystems.
•The effects of seawater intrusion, groundwater-seawater exchange, benthic bioturbations, and rainstorms on coastal nutrient flux and carbon biogeochemistry.
The land-sea continuum, such as sandy beaches, mud flats, salt marshes, mangrove swamps, and estuarine intertidal zones, is a unique transition zone connecting terrestrial and marine ecosystems. Such regions provide resources and habitats to a wide variety of plants and animals, as well as serve as “reaction pools” for large amounts of chemical constituents including nutrients. Since the Industrial Revolution, anthropogenic activities have greatly increased the level of terrestrial nutrients (e.g., reactive nitrogen and organic phosphorus). Traditionally, rivers have long been regarded as a major discharge pathway of nutrients to the ocean. However, recent studies showed that Submarine Groundwater Discharge (SGD) can be a dominant pathway for terrestrial nutrient delivery to the ocean. Furthermore, the biogeochemical reactions hosted within the land-ocean transition zone have shown to be the main driver influencing the chemical composition of SGD. Thus, studies on how onshore biogeochemistry and microbiological processes influence the environment offshore through SGD are eagerly required.
To date, many nutrient studies in the land-sea continuum focus on physical interactions or geochemical reactions only with no regard for community composition within the setting. Comparatively fewer studies couple microbial processes to the geochemical reactions, even though microbial communities and their activities, influenced by environmental factors such as temperature, redox gradients, and salinity, control the transformation of nutrients and carbon delivered by SGD to coastal waters. Whether microbial processes in the land-ocean continuum act as a source or sink for terrestrial nutrients and carbons during their transportation is still not clear. Furthermore, the land-sea continuum is an environment with complex hydrodynamics, steep salinity and redox gradients, and alternatively varied oxic and anoxic conditions. Our understanding of how the linked mechanism of physical interactions, geochemical reactions and microbial processes influence the transformation of nutrients and carbon is still limited.
We invite researchers to submit original research work or comprehensive review that advances understanding of the nutrient and carbon biogeochemistry in the land-sea continuum. This Research Topic welcomes the collaboration between biogeochemical oceanographers, coastal hydrogeologists, and microbial ecologists. Potential topics include but are not limited to the following:
• The activity (nitrification/denitrification/anammox), community diversity (novel groundwater microbial taxa) and metabolic functions (C, N, P biogeochemistry) of microbes in the land-sea continuum.
• The SGD, saltwater intrusion, and related groundwater-surface water interaction via environmental isotopes (e.g., hydrogen, oxygen, carbon, nitrogen, radium and radon) and numerical simulations.
•Nutrient and carbon fluxes carried by SGD or benthic porewater exchange.
•The fluxes and processes of greenhouse gas (N2O, CH4 & CO2) emissions in coastal ecosystems.
•The effects of seawater intrusion, groundwater-seawater exchange, benthic bioturbations, and rainstorms on coastal nutrient flux and carbon biogeochemistry.