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James Bishop

Graduate Trainee

Submarine groundwater discharge (SGD) is the flow of fresh, brackish, and saline groundwater from the land into the sea.  SGD can deliver significant quantities of nutrients, heavy metals, and bacteria directly to coastal oceans and in areas where stream flow is ephemeral or non-existent SGD may be the major pathway for the delivery of chemical species to coastal waters.  In many coastal areas in the Hawaiian Islands macroalgae growth is impeding coral growth and it is hypothesized that excess nutrients carried by SGD are responsible for the macroalgae blooms that have been observed.

On Maui the problem has been particularly acute and nutrient loading from areas with high population densities, intensively fertilized agricultural lands, or wastewater injection wells have all been blamed. In my work I am testing the hypotheses that (1) SGD is occurring in large volumes in coastal areas of Maui, (2) nutrient loading via SGD is related to the watershed land-use practices, (3) chemical data from nutrient species in groundwater can be used to determine the source of nutrients, (4) algal percent tissue nitrogen is directly related to the nitrogen concentration in the water column and (5) there is a correlation between SGD nutrient flux and algal growth.  This work will help to identify land-use practices which may be detrimental to groundwater quality and coastal ecosystems.

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Advisor: Dr. Craig R. Glenn