Abstract


ALGAL BIOASSAYS SHOW LAND-BASED, ANTHROPOGENIC NITROGEN IS DELIVERED TO REEF BIOTA BY GROUNDWATER IN HAWAII AND AMERICAN SAMOA

Submarine groundwater discharge (SGD) is a source of land-based contaminants to coastal ecosystems, yet the impact of this process on marine biota remains understudied. To determine if plants assimilated SGD-derived nitrogen (N) on otherwise oligotrophic reefs, we compared the N parameters (δ15N values and N concentration) of naturally occurring macroalgae with those of surface water, coastal groundwater, and terrestrial groundwater in Hawaii and American Samoa. In addition, tissues of Ulva spp. were deployed for 5-6 days to determine the extent of nutrient pollution at 8 coastal sites in Hawaii. Reduced salinity, elevated 222Rn, and high nutrient levels in beach porewater and surface water relative to ambient marine water provided evidence that SGD was a substantial vector for nutrient delivery to all study sites. The highest δ15N values in algal and water samples were found adjacent to wastewater treatment facilities that dispose treated effluent into groundwater via injection wells in Hawaii. The lowest δ15N values and highest N concentrations in water and algal tissues were found at locations adjacent to sugarcane fields. On Tutuila, high δ15N values in nearshore algal and water samples, relative to a control site, suggest that wastewater was a source of N to reefs adjacent to three villages. In general, regions with little human impact had relatively low N concentrations and δ15N values. Within developed regions of Hawaii and American Samoa, SGD delivered N derived from wastewater and fertilizer to marine macroalgae across large spatial scales.

Authors

Amato, D. W., University of Hawaii at Manoa, USA, dwamato@hawaii.edu

Shuler, C., University of Hawaii at Manoa, USA, cshuler@hawaii.edu

Gibson, V., University of Hawaii at Manoa, USA, vgibson@hawaii.edu

Baker, L., University of Hawaii at Manoa, USA, bakerlyd@hawaii.edu

Alegado, R. A., University of Hawaii at Manoa, USA, ralegado@hawaii.edu

Glenn, C. R., University of Hawaii at Manoa, USA, glenn@soest.hawaii.edu

Dulai, H., University of Hawaii at Manoa, USA, hdulaiov@hawaii.edu

Smith, C. M., University of Hawaii, USA, celia@hawaii.edu

Details

Oral presentation

Session #:38
Date: 06/21/2016
Time: 10:45
Location: 306 A/B

Presentation is given by student: No