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SPATIAL DISTRIBUTION AND SOURCES OF NUTRIENTS AT TWO COASTAL DEVELOPMENTS IN SOUTH KOHALA, HAWAI‘I
|Title:||SPATIAL DISTRIBUTION AND SOURCES OF NUTRIENTS AT TWO COASTAL DEVELOPMENTS IN SOUTH KOHALA, HAWAI‘I|
|Authors:||Panelo, Jazmine R.|
|Contributors:||Wiegner, Tracy N. (advisor)|
Tropical Conservation Biology & Environmental Science (department)
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|Date Issued:||Dec 2020|
|Abstract:||Non-point sources of nutrients to coastal waters are not well-characterized for watersheds with coral reefs, which are vulnerable to excess nutrient inputs. Objectives of this study were to: 1) document the spatial distributions of nutrient concentrations within nearshore waters along two coastal developments with fringing coral reefs, and 2) identify nutrient sources in these bays by: measuring nutrient concentrations, developing nutrient mixing plots, assessing 15 of nitrogen (N) in macroalgal tissue, and developing 15N and 18O of NO3- stable isotope mixing models. Our results indicate that nutrient concentrations decreased from fresh groundwater to offshore waters. Within the bays, nutrient concentrations were higher at the shoreline and decreased offshore, with some surface waters higher in concentrations than benthic ones. There was conservative and non-conservative mixing between fresh and ocean waters within the bays, with the latter suggesting local nutrient sources and biological removal. Stable N isotopes in algal tissue and NO3- concurred revealing that fresh groundwater, ocean water, and fertilizers were dominant N sources in the bays. The significant relationship between benthic salinity and NO3- + NO2- concentrations demonstrated that submarine groundwater discharge (SGD) was an important nutrient source to reefs at both bays. Data from benthic conductivity loggers assessed salinity trends and the length of time that nutrients obtained from groundwater stayed on the benthos, revealing that nutrients were delivered to the reefs through SGD pulses, ranging from a few min to 2 d. These findings allow for the identification of reef areas more susceptible to nutrient pollution that may be susceptible to increased algal growth. Quantifying nutrient concentrations and identifying their sources in areas with coral reefs is imperative for reducing land-based nutrient loads, which may make the reefs to be more resilient to more global stressors.|
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|Appears in Collections:||
Tropical Conservation Biology and Environmental Science|
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