Shifts in Carbon Flux from a Hawaiian Watershed due to Climate Change

Date
2023-12
Authors
Boger, Walter Loc-Ming
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Wiegner, Tracy N.
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Tropical Conservation Biology & Environmental Science
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Climate change is affecting the quantity, quality, and sources of riverine carbon (C) that are exported from terrestrial ecosystems to coastal waters. While tropical islands in Oceania comprise 3% of the Earth’s land mass, they contribute 21% to 38% of total organic carbon (OC) flux to the world’s oceans. This study focuses on climate change induced shifts in carbon exports on the Wailuku River, Hawai‘i, USA. Concentrations of coarse particulate organic carbon (CPOC), fine particulate organic carbon (FPOC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) were measured as well as carbon: nitrogen (C:N) ratios, CPOC composition, δ13C values for different carbon forms and species, and δ18O- and δ2H of H2O to identify carbon sources and quality. Concentration and discharge data were used in LOADEST to calculate current monthly and annual carbon fluxes, as well as potential future fluxes impacted by climate change. Concentrations of all carbon forms were affected by discharge, except CPOC. The primary source of OC to the river was leaf litter, and the source of DIC was basalt weathering; neither changed with discharge. Wailuku river δ18O and δ2H values of H2O decreased with increasing river discharge. Although a large variation in C:N was observed, the quality of FPOC decreased with increased discharge. Shifts in total carbon fluxes were linked to climate change driven variations in baseflow, which in turn caused significant variations in DIC, but not in CPOC, FPOC, and DOC. To best advise public policy and take adaptive management actions to mitigate the effects of climate change, a better understanding of Oceanic river contributions to the global carbon flux is needed. An important step in that direction is to quantify the different forms of carbon that contribute to the riverine carbon budget.
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Biogeochemistry, Environmental science, Climate change, Carbon, Climate Change, Discharge, Sources, Watershed, Yield
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76 pages
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