A baseline of terrestrial freshwater and nitrogen fluxes to the Southern California Bight, USA
2021
Sutula, Martha | Ho, Minna | Sengupta, Ashmita | Kessouri, Fayçal | McLaughlin, Karen | McCune, Kenny | Bianchi, Daniele
Time series were compiled of terrestrial nitrogen, phosphorus, carbon, iron, and silica fluxes to the Southern California Bight (SCB), a U.S. West Coast embayment (Sutula et al., 2021). Monitoring data and model output were used to construct a baseline of inputs from direct point source (PS) discharges of wastewater treatment (WWT) effluent (via ocean outfalls) and PS, non-point and natural sources from coastal rivers. The baseline covers 1971—2017 for large WWT plants discharging >50 million gallons per day (MGD) and 1997–2017 for small WWT plants and rivers. PS are the dominant nitrogen source, with contributions of 70% of the total annual freshwater discharge and 95% of nitrogen loads. WWT upgrades have reduced organic nitrogen loads by 73% since 1971. Inorganic nitrogen loads have generally held constant (35–40 Gg y⁻¹) for the large WWT plants. This baseline represents a period prior to extensive wastewater and stormwater recycling that is increasing in the region.
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