Nload: An Interactive, Web‐based Modeling Tool for Nitrogen Management in Estuaries

Abstract

Abstract. Eutrophication of estuaries is an increasing global concern that requires development of new tools to identify causes, quantify conditions, and propose management options that address this environmental problem. Since eutrophication is often associated with increased inputs of land-derived nitrogen to estuaries, we developed NLOAD, a user-friendly, web-based tool that brings together six different published models that predict nitrogen loading to estuaries and two models that estimate nitrogen concentrations in coastal waters. Here we describe each of the models, demonstrate how NLOAD is designed to function, and then use the models in NLOAD to predict nitrogen loads to Barnegat Bay, New Jersey (USA). The four models that we used to estimate nitrogen loads to Barnegat Bay, when adjusted, all had similar results that matched well with measured values and indicated that Barnegat Bay receives roughly 26 kg NÁha . Atmospheric deposition was the dominant source of nitrogen to Barnegat Bay, followed by fertilizer nitrogen. Wastewater in Barnegat Bay is diverted to an offshore outfall and contributes no nitrogen to the system. The NLOAD tool has an additional feature that allows managers to assess the effectiveness of a variety of management options to reduce nitrogen loads. We demonstrate this feature of NLOAD through simulations in which fertilizer inputs to the Barnegat Bay watershed are reduced. Even modest cutbacks in the use of fertilizers on agricultural fields and lawns can be shown to reduce the amount of N entering Barnegat Bay.

Nitrogen loadings to two small estuaries, Prince Edward Island, Canada: a 2‐year investigation of precipitation, surface water and groundwater contributions

“…While our result for the Trout River estuary (380 kg NO 3 ‐N/ha estuary/year) is comparable to an intermediate loading, it is evident that the McIntyre Creek load of 1700 kg NO 3 ‐N/ha estuary/year significantly exceeds values for Waquoit Bay sub‐estuaries or other estuaries in the Cape Cod, MA, USA, area (Carmichael et al , 2004). Indeed the annual loading to McIntyre Creek estuary appears to be one of the highest values reported in the literature (Table IV in Bowen et al , 2007b). Although many factors other than N loading may affect estuarine functioning (e.g.…”

Effects of Coverage by Benthic Seaweed Mats on (Northern Quahog = Hard Clam) Mercenaria Mercenaria in a Eutrophic Estuary

“…This increase from surface water runoff over~10 years suggests that continued development and land alteration of the BB-LEH watershed likely play significant roles in nitrogen enrichment of this estuary. These TN load estimates were based on a measure of both DIN (NH 4 þ þ NO À 3 þ NO À 2 ) and dissolved organic nitrogen (DON) species in major river basins and represent the TN load delivered from the watershed to the receiving estuarine waters estimated by applying the NLOAD model described by Bowen et al (2007). The ratios between TN and TP loads are thus not representative of the nutrient ratios in the water column.…”

Model inter-comparison design for large-scale water quality models

“…These previous nutrient/water temperature model inter-comparison studies have shown the importance of evaluating the performance of water quality models and highlighted the need of common input data to provide consistent water quality model output for comparison [41,43,45].…”