Abstract

An expansive hypoxic zone in the Northern Gulf of Mexico (NGOMEX) affects ecologically and economically important living resources, but the magnitude, predictability and even the direction of these effects are not well-documented. Managers and stakeholders alike need readily available and quantitative tools to assess the effects of nutrient reduction strategies aimed to minimize the hypoxic zone. The goal of our work is to couple spatially explicit ecosystem and water quality models to evaluate effects of hypoxia and nutrient loading on fish and fisheries together and separately, and to develop a decision support tool that visualizes the output. After our initial simulations emphasized the importance of (bottom-up) food web dynamics on NGOMEX living resources (De Mutsert et al., 2016), we focussed on simulating nutrient reduction scenarios recommended by the Mississippi River Gulf of Mexico Watershed Nutrient Task Force, or Hypoxia Task Force. The current Gulf hypoxia action plan goals of the Hypoxia Task Force are to reduce the 5-year running average size of the Gulf hypoxic zone to 5,000 km2 by 2035, with an interim goal of a 20% reduction in nitrogen (N) and phosphorus (P) loading from the Mississippi Atchafalaya River Basin by 2025. Here we focus on the long-term coastal goal to answer the following research question: “What is the effect of reductions in nutrient loading on living resources to reach the goal of the Hypoxia Task Force to reduce the size of the hypoxic zone to 5,000 km2?”

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