Visualization of Productivity Zones Based on Nitrogen Mass Balance Model in Narragansett Bay, Rhode Island

Summary

Here, we aim to visualize the zonation of biological productivity in Narragansett Bay, Rhode Island, based on the nitrogen mass balance model. The results will inform nutrient management in the coastal regions to reduce hypoxia and eutrophication.

Abstract

Primary productivity in the coastal regions, linked to eutrophication and hypoxia, provides a critical understanding of ecosystem function. Although primary productivity largely depends on riverine nutrient inputs, estimation of the extent of riverine nutrient influences in the coastal regions is challenging. A nitrogen mass balance model is a practical tool to evaluate coastal ocean productivity to understand biological mechanisms beyond data observations. This study visualizes the biological production zones in Narragansett Bay, Rhode Island, USA, where hypoxia frequently occurs, by applying a nitrogen mass balance model. The Bay is divided into three zones - brown, green, and blue zones - based on primary productivity, which are defined by the mass balance model results. Brown, green, and blue zones represent a high physical process, a high biological process, and a low biological process zone, depending on river flow, nutrient concentrations, and mixing rates. The results of this study can better inform nutrient management in the coastal ocean in response to hypoxia and eutrophication.

Introduction

Primary productivity, the production of organic compounds by phytoplankton, fuels ecosystem food webs, and is important for understanding the system's function in response to environmental changes^1,2. Estuarine primary productivity is also closely linked to eutrophication which is defined as excessive nutrients in the ecosystem¹, causing several harmful consequences in the coastal regions, such as an overgrowth of phytoplankton leading to large algal blooms and subsequent hypoxia^3,4. Importantly, primary productivity in estu....

Protocol

1. Applying the N-mass balance model

1. Download the dissolved inorganic nitrogen (DIN) data from the US Environmental Protection Agency (USEPA) for 166 stations in Narragansett Bay from 1990 to 2015.
   NOTE: In this study, the sum of ammonium (NH₄⁺), nitrite (NO₂^-), and nitrate (NO₃^-) concentrations were considered as the DIN concentration.
2. Split the Narragansett Bay into fifteen boxes along its axis modified from .......

Discussion

This study estimated the extent of nutrient impacts from riverine inputs in Narraganset Bay (NB) based on the N-mass balance model by defining the three theoretical zones. Historically, hypoxic zones appeared near the Providence River, the western side of Greenwich Bay, and Mount Hope Bay during the summer period¹⁸, which were defined as brown zones in this study. Moreover, the zonation of NB is comparable to the results of a previous study¹⁹, which examined nutrient concen.......

Materials

Name	Company	Catalog Number	Comments
Adobe Illustrator	Adobe	version 27.6.1	https://www.adobe.com/products/illustrator.html
Ampersand Gessobord Uncradled 1/8" Profile 8" x 8"	Risdstore	70731053088	https://www.risdstore.com/ampersand-gessobord-8x8-flat-1-8-profile.html
Ocean Data View software			https://odv.awi.de/en/software/download/
W-Series (Wide) Flexible LED Strip Light - Ultra Bright (18 LEDs/foot)	aspectLED	SKU AL-SL-W-U	https://www.aspectled.com/products/w-wide-5050-ultra-bright?gclid=CjwKCAjwm4ukBhAuEiwA0z QxkyqisRPqBcHvXEW8KcJE-bK0d2cvGtqlOxXWJI_ E2rd6DzttPR0FLRoCgfkQAvD_BwE