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

This study estimate the extension of the riverine nitrogen impacts and the primary productivity for better nutrient management in Narragansett Bay, the coastal area in the Rhode Island, USA. With increased primary production and hypoxia due to anthropogenic emissions of nutrients, understanding the nitrogen inputs into the bay is critical to managing and addressing coastal issues such as eutrophication and hypoxia. However, estimating the extent of nutrient inputs in coastal areas remains challenging.

In this study, three different primary productivity zones were identified to visualize the extent of nitrogen influence from the river in the bay using the N mass balance model. This study also produced the results into a 3D representation for better visualization and nutrient management in the bay. As explained in the manuscript, the three theoretical zone can change over time depending on the nutrient concentration of the freshwater, mixing rate, and the river flow.

As a result, the future work are the required to quantify these factors attributed to the flexibility of these regions better. To begin, after downloading the DIN data from the U.S.Environmental Protection Agency, use Adobe Illustrator to divide Narragansett Bay into 15 boxes along its access modified from the previous study. Using the given formula, calculate the mean concentration of DIN at each box.

Calculate the potential primary production or PPP rate based on the N mass balance model by converting the net DIN removal to carbon units using the Redfield ratio. Save the PPP rate data of each box as a txt file. Then open the Ocean Data View software and load the PPP rate data by clicking the File menu and selecting Open.

In the Metadata Variable Association window, click the associate variables Box, latitude, longitude with station, latitude degrees north, and longitude degrees east. From the Import window, click the OK button. Next, right click on the map and click Zoom.

Then drag the red box to zoom into the data area of the map, and click on Enter. From the View menu, click the one Scatter Window of the layout templates. Then right click in the sample panel and select Derived Variables.

From the list of choices panel, under Metadata, select Latitude and click the Add button. Repeat the same step for longitude and click OK.Next, by right clicking on the Scatter window, select X variable as DRVD longitude degrees east. Similarly, select Y variable as DRVD latitude degrees north and Z variable as PPP in gram carbon per square meter per day.

Select Properties by right clicking on the scatter window and go to the Display Style option. Select the gridded field, then move to the Contours option and click the left shift button to make 0, 0.1, and 2 values only remain in the already defined panes of the left. Finally, click the OK button.

Based on the contour plot from the software, define the edge of the brown, green, and blue zones in Narraganset Bay. Then using Adobe Illustrator, visualize these zones in the map. The N mass balance model identified three theoretical zones in Narraganset Bay for the summer.

Brown zones had PPP rates greater than two gram carbon per square meter per day, indicating strong physical and biological processes with high turbidity and light limitation. Green zones had PPP rates between 0.1 to 2 gram carbon per square meter per day, displaying nutrient limitation in high primary production. Blue zones had PPP rates less than 0.1 to 2 gram carbon per square meter per day, representing low biological productivity.

Physical frameworks were created using acrylic panels with LED lights to show overlaps of zone boundaries and sediment turbidity levels in each zone.