Gammon Koval | Critical Depth Web App

Critical Depth Web Application

As part of one of my graduate, oceanography classes, our final project was to create an outreach tool. For my project, I decided to focus on Sverdrup's Critical Depth Hypothesis. I applied my coding skills and created a web application from scratch with an interactive graph demonstrating the theory. I chose to use R shiny and host it on shinyapps.io. If you're interested in checking it out, you can do so here: Critical Depth Web App.

critical depth growth — **Caption:** The left figure show phytoplankton population growth through photosynthesis. The y-axis represents depth and the curve starts to drop off as you get deeper there is less light and therefore photosynthesis is limited. The right figure shows phytoplankton loss due to respiration. Because respiration isn't affected by light, it is constant all depths.

critical depth loss — **Caption:** The left figure show phytoplankton population growth through photosynthesis. The y-axis represents depth and the curve starts to drop off as you get deeper there is less light and therefore photosynthesis is limited. The right figure shows phytoplankton loss due to respiration. Because respiration isn't affected by light, it is constant all depths.

Sverdrup's hypothesis was related to the depth of the mixing layer in the ocean that would result in a phytoplankton bloom. Specifically, he defined the critical depth as the depth of the mixing layer where the production of phytoplankton from photosynthesis was equal to the loss due to respiration (see below). He published his theory in 1953 and since then it has undergone some scrutiny for its large assumptions and other theories have been proposed for the result of a phytoplankton bloom. If you're interested in learning more about Sverdrup’s Critical Depth hypothesis and some of the newer theories check out the link. If you're interested in viewing the code to run the web app, check out the link below to GitHub.