A low-cost, accessible, and high-performing Arduino-based seawater pH control system for biological applications

Abstract

In the last two decades, the need for seawater pH control methodologies paralleled the rise in attention to the biological impacts of ocean acidification. Many effective and highperforming systems have been created, but they are often expensive, complex, and difficult to establish. We developed a system that is similarly high performing, but at a low cost and with a simple and accessible design. This system is controlled by an Arduino Nano, an open-source electronics platform, which regulates the flow of CO 2 gas through electric solenoid valves. The Arduino and other inexpensive materials total $$150 (plus CO 2 gas and regulator), and a new treatment can be added for less than $35. Easy-to-learn code and simple wire-to-connect hardware make the design extremely accessible, requiring little time and expertise to establish. The system functions with a variety of pH probes and can be adapted to fit a variety of experimental designs and organisms. Using this set up, we were able to constrain seawater pH within a range of 0.07 pH units. Our system thus maintains the performance and adaptability of existing systems but expands their accessibility by reducing cost and complexity.

Learning Circuits and Coding with Arduino Board in Higher Education Using Tangible and Graphical User Interfaces

“…Educators and researchers use Arduino boards as an educational and prototyping tool, integrating them into diverse research fields [35][36][37]. For example, Papadimitropoulos et al [38] conducted chemistry experiments for middle school students, incorporating Arduino as a pH-meter.…”

The Open acidification Tank Controller: An open-source device for the control of pH and temperature in ocean acidification experiments

“…Pinpoint pH Controller costing $200 [13] . More recently, open-source applications have been published to control aquarium pH, but these devices have invariably been feature-poor, relied on expensive external equipment, or both [14] , [15] , [16] .…”

“…The pH probe connects to the Tank Controller via a BNC female connector on an Electrically Isolated EZO™ Carrier Board (P10; $42) to which is attached an EZO™ pH Circuit (P9; $42) that provides pH readings to the CPU from 0.001 to 14.000 with a resolution of 0.001 and an accuracy of +/- 0.002. This brings the cost of the pH meter assembly to under $90, while other open-source projects have employed high-end external pH meters, such as the Honeywell UDA 2182 Dual Analyzer which costs approximately $1500 [15] . However, this pH meter system performs admirably and was selected from an array of other possible pH meter circuits because, in our testing while developing this system, it could perform high accuracy pH measurements with inexpensive pH probes.…”