Ocean acidity

In the first citizen science session in 2019, we set up a pilot ocean acidification monitoring station, monitoring pH, D.O. and temperature. In 2021, we will collaboratively build and install additional sensor stations aiming to explore readings on both sides of the island, and different depths of the ocean, with a focus on coral reef areas. Monitoring buoys will have autonomous power supply and communication using solar panels and GSM connections. Open workshops to build the stations will be held at Brenchie’s Lab on Wednesday evenings beginning November 24th. Once they’re built, we’ll organize weekend field sessions to test them in the ocean in various locations. In the end we’ll share our code, designs for building, programming, and deciding where to install the sensor stations online so others can learn from our experiences.

2019 (v1)

Our first version of this water quality sensor was put together using sensors from Atlas Scientific, including their pH probe, temperature probe, and dissolved oxygen probe. Atlas has links on each of the probe pages about how to read the sensors using an Arduino, so we combined those into one program and added some code to send the information out online by using an ESP8266 based Arduino compatible chip with wifi. The monitoring station isn’t currently plugged in, but you can see what the output looked like here. This pool kit they sell gives you an idea of what the circuit looks like, with slightly different sensors.

The original code is on Github here: https://github.com/brenchies/water-quality/

We built the system, tested it, and were on the verge of installing it in the ocean when the pandemic hit last year, so we’re working out a new place to put it. We’ve also found a better option for sharing the data online, through the Adafruit IO platform. It let’s you put together a dashboard with live data and chart displays (here’s one of our air quality sensor dashboards) and saves your data for the last 30 days, so you can download it and put it into a spreadsheet or database. You have have 10 sensors and 30 days of data for free, or unlimited sensors and more data storage for a small monthly fee.

2021 (v2)

With the second round of development, we’re going to start by updating the previous version to connect to Adafruit IO, and verify that it works and is water tight for installation outdoors. Then we’ll arrange a spot where we can install it that has wifi and a power outlet, ideally somewhere we can check on it easily.

For additional monitoring options, we’ll try out stations installed on existing buoys or moorings, and also put one together that can be taken on short excursions. Differences between the three options are below.


Pier – Stationary, connected to a fixed structure with wifi and power plugged in. Starting with pH, T, and DO.

Buoy – Floating but anchored, requires better power control and battery with solar charger, and GSM communication. Ideally also measuring ORP and conductivity (salinity)

Kayak – Straps onto a kayak to monitor the ocean while you paddle, needs a battery and GPS to track location, and onboard data storage. Would like to measure as many parameters as possible. Could be coupled with seafloor mapping with a GoPro or other camera in the future, as well as bathymetry measurements of water depth. We have a foldable Kayak on the way so it can be fit into a car and taken to different sites around the island.

Relevant links

Public Labs water quality measurement (mostly freshwater focused) – https://publiclab.org/notes/anngneal/12-08-2017/7-ways-to-measure-monitor-and-evaluate-water-quality

Atlas Scientific adding DO to hydroponics kit – https://www.hackster.io/atlasscientific/add-dissolved-oxygen-to-the-wifi-hydroponics-kit-386601