High-Definition Water Data: an interview with Dr. Michael DeGrandpre (Part 2)

You can read the first part of Dr. DeGrandpre’s interview right here!

Dr. DeGrandpre is a Professor at the University of Montana in Missoula, Montana. His research focuses on the development of autonomous chemical sensors with applications in both marine and freshwater chemistry. He is leading the High Definition Water Data segment of research for The Longest Swim.

The temperature and electrical conductivity (a measurement which is then used to calculate salinity) of seawater relative to its depth might seem like basic information, but these properties can actually help scientists understand large-scale activity in our oceans. For example, researchers use salinity data combined with temperature measurements to calculate seawater density, which is a primary driving force in the movement of major ocean currents. Every day of the expedition, The Longest Swim crew will use a conductivity, temperature, and depth (CTD) device to gather measurements key to several other research projects taking place on-board.

Alongside a CTD device, the crew will be deploying the XPRIZE award-winning i-SAMI Ocean pH Sensor prototype. Scientists can use pH data gathered across the Northern Pacific to track the absorption of anthropogenic, or human-generated, CO2 from the atmosphere. An increased uptake of carbon dioxide gas into the ocean, where it can react with water molecules to release hydrogen ions, results in a decrease in pH known as ocean acidification. This can cause serious damage to coral reefs and other marine organisms whose skeletons may dissolve once their environment’s pH drops too low. The i-SAMI measurements taken during The Longest Swim will help scientists establish a baseline of natural variability in the ocean’s pH, as well as to better track one of the harmful effects of climate change on the marine environment.

What kind of impact does changing pH have for ocean life – and life on land as well?

We know that the pH of the ocean is going down, which means it’s getting more acidic, and that’s happening pretty slowly. It’s happening due to the uptake of carbon dioxide produced by humans, but we don’t have a good idea of the natural variability of pH in a lot of these waters. We can track that really effectively as The Longest Swim moves across the Pacific Ocean. Unusually so, just because you’ll be moving much slower than a normal ship would. That will give us a better idea of the natural variability in these regions of the oceans so that we can then say what might happen ten or twenty years down the road. It’s good baseline data.

So this acidity from human-produced carbon dioxide is one way to see the impact we’ve had on the environment?

That’s correct. It’s been shown that these decreasing pH levels have direct effects on many different organisms, particularly coral reefs of which there are many in the Pacific Ocean region you’ll be travelling through. There are many studies showing corals suffer negative effects due to this ocean acidification which is human-caused.  They’re very sensitive to pH levels because their calcium carbonate skeletons have a higher solubility at a lower pH. Other calcifying organisms like pterapods [free-swimming sea snails and sea slugs], which are abundant in the Pacific Ocean as well, are also affected by acidification.

And is there any other reason that the ocean’s pH could be dropping?

No, human activity is the only reason that we know of. pH varies a small amount over seasonal and decadal time ranges but over time there hasn’t been a real trend in pH for many thousands of years in the surface ocean. It’s been incredibly stable and for that reason organisms are not very adaptable to changes in pH because they’ve had this very static, chemically stable environment that they’ve lived in for thousands and thousands of years. That pH decline is human-caused, irrefutably human-caused.

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