The Art of Alkalinity

May 27th

Hi everyone, my name is David and I’m excited to be participating in my first research cruise. I was first introduced to oceanography, specifically cold-water corals, as a summer intern in 2009 by our chief scientist, Laura Robinson. Since then I’ve continued focusing on coral geochemistry and was quick to jump on an opportunity to study them in their natural habitat.

My background is in chemistry, which I use as a tool for examining and understanding the world around us. In particular, I study the chemical composition of fossil coral skeletons. As coral geoscientists, it’s our hope that the chemistry recorded in coral skeletons is representative of the chemistry of the ocean water in which the corals grew. If so, then we can use ancient corals as archives of the ingredients that made up the ocean in the past. Coupled with observations of how the oceans work today, we’d be well on our way to unraveling how one of our planet’s most dynamic and complex systems behaves!

One way we can test whether coral skeletons record the composition of the seawater around them is to analyze modern corals and compare them to water samples that we obtain while on cruises like this one. In her blog post, Tina mentioned that one measurement we make onboard is of seawater alkalinity. One reason we measure alkalinity is so that when the modern corals we’re collecting go back to various labs for analysis, we can compare their skeletal composition to the alkalinity of the water bathing the corals as they grow. If we find a strong correlation, then we know we’ve found a good “proxy” for discovering what seawater alkalinity was like in the past – we would just have to look in the skeletons of ancient corals!

You might be wondering, `what is alkalinity?` You might have heard of pH, which is a measure of the acidity of water. Alkalinity is the acid neutralizing capacity of that same water. For example, pretend I have two buckets of water at the same neutral pH. In the first bucket I pour in some sulfuric acid and the pH drops really low, which is to say the bucket became highly acidic. In the second bucket I pour in the same amount of sulfuric acid, but the pH doesn’t change all that much. We would say that the second bucket had a higher acid neutralizing capacity, or that the second bucket had higher alkalinity.

Besides getting excited about alkalinity, I’m enjoying helping out with every odd job I can on the boat. My favorite task is going on the back deck of the boat whenever new samples come up from the seafloor. For safety and warmth everyone has to wear orange “float coats” and hardhats. It’s one of the few times every day I get outdoors and have a chance to marvel at the endless waves around us.

By David

Weather: Temperature 37 °F, windchill 5 ºF, windspeed 10-55 (!) knots, cloudy with building seas…