When everyone had gone off to prepare for the night shift or to watch a movie or sleep, Helen settled into a corner of the galley with licorice from the candy drawer and began reading her advanced organic chemistry text, the section on aliphatic nucleophilic substitution. She was still on the first page when Annabel returned—wrapped now in a pink woven shawl pinned at her chest with a green papier-mâché brooch the size of a fist. “I don’t want to bother you,” she said. “I can see you’re studying. But I’m told you’re the one I should talk to about ocean acidification. I need to understand the chemistry. Can we talk sometime?”
Helen closed her book on a scrap of napkin. “We could do it right now if you want.” She’d heard this at a conference: never pass up an opportunity to educate.
Annabel nodded vigorously, hair beads jangling. “Formidable!” she shouted in a French accent. “Tout de suite I’ll be back.”
And she was, as though she had flown to her cabin. She thumped onto the bench across from Helen and opened her drawing pad to a clean sheet. “Pretend I’m a third-grader,” she said. “I’m that stupid.”
“I doubt you’re stupid,” Helen had to say. “But stop me if I start getting too detailed for your purposes. The basic chemistry isn’t too complicated. And, by the way, you’ll be hearing us shorthand ‘ocean acidification;’ we call it OA.”
She talked, and Annabel, several rings sparkling on each hand, made chicken-scratch notes in green ink.
She wanted to make sure Annabel understood that the ocean wasn’t turning to acid, only becoming more acidic, while still being on the alkaline side of the pH scale. “Sea life evolved in a very stable pH situation. We’re asking creatures to live in a different environment now, very suddenly. This is the hard part—we don’t know exactly how individual species will respond—are responding. We know that corals are having a very hard time. And you heard Ray talking about pteropods, the marine snails. They’re very vulnerable. Anything with a carbonate shell is affected.”
She drew a carbon dioxide molecule on Annabel’s paper, then a water molecule and one for carbonic acid. “This is the thing,” she said. “In the atmosphere, carbon dioxide stays carbon dioxide. The carbon and oxygen atoms stay bonded. In the ocean, CO2 reacts with seawater. It forms carbonic acid, which releases these hydrogen ions and reduces the pH. The hydrogen ions combine with carbonate ions to form bicarbonates. Then there are fewer carbonate ions left to make calcium carbonate, the major building blocks needed by shell builders.”
Annabel was studying her crude drawing. Helen hesitated to get into the aragonite versus calcite distinction or to be specific about saturation horizons. She knew how easy it was to pile on too much, to let her passion for the subject overtake another person’s tolerance for it. Keep it simple, Jackson was always saying.
Annabel looked up. “So you could say that reduced carbonate ions lower the saturation state.”
Helen tried not to be surprised by the non-third-grade reference. “That’s exactly what we say. We say the water is undersaturated with aragonite, one of the main forms of calcium carbonate.”
Annabel said, “Ray showed me some pictures. His little animals have to work harder to form the calcium carbonate for their shells, and if it gets too bad, their shells actually start to dissolve.”
“That’s exactly right. In the Arctic we’re already seeing corrosive water.”