Shell Shocked

The impact of environmental changes on our world’s oceans is becoming increasingly well documented, with reports of chemical pollution, a trebling of plastic waste and dying coral reefs. With ocean acidification – a shift towards pH-neutral conditions caused by excess CO₂ in the atmosphere – mussels look to be the latest to suffer. A team of scientists from the universities of Florida, Glasgow and Chicago analyzed Mytilus californianus to assess the damage – and to discover what it could mean for these mighty mollusks.

The group hit the waters around Tatoosh Island, and compared modern muscle shells with archival records of shells from the 1970s, as well as some dating back 1,000–2,400 years. The team discovered that the calcite crystals within the shells have been uniform in size and structure for thousands of years, but those from the last 15 years show “increased disorder.” Raman spectroscopy also uncovered greater variability in the quantity of calcium carbonate (CaCO₃), as well as elevated levels of magnesium – a sign that shell formation has been disrupted. According to the researchers, this trend in the shell structure corresponds with an increased rate of ocean acidification. Mussels may not find themselves all at sea though, according to lead author of the paper, Sophie McColl: “Variability is the basis of natural selection, and the fact that we now see so much variability in the mussels’ individual shells means there is potential for natural selection to act,” she said in a press release (2). “I have too much confidence in the natural processes of ecology and evolution to think that we’ll have barren oceans.”

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