Marah Hardt

Marah J. Hardt is a research fellow with the Blue Ocean Institute. Her background is in coral reef ecology and the history of science.

Recent Articles

Carbon Dioxide: The Curse of the Deep

Ocean warming, acidification, and corrosion wreak havoc on marine populations.

I was 8 years old, diving down in the waters off Cape Cod, when I first saw a strange shimmering within the sea. About 7 feet beneath the surface, I cautiously extended my hand to where the water appeared blurry, as if I were gazing down through a thick, melting pane of glass. My fingertips struck very cold water. I had encountered a thermocline, literally a line of temperature, and discovered that the ocean is far from a uniform pool of blue. Different layers of warm and cold water, some with more minerals, some with fewer, alternately rise and sink, creating currents, distributing nutrients, and forming distinctive habitats. Temperature and chemistry govern ocean life in a way not seen on land. When water warms, it absorbs less oxygen and increases stratification, reducing its ability to mix with waters below. As a result, deeper waters do not receive as much oxygen from the surface, and surface waters do not receive as many nutrients from below. Marine animals have a hard time...