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Explainer

How Extra Nutrients Trigger Algal Blooms

A slick of bright green on a lake can look almost unreal. Seen from shore it can pass for paint, pollen, or a strange summer stain. In water, though, that color often marks a sudden population boom, one driven by the same ingredients that help crops and lawns grow. Algae and cyanobacteria need light and…

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Green red sea
Chemistry

Why Some Coastal Waters Turn Green or Red

Seen from a beach, coastal water can look like it changes moods overnight. One week it glows blue-green in the sun. A few days later it turns murky olive, rusty brown, or even a startling brick red. Those shifts can feel dramatic because they are dramatic. They reveal a moving mix of life, light, sediment…

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Chemistry

Why Is the Ocean Salty?

Take a sip of seawater and your mouth gets the answer before your brain does. The ocean holds a huge load of dissolved minerals and that gives it its sharp, familiar taste. For a question that sounds almost childlike, the real answer stretches across rainstorms, rivers, deep cracks in the seafloor and spans of time…

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Chemistry

How Rising Acidity Changes Ocean Water

The ocean looks steady from the shore. Under the surface, though, it is constantly trading gases with the air above it. That exchange has always been part of Earth’s rhythm. What’s changed is the amount of carbon dioxide we’re adding to the atmosphere and how much of it the sea is taking in. That matters…

Low oxygen ocean
Chemistry

What Low Oxygen Does in the Sea

The sea looks full of motion. Waves roll. Fish flash by. Plankton bloom and vanish. Beneath all that movement sits a quiet requirement, dissolved oxygen. Every breathless patch of water changes the rules for life below the surface. Scientists have a striking phrase for the recent shift. In one 2024 paper, researchers wrote that the…

Ocean carbon
Chemistry

How Carbon Moves Between the Air and the Ocean

Every day, the planet runs a huge exchange program at the sea surface. Carbon slips out of the air, into the ocean, back to the air again and onward through currents, chemistry and living things. The motion is invisible, though its effects reach from climate to coral reefs to the fish on dinner plates. The…