A Moment of Science

Coral in Danger

Learn about the danger sedimentation poses for today's marine life, on this Moment of Science.

Aah, snorkeling in the Great Barrier Reef–blue, clear water, magnificent coral, beautiful fish. However, cloudy waters and dying coral are becoming more abundant these days. It’s getting harder and harder to even spot a fish!  Sadly, we may face more problems than disappointing snorkeling vacations if we keep harming the coral reefs of the world.

We could lose one quarter of all marine animals and plants. One example of a way we’re destroying coral reefs around the world is farming near reef coastlines. In the Great Barrier Reef off Australia, for instance, scientists studied changes in the composition of coral over time and compared that to logs recording the local flood history. Barium, a metal rich in terrestrial soil, but usually low in seawater, began to rise soon after Europeans settled the area in 1862.

After the settlers moved in and tilled land for farming, from then on, when a nearby river flooded, it washed loose soil into the reefs. These sediments cloud the water, blocking out sunlight that is necessary to the corals’ growth. In fact, when sedimentation run-off is extremely bad, it can smother the coral and kill it.

Sedimentation can also introduce nutrients that lead to excess growth of green algae, which can compete with the corals for space, impeding their growth and survival. This is just one way we’re harming coral. If we don’t take action, marine scientists predict that the majority of the coral reefs of the world will be destroyed in just 40 years.

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