Thursday, August 6, 2020

TedEd: The big-beaked, rock-munching fish that protect coral reefs

A TedEd by Mike Gil

There are many different types of fish in a coral reef. One of them, the parrotfish, eats rocks. It is named for its vibrant colors and beak-like teeth. Their behavior may be odd, but it helps protect the reef ecosystem. Corals start as tiny larvae, which latch onto rocks and hard seafloor, and metamorphosis into polyps. They build skeletal structures made of calcium carbonate and eventually become a full reef. Despite occupying just 1% of the seafloor, they house 25% percent of sea life, creating lots of biodiversity. It provides food and shelter for all of its occupants. Many of the animals eat seaweed, which is also vital to the environment. However, excessive numbers of these are bad because they need the same hard surfaces as coral to grow on, and even synthesize destructive substances to create more space. Parrotfish can help avoid this by using their hard teeth to scrape away all traces of seaweed from the seafloor, making space for the coral. Their complex social cues also assist many other fish in the reef. When a school of parrotfish enters the reef to eat, it signals safety, whereas alarm means danger is coming. Human activity has hurt this complex system. Overfishing of seaweed eaters has led to seaweed destroying many reefs, and their reduced numbers make parrotfish social networks less effective. Fortunately, research could help revive these important fish and ecosystems.

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