Hawaii on alert: this is the unexpected invader that is wiping out its reefs
Already under pressure because of the rising temperature of the ocean and water pollution, the coral reef in Hōnaunau Bay faces a new threat.
The coral reef in Hōnaunau Bay in Hawaii is coming under serious threat as a result of a huge increase in the number of sea urchins in the area, according to a new study.
Why are sea urchins harmful?
Sea urchins are marine invertebrates, characterized by their spherical bodies and sharp spines. They have an important role to play in regulating algae overgrowth, which can prevent much-needed oxygen from reaching coral. The downside, however, is that sea urchins also eat the reef and they can cause damaging erosion if too many congregate in the same area.
Another view of Hanauma Bay, Portlock, Hawaii Kai and Koko Head.
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Research shows that coral reef growth in Hōnaunau Bay, popular with snorkelers and divers, has suffered an alarming slump. In addition to the influx of sea urchins, the coral was already suffering due to the rising temperature of the ocean and water pollution.
Huge worry over Hōnaunau Bay coral reef
“We found on average 51 urchins per square meter,” explains Kelly J. van Woesik, a researcher at the North Carolina State University Center for Geospatial Analytics. “That is among the highest recorded densities on coral reefs anywhere in the world.”
The study also discovered the reef in Hōnaunau Bay is currently growing 30 times slower than it did 40 years ago. According to research done in the 1980s, healthy production levels in Hawaii were considered to be something in the region of 15 kilograms (33 pounds) per square meter. Today’s level is only 0.5 kg (1.1 pounds) per square meter, further explaining, and emphasizing, the decline.
Sea urchin influx explained
Sea urchins have moved into Hōnaunau Bay in greater numbers as a by-product of overfishing, which has caused a drop in the number of fish species that would normally limit their presence in the area.
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