Scientists say a recently discovered kind of seaweed plant is killing large numbers of very small but important ocean animals called corals.

A new study from the University of Hawaii says the deadly seaweed is spreading quickly in the Pacific Ocean around the Northeastern Hawaiian islands. The area is one of the most protected environments on earth.

Corals live closely together forming large, hard, ocean structures called reefs. The researchers say the seaweed grows over the reefs, blocking the coral from the sunlight and food it needs to survive.

"This is a highly destructive seaweed," said scientist and seaweed expert Heather Spalding, who helped write the study. She said it could overgrow entire reefs.

In 2016, the United States government researchers were studying the Pearl and Hermes Atoll when they found small amounts of a seaweed they had never seen before. Last summer, they returned to the area and discovered the plant seemed to be everywhere. Spalding said in some places she examined, the seaweed covered "everything, as far as the eye could see," in thicknesses of up to 20 centimeters.

"Everything underneath of it was dead," she said.

The area was almost empty of fish and other sea life that usually populate the area.

Scientists say the seaweed probably covers an even larger area than they were able to document in the study.

Pearl and Hermes Atoll is in the middle of the Pacific Ocean, about 3,200 kilometers from Asia and North America. It is part of the 1.6 million-square-kilometer U.S. Papahanaumokuakea Marine National Monument.

The scientists said that some of the seaweed extended across areas the size of several soccer fields. They also said it threatens the atoll, and could endanger the entire Hawaiian archipelago if it spreads.

"We have not, until now, seen a nuisance species that's come in and made such...changes over a short period of time to the reefs," said the University of Hawaii's Alison Sherwood, who led the study.

The scientists carried out genetic studies that showed the seaweed was a new species. They named it Chondria tumulosa.

The new seaweed might have been carried into the area by a boat, although all boats must be cleaned and inspected in order to enter. The scientists say the species also might have been in the area for a long time, but in small amounts. Sometimes, environmental changes can cause an explosion in growth, they explained.

The study was published in the journal PLOS ONE.

I'm Susan Shand.

The Associate Press reported this story. Susan Shand adapted it for Learning English. George Grow was the editor.

________________________________________________________________

atoll - n. a ring-shaped reef, island, or chain of islands formed of coral.

archipelago - n. a group of islands

nuisance - n. something that is annoying or destructive

species - n. a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.