Scientists are baffled by the origins of a recently discovered species of red algae, which are threatening and smothering coral reefs in Hawaii discovered during a 2016 routine marine wildlife monitoring trip.
Last summer, they saw how the algae had grown exponentially, with vast areas of corals covered by mat-like algal colonies. These are the corals of the uninhabited and remote Holoikauaua or Pearl and Hermes Atoll.
This prolific algal species was previously undiscovered, said the University of Hawaii researchers who published their findings last Tuesday in the online journal Plos One.
The researchers said it is a threat to the corals and the other marine organisms in that area. Lead study researcher Alison Sherwood says that this has never been seen before in the Northwestern Hawaiian Islands. She says that it is very alarming to observe how it is taking over the area in such a short time.
The scientists named the alga Chondria tumulosa, and although its behavior is similar to that of an invasive species, they could not consider it as invasive because they have not so far determined if it originated from an external source. Instead, the researchers call it a nuisance species.
Algae covering corals block the sun, which essentially kills living organisms that are beneath them, says Dr. Sherwood. Such a species also takes over the space of seaweeds and other algae that naturally occur in the area and which serve as food for the herbivores there. She says the alga is altering the reef community, causing ripple effects throughout the food chain.
The Holoikauaua or Pearl and Hermes Atoll is part of the Papahanaumokuakea Marine National Monument, the largest protected marine reserve in the world, and part of the World Heritage List.
NOAA Deputy Superintendent and Research Coordinator of the monument Randall Kosaki was the chief scientist of the expedition which discovered the algae. He says the species can potentially overrun the entire atoll or a whole island, and the only way to keep them from becoming a problem is to prevent their foothold.
Kosaki and the research team treated their diving gear with bleach to make sure they do not bring the red algae to the other islands, which, according to Kosaki, will be an economic and ecological disaster. The economy of Hawaii is heavily dependent on tourist revenue.
The researchers also observed that surgeonfishes and other local grazers did not eat the red algae, which could indicate that it isn't native to the area because native algae usually have natural predators. Kosaki said they do not know if it was merely an overlooked native species. According to Dr. Sherwood, it is the first algal species whose origins they failed to track, saying currents could have moved the algae and drifted here, or their spores may have helped them spread.
Great Barrier Reef Foundation chief scientist and University of Queensland Professor Peter Mumby speculated that unusual chemistry of the water or the absence of natural algal consumers might have caused the algal bloom.
Dr. Sherwood concludes that the situation does not have a good outlook for the corals.
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