The Great Barrier Reef May Be Further Stressed by Poisonous Seaweeds

Researchers from Griffith University have made a grim discovery; the Great Barrier Reef will be slowly poisoned by algae as carbon dioxide levels continue to increase due to climate change. Important reef-building coral are strongly affected by toxins released by algae and rising carbon dioxide concentrations will make the algae even more poisonous. The details were just published in the journal Scientific Reports.

Climate change, which scientists agree is mostly driven by human activities, is causing a number of major ecological and environmental changes globally. Coral reefs, which are already being damaged by pollution and bleaching events, are also vulnerable to a phenomenon called ocean acidification. Ocean acidification causes the pH to drop in the ocean as more carbon dioxide is released into the atmosphere, leading to a more acidic environment. This prevents coral from absorbing the amount of calcium necessary to continue building reefs. Unfortunately, ocean acidification also gives certain types of algae an edge—allowing them to proliferate and smother other forms of sea life. There has been little research on other possible effects of algae blooms on coral reefs. This has prompted scientists to study how macroalgae, a group that includes seaweeds and kelp, affects reef-building corals.

Researchers evaluated the effects of increased carbon dioxide levels on three common macroalgae species found in the Great Barrier Reef, Canistrocarpus cervicornis, Chlorodesmis fastigiata, and Amansia glomerata. All three species are capable of releasing toxins that poison coral. Normally, this simply gives them a chance of finding space to grow in a crowded reef. When the team grew the algae with increased carbon dioxide, however, C.cervicornis produced significantly more toxins and was capable of killing the most important reef-building coral species. C.cervicornis is an extremely common algae species and the research team predicts that it alone could kill all reef-building coral in the Great Barrier Reef by the year 2100, though severe damage will occur by 2050.

The research team’s findings are not good news for reefs, which are already under severe stress. The authors emphasize that atmospheric carbon dioxide levels need to be reduced to save our coral reefs, including the Great Barrier Reef.


Del Monaco et al. Effects of ocean acidification on the potency of macroalgal allelopathy to a common coral. Scientific Reports (2017).

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