Interaction between light and temperature affect algae levels on corals

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Scientists and regular divers have noticed for a long time that the amount of algae on coral reefs fluctuate significantly over time. They wanted to see what exactly is causing these changes and so a two-year study began at the University of Queensland in Australia. Scientists found that there are two main factors influencing the amount of algae on coral reef – interaction between light and temperature and human activity.

Algal levels on corals change naturally but humans are affecting them too. Image credit: Derek Keats via Wikimedia (CC BY 2.0)

Actually, the role of human activity in algae fluctuations is nothing surprising. There have been studies before that linked human impact to the increase of algae populations for the disadvantage of reef-building corals. However, it seems like scientists before neglected looking into some of the natural causes that could encourage these changes. Now scientists analysed the reef composition and coral-algal competition across Heron Island, on the southern end of the Great Barrier Reef. They paid specific attention to natural processes that could be influencing algae levels. And they found that that there is a specific interaction between light, temperature and abundance of algae on coral reefs.

Up until now it was widely believed that algae fluctuations can be explained through seasonal peaks. However, this does not seem to be correct anymore, because sometimes changes in algae levels are not in sync with changing seasons. Scientists are also trying to stress that we don’t know enough about how changes in algae affect corals themselves. They say that changes in algal biomass are actually affecting the composition and frequency of coral-algal interactions. When there is too much algae, structural corals are struggling to grow.

Algae and corals live together, but scientists are willing to call this relationship a “competition”. Kristen Brown, one of the authors of the study, said: “Competition between coral and algae can lead to reductions in coral growth and survival, which can have implications on the structure and function of coral reef ecosystems. Algae and their interactions with corals are more relevant than ever, especially given the rapidly degrading coral reef ecosystem dynamics”.

It is hard to plan future without disturbances in coral reefs. Human activity is putting reefs at danger and there is not much we can do to stop it. But scientists say that understanding seasonal and spatial variations of algae levels can help us predict the future of coral reefs and prepare for it.

Source: University of Queensland

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Interaction between light and temperature affect algae levels on corals

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Tuesday, May 29, 2018