Dr. Andi Haas

Biogeochemist Andreas Haas studies changes in coral reef ecosystems as a consequence of human influence. ‘The infamous bleaching of coral, due to the loss of associated symbiotic algae under warm seawater conditions is well known. That often happens in a relatively short time and yields shocking images that capture our attention. A lesser-known threat for corals comes from other algae. Macroalgae, or filamentous turf algae, can emerge if there is an excess of nutrients in the water - for example from wastewater, or when the ecosystem is disrupted due to overfishing or pollution.’

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‘A coral reef system is a complex community comprising a multitude of organisms that coexist in a delicate and co-dependent balance. For instance, when algae increase, then the bacteria seize their chance too. Most algae release sugars that provide a tasty and readily available food source for them. Subsequently, the entire balance shifts and ultimately, algae and other non-calcifying organisms like sponges emerge that can even decompose the calcium carbonate of the corals. We see this effect occurring throughout the world and mainly at locations that are exposed to much human influence. In a comparative study of coral reefs across the pacific, including some exposed to significant human influence, and some of the most pristine reefs on this planet (e.g., Millennium Atoll, 3000 kilometres south of Hawai’i), we could see clear evidence of this fast-food effect.’

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‘In my research, I am primarily trying to understand exactly how the balance between algae, corals and bacteria works. Currently we are quantifying tens of thousands of different organic molecules in seawater. That will hopefully provide starting points to tackle the underlying chemical causes of this problem. In addition, we are examining how the negative effects of people on coral can possibly be reduced. For example, it seems the corals experience less damage from harmful algae if the water around a reef is refreshed more often. We can take something like that into account during the design of new waterfronts and harbours. Ultimately we need to understand the biogeochemical mechanisms of coral reefs in detail to save the immense biodiversity and ecosystem services that coral reefs provide.’