Health & Beauty
Cosmetics chemicals and coral
Sunscreen and cosmetics compound may harm coral by altering fatty acids.
21 January 2019
Main image: Coral reef in the Red Sea in Ras Mohammed national park
Coral reefs are often described as biodiversity hotspots, but new research shows they also act as powerful regulators of the microscopic life in the surrounding ocean.
A new study reveals that coral reefs impose pronounced daily rhythms on nearby microbial communities, reshaping their composition and abundance over the course of a single day.
The study was led by Dr Herdís G. R. Steinsdóttir, a postdoctoral researcher, under the guidance of Dr Miguel J. Frada of the Department of Ecology, Evolution and Behaviour at the Hebrew University of Jerusalem and the Interuniversity Institute for Marine Sciences in Eilat, and Dr Derya Akkaynak from the University of Haifa and the Interuniversity Institute for Marine Sciences in Eilat. It has been published in Science Advances.
The study tracked microbial populations in waters above a coral reef in the northern Gulf of Aqaba in the Red Sea, comparing them with nearby open waters across winter and summer seasons.
Using high-frequency sampling every six hours, the researchers uncovered previously undocumented daily and seasonal cycles affecting bacteria, microalgae and microscopic predators.
‘We found that the reef is not just passively surrounded by microbes. It actively structures microbial life in time, creating daily patterns that repeat across seasons and influence how energy and nutrients move through the ecosystem.’
DR MIGUEL J. FRADA
Department of Ecology, Evolution and Behaviour at the Hebrew University of Jerusalem and the Interuniversity Institute for Marine Sciences in Eilat
The research team discovered that reef waters consistently contained significantly fewer bacteria and microalgae than adjacent open waters, suggesting active removal by reef organisms.
At the same time, populations of heterotrophic protists, microscopic predators that feed on bacteria, increased sharply at night, sometimes by as much as 80%, suggesting predation as a major force shaping microbial dynamics.
One of the most striking findings involved Symbiodiniaceae, the family of dinoflagellates best known as coral symbionts.
Genetic signatures of these organisms consistently peaked around midday in reef waters, pointing to daily cycles of release, growth or turnover that may be linked to light conditions and coral metabolism.
‘These daily microbial rhythms were as strong as, and sometimes stronger than, seasonal differences. This shows that time of day is a critical factor when studying reef-associated microbial communities.’
DR HERDÍS G. R. STEINSDÓTTIR
Study lead, postdoctoral researcher
By combining genetic sequencing, flow cytometry, imaging technologies and biogeochemical measurements, the interdisciplinary team has provided one of the most detailed temporal views to date of microbial life around coral reefs.
The findings suggest that microbial daily cycles could serve as sensitive indicators of reef functioning and ecosystem health in a changing ocean.
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