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Identifying the Airborne Assassins of Algal Blooms

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Lucie Malard

Phytoplankton (algae) communities are major contributors to primary production through photosynthesis and therefore, are a key component of large biogeochemical cycles in the ocean. Massive phytoplankton blooms – when the algal population rapidly increases – occur annually and can reach thousands of square kilometers. The algal cells are regulated by abiotic properties (e.g UV light and nutrient limitation) and biotic interactions (e.g. predation and pathogens), which can lead to cell death and eventually the end of the algal bloom. These blooms occur when sea temperature, nutrients and light levels are just right and they can disappear quickly, sometimes all at the same time, raising questions on this synchronous bloom end.

The study by Lang-Yona investigated this question of synchronous bloom ends despite geographical separation and the mechanisms associated. They hypothesized that microorganisms infecting algae are transported through the air, allowing for large-scale infections of algal blooms leading to these synchronous ends. Taking advantage of the Tara Ocean mission, the team sampled air from the sailing ship to characterize the microbial communities living/being transported in the air. In the laboratory, they exposed algal cultures to the collected air samples and recorded infections via the observation of algal cell death. When infection occurred, they cultured the microorganisms from these infected samples and extracted the DNA to identify these microorganisms. Through cultures and DNA analysis, they identified a pathogenic bacteria (Roseovarius nubinhibens) killing the algae, leading to the end of the bloom. The presence of this bacteria in the air samples and its ability to infect the algae suggest that they could travel through the atmosphere for kilometers and infect other algal blooms (see figure below). The findings suggest that airborne marine bacteria may play a key role in the open ocean’s large-scale infection of algal blooms.

The algal bloom on the left is infected with bacteria, leading to cell death. The bacteria are aerosolized, transported into the atmosphere across tens of kilometers, and start infecting other algal blooms. Made by Lucie Malard with adobe stock and inkscape.

Link to the original post: Naama Lang-Yona, J Michel Flores, Tal Sharon Nir-Zadock, Inbal Nussbaum, Ilan Koren, Assaf Vardi, Impact of airborne algicidal bacteria on marine phytoplankton blooms, The ISME Journal, Volume 18, Issue 1, January 2024, wrae016, https://doi.org/10.1093/ismejo/wrae016

Featured image: Caption: Intensifying phytoplankton blooms in earth’s coastal oceans. Credit: Lian Feng
https://phys.org/visualstories/2023-03-satellite-images-coastal-algae-blooms.amp