PREDICTABLE RISKS

A Shift in Sea Bacteria Can Predict Harmful Algal Blooms Over a Day in Advance

Washington, USA, 12 June 2025 |

Boya en el océano abierto

Researchers have discovered a reliable early warning signal for harmul algal blooms: a measurable shift in the protein of ocean-dwelling bacteria. According to a new study published in Nature Communications, specific bacterial peptides-fragments of proteins- change in a predictable way well before these blooms begin to form, offering a potential breakthrough for aquaculture and marine ecosystem protection.

The mechanism hinges on the rapid response of free-living marine bacteria to environmental cues. “Free-living bacteria quickly respond to small physical and/or chemical environmental changes by adjusting their proteome,” the authors explain. This microbial response, captured through high-resolution mass spectrometry, acts as a biological signal that a bloom is on the horizon.

To test this, a team led by the University of Washington’s Department of Genome Sciences conducted an intensive sampling campaign off the coast of Washington State, USA. During two separate periods leading up to blooms of Chaetoceros socialis-a diatom known to cause mass fish mortality by irritating their gills-the researchers tracked over 4,600 bacterial peptides. Out of these, they identified 314 that consistently shifted in abundance ahead of the algal events, and eventually validate 12 as robust predictive biomarkers.

“This study identifies proteomic shifts in bacterial peptides which may be used as predictive biomarkers for forecasting harmful algal bloom initiation,” the authors write, highlighting their potential to “mitigate detrimental algal bloom outcomes in the future.”

Six of the key peptides were linked to TonB-dependent receptors- proteins that help bacteria scavenge carbohydrate metabolism. Crucially, the abundance of these peptides changed between 24 and 66 hours before the peak chlorophyll signal that typically marks the onset of a bloom.

“The state shift for all pepetides occurred at least 24 hours prior to the observed BSD for both blooms,” the study notes.

This microbial forewarning system offers a significant improvement on current monitoring techniques, which often rely on the detection of algal cells or toxins after a bloom is already under way. Bacterial peptides, by contrast, serve as indirect but advance indicators, enabling more proactive responses and potentially reducing economic losses in fisheries and aquaculture.

Given the increasing frequency and intensity of harmful algal blooms worldwide-with serious consequences for seafood production and coastal economies-this approach paves the way for next-generation early warning systems grounded in marine microbiology.

Reference: Mudge, M.C. et al. (2025). Harmful algal blooms are preceded by a predictable and quantifiable shift in the oceanic microbiome. Nature Communications. https://doi.org/10.1038/s41467-025-59250-y