Scientists have identified a marine fungus that was previously unknown and is capable of killing toxic algae known to threaten human health.
Scientists at Yokohama National University in Japan have identified a previously unknown marine fungus capable of killing algae that form harmful blooms.
The organism, named Algophthora mediterranea, is a microscopic chytrid fungus that can infect many different hosts. This unusually wide host range points to chytrid fungi, a diverse group of aquatic fungi, as potentially more important players in marine ecosystems than researchers had recognized before.
Importantly, the fungus acts as a lethal parasite of the alga Ostreopsis cf. ovata, a species responsible for toxic blooms that can negatively affect human health. The research describing this discovery was published online in the journal Mycologia.
Toxic algae
Algal blooms are becoming increasingly common in oceans, rivers, and lakes around the world. They occur when algae grow rapidly and uncontrollably, usually fueled by excess nutrients and warmer water conditions, leading to poor water quality and widespread ecological disruption. Some blooms also release toxins that can harm both animals and people.
Huge blooms of Ostreopsis cf. ovata have been increasingly reported in the Mediterranean in the past few decades. The alga produces a toxin called ovatoxin (OVTX), which can cause major issues in humans including a runny nose, cough, breathlessness, conjunctivitis, itching, and dermatitis.
Algae-killer
Algophthora mediterranea was discovered in Spanish seawater in 2021 by the team from the Institut de Ciències del Mar (ICM) in Spain, led by Dr. E. Garcés and Dr. A. Reñé, and it has now been described by Professor Maiko Kagami and PhD student Núria Pou-Solà, both from YOKOHAMA National University.
DNA analysis confirmed the fungus represents not only a new species but also a new genus. The team have named the new genus Algophthora, combining ‘alga’ and the Greek word ‘phthora’, meaning ‘destruction’.
The fungus was found as a parasite in cells of O. cf. ovata, which it kills within days. Further analysis showed it can also infect several other species of algae and can even feed off pollen grains.
“Although previous DNA-based surveys have revealed a wide diversity of marine fungi, only a handful of parasitic species have ever been isolated, and their ecology has remained largely unknown,” said Pou-Solà. “Our newly described species stands out for its unusually broad host range and distinctive feeding strategy, demonstrating that some chytrid fungi possess remarkable ecological resilience.”
The researchers isolated the fungus and took time-lapse photos every ten minutes for four days. Samples of the fungus were also analyzed using scanning electron microscopy (SEM), where a focused beam of electrons scans the surface of a sample, creating a high-resolution image. The fungus was then sampled for DNA.
“The next step is to investigate how such versatile parasites operate within complex marine communities,” said Kagami. “Ultimately, our goal is to understand how parasitic fungi contribute to — and potentially shape — the ocean’s biogeochemical cycles, an ecosystem role that has been largely overlooked until now.”
“In the future, we aim to build the necessary knowledge to improve our predictive capacity and support the management of harmful algal blooms,” adds Pou-Solà.
Reference: “Algophthora mediterranea, gen. et sp. nov.: Novel dinoflagellate- and diatom-infecting generalist marine chytrid from the Mediterranean Sea” by Núria Pou-Solà, Kensuke Seto, Alan Denis Fernández-Valero, Jordina Gordi, Esther Garcés, Albert Reñé and Maiko Kagami, 15 December 2025, Mycologia.
DOI: 10.1080/00275514.2025.2577604
Funding: Spanish Ministry of Science, Innovation, and Universities, Japan Society for the Promotion of Science, Japan Science and Technology Agency
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