UniversidaddeCádiz

A study published in Marine Environmental Research reveals how diatoms generate more biologically active substances after long periods without light, helping to explain their remarkable ability to survive in the ocean.

A multidisciplinary team from the University of Cádiz has discovered that prolonged darkness enhances the production of a group of bioactive compounds in coastal diatoms —microalgae responsible for around 20% of the planet’s primary production. The research, published in the journal Marine Environmental Research, was carried out by the research groups RNM-214: Structure and Dynamics of Aquatic Ecosystems and FQM-169: Isolation, Structural Determination and Synthesis of Natural Products, both affiliated with the University of Cádiz’s Institute of Marine Research (INMAR) and the Institute of Biomolecules (INBIO).

The study, conducted within the framework of the FICOEXPLORA project funded by the Spanish Ministry of Science, Innovation and Universities, provides solid scientific evidence of how prolonged periods of darkness—such as those experienced by diatoms when their blooms end and they sink to the seabed—affect the production of a type of organic compound with key ecological functions known as polyunsaturated aldehydes. These molecules play important roles in cell-to-cell communication, defense against predators, and the regulation of marine food webs. When blooms collapse due to nutrient depletion, diatoms settle on the seafloor and remain dormant until environmental conditions become favorable again, activating survival mechanisms such as dormancy states or the formation of resting structures. Until now, it was unknown how this period without light could influence their metabolism and the synthesis of these natural substances.

To investigate this, the research team recreated in the laboratory blooms of two common coastal diatom species from the Gulf of Cádiz: Cyclotella cryptica and Skeletonema pseudocostatum. After maintaining the cultures in darkness for 75 days—an interval equivalent to the time they may remain in marine sediments—it was observed that both species survived and recovered their photosynthetic activity once light was restored. The analyses revealed a remarkable increase in the production of these bioactive compounds: Skeletonema pseudocostatum multiplied its levels sevenfold, while Cyclotella cryptica showed a fivefold increase compared to normal light conditions. Moreover, each species adopted different strategies to withstand the absence of light: the former produced resistance forms known as hypnospores, while the latter reduced its metabolism without showing morphological changes.

These findings indicate that the dark periods diatoms experience during their life cycle may be a key factor in their ecological success, as they modulate the production of substances that strongly influence planktonic communities and the dynamics of coastal ecosystems. The work carried out by the University of Cádiz thus contributes to unraveling the physiological mechanisms underlying the resilience and ecological role of these organisms in the ocean, and opens new avenues for research into the biotechnological applications of the natural compounds they produce.

Reference:
Rodríguez-Márquez, J., Ortega, M. J., Úbeda, B., & Bartual, A. (2025). Darkness modulates polyunsaturated aldehyde production in two coastal diatoms. Marine Environmental Research, 212, 107550. https://doi.org/10.1016/j.marenvres.2025.107550