Tiny Warning Signs: Why Smaller Algae Mean Bigger Blooms

Harmful algal blooms (HABs) pose a significant threat to marine ecosystems worldwide. To better understand these events, scientists investigated Noctiluca scintillans, a globally prevalent dinoflagellate—a type of single-celled marine plankton—that frequently causes such blooms. By manipulating laboratory conditions, including temperature and food supply, the team analysed how environmental factors impact the organism's behaviour.

The study revealed a distinct inverse relationship: the faster the population grows, the smaller the individual cells become. The researchers observed that binary cell division, which primarily occurs when the environment shifts from dark to light, leads to a significant reduction in cell diameter. Optimal proliferation took place between 20–25°C, where rapid exponential growth coincided with the smallest mean cell sizes. In contrast, cells in a dormant or stationary phase remained much larger. These findings suggest that monitoring the shrinking size of these cells could act as a reliable biomarker, helping conservationists predict the onset of destructive blooms with greater accuracy.