by InTrieste
The waters near Molo Audace took on an eerie white hue this morning, a result of rare mucilaginous emulsions observed along the coast. This gelatinous phenomenon, which has been documented across the Upper Adriatic Sea, has captured the attention of scientists from the Miramare Marine Bioreserve and other research institutions.
A dense layer of mucilage has emerged near the Gulf of Trieste’s shores in recent days. According to analyses conducted by Arpa FVG and the National Institute of Oceanography and Applied Geophysics (OGS), the presence of the dinoflagellate Gonyaulax fragilis—a common but typically benign microalga—has been significant. This species, while non-toxic to humans, has proliferated to unusual levels.
“The phenomenon is very widespread,” said Maurizio Spoto, head of the Miramare Marine Protected Area. “It involves Grado, Lignano, and there are reports from Slovenia and Croatia as well. It usually lasts a short time and not with this intensity. Probably, it has to do with favorable weather conditions and stratified waters because there is a significant difference between the surface waters and the bottom. The abundant freshwater inputs from recent rains have also probably favored the growth of these polysaccharide aggregates.”
These mucilaginous blooms are often linked to sudden nutrient surges from river runoff, which appear to have been exacerbated by recent heavy rainfall. The influx of freshwater, combined with nutrient overload, has likely triggered the rapid proliferation of these microalgae, resulting in the extensive marine bloom now witnessed.
Captured in vivid video footage, the phenomenon affects not only the surface but also penetrates the water column and blankets the seafloor. Such a comprehensive spread of microalgae raises significant concerns for marine ecology and local ecosystems, which are highly sensitive to environmental disturbances.
Spoto further explained that such a large presence of mucilage is “an infrequent phenomenon, which in the 80s and 90s had assumed significant proportions for a long time. Now we need to see how long it will last.” Arpa FVG also noted that this species is known for its ability to produce mucus, a completely normal physiological process.
Pelagic mucilaginous aggregates are amorphous clumps of organic and inorganic material that can trap bacteria, phytoplankton cells, zooplankton organisms, inorganic detrital material, “fecal pellets,” and suspended materials. Mucous substances can be secreted by a wide variety of plants, animals, and microbial flora. Further controls will be carried out in the coming days to monitor the phenomenon.
