The facility I work in is located a few hundred meters from the coast shown in the photograph: the National Institute of Oceanography and Experimental Geophysics. Every day I watch the sea, blue, transparent, murky, calm, rippled, stormy. Trieste is the city of the Bora, a strong wind with gusts that reach 100 km/h, when the sea becomes turbulent. The earth’s climate varies due to the pressures of human activities, which generate climate change. Plentiful spring rainfall brings nutrients, and invisible diatoms flourish in the Gulf of Trieste. This spring the water turned red due to the abundant presence of Noctiluca scintillans, a large heterotrophic dinophyte (1-2 mm) that “sparkles” (scintillans) at night due to the presence of a protein system that gives it bioluminescence. N. scintillans causes extensive flowering, from the China Sea to the Arabian Sea to the coasts of the Atlantic, proliferating and spreading into many seas around the world. Lacking in chloroplasts, it feeds on nanoplankton, which is toxic for fish because of the high concentrations of ammonia contained in its vacuole. After this red tide came an explosion of Rhizostoma pulmo, an innocuous jellyfish that covered the waters of the gulf for over a month. What is the cause of coloured water and swarms of jellyfish? What is happening to the marine ecosystem? Are these natural phenomena, or are these anomalies influenced by the pressure of human activities? Temperature is the first factor that interacts on the development of microalgae, and the warming of the water facilitates their flowering. Plankton is endowed with resilience, changing the specific composition that will lead to changes in the functioning of ecosystems. This fosters the spread of red tides and explosions of jellyfish, as happened this year. If nature can respond to climate changes, selecting the species best suited to survive in new ecosystems, we too should take action. People with awareness can change their lifestyle to reduce the presence of CO₂, and they can support policies that formulate ecosustainable solutions to guarantee the wellbeing of everyone, above all in the countries most impacted by climate modifications. In the era of the Covid pandemic, of continuing migrations of millions of people by land and by sea, the political choices of citizens are a priority to form governments that implement actions for the benefit of the world’s weakest populations.

A lead researcher at the National Institute of Oceanography and Experimental Geophysics (Trieste), Marina Cabrini studies biodiversity and ecology of microalgae and their impact in relation to climate change. She is a professor of terrestrial, marine and landscape ecology. She has overseen the environmental impact assessment of coastal areas, and conducted studies for environmental landscape protection, as well as participating as an evaluator of projects regarding aspects of ecology and governance of coastlines and lagoon-estuarine environments.