Volcanic ash acts as a natural fertilizer for the ocean by providing essential minerals like iron and phosphorus.

Volcanic ash is a potent source of bioavailable nutrients, particularly iron, which is a limiting factor for biological productivity in many parts of the global ocean. When ash particles settle on the ocean surface, they undergo a process called leaching. This releases trace metals and macronutrients into the water column within hours of contact. Research published in the journal 'Nature' has documented how large-scale eruptions, such as the 1991 eruption of Mount Pinatubo, triggered massive phytoplankton blooms in the North Pacific.Phytoplankton are microscopic algae that perform photosynthesis, and their growth is often restricted by a lack of iron in 'High-Nitrate, Low-Chlorophyll' (HNLC) regions. A study by the GEOMAR Helmholtz Centre for Ocean Research Kiel found that even a thin layer of ash can increase primary production by up to 40 percent in these areas. This sudden influx of nutrients stimulates the entire food chain, as zooplankton consume the algae, followed by larger predators like fish and cetaceans.Beyond immediate fertilization, volcanic activity plays a critical role in the long-term carbon cycle. By stimulating phytoplankton growth, volcanoes indirectly help remove carbon dioxide from the atmosphere through the biological pump. As these organisms die, they sink to the deep ocean floor and sequester carbon for centuries. This geological and biological synergy is a key reason why volcanic archipelagos like the Galápagos Islands are among the most biodiverse marine environments on Earth.