Why have phillophora fields in the northwestern Black Sea declined since the 1960s?

The extensive fields of Phyllophora—a type of red algae—in the northwestern Black Sea have declined significantly since the 1960s primarily due to the deterioration of water quality.1

This degradation is largely attributed to cultural eutrophication, a process driven by human activities that introduce excess nutrients, such as nitrogen and phosphorus, into the marine ecosystem. These nutrients often enter the sea via runoff from agricultural areas, sewage, and industrial sources. The resulting nutrient enrichment stimulates excessive growth of phytoplankton and algae, which can create murky conditions that limit light penetration and lead to hypoxia—a state of critically low oxygen levels in the water—thereby harming native benthic vegetation like Phyllophora.231