I captured this scene during a night dive. Sea urchins in Japan often spawn in summer. This image shows a male releasing sperm — a breathtaking and mesmerizing sight that I never tire of witnessing. In recent years, rapidly rising seawater temperatures have caused sea urchin populations to increase explosively. They consume vast amounts of seaweed, leading to barren “sea deserts.” Without seaweed, shellfish lose their food sources, and fish lose their hiding places, reducing biodiversity. Over the past two decades, various new sea urchin species have settled in Tokyo Bay. The ocean around Tokyo, like the polar regions, is warming quickly and sensitively — transforming the ecosystem before our eyes.