Marine darkwaves describe sudden underwater blackouts in coastal seas.

Researchers introduced a framework called 'marine darkwaves' to identify short, intense periods of underwater darkness that in some cases nearly eliminate light reaching the seafloor, and they found events lasting days to months in California and New Zealand data.

Scientists have introduced the term "marine darkwaves" to describe brief but intense reductions in underwater light that can reach the seafloor. The research team developed a standardized framework to detect and compare these events across regions. The work draws on long-term measurements and satellite estimates from coastal California and New Zealand. The authors present the framework as a new monitoring tool alongside existing systems for marine heatwaves and other ocean stressors. Key findings: - The framework and concept were reported in Communications Earth & Environment and are intended to make extreme losses of seafloor light measurable and comparable worldwide. - The study used long-term records including 16 years of measurements from the Santa Barbara Coastal LTER, 10 years of observations in Hauraki Gulf/Tīkapa Moana and the Firth of Thames, and 21 years of satellite-derived seafloor light estimates along New Zealand's East Cape. - Marine darkwaves in these records ranged from a few days to more than two months, and in some cases light reaching the seabed was reported as almost completely eliminated. - The researchers identified many East Cape events since 2002, some linked with strong storms, and the team plans to expand work in California to investigate how sedimentation and turbidity affect kelp forests. Summary: The findings indicate that sudden, short-term losses of underwater light can occur across coastal regions and have the potential to affect photosynthetic organisms such as kelp, seagrasses, and corals, as well as animal behavior. The marine darkwave framework adds a new way to track this form of stress, and the research team plans further study of sedimentation and turbidity impacts in California.