Mysterious ‘Darkwaves’: How They Blanket the Ocean in Darkness for Months!

When you envision the ocean’s depths, you likely picture a scene split in two: dark waters below and sunlit, clear waters above. This sunlight is crucial as it powers everything from tiny plankton to expansive kelp forests, which serve as either sustenance or habitat for creatures in the darker waters below.

However, researchers are now reporting that areas of the ocean which are typically illuminated are experiencing increased periods of darkness.

The scientific community has introduced the term “marine darkwaves” to describe these abrupt and severe reductions in underwater lighting, which can persist from several days to months. While gradual ocean darkening over decades is well documented, darkwaves represent sudden and severe reductions in light caused by various factors including storms, sediment runoff, algal blooms, and human activities like dredging and coastal development.

Similar to how terrestrial plants need sunlight to thrive, marine organisms rely on light for photosynthesis. Without light, photosynthetic processes stop, ecosystems begin to destabilize, and the marine life dependent on these plants starts to decline. Previously, there was no consistent method to track or even recognize these dramatic events, and they weren’t formally named until recently.

To establish a foundational language and understanding for future research, scientists analyzed decades of data from coastal regions in California and New Zealand, complementing this with satellite imagery from New Zealand’s East Cape. Their research, published in Communication to Earth & Environment, uncovered that from 2002 to 2023, as many as 80 marine darkwaves struck just that area, typically lasting one to two weeks, with one event extending over two months.

Many darkwaves were triggered by major storms, such as the one induced by Cyclone Gabrielle in 2023, which led to significant sediment and pollutant discharge into coastal waters. Other causes included deforestation, wildfire residue, and plankton blooms. At their peak, these darkwaves produced some of the dimmest conditions these marine areas faced throughout the year.

While the study didn’t measure the ecological impacts directly, previous research indicates that even short-term losses of light can severely stress seabed vegetation such as kelp and coral. Minor interruptions in light availability can disrupt the natural cycles of various marine species, including fish, sharks, and marine mammals. With climate change expected to intensify, these phenomena may become frequent stressors for coastal marine ecosystems.