Citizen divers help build SZ's first coastal coral spawning database

As Shenzhen advances its goals of building a global ocean city and strengthening marine ecological protection, a growing team of volunteer divers is playing an important role in marine conservation by monitoring coral spawning along the city’s coastline.

Since 2021, Shenzhen has adopted a collaborative monitoring model combining scientific research with public participation. Trained volunteer divers — including instructors, designers and office workers — assist researchers in documenting coral spawning, a key indicator of reef health that has historically lacked long-term observation data.

A volunteer observes coral spawning during a night dive. Photos by Chen Rongbin, Zhang Hanzheng, Zhou Hongsheng

Volunteers tie a temporary buoy in a coral spawning zone to mark their diving positions.

The volunteer team has expanded from seven members to 56 core participants over the past five years. Together, they have completed more than 530 night dives and logged over 1,060 hours of underwater observation, creating Shenzhen’s first coral spawning database in coastal waters. The records now cover the spawning behavior of 12 coral species in local waters.

During the annual spawning season, which lasts more than a month, volunteers conduct repeated night dives carrying heavy equipment and working in low-visibility conditions to collect data.

A volunteer observes corals underwater.

Volunteers exchange ideas.

Analysis of five years of monitoring has produced both encouraging and cautionary findings. Threatened staghorn corals continue to reproduce regularly, and coral coverage has recovered at some sites. At the same time, spawning periods have shifted significantly, with staghorn corals spawning about 40 days later than they did five years ago, a trend scientists associate with rising ocean temperatures.

The monitoring effort has also attracted growing public attention. Live underwater broadcasts, once available only to scientists, have reached a wider audience, with viewership increasing from about 3 million in 2021 to more than 200 million in 2026.

Researchers say the long-term dataset is providing valuable insights into the health of Shenzhen’s coastal ecosystems while helping raise public awareness of marine conservation and the impacts of climate change.

Volunteers check their equipment.

A volunteer catalogs and photographs a wild stony coral for documentation.