Standing watch over coral reefs, every day

Why we exist

Coral reefs support abundant marine life and are closely connected to the livelihoods of coastal communities. The fourth global mass coral bleaching event, announced in 2024, underscored the need to monitor marine heat stress continuously and identify risks early.

Marine heatwaves can form quickly, while periodic coral surveys may not capture changes between surveys. Through year-round monitoring and daily risk updates, ReefBeacon helps conservation teams identify unusual conditions earlier.

What we monitor

• The monitoring network covers 65 coral reef sites across 8 marine regions worldwide. The Hong Kong region also shows 9 marine protected areas as geographic references. Hoi Ha Wan, Yan Chau Tong, and Tung Ping Chau are daily heat stress monitoring sites; the others are shown for their boundaries. Areas such as Cape d’Aguilar, where official boundaries are not currently available, use clearly marked approximate extents.
• Daily heat-stress readings: SST, HotSpot and DHW (°C-weeks) from the NOAA Coral Reef Watch 5-km satellite products.
• Two risk levels: DHW > 4 indicates a “Heat-stress watch,” and DHW > 8 indicates “Bleaching risk.” Every site follows the same scientific standard, and levels are not subject to manual intervention.

Daily monitoring and alerts

Helping conservation teams stay informed about changing risks:

• Track changes: sea temperature and heat stress readings are updated daily, with their sources identified.
• Identify risks: heat stress levels are provided for each site using a consistent standard.
• Understand readings: clear assessment notes help explain the risks without changing the classification.
• Receive notifications: The notification process aims to send an alert within 30 minutes after detecting that a threshold has been exceeded. Actual email sending depends on recipient settings, the delivery service, and network status; sending status is retained for review.

Consistent standards, traceable evidence

Risk levels are determined by consistent DHW thresholds and are not subject to manual intervention. Supplementary assessment notes help explain risks without changing original readings or classifications.

Every alert includes data sources and relevant version records for review and citation. Alerts remain available with monitoring readings and risk levels when supplementary assessment notes are temporarily unavailable.

Surveys and long-term observation

• Survey photo review: assists with assessing bleaching severity (mild / moderate / severe) in authorized underwater survey photos, indicates confidence, and flags low-confidence results for human review.
• Questions about past events: questions are answered using information about bleaching events, with traceable citations. Any lack of historical cases is stated clearly.
• Quarterly trend reports: the previous quarter’s bleaching-trend report is generated automatically, with the data time-window and sources labelled.

Data sources

ReefBeacon is independently built and operated using public or authorized data. It is not an official product of NOAA, the Agriculture, Fisheries and Conservation Department, or any other data source organization. Publicly accessible data is not necessarily in the public domain; use and redistribution must follow each data source’s license and attribution requirements.

• NOAA Coral Reef Watch: daily satellite products for SST / HotSpot / DHW (public data).
• Hong Kong coral survey records: surveys began in 1997, with the Agriculture, Fisheries and Conservation Department participating from 2000. Records from previous years serve as references for local surveys.
• Protected area and reef boundaries: official protected area boundaries or UNEP-WCMC reef boundaries are used. Sites without an official boundary use an approximate area clearly marked “Unofficial boundary.”
• EPD marine water quality and other local open data: auxiliary variables.

Capability boundary (stated honestly)

• This system provides heat stress alerts; it does not confirm bleaching in real time. Confirming whether corals are bleached still requires field surveys, and annual surveys are only one way to do this.
• It does not predict when the next bleaching event will occur, nor does it measure pixel-level live-coral cover.
• Satellite sea temperatures may differ from conditions close to shore; delayed data is clearly marked “using previous day’s data.”
• Daily heat stress monitoring covers all 65 sites. Survey photo review and local supporting information currently focus mainly on the Hong Kong region. Where historical information is limited, this is stated clearly; regional capabilities are not described as complete global coverage.

Who it serves

• Conservation coordinators (AFCD Marine Conservation Division and conservation agencies worldwide): receive heatwave alerts, decide whether to activate contingency plans, plan the annual survey.
• Marine researchers (local universities and global institutes): long-term time-series data for bleaching attribution research.
• Conservation NGOs (Hong Kong and worldwide): data to support public advocacy and environmental education.
• Park managers and regulators: a reference for issuing temporary conservation notices and adjusting park management.

Diverse, open, and answerable to the ocean

• Five-language service — 简体中文, 繁體中文, English, Español and Português (Brasil) — so guardians in different language communities read the same traceable numbers.
• Open and verifiable: threshold rules, grading conventions and capability boundaries are all published, and researchers and conservationists everywhere are welcome to examine, reuse and build on them.
• Coral reefs sustain a quarter of all marine species and the livelihoods, cultures and futures of coastal communities — what we protect is not just data, but the ocean we share.

Operator and contact

ReefBeacon is produced, operated, and maintained by Noviai Limited. For conservation collaboration, research partnerships, data use inquiries, media inquiries, or website feedback, email [email protected].