Standing watch over Hong Kong’s coral reefs

Why we exist

Hong Kong has 84 species of reef-building coral — more diversity than the Caribbean — and the reefs they form are the core engine of local marine biodiversity. But the bleaching threat is real and growing: a significant bleaching event hit Hong Kong in 2017, and the fourth global mass-bleaching event reached local corals again in 2024.

Marine heatwaves strike on a daily scale, yet the Hong Kong Observatory publishes its public sea-surface-temperature products monthly, and the AFCD coral survey runs only once a year — the existing monitoring cadence cannot catch acute heat stress between surveys. ReefBeacon exists to close that gap: a year-round, daily-updated early-warning loop that runs without manual intervention.

What we monitor

• All nine monitored marine protected areas: the eight marine parks — Hoi Ha Wan, Yan Chau Tong, Tung Ping Chau, Sha Chau & Lung Kwu Chau, The Brothers, Southwest Lantau, South Lantau and North Lantau — plus the Cape D’Aguilar Marine Reserve.
• Daily heat-stress readings: SST, HotSpot and DHW (°C-weeks) from the NOAA Coral Reef Watch 5-km satellite products.
• A two-tier risk grading: DHW > 4 is a heat-stress watch and DHW > 8 is a bleaching risk. The thresholds follow internationally agreed conventions and are applied strictly by deterministic code — never overridden by hand.

How the system works

The daily loop (year-round):

• Ingest: read the daily-updated NOAA CRW SST / HotSpot / DHW products and cross-check them item by item against the NOAA portal.
• Grade: deterministic code applies the DHW thresholds to grade each park’s heat stress.
• Orchestrate: AI (Gemini) orchestrates the pipeline and writes the natural-language narrative — it never performs the arithmetic.
• Deliver: a threshold breach produces a structured alert that reaches coordinators by email and in-app notification within 30 minutes, with delivery receipts and an audit log.

Deterministic first, AI-assisted

Every number and threshold decision is made by deterministic code; the large language model never touches arithmetic. AI only orchestrates the pipeline and generates narrative text.

Every alert is bound to a raw-data snapshot reference and a model/threshold version, so any conclusion can be traced back to the NOAA data and the rule that produced it. When the AI service is unavailable, the system degrades gracefully to deterministic/template paths — the alerting pipeline never stops.

The annual offline loop

• Survey-photo grading: annual AFCD underwater survey photos are graded for bleaching (mild / moderate / severe); every grading carries a confidence score, and low-confidence results are flagged for human review.
• Event library and historical Q&A: gradings feed a bleaching-event library; retrieval-augmented answers must carry traceable citations, and when history is insufficient the system says so honestly rather than fabricating.
• 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 built and run independently on the public data sources below; it is not an official product of NOAA, the AFCD, or any other agency. Copyright in each data source remains with its originating agency:

• NOAA Coral Reef Watch: daily-updated SST / HotSpot / DHW satellite products (public data, ingested via ERDDAP).
• AFCD annual coral survey: a long-term baseline of 80+ sites since 1997 (calibration and attribution reference).
• Marine-park boundaries: official polygons; the Cape D’Aguilar Marine Reserve currently uses an approximate placeholder boundary, honestly labelled in the interface.
• EPD marine water quality and other local open data: auxiliary variables.

Capability boundary (stated honestly)

• The system provides heatwave early warning, not real-time bleaching confirmation — field confirmation still depends on the annual survey.
• It does not predict when the next bleaching event will occur, nor does it measure pixel-level live-coral cover.
• Satellite-derived sea temperatures can deviate from near-shore reality; when data is delayed, the system labels it “using previous-day cache” rather than substituting silently.

Who it serves

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

Contact us

ReefBeacon currently operates through institutional collaboration. For conservation coordination, research collaboration, or data-licensing matters, please reach us via your organisation’s liaison channel for this system; feedback on site content can be relayed through the console team after signing in.