Michelle's Oyster Weather Indicators
Early warning for harmful algal blooms & red tides in South African shellfish waters — from satellite chlorophyll & sea-temperature data.
Keep an eye on the water
Chlorophyll slightly elevated. Keep an eye on the trend. 1 site showing rising algae.
🗺 Coastline at a glance
🎯 Where to source today
✅ Your usual — Saldanha Bay — is good to source today.
- 1⭐ Saldanha BayWest CoastOrder anytime
- 2KnysnaGarden RouteOrder anytime
- 3Algoa Bay (Gqeberha)Eastern CapeOrder anytime
- 4St Helena BayWest CoastOrder anytime
Latest cloud-free chlorophyll pass: 28 Oct · Sea temp, waves, tide, wind & rain are live
Read this first.The algae reading comes from satellites that can't see through cloud, so it's the freshest clear pass — often a few days to a week or two old (worse in winter), never guaranteed “today.” That makes this a trend & early-warning tool. Each site shows its pass date and greys out when stale. For same-day confirmation before harvesting, the OCIMS red-tide tool is the authoritative check.
Saldanha Bay
West Coast
⭐ Michelle's main sourceSouth Africa's main oyster & mussel farming bay.
Bloom risk stays low across the forecast window.
- Algae now: Low and stable.
- Benguela wind: Upwelling-favourable wind — cold, nutrient-rich water at the surface.
- Wind outlook: Southerly / mixing winds ahead.
- Sea state: Big waves will mix the surface.
A transparent blend of algae trend + wind + sea temperature — an estimate, not a lab result.
🛰 True-colour satellite view
NASA GIBS (VIIRS true colour) for the latest pass. Look for brown/red discolouration; cloud may hide the bay.
Southerly winds mixing the water — bloom risk easing.
St Helena Bay
West Coast
Classic Benguela red-tide zone — frequent blooms & rock-lobster walkouts.
A bloom could develop in the next few days — worth watching closely.
- Algae now: Low but rising.
- Benguela wind: Upwelling-favourable wind — cold, nutrient-rich water at the surface.
- Wind outlook: Southerly / mixing winds ahead.
- Sea temperature: Warming ~1.0°C over the window (stratifies).
A transparent blend of algae trend + wind + sea temperature — an estimate, not a lab result.
Most likely a Mixed diatoms bloom — usually not a toxin risk, but watch the oxygen if biomass is high.
Indicative prior from season + conditions + site history — not a species ID. Confirm with DFFE.
🛰 True-colour satellite view
NASA GIBS (VIIRS true colour) for the latest pass. Look for brown/red discolouration; cloud may hide the bay.
Southerly winds mixing the water — bloom risk easing.
Knysna
Garden Route
Home of the famous Knysna oyster.
Bloom risk stays low across the forecast window.
- Algae now: Low and stable.
- Wind outlook: Southerly / mixing winds ahead.
A transparent blend of algae trend + wind + sea temperature — an estimate, not a lab result.
🛰 True-colour satellite view
NASA GIBS (VIIRS true colour) for the latest pass. Look for brown/red discolouration; cloud may hide the bay.
No strong bloom driver in the next few days.
Algoa Bay (Gqeberha)
Eastern Cape
Aquaculture Development Zone — mussels & oysters.
Bloom risk stays low across the forecast window.
- Algae now: Low and stable.
- Wind outlook: Southerly / mixing winds ahead.
- Sea temperature: Warming ~0.5°C over the window (stratifies).
A transparent blend of algae trend + wind + sea temperature — an estimate, not a lab result.
🛰 True-colour satellite view
NASA GIBS (VIIRS true colour) for the latest pass. Look for brown/red discolouration; cloud may hide the bay.
No strong bloom driver in the next few days.
📜 Recent alert changes
- 27 OctSt Helena Bay▲ Watchwas Safe · 4.4 mg/m³
- 25 OctAlgoa Bay (Gqeberha)▼ Safewas Warning · 2.8 mg/m³
- 24 OctSt Helena Bay▼ Safewas Warning · 2.4 mg/m³
- 23 OctSt Helena Bay▲ Warningwas Watch · 6.1 mg/m³
- 23 OctSt Helena Bay▼ Watchwas Warning · 7.6 mg/m³
- 23 OctSt Helena Bay▲ Warningwas Watch · 6.6 mg/m³
- 20 OctSt Helena Bay▼ Watchwas Warning · 7.6 mg/m³
- 17 OctSt Helena Bay▲ Warningwas Watch · 6.6 mg/m³
- 17 OctSt Helena Bay▼ Watchwas Warning · 5.0 mg/m³
- 16 OctAlgoa Bay (Gqeberha)▲ Warningwas Safe · 3.3 mg/m³
- 16 OctSt Helena Bay▲ Warningwas Safe · 6.6 mg/m³
- 13 OctAlgoa Bay (Gqeberha)▼ Safewas Watch · 2.7 mg/m³
- 13 OctKnysna▼ Safewas Warning · 2.9 mg/m³
- 13 OctSaldanha Bay▼ Safewas Warning · 2.6 mg/m³
Over a season this shows how often each bay blooms, how long events last, and whether today is normal for the time of year.
📊 Bloom track record
How each bay has behaved since tracking began (05 Jul 2026) — a “bloom episode” is a spell in the Warning band or above.
- Saldanha Bay6 bloom episodes · typically ~3.3 days · longest 13.1d
- St Helena Bay18 bloom episodes · typically ~0.8 days · longest 26.1d
- Knysna6 bloom episodes · typically ~3.8 days · longest 27.4d
- Algoa Bay (Gqeberha)5 bloom episodes · typically ~9 days · longest 21.5d
Built from what the 6-hourly checker actually saw — honest hindsight, not a forecast. Recording official DFFE closures over time would let this measure how many days of early warning the algae signal gives before a bed closes.
🎯 Track record & accuracy
How well the alerts have matched reality — the tool's honesty check. It earns trust by keeping score.
No field observations logged yet. Record what you see at the water (colour, foam, dead fish, taste, any lab result) on the settings page, and this scoreboard fills in — the satellite then calibrates itself to the ground truth.
How to read this
Chlorophyll-a is the amount of algae in the water, measured from space by satellite ocean-colour sensors. When it climbs — and especially when it climbs fast— a phytoplankton bloom is building. Some of those blooms are toxic “red tides” whose biotoxins — the shellfish poisons PSP (paralytic), DSP (diarrhetic) and ASP (amnesic) — build up in oysters, mussels and other filter-feeders, making them unsafe to eat until the toxins clear.
A rapid rise (currently +50% over baseline) bumps the alert up a level even before the water is technically “high” — the goal is to catch a bloom while it's still building. These ranges are adjustable on the settings page.
Beyond the algae — the other warnings
- Harvest verdict — the green/amber/red call at the top of each card, combining algae, rain runoff and water temperature into one plain answer.
- Runoff — heavy rain washes bacteria and freshwater into growing waters; beds often close after big rain even with no red tide.
- Vibrio— warm water (≈18°C+) lets these bacteria build up in raw oysters; when it's high, cook rather than eat raw.
- Upwelling — southerly winds pull up cold, nutrient-rich water; when they relax the sea warms, stratifies and blooms can build.
- Tide & moon — spring tides (near new/full moon) flush growing waters harder than neap tides.
- ◌ Modelled value— NOAA's gap-filled product statistically estimates the algae level under cloud, so it runs near-daily where the real observations lag. It's a model, not a measurement — it bridges the gap on the chart but never sets the alert level.
- Official DFFE status— the shellfish-sanitation classification of each harvesting area (Class A: direct harvesting · B: depuration first · C: relaying). There's no public feed, so it's recorded by hand on the settings page with the date it was last checked.
Before you harvest — check the officials
This dashboard is an early-warning screen, not a food-safety clearance. For South African waters, confirm against the authoritative red-tide & biotoxin monitoring: