19/05/2026
Blue Green Algae
A gentle reminder β because the weather being grey doesn't mean the risk has gone away. The forecast keeps promising the warm weather will be back, so be vigilant and informed.
Blue-green algae has already been recorded on the River Hamble this year. We're barely into spring, the sun hasn't exactly been 'putting it's hat on', but we had those few days of brilliant sunshine earlier on, that were enough.
If, like me, as a dog owner, you werenβt even aware of this danger, it's worth knowing a bit about it. Despite the name, it's not actually algae β it's a bacteria called cyanobacteria, and it occurs naturally in fresh water. It typically blooms in warmer months when conditions are right: still or slow-moving water, nutrients in the water, and sunlight. Most blooms happen between May and September β but it can appear at other times of year too.
What to look for:
Green or greenish-brown scum on the surface of still or slow-moving water β sometimes described as looking like a thin layer of green paint, or pea soup. It can also appear with a bluish-green tinge. Look out for warning signs posted by local authorities near water β they do put them up, so don't ignore them.
The important bit for dog owners:
Your dog doesn't have to go in the water. The wind can blow blooms to the edges of ponds or lakes β which is exactly where dogs are likely to drink from. It's also worth knowing that not all types of blue-green algae are harmful, but you cannot tell by just looking at it. So to be on the safe side, treat all scum as suspect.
Symptoms to watch for, if your dog has been near affected water: vomiting, diarrhoea, drooling, disorientation, trouble breathing, seizures, and blood in faeces. They can appear within a few minutes or hours of exposure and prompt treatment is critical.
If you're at all concerned β get to the vet, and don't wait.
You can download the Bloomin' Algae app (free) to record any sightings near you and help with monitoring. π