Togs? Check. Fishing rod? Check. Algae bloom? Let’s hope not. Each summer, thousands of Kiwis are drawn to Aotearoa’s beautiful lakes and rivers to swim, play and fish in. Unfortunately, a number of our lakes and rivers are prone to potentially lethal algal blooms, particularly in the warmer months.
Potentially toxic algae (cyanobacteria or blue-green algae) are microscopic organisms living in the water that play a key role in the ecosystem.
Algal blooms happen when there is a rapid increase in the number of algae in the water, usually due to favourable weather conditions.
Exposure to high levels of the toxins produced can make humans and animals sick, sometimes fatally.
Here are some tips to help you tell if a lake or river is safe to swim, fish or play in. But remember – if in doubt, stay out.
1. Jump online
There are several websites you can check that monitor water quality and potentially harmful algal blooms around the country. The Land Air Water Aotearoa website regularly monitors lake, river and beach water quality. Jump online before you hit the water to see where it’s safe to swim, play and fish. The Toi Te Ora Public Health website also monitors algae blooms in the Bay of Plenty area and the Ministry for Primary Industries website has helpful information regarding toxic algal blooms and shellfish.
2. Look out for signs
Local councils and other organisations may post signage around a lake or river warning people of an algae bloom. If you see one, don’t enter the water.
3. Look out for a bad smell
Algae blooms can happen suddenly or unpredictably, so a warning may not be online when you check. If a lake or river has an unpleasant smell, then it’s probably a sign that something isn’t right, and you should stay out of the water.
4. Do a visual check
If the lake or river looks discoloured, has surface scum, green or brown particles suspended in it, or brown-black algal mats attached to streambeds, then don’t enter the water as it could be toxic.
If you think you’ve been exposed to toxic algae and are experiencing symptoms such as nausea, vomiting, diarrhoea, irritation to the skin, nose, mouth and eyes, seek medical attention immediately. If you think your pet has been exposed, take them to the nearest vet immediately.
References
- Lake water quality Land Air Water Aotearoa, 2020
- Health warning and alerts Toi Te Ora Public Health, 2020
- What are toxic algal blooms? Ministry of Primary Industries, NZ, 2020
- Q&A - Bloomin' algae! NIWA, NZ, 2018
- Frequently asked questions Greater Wellington Regional Council, NZ, 2020