Nelson Marlborough Health's Public Health Service issues warnings when beaches and rivers are contaminated by faecal micro-organisms and toxic algae.

From November to March, councils test water at popular swimming spots. If the test results exceed the maximum level allowed, they notify the Public Health Service.

If recreational water is contaminated by human or animal faeces, the presence of disease-causing micro-organisms (bacteria, viruses and protozoa) is likely. Freshwater (rivers) may also contain harmful toxic algae (cyanobacteria).

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