Constance Lake holds the title of the clearest lake in the world

(Patria) - Lake Constance, or Blue Lake, within Nelson Lakes National Park on New Zealand's South Island is a popular tourist attraction among hikers, especially in the last decade since its photos went viral on social media.

This glacial lake, surrounded by mountains and beautiful nature, is characterized by its unusually blue water, writes Punkufer.

A decade ago, scientists confirmed that the lake has exceptional optical clarity - with visibility up to 80 meters deep, and it is considered the visually clearest freshwater source they had recorded to date.

The title of the clearest lake in the world has doubled the number of visitors in a relatively short time and has caused fear among the local population in New Zealand that it will threaten its purity.

They most fear the spread of the microscopic alga lindavia, which creates slime in the water and makes it cloudy.

The aforementioned alga is already present in the New Zealand lakes Rotoiti, Rotoroa, and Tennyson, and there is a great danger of it spreading to this lake.

This is not as difficult as you might think. It is enough for just one drop of water containing this invasive microscopic alga - from hiking boots or a water bottle - to enter the lake and endanger its ecosystem.

For the Māori tribe Ngāti Apa, who originally discovered the lake and named it Rotomairewhenua - meaning lake of peaceful lands - it has an important cultural and spiritual component - they consider it a sacred place that helps the souls of the deceased cross to the other side.

For this reason, entering the water is forbidden. Swimming, wetting a towel to cool off on a warm summer day, or dipping a GoPro into its depths to capture an attractive underwater photo is prohibited.

Entering the water is also forbidden to prevent the spread of the invasive alga. To further protect against this possibility, the New Zealand Department of Conservation, in cooperation with the Ngāti Apa community, has set up cleaning stations near the lake where lindavia is present.

Educational signs have also been erected, requiring hikers to clean their boots and equipment before heading to Rotomairewhenua.