The Great Purifier

“Water that is too pure has no fish” goes the saying. That may be true in some contexts but not at Lake Ohrid, where the exceptional clearness of waters is one reason for both its jaw-dropping diversity of life and the IG-perfect sexiness of its appearance. How does it keep in such great shape? A low nutrient diet filtered by the ultimate detox gadget: wetlands!

To many people, saying that Ohrid is a low-nutrient lake sounds like a bad thing. However, the flora and fauna here have adapted to specific local conditions over millions of years. For them, too many nutrients entering the water is a life-threatening situation.

This is because more nutrients lead to accelerated plant and algae growth. When the plants and algae die, they are broken down by micro-organisms, a process which consumes the dissolved oxygen in the water, leaving little for fish and other animals to breathe. In extreme cases, it can even cause a Dead Zone.

Since Lake Ohrid species have evolved to match high-oxygen waters, they may be particularly sensitive to even small changes in dissolved oxygen. Meanwhile, accelerated algal growth also blocks sunlight and causes water clarity to be lost. Associated phenomena such as algal blooms can be a hazard to human health too, meaning stinky no-swim zones, which are not the best image for tourism…

Luckily, Lake Ohrid has sophisticated natural protection systems to keep nutrients low. One of largest and most important of these is Studenchishte Marsh, which traps and absorbs nutrients such as phosphates and nitrates, preventing them washing in to the lake.

If Studenchishte Marsh is ever lost, the number of nutrients entering Lake Ohrid will slowly rise, as will the amount of algae. Major damage to ecosystems, water quality and water clarity will gradually follow, which will not only be desperately and irreversibly sad, but also extremely expensive, because the costs of dealing with the problem are typically high.

That’s why Ohrid SOS isn’t going to let it happen…

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