Mrs. Sippi’s SmarterScience site

What's the Black Sea's problem?

For starters, there is too much food in the water (too many nutrients; this is called eutrophication). As a result, there is often too much algal growth and then less and less oxygen in the water.

Would you like to swim in this green pea soup on the left? It's what some of the Black Sea's beaches look like. (Cladophora)

The Black Sea is large and it exchanges very little water with the Mediterranean. (Its salinity is less than 20 per mil., a lot less than for seawater, which indicates that it gets a lot of fresh water.)

Other coastal seas - like the North Sea - are constantly flushed. The Black Sea is not flushed. As a result, it contains very little oxygen while pollutants accumulate. It is virtually stagnant (which means that the little oxygen that is present in the upper water layers stays there). A healthy sea needs oxygen, not just for the animals, but also to break down dead plants and dead animals.

Secondly, there are many living things in the water that do not belong there. An example is a certain kind of jellyfish (Mnemiopsis leidyi) from North America.

This type of jellyfish ended up in the Black Sea by mistake. It was carried there by ships and released from the ships' bilge waters.

These jellyfish ate all the zooplankton in the Black Sea. Zooplankton is what deep-sea fish eat. The jelly fish also ate the eggs and larvae of those fish.

So the local fish stocks collapsed. The catch declined from over 700,000 in the past to less than 100,000 tonnes per year. The jellyfish kept spreading and spreading. Eventually, it also reached the Caspian Sea, through the Lenin Channel, which connects the rivers Volga and Don.

Thirdly, there are many pollutants in the water - from untreated discharge (sewage). Proper treatment of waste water and sewage would not only remove toxic substances but also organic matter and some or most nutrients.

Fourthly, many oil tankers and other ships travel in the Black Sea. That means there is a large oil spill risk. In November 2007, a large oil spill in the Black Sea caused many birds and fishes to die. Oil is transported all over the world, so here is a very clear link to the rest of the world.

Fifth, there has been chronic overfishing. The famous sturgeon that produces caviar for you is having a tough time, but that is not the only fish that is in trouble.

(Jason Kottke took the photograph on the left and holds the copyright to it. Please do not re-use without his permission.)

Sixth, there is too much litter on many beaches.

Too much, too little, too different. It's all a question of balance.

If you need something to compare it with, think of upset stomachs. Think of kids eating nothing but cake and candy, and lots of it. When we humans don't get the right nutrients, and eat too many things that are bad for us, our bodies are no longer in balance and the biochemistry in our bodies starts to go haywire. We become ill.

Ecosystems can lose their balance too. Often, this is a natural process and the ecosystem will evolve into something else. Change is a natural thing. But when humans mistreat ecosystems, things can go really wrong and life maye even disappear from them.

The Black Sea is a bit like a kid with a permanently upset stomach. The balance is gone.

Balance is a keyword in nature. Nature is a complicated system of all sorts of feedback mechanisms, a delicate equilibrium between balances. Whenever one of these balances changes, nature adjusts for it, through the system of feedback loops. It creates a new equilibrium.

This new equilibrium may not be what we like, even though we may not notice the subtle changes at first.

But when they proceed, we tend to perceive the changes as a bad thing: when fishes start dying and disappear, for instance, and other plants and critters take over.

And not in the least, we mind because it often affects the economy! Tourism may suffer and so may the fishing industry and other forms of trade that depend on the local ecosystem (but may not be aware of it).

Take a coral reef as an example. If we add more food to it (nutrients) - for instance by dumping untreated sewage - the reef's ecosystem starts to change. The coral dies and the colorful fishes disappear. A new type of ecosystem develops. But we like coral reefs and colorful fishes! We don't want them to disappear and we don't want the associated tourism to suffer either.

Something similar is going on in the Black Sea.