Fun Fact

Salmon and cod - once abundant in the Baltic Sea - are becoming increasingly rare. These species are on the brink of extinction, not only because of overfishing, but also because their spawning grounds have been reduced. According to scientists, the Baltic is already considered a dead zone in waters more than 80 metres deep, because there is not enough oxygen for living organisms. Climate change is reducing the rate of water renewal, creating serious problems for this semi-enclosed ecosystem. Periodically, oxygenated water from the depths mixes with surface water. This happens, for example, when the cold, salty surface water becomes dense enough to sink to the bottom. In coastal waters, which receive intense organic inputs, if water renewal times are slow, dead zones will increase. Certain so-called ‘closed’ seas, such as the Baltic, can take up to 75 years to see their waters renewed. The oxygen supply is then even more limited.

Call to Action

Exploring the underwater world has become much more popular these days, thanks to travel and the availability of diving and snorkelling equipment. However, just like other ecosystems, the underwater environment also suffers from the disturbance caused by such tourism. When you dive, whatever the depth, remember: we're just visiting! Don't take any shells, sand, animals or plants with you that could provide food or shelter for local species. Many shells are home to hermit crabs, for example, but sometimes also octopuses! These can grab two empty shells and lock themselves inside to protect themselves from predators, including sharks of all sizes.

Riddle

Which aquatic animal is also an artist and can draw underwater?

A) the eel, using its tail as a paintbrush

B) the octopus, thanks to its ink jets

C) balloon fish, to attract females

D) the shrimp, very precise thanks to its small legs