Biodiversity in the Baltic Sea

In the spring of 2011, Oceana launched a research expedition in the Baltic Sea. The two-month journey took place aboard the Hanse Explorer, a 48-meter ice class vessel built for long exploration voyages and diving operations.

Oceanographer and executive director of Oceana Europe, Xavier Pastor, led the Baltic Sea expedition. The crew covered more than 7,000 nautical miles and completed more than 130 dives to collect samples and take underwater video and photos. This documentation will help the team prepare proposals for new marine protected areas or the extension of existing ones.

The Hanse Explorer crew used a remotely operated underwater vehicle, or ROV, capable of diving to depths greater than 300 feet (91 meters). The ROV helped the crew document life in the waters off all nine countries bordering the Baltic. 

The Baltic is a brackish sea, a unique combination of freshwater from rivers in the surrounding countries and salt water from the ocean. The low salinity levels are one of the factors that determine which plants and animals can live there. The sea anemone Urticina feline, a member of the Cnidaria Phylum, is shown here.

Acorn barnacles (Balanus crenatus) make a home on the carapace of an edible crab (Cancer pagurus). Much of the Baltic suffers from eutrophication that leads to oxygen depletion. The algae blooms caused by eutrophication can give the water a green sheen.

Dead man’s fingers (Alcyonium digitatum) are soft corals named for their appendage-like appearance when thrown ashore by storms.

Nudibranchs are mollusks that have evolved from shelled ancestors. Like the reddish-orange Coryphella verrucosa shown here, they're often noted for their vibrant colors and striking forms.

The Baltic’s waters are so frigid that the sandy seabed was often frozen during Oceana's 2011 expedition. The divers’ underwater cameras had to be put on automatic settings to take photos, as their fingers were too numb to operate the buttons.

On many of the dives, the team saw little wildlife in the oxygen-depleted areas. But near some marine protected areas, the crew saw an array of marine life, including kelp, starfish, mussels, and sea-snails, like the Liparis liparis shown here.

For centuries, the Baltic Sea has provided European flounder (Platichthys flesus) and other fish for millions of people. Since the early 1980s, the nations surrounding the sea have coordinated their efforts to protect its health through the Helsinki Commission. In addition to being overfished, the Baltic Sea is one of the more polluted bodies of water in the world. You can read about some of the impacts that chemical pollutants have had on European flounder on the IUCN's Red List of Threatened Species website.

The team covered more than 7,000 nautical miles and completed more than 130 dives.