the baltic sea is full of life!

For most divers, the Baltic Sea is probably best known for it's many well preserved wrecks. From a biological point of view, it is also an interesting story. It is a very young sea, which has undergone several changes during the past 10.000 years. When the inland ice gradually melted, a freshwater lake was formed. Then, approximately 9.900 years ago, a connection opened right across Sweden (where the great lakes are situated today), allowing oceanic salt water to enter, forming the "Yoldia Sea". During this period, an ecosystem formed that was probably similar to that of the Barents Sea today.

Some of the species that entered at that time were trapped and has managed to survive until today, e.g. the Four Horn Sculpin (Triglopsis quadricornis) and the Ringed Seal (Phoca hispida). Later, as the land masses gradually elevated, the Baltic Sea was once more isolated from the ocean, forming the "Ancylus Lake", which gradually turned into a freshwater lake again. Approximately 6.500 years ago, salt water entered again, this time from the south via the Belts of Denmark, turning the lake into the "Littorina Sea", with a salt content somewhat higher than today. Finally, the present Baltic Sea formed, with a little bit poorer draining than 6.500 years ago, and consequently more brackish. As a consequence of this fluctuation of salt content, and the fact that it is a very young sea, there has been no opportunity for new and specially adapted species to evolve. Thus, life in the Baltic Sea is a mix of salt water species which can handle reduced salt concentrations and freshwater species which can stand a little bit of salt.

Right outside where I live, in the proper Baltic Sea, the number of macroscopic species is limited to less than 80. This is part of the reason why the wrecks are so well preserved; no shipworms (the "ship worm" is actually a clam, Teredo navalis) are present to destroy the wooden constructions. The bulk of fish (80-90%) consists of three species, Atlantic Cod (Gadus Morhua), European Sprat (Sprattus sprattus) and Atlantic Herring (Clupea harengus). What is more worrying is that today, approximately 1/3 of the bottoms of the proper Baltic Sea is dead, due to over-feeding and other human pollution. Over-fishing of cod is another problem of great concern.

Not much use in diving here, then, from the biological point of view? Well, I cannot quite agree. There are still some quite exciting encounters to make. I would like to illustrate that by this little portfolio of pictures from a single dive trip. This was a land-based dive from the east coast of the island of Öland, just south of the small village Byrum. The whole island of Öland is a vast Ordovician sedimentary limestone platform, and this dive site shows beautiful proof of this, with plateaus at several levels, making it excellent for a shallow dive in the vegetation zone close to the shore. Furthermore, there is a small wreck some 100 meters from the shore, providing an additional target for the dive. We went there on a sunny morning by mid June 2003. By then, the water temperature in the shallow waters had already reached +15 degrees C. We made two dives, each time starting by a visit to the wreck at a max depth of 11 meters, and then returning for a thorough scan of the plateaus. The first dive lasted for a bit more than an hour, the second one roughly 45 minutes. I carried my Olympus C-4040Z in a Light&Motion Tetra Housing, with a Wetmate macro lensand two Sea&Sea YS-90DX Duo strobes. No focus light was necessary, as it was bright sunlight.

My two buddies, Alexander Aisenberg and Ulf Lorentzon, were not carrying any photo equipment, and were polite enough to give me plenty of time and space to perform my act. They kept in the background, and assisted by looking for objects. (As some of you know, it is sometimes tough to find buddies that can handle UW photographers, providing company and additional safety without disturbing or getting impatient. Alex and Ulf were however great in this respect!)

Well, that was a long introduction. Now for the pictures that resulted from these two dives.