Fauna and flora of the Baltic Sea

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The fauna and flora of the Baltic Sea is characterized by a relative poverty of species due to the extensive isolation of the Baltic Sea from the North Sea, the low oxygen and salt content and (from a geological point of view) only recently emerged after the last Ice Age.

The Baltic Sea is a 413,000 km² and up to 459 meters deep inland sea in Europe . Although it is the second largest brackish sea on earth, it is extremely species-poor. Reasons include that the water exchange with the North Sea and thus the immigration of animal and plant species is hindered by swellings and that deep parts of the central Baltic Sea are poor in oxygen. Flat regions of the Baltic Sea are subject to strong temperature fluctuations. The Baltic Sea is a sea of ​​immigrant species, there is only one endemic species (the Tang Fucus radicans ) more could not develop during the short existence of the inland sea since the last ice age . The marine immigrants are divided into northern fish and southern fish. The northern fish come from the colder areas of the northern North Sea and the waters between Norway and Iceland. These include cod , whiting , dab and plaice . The southern fish come from the Bay of Biscay and the English Channel . They include garfish , black and sand gobies . Both groups immigrated to the Baltic Sea via the North Sea. In addition, species of fish have migrated from the rivers that flow into the Baltic Sea.

For marine fish and invertebrates , it can be observed that their number of species decreases with decreasing salt content, i.e. from the Belten and Sunden over the southern and central to the northern Baltic Sea. The lower threshold for the occurrence of these species lies at a salinity of about 5 ‰ to 10 ‰. The regions in which the salinity is between 5 ‰ and 8 ‰ have a minimum of species, as the salinity here is too low for marine species, but already too high for freshwater organisms. This border is a little east of the Darßer Schwelle north of Rostock . In brackish water, marine species often form stunted shapes, grow more slowly, stay smaller and have a shorter life expectancy. Fish have a reduced number of vertebrae , shell-forming invertebrates produce thinner shells. In the border region, many species are no longer able to reproduce and the stocks are only maintained by inflowing larvae. The eggs of marine fish often develop pelagic (floating in the water) and need a certain specific weight of the surrounding water to stay in the floating state. As an adaptation to this, the egg diameter of some species increases with decreasing salinity. In the case of the flounder and plaice , whose eggs are normally pelagic, the eggs in the Baltic Sea develop on the seabed, but have thicker skin here. Fish that do not succeed in such an adaptation, such as the anchovy , the mackerel and the horse mackerel, can only be found as random visitors in the western Baltic Sea.

In the deep areas of the western and central Baltic Sea near Bornholm , off Gdańsk and near Gotland , oxygen is almost completely absent. Instead, high concentrations of hydrogen sulfide are present and higher life ( multicellular animals (Metazoa)) is absent. Instead, there is a high concentration of bacteria , archaea and eukaryotic unicellular organisms ( protists ). This is particularly true of the chemocline in the western Baltic Sea.

The Baltic Sea in March 2000, satellite photo from the north
Gray seal
Baltic ringed seal
Common porpoise

Mammals

Porbeagle

Cartilaginous fish

Bony fish

Disturb

Atlantic sturgeon

Herring-like

Carp-like

Bream
Rudd

Salmonids

Ostseeschnäpel

Cod-like

cod

Gobies

Glass goby

Pipefish-like

Large snake needle

Scombriformes

Jackfish

Flatfish

flounder
plaice

Perchy

Perch
Three-spined stickleback
Striped sea wolf

Other perch relatives

Others

Lampreys

Mace sea squirt
  • River lamprey ( Lampetra fluviatilis )
  • Sea lamprey ( Petromyzon marinus )

Sea squirts

Echinoderms

Common starfish

Crustaceans

Brackish barnacles on a sand clam
Ghost crab

Bristle worms

Lugworm

Cordworms

Molluscs

Housing snails

Common periwinkle

Nudibranchs

Soft black star snail

Shellfish

mussels
Carpet clams ( Venerupis pullastra )

Beetle snails

Moss animals

Glass lobed jellyfish

Rib jellyfish

Cnidarians

Sea carnation
Ear jellyfish
A jellyfish Haliclystus octoradiatus (on seagrass ) from below

Sponges

Seaweed

Sea salad
Bladderwrack

211 (181) species of algae have been identified on the German Baltic Sea coast (the poorer species on the eastern coast in brackets). These include 54 (52) types of green algae, 79 (71) types of brown algae and 72 (51) types of red algae. Here is a selection of common types:

Green algae

Brown algae

Red algae

plants

Sea grasses

literature

  • Peter Jonas: Underwater World Baltic Sea. Fish, invertebrates, plants . Jahr-Verlag, Hamburg 1997, ISBN 3-86132-211-0 .
  • Bent J. Muus, Jørgen G. Nielsen: The marine fish of Europe in the North Sea, Baltic Sea and Atlantic. Kosmos, Stuttgart 1999, ISBN 3-440-07804-3 .

Individual evidence

  1. ↑ Ricardo T Pereyra, Lena Bergstrom, Lena Kautsky & Kerstin Johannesson: Rapid speciation in a newly opened postglacial marine environment, the Baltic Sea. BMC Evolutionary Biology, March 31, 2009 doi : 10.1186 / 1471-2148-9-70
  2. ^ Klaus Jürgens: Microbial life in the hostile depths of the Baltic Sea. in Traditio et Innovatio, research magazine of the University of Rostock , 02-08 ISSN  1432-1513
  3. ↑ Dirk Schories, Uwe Selig, Hendrik Schubert: Species and synonym list of the German marine macroalgae based on historical and recent records (list of species and synomes of macroalgae in German coastal waters - evaluation of historical and recent findings) . In: Rostock. Marine biologist Contribution , Issue 21, pp. 10-11, 2009. PDF file

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