Ensuring good condition of the Baltic Sea waters is the goal of the Marine Waters Protection Program – POWM, updated by PGW Woda Polskie. Biodiversity is one of the features that testify to the state of our sea. On the Biological Diversity Day, we would like to remind you that by protecting the Baltic Sea, we provide the opportunity to develop and maintain species diversity of marine flora and fauna.

The Baltic Sea is one of the shallowest and most polluted seas in the world. The Baltic Sea is surrounded by economically highly developed countries inhabited by nearly 100 million people. The economic and social progress of the last century has had a significant impact on the marine ecosystems of the Baltic region. The inflow of nutrients to the sea basin, overfishing and other forms of our economic activity, together with the observed climate changes, do not remain indifferent to the animals and plants found in the Baltic Sea.

What does Baltic biodiversity look like?

Due to the specificity of our sea, the most abundant species in the Baltic Sea are those with high tolerance to changes in salinity of its waters. Too low salinity makes it impossible for typical marine species to live, therefore in the Baltic Sea we meet much less species than in the neighboring North Sea. This is of course related to the limited possibility of inflow of the highly salty waters of the North Sea and the inflow of large amounts of fresh waters by the extensive network of rivers flowing into the Baltic Sea. Interestingly, some animals also reach much smaller sizes than their northern relatives, the best example of which are marine mollusks, the size of which can be easily verified by comparing the shells of the same species found on the beaches of the Baltic Sea and other seas. A very popular common cockle, whose shells can be found not only on the beach, but also as part of numerous souvenirs, in the Baltic Sea reaches a size of 30 mm, while outside the Baltic Sea – even 50 mm. Another example is the sand-climber, which in the Baltic Sea reaches only 60-80 mm, while in fully salty seas, it grows up to 15 cm!

What floats in the depths of the Baltic Sea? [1]:

Although the gray seal is the most recognizable representative of the Baltic Sea, there are many more organisms inhabiting this reservoir. Many of them are practically imperceptible to the human eye, and it is they that inhabit the Baltic Sea in such great numbers. The following are the groups of organisms inhabiting our sea:

– phytoplankton – microscopic plant organisms (algae) passively floating in the overexposed layer of water. Over 700 species have been found in the phytoplankton of the Baltic Sea – diatoms, cyanobacteria and dinoflagellates dominate.

– phytobenthos – plants growing on the seabed. In the Baltic Sea, sedentary vegetation is composed of green algae (e.g. seaweed, tape), brown algae (e.g. algae), red algae (e.g. rose and fork) and flowering plants (e.g. seagrass).

– zooplankton – animal organisms more or less passively floating in the water. This group includes both single-celled animals and multi-celled organisms with a complex structure: rotifers, crustaceans (e.g. copepods), and jellyfish that grow up to several dozen centimeters in diameter – cyanea and  Aurelia aurita. Moreover, there are numerous fish larvae, polychaetes and molluscs in the zooplankton of the Baltic Sea.

– zoobenthos – animals living on the seabed. The benthic fauna of the Baltic Sea is dominated by representatives of mussels, e.g. mussels, cockles, sand clams, Baltic hornbeam, crustaceans, e.g. barnacles, shrimp, gudgeon, double, shrimp), snails, e.g. aquatic fish, polychaetes e.g. nereid and oligochaetes. The most diverse benthic communities can be found on the rocky bottom.

– nekton – large animals, actively swimming in the water. In the Baltic Sea,  there are26 species of marine fish and several species of freshwater and bi-environmental fish. Four species of marine mammals live here: gray seal, ringed seal, harbor seal and porpoise.

According to the Marine Strategy Framework Directive, biodiversity is one of the 11 features determining the quality of the Baltic waters, defined as the diversity of life forms around the globe on various levels: within species, between species and the diversity of ecosystems. In order to improve or maintain the good condition of the Baltic Sea, every 6 years, each country in the region prepares a set of corrective actions included in the directional document. In Poland’s case, the most important strategic document is the Sea Waters Protection Program [2], the first update of which (aPOWM) is currently being prepared by PGW Woda Polskie.

Save the sea! What actions for biodiversity are included in the Marine Waters Protection Program?

Ensuring a reduction in the inflow of nutrients (nitrogen and phosphorus), causing uncontrolled growth of harmful organisms, e.g. cyanobacteria, and proper biodiversity was one of the key tasks set out in the first Marine Waters Protection Program prepared in 2016. This is still the current goal and many of the eutrophication activities will also be included in the program update. This is a pressure that directly contributes to the health of many species and their habitats in the Baltic Sea. Apart from them, a set of activities dedicated to the improvement of the condition of sea mammals and birds was prepared, e.g. reducing disturbance of seals by humans at their place of breeding, adding the porpoise as an object of protection in the Natura 2000 area – Słupska Bank, active protection of the ringed plover. These are just some of the measures proposed in aPOWM, aimed at improving or maintaining the proper state of biodiversity, as well as the entire trophic chain.

The Baltic Sea is home to many living organisms. Man, as a user of this ecosystem, has a duty not to harm and even help the organisms living in it. Let us preserve the richness of fauna and flora – let us protect the sea together.

[1] https://naszbaltyk.pl/bioroznorodnosc/

[2] The development of the Marine Waters Protection Program is imposed by the Directive of the European Parliament and of the Council of 17 June 2008 establishing the framework for community activities in the field of marine environmental policy (Marine Strategy Framework Directive) and transposing its provisions – the Water Law.