Odra

How is it that a golden alga has developed in the Oder River?

Prymnesium parvum, the so-called golden algae, belongs to the brackish species. The first identification of this alga occurred in brackish waters from a pond in the UK in 1937. Subsequent studies have confirmed that the species also has a predilection for saline, brackish and fresh waters. In the Oder River, the invasive algae thrive in water whose salinity (determined by electrolytic conductivity) is maintained at around 800 µS/cm and above. The data provided by the literature shows that the possibility of mass multiplication occurs at electrolytic conductivity levels even above 1500 µS/cm. However, salinity is not the main factor determining the growth of Prymnesium parvum. The golden alga is a microscopic alga that occurs in clusters and is a mixotrophic organism, capable of feeding either autotrophically or heterotrophically, depending on environmental conditions.

It moves to and thrives in areas with favourable conditions for growth, including suitable temperature and low water flow and a constant supply of nutrients in the form of nutrients, especially nitrogen and phosphorus, from, among other things, municipal wastewater. The golden alga releases the toxin, among other things, due to a sudden change in the physicochemical parameters of the water. Despite decades of worldwide research, scientists have yet to fully understand the production mechanism of toxin release.

Why does golden alga choose oxbow lakes if it prefers saline waters?

The algae prefer saline waters, but the reservoir type determines their occurrence and intense multiplication. As I mentioned earlier, it is not a picky organism in terms of salinity, and when "selecting" an environment, it is also guided by other criteria necessary for its occurrence and intensive development. In oxbow lakes, it finds such conditions: low water flow, suitable temperature and abundant essential nutrients.

What are the characteristics of the Oder algae – the Oder strain of golden algae – compared to those found worldwide?

Prymnesium parvum is an invasive species found in various regions of the world. Its occurrence is determined by climatic and direct environmental issues related to water chemistry. The Oder strain differs from other strains of its species primarily in terms of its genetics and the type of ichthyotoxins produced, called prymnesins: the algae found in the Oder produces group B prymnesins, while other strains also secrete group A and C toxins. The differences in the types of toxins produced are also determined by the degree and type of pollution in the environment.

Can we rid the Oder River of golden algae completely?

Unfortunately, this is not possible – the golden alga, under conditions unfavourable to its development, is able to produce survival forms (spore cells) and continue to exist in this specific form of hibernation for the duration of conditions unfavourable to its development. When these conditions change to optimal for its development, Prymnesium parvum can again multiply in quantities characteristic of blooms.

Can the golden algae survive without water? How long do the algae persist on objects that have been in contact with an infected tank?

The previously mentioned spore cells allow golden alga to survive without water, but in low humidity conditions, for up to several months. It can also persist on objects for a similar period. This is possible because, in spore form, the alga has very few requirements for survival. It is imperative that infected tanks, such as nets or boats, are disinfected before being used again to get rid of this persistent algae from objects that have come into contact with them.

Interview: The Editorial Team of the portal gov.pl/odra