Azov Sea salinity reaches historic levels as freshwater inflows decline

13:05

By: Azzat Manal

Azov Sea salinity reaches historic levels as freshwater inflows decline

The salinity of the Azov Sea has reached a historic high, according to data from the Southern Scientific Center of the Russian Academy of Sciences, highlighting significant changes in the marine environment over the past two decades.

Scientists reported that the average salinity of the sea rose by around 60% between 2007 and 2026, increasing from approximately 10–11 parts per thousand to 16 parts per thousand. The latest figure brings the Azov Sea considerably closer to the Black Sea, whose average salinity is estimated at around 18–19 parts per thousand.

Researchers said the current period of increasing salinity is unusual compared with the roughly 150 years of observations available for the region. The trend has been particularly pronounced in Taganrog Bay, where salinity has more than doubled over the same period.

The changes are largely associated with declining freshwater inflows, particularly from the Don River basin, where lower levels of rainfall in recent years have reduced the amount of freshwater reaching the sea. Scientists have estimated that salinity has been increasing by about 0.25 parts per thousand annually since the trend accelerated in 2007–2008.

The environmental consequences are already becoming apparent. The Azov Sea was historically known for its relatively low salinity and high biological productivity, supporting a wide range of fish species and important commercial fisheries. Increasing salinity is now contributing to changes in the composition of marine life, with anchovy, goby and kilka becoming increasingly prominent in catches.

The diversity of fish species has also declined sharply. According to the scientific center, more than 140 fish species belonging to 47 families and 20 orders had historically been recorded in the Azov Sea basin. By 2026, that number had fallen to around 80 species, including six species considered relatively recent additions to the ecosystem.

Around 40 species are currently subject to commercial fishing, while only about 10 are considered particularly important to the region’s fisheries. Scientists attribute the decline in biodiversity to several factors, including rising salinity, overfishing and water pollution linked to human activity.

The changing conditions are also affecting other marine organisms. Researchers have previously pointed to an increase in jellyfish populations as one of the visible signs associated with the transformation of the sea’s ecological balance.

The Azov Sea is the world’s shallowest sea, with a maximum depth of only about 13.5 meters. Its shallow waters and dependence on freshwater inflows make it particularly sensitive to changes in precipitation, river discharge and other environmental pressures.

Scientists say the continuing rise in salinity could have lasting consequences for the region’s ecosystem and fisheries. The latest findings underline the extent to which changes in freshwater availability can reshape the biological characteristics of shallow marine environments.