Georg Martin, head of the marine biology department at the Estonian Marine Institute, said the report rated nearly 57 percent of Estonia's official bathing sites as having excellent water quality, while only three were classified as poor.

"You can't really expect conditions to be equally good everywhere all the time," Martin told ERR.

He said comparisons between countries should also take into account how water samples are collected. The EU Bathing Water Directive requires at least four samples to be taken each year, but countries that collect more samples get a more accurate picture of water quality.

"If an assessment is based on just four measurements, the role of chance is fairly significant. Weather, recent rainfall, water temperature and even the number of people at the beach can all affect the results," he explained.

Martin said the report does not support the conclusion that swimming in Estonia's coastal waters is more dangerous than elsewhere in Europe. Instead, the comparison is influenced by the fact that Estonia assesses many inland bathing sites.

Bathing water quality is evaluated using two bacterial indicators: Escherichia coli and intestinal enterococci. These bacteria generally die off more quickly in seawater than in freshwater. As a result, countries where most official bathing sites are on the coast often dominate the top of the European rankings. Cyprus, for example, has very few inland bodies of water.

"These broad generalizations shouldn't cause alarm. A great deal depends on which bodies of water are being assessed and how the samples are collected," Martin said.

Common sense to the rescue

In natural bodies of water, water quality depends on constantly changing conditions. Martin said people should also judge the water's condition for themselves before going for a swim.

"If the water doesn't look appealing, it may not be a good idea to jump in or let children swim there," he said.

Aquatic life is most abundant during warm, sunny weather, when both algae and bacteria thrive.

"The more sunlight, warmth and nutrients there are, the more life you'll find in the water," he said.

This year, cyanobacteria, or blue-green algae, appeared in Estonian waters somewhat earlier than usual. Martin said this is not an unusual phenomenon. Cyanobacteria are always present in the water but become visible when conditions favor their growth. Those conditions include warm water, abundant sunshine, nutrients and calm winds.

"What we're seeing is their mass accumulation at the water's surface," he explained.

The current rainy and windier weather may disperse the first bloom, but that does not mean cyanobacteria will not return later this summer.

"If conditions become favorable again, another bloom could develop in a few weeks," he said.

Climate change putting additional pressure on the sea

Climate change is also affecting Estonia's bodies of water. Although winter snow cover has declined, overall precipitation has increased, carrying more nutrients and other land-based runoff into the sea.

Martin said that does not mean changes are happening overnight. He also stressed that the condition of the Baltic Sea has not simply deteriorated in recent years. Investments in wastewater treatment, sewer systems and other environmental protection measures have produced results and several indicators are moving in a positive direction.

"We've invested heavily in the Baltic Sea and the results are clearly visible. Many indicators are actually showing an improving trend," he said.

Martin said people can generally continue to swim at Estonia's official bathing sites without concern. Regular water quality monitoring is intended to ensure that the public is quickly informed if any problems arise.

"If something is wrong, people are notified and told not to come. In general, we have plenty of water that's suitable for swimming," he said.

Martin said the European rankings should not be taken as evidence that Estonia's bathing water is of poor quality. Instead, people should pay attention to official warnings and exercise the usual caution when swimming in natural bodies of water.

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