Warmer seas bring algal bloom explosion

Toxic algal blooms are flourishing across Europe's coastal waters, fuelled by this summer's hot weather and fertilized by human-induced pollution - a phenomenon that is likely to become a common sight in a warmer Europe, the European Environment Agency has warned.

While algae form an essential part of the marine eco-system as a nutrient for zooplankton, and populations usually increase in the summer months, the EEA said this season’s blooms were “excessive” and warned against health effects on holidaymakers.

Algae feed off nitrogen and phosphorous in sea water, and thrive when concentrations of these chemicals rise in water polluted by agricultural run-off, fish farming or wastewater.

Phosphorous, present in a number of common household products such as detergents and soap, and finds its way into the sea through wastewater. Some species, such as blue-green algae popular in Scandinavia, extract their nitrogen from the air and only need water high in phosphorous for their populations to explode.

The last three decades have seen rising amounts of algal blooms worldwide as concentrations of both chemicals in coastal waters increased. Rising seawater temperatures are now acting as a catalyst and further stimulating the blooms.

Global seawater temperatures increased by around 0.6 degrees C since the late nineteenth century, according to an EEA report. In Europe, the Mediterranean, Baltic and North seas have warmed by about 0.5 degrees C over the last 15 years.

Other effects on ecosystems include the recent explosion in jellyfish populations that hit European coastal waters at the peak of the holiday season (see related story) and rising populations of other warm-temperate species.

Ingesting algae-infested water can cause poisoning, manifesting itself through nausea, bowel or intestine problems and fever. Although adults are only at serious risk if they swallow substantial amounts of sea water polluted by toxic algae, the EEA warned holidaymakers to take particular care with small children.

Goska Romanowicz

Action inspires action. Stay ahead of the curve with sustainability and energy newsletters from edie