12

March 2026 ESRFnews

I

T MAY look beautiful but it s an environmental

disaster vast turquoise blooms of algae swirling

across the Baltic Sea Captured by the European

Space Agency s Copernicus satellites the image above

shows cyanobacterial blooms that strip oxygen from

the water disrupt food webs and in some cases release

toxins harmful to fish wildlife and people

The culprit is phosphorus Much of it entered the Baltic

decades ago washed from fertilised fields and discharged

from cities before settling into the seabed Even though

phosphorus inputs have since been reduced the blooms

persist fed not so much by today s fertiliser as by legacy

phosphorus recycled from sediments and stirred back

into the water when conditions permit

The Baltic s stubborn failure to recover shows that

phosphorus cannot be controlled simply by reducing

Runof f phosphorus causes algal blooms the world over .

ESRF studies reveal that chemistry not just quantity is

to blame

The fertiliser

problem