Gulf of Finland in record-poor shape; bottom is dead and oxygen low in many areas
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The bottom of the Gulf of Finland is in worse shape new than it has been anytime this decade. The area of water that is depleted of oxygen is exceptionally wide this summer, according to the findings of two marine research vessels Muikku of the Finnish Environmental Administration, and Aranda of the Marine Research Institute.
The two ships found record-low oxygen levels in deeper waters. Large amounts of hydrogen sulphide was found throughout the gulf, and the phosphorous content has risen in most areas.
The deteriorating oxygen situation and the high phosphorous level in the Gulf of Finland are attributed to increased saline stratification since the beginning of the year.
The layered effect prevents the oxygen-poor bottom water from mixing with the surface water, which has a higher oxygen content. When oxygen is depleted, phosphorous that has accumulated in the sediment on the bottom starts to dissolve into the water.
"This so-called internal load can only be influenced by reducing the external load of the Gulf of Finland", notes limnologist Seppo Knuutila of the Finnish Environment Institute, who was the head of the Muikku voyage.
The condition of the bottom sediments and that of the fauna in it is worse than it has ever been since the Muikku was first launched, in 1999.
Animals living at the bottom could only be found in nine locations out of 47 observation sites in the Gulf of Finland; only four of them had an abundance and diversity of animal life.
The Archipelago Sea was in considerably better shape than the Gulf of Finland. Even in the worst-hit areas of the Archipelago Sea, the phosphorous content at the bottom was significantly lower than in the Gulf of Finland. The oxygen condition and the state of bottom fauna were both good this summer.
There has been less toxic blue-green algae this year than in previous summers. There were hardly any surface blooms in August, and there was less algae in eastern parts of the Gulf of Finland than in recent years.
The two ships found record-low oxygen levels in deeper waters. Large amounts of hydrogen sulphide was found throughout the gulf, and the phosphorous content has risen in most areas.
The deteriorating oxygen situation and the high phosphorous level in the Gulf of Finland are attributed to increased saline stratification since the beginning of the year.
The layered effect prevents the oxygen-poor bottom water from mixing with the surface water, which has a higher oxygen content. When oxygen is depleted, phosphorous that has accumulated in the sediment on the bottom starts to dissolve into the water.
"This so-called internal load can only be influenced by reducing the external load of the Gulf of Finland", notes limnologist Seppo Knuutila of the Finnish Environment Institute, who was the head of the Muikku voyage.
The condition of the bottom sediments and that of the fauna in it is worse than it has ever been since the Muikku was first launched, in 1999.
Animals living at the bottom could only be found in nine locations out of 47 observation sites in the Gulf of Finland; only four of them had an abundance and diversity of animal life.
The Archipelago Sea was in considerably better shape than the Gulf of Finland. Even in the worst-hit areas of the Archipelago Sea, the phosphorous content at the bottom was significantly lower than in the Gulf of Finland. The oxygen condition and the state of bottom fauna were both good this summer.
There has been less toxic blue-green algae this year than in previous summers. There were hardly any surface blooms in August, and there was less algae in eastern parts of the Gulf of Finland than in recent years.
Helsingin Sanomat