Experts fear more toxic blue-green algae than last year

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The Gulf of Finland and the Archipelago Sea face a considerable risk of large amounts of toxic blue-green algae this summer, according to a forecast by the Finnish Institute of Marine Research and the Finnish Environment Institute.
      More of the algae is expected than last year, but not as much as in some years. In the northern reaches of the Gulf of Bothnia, the risk is quite small.
     
The heaviest blooms of the algae are expected in late July. If the early summer is calm and warm, the growth could begin earlier in July.
      The summer weather will determine whether or not the algae will form rafts on the surface. "We are at the mercy of the weather in this respect. In cold and windy summers, blue-green algae mixes into the surface layers of the water, and visible algae rafts do not form on the surface", says Heikki Pitkänen, a leading researcher of the Finnish Environment Institute.
      In the right weather conditions, rafts of algae can drift toward the shoreline. The forecast mainly applies to the open sea.
     
The reason for the increased risk of blue-green algae is that there has been more phosphorous in the Gulf of Finland this spring than there was last year at the same time.
      "Phosphorous is a difficult nutrient, because in the Baltic Sea, it does not stay in the sediments of the sea bottom very well", Pitkänen explains.
      Storms last autumn and winter mixed up the bottom of much of the Gulf of Finland, which meant that phosphorous released from the bottom layers of the sea mixed with the surface water, providing food for algae.
     
Forecasts for blue-green algae have generally proven to be fairly accurate.
      "In a comparison over ten years, the forecast for the coming summer can be seen as average. The worst summers for algae blooms were 1997, 2002, and 2004", Pitkänen says.


Previously in HS International Edition:
  Blue-green algae affecting some beaches (9.8.2006)

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