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Rash, and not the good kind

In recent weeks, an unusual bloom of blue algae has been observed in the waters of the Sea of ​​Galilee, which may harm the health of people who drink them or swim in them. The hot weather we have experienced in recent weeks is one of the causes of its appearance, which raises concerns that the situation will get worse in the future

Dr. Gideon Gal, Angle - Science and Environment News Agency

A satellite image from February 3, 2016 that shows the widespread distribution of the blueberry bloom in the Sea of ​​Galilee. Photo: Dr. Gideon Tibor, Israel
A satellite image from February 3, 2016 that shows the widespread distribution of the blueberry bloom in the Sea of ​​Galilee. Photo: Dr. Gideon Tibor, Hial

February 25, 2016

A satellite image from February 3, 2016 that shows the widespread distribution of the blueberry bloom in the Sea of ​​Galilee. Photo: Dr. Gideon Tibor, Hial

In recent weeks, a brown layer covers large parts of the Sea of ​​Galilee. It is made up of millions of tiny algae called blue-green algae (cyanobacteria), what is special about them is the fact that they have chlorophyll that allows them to use sunlight for the production of sugars for energy and building the body.

From time to time there is an event of algal blooms - they multiply quickly until they cover huge areas. Blooming events of the blue flowers are not rare in the Sea of ​​Galilee since the seventies of the 20th century, but the intensity of the blooms and their frequency have been on a clear upward trend since the nineties.

In recent years, and especially since the beginning of the XNUMXs, these rashes are visible and they become an aesthetic nuisance. A more serious issue is that some of the blue-green species produce toxins that in exceptional cases may harm the health of humans who drink them or swim in them. Particularly large blooms, which fortunately have not yet occurred in the Sea of ​​Galilee, are problematic because it can be difficult to filter the blue-green algae from the water intended for drinking and agriculture, and also because the concentrations of dangerous toxins can be high.

Every year such cases are discovered in different parts of the world. Lake Erie in the state of Ohio in the USA is one example: in the days between August 2 and 4, 2014, half a million residents of the city of Toledo could not use the water in the municipal water supply system due to a toxic algal bloom in the lake, which is a main source of water for the city.

future algae

Bloom events of cyanobacteria, which sometimes appear as a substance that floats on the surface of the water (flood), occur under certain environmental conditions that allow these species to take advantage of the relative advantage they have over other species. The bloom appears once every winter, but there are years when it does not appear at all.


The mucus consists of a large number of blue cells in a very high concentration that appear in the form of colonies. It is formed when there is no wind, which allows the colonies to float on the surface of the water (the concentration of cells under the cocoon is much lower), whereas when the winds blow, the tiny cells cannot fight them, so they mix in the water column and the cocoon is not formed. In this situation, the growth rate of the blue cells is also lower.

In the last few weeks we have witnessed a large bloom of bluebells that started in the first half of January and reached its peak in the middle of February. The formation of the bloom, especially with the intensity we have witnessed in recent weeks, was made possible by a combination of conditions: the water has a high concentration of nutrients (nutrients) which are part of the natural processes occurring in the lake this season, and there was an addition of nutrients from the streams following the rainfall events. On top of that, the weather conditions were good for the algae - sun, heat and the absence of wind are perfect for creating blooms. The concentrations observed in the lake are definitely unusual compared to those observed so far in similar events in the lake, and therefore they require continued monitoring.

The need for spring weather in the middle of winter to create a large bloom indicates a possible connection to the weather changes we have witnessed in recent years. The amount of precipitation and the number of rain events in the north of the country have decreased in recent years, along with the lengthening of the period between rains.

Do these changes indicate the effect of the long-term changes in weather conditions on the Sea of ​​Galilee? And if so, is the current boom a warning of what is expected to happen with increasing frequency in the coming years? We can only give answers to these questions while continuing to follow and monitor in the coming years, but they certainly require thought and finding solutions.

Dr. Gideon Gal is the director of the Kinneret Research Laboratory at the Israel Seas and Lakes Research Institute

4 תגובות

  1. Cyanobacteria are many things, algae is not one of them.
    Although in the past they were called that, by mistake, but it is possible/correct/should refer to them as photosynthetic bacteria.

  2. The increase in the concentration of nutrients is not a "natural process"
    but the result of seepage of fertilizers from agriculture into the water systems,
    Added to this is the result of drying the patient
    that there was a natural filter,
    Everything is made by us...

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