Kategorie: News
Death comes from the Baltic Sea
Climate change has a strong impact on the oceans and thus also on European waters such as the Baltic Sea. Fundamental changes in the ecosystem of the Baltic Sea, have far-reaching effects that can even be dangerous for human health. An example of these changes are the so-called cyanobacteria more commonly known as "blue-green algae".
The Baltic Sea ecosystem is located in the mid-latitude temperate climate zone. It borders nine states and the coastline covers about 8,000 kilometers. Due to the small opening to the ocean between Sweden and Denmark, the Baltic Sea is called an inland sea. It was formed by the warming of northern Europe after the last ice age. The glaciers began to melt about 20,000 years ago, causing sea levels to rise.
The special feature of the Baltic Sea ecosystem is the mixture of salt and fresh water. This mixture is called brackish water. Today, the Baltic Sea is the largest brackish water sea on earth. Salty water flows from the North Sea into the Baltic Sea through the narrow sea opening. Due to the elevations on the Baltic Sea floor, also called sea swells, the salty seawater only penetrates very slowly towards the east. Numerous tributaries, such as the Oder River and the regular ice melt in spring, ensure a steady supply of fresh water.
Consequently, the salinity decreases towards the east and north. This leads to a nutrient deficiency of the ecosystem and to difficult living conditions for animals and plants. All marine life in the Baltic Sea ecosystem must adapt to these changing conditions. Some are particularly good at this. For example, mussels and lugworms filter the seawater and excrete excess salt. Other typical Baltic Sea animals are the shore crab, which is a shellfish, the flounder, which is a flatfish, and the grey seal, which is a mammal.
Cyanobacteria, a consequence of climate change
For the proliferation of cyanobacteria, also called cyanophyta or blue-green algae, the sea surface temperature plays a decisive role. Optimal growth conditions are given at 25°C water temperature but even temperatures above 20°C are sufficient for increased growth. An increase in sea surface temperature due to climate change could double the number of cyanobacteria. Just in the last decades the temperature was regularly about 0.4°C above the average.
A mass occurrence of the blue-green algae at the sea surface, as can be increasingly expected in the following decades due to climate change, also amplifies the warming of the sea surface temperature through radiation absorption. The darker algal carpets absorb warming solar radiation more strongly than water.
The increase in sea surface temperature leads to increased algal growth and algal blooms, which amplify the increase in sea surface temperature by absorbing solar radiation.
Why are blue-green algae so dangerous?
Cyanobacteria produce an impressive arsenal of different toxins. Among others, the toxin anatoxin is responsible for most cases of poisoning, especially in pets:
In the healthy body, acetylcholine binds to postsynaptic receptors and causes a conformational change that opens the ion channel. Positive ions subsequently flow into the cell, depolarize it, and can thus trigger an action potential (or muscle contraction).
Anatoxin A binds to the same receptors and causes an irreversible conformational change that permanently opens the channel. After a while, the ion channel becomes desensitized and can no longer allow cations to pass, ultimately blocking signal transduction.
Anatoxin is similar in action to other acetylcholine receptor agonists such as tobacco nicotine.
Another toxin of cyanobacteria is hepatotoxins. They are among the toxins that exert their toxic effects only in the liver, where they cause damage.
The hepatotoxins damage the cell membrane and the endoplasmic reticulum and inhibit protein biosynthesis in the liver; this usually causes vomiting and abdominal pain in affected individuals. At high toxic doses, the hepatotoxins can also be fatal.
Even at low doses, the long-term effects of hepatotoxins can be devastating, as studies have shown that ingesting these cyanotoxins over a long period of time greatly increases the risk of developing liver cancer.
If a young child swallows large amounts of the contaminated water, the consequences can be fatal. For pets, however, the risk is particularly high: if dogs lick the blue-green algae out of their fur or eat the dangerous algae, they can die from it.
There is also a health risk for divers, especially if water with high concentrations is swallowed or gets into the respiratory tract.
This is most likely to happen during water sports with intensive water contact, such as diving; but also when water skiing or windsurfing, one should pay special attention to warnings or not go into the water if it is greenish-cloudy, or if a green layer is floating on it.