The natural phenomenon has caused strangeness and concern among beachgoers. However, there are no health risks, says an expert, and currently the situation is "more or less defused".
Recently some tourists have complained of the Algarve’s beaches being overrun with algae, which was unpleasant to look at, as well as to swim in. While children “thought it was funny because they played with it," adults complained. "Not only is it not pleasant to the eye and touch, but it is unknown what is in the middle of the algae."
At the beginning of the month, the Algarve coastal area, especially the leeward sections of the Algarve coast, was invaded by a large amount of algae, which were of concern to swimmers. "It is not a normal situation, but it happens. For a number of years we have not seen such a large amount though, but it is something that has happened many times throughout recent history," explains Rui Santos, professor at the University of Algarve.
According to the researcher at the Centre for the Sea Sciences (CCMar) at the University of Algarve, green algae (Ulva sp.), which were notably found in the eastern Algarve, are organisms that "thrive inside estuaries when conditions are right". He refers to high nutrient concentrations and optimal light and temperature conditions.
"There are years when they grow up a lot in the Ria, when they grow they sometimes end up being moved and deposited by the currents on the beaches." It happens as much in the Algarve coast as in the south of Spain. "It has everything to do with the nutrient load. The Ria is a receiver for urban effluents, from the nearby waste treatment plants that have high nutrient loads," explains Rui Santos.
In the Albufeira area, for example, the algae were darker, which, according to the researcher, is related to the fact that they come from "rocky areas". Like those in the Ria, they develop when there is a high concentration of the correct nutrients.
The water temperature, which has been colder than usual this month, may also help explain the phenomenon. An intense wind throughout many days earlier this month may have caused the deeper waters to surface near the shore. And these waters are "colder and have more nutrients, which is conducive to algae development."
It is difficult to predict how things are going, but, according to Rui Santos, the expected temperature rise these days "may be beneficial in not encouraging algae growth", as the correct conditions for algae development will be lessened.
Elidérico Viegas, president of the Association of Algarve Hotels and Tourism Enterprises (AHETA), said that the situation at this point is "more or less sorted". "Algae cause strangeness and concern amongst tourists, but we can confirm that it does not cause harm to health to them," said the representative, noting that health authorities confirmed that these organisms pose no risk to public health.
From a tourism point of view, despite being a cause for complaint, algae development "does not have much negative impact on the region's image. They do not create widespread discontent or panic.” concluded Viegas.
In addition to the impact from an aesthetic point of view, Rui Santos states that "when they settle in the sand, the algae rots and, when decomposing, they smell bad because they release hydrogen gas." If it is in very high quantities, this accumulation can even be toxic. However, says the university lecturer points out it would take an incredibly large deposit of algae cause problems of this kind.
