The appearance of large concentrations of algae on the Algarve coast is an increasingly frequent phenomenon.

“Researchers have identified three distinct areas of algae accumulations on the Algarve coast and warned that this observation could indicate an imbalance in marine ecosystems”, revealed the University of Algarve (UAlg).

In a press release, the researchers admit that “more data is needed to validate the observations” but underline that “the results obtained so far have already made it possible to understand these phenomena better and to investigate potential uses and ways of valuing these algae”.

The appearance of large concentrations of algae on the Algarve coast is an increasingly frequent phenomenon, motivated, in most cases, by invasive species introduced, namely, through ships that move them on their hulls, without affecting the quality of the water.

For the third consecutive year, researchers from the Centre for Marine Sciences (CCMAR) at the UAlg have called on citizens to collaborate in identifying significant accumulations of algae in the sea or on the beaches of the Portuguese coast, including in the Azores and Madeira archipelagos.

Analysis of the records sent in the framework of the “Algas na Praia” (Algae on the Beach) programme, carried out by marine biologist Rui Santos, a researcher at CCMAR, allowed to “identify” three distinct zones of accumulations of macroalgae on the Algarve coast.

According to the statement, on the rocky coasts of the western Algarve, the accumulations were caused by invasive brown algae originating in the seas of Japan and Korea, whose scientific name is Rugulopteryx okamurae, and “seem to be increasing in extent”.

On the beaches of the central Algarve, between Albufeira and Faro, the invasive red algae Asparagopsis armata, native to the waters of Australia and New Zealand, was responsible for accumulations recorded in 2021 and 2022.

Finally, on the sandy coast of Sotavento (eastern Algarve), the green algae Ulva sp., native to Portuguese waters, was mainly responsible for the significant accumulations observed in 2021. However, in 2022 there were few accumulations of these algae, which may be due to different environmental conditions.

According to the researchers quoted in the statement, “although nutrients are generally the main cause of excessive algae growth, the results obtained so far do not show a significant correlation between the concentration of nutrients in the water and the occurrence of these accumulations”.

On the other hand, “a significant relationship was observed with other environmental parameters, namely temperature and wind”, reads the note.

According to the technicians, the accumulations of the species Asparagopsis armata, on the beaches of Quarteira and Faro, and Ulva spp., in the Sotavento, are related to the north and northwest winds, while the accumulations of Rugulopterix okamurae, in the Barlavento, are associated with a higher water temperature.

The researchers conclude that “data from more years will be needed to validate these observations”.

Regarding the impact on biodiversity and community structure, the “Algas na Praia” project did not assess the impact of significant developments of algae species but “made it possible to identify that there are three species that appear in large quantities on beaches throughout the Algarve “.

So far, the researchers explain, “the results suggest that the increase in sea temperature may favour the large development and accumulation of the exotic brown algae Rugulopterix okamurae. While the wind from the north quadrant may be a key factor for developing species native to the green algae Ulva spp. and the exotic red algae Asparagopsis armata”.

The scientists say it will be necessary to investigate in greater detail “the importance of these and other factors, such as currents, to develop an early detection system of large accumulations of algae on the beaches”. Such a system would enable the implementation of mitigation and adaptation strategies, such as harvesting biomass and economically valuing it”.

“Research into potential uses and ways of valuing these algae can turn this problem into an opportunity likely to generate wealth”, says Dina Simes, professor at the University of Algarve and researcher at CCMAR.

Holidaymakers interested in contributing to studying these algae can fill out a short survey on the “Algas na Praia” platform at https://www.ualg.pt/algas-na-praia.

Since its launch in July 2021, many citizens and beach professionals have participated in the project. One hundred sixty-seven registrations were submitted in 2021 and 161 in 2022.