Coastal authorities in southern Spain are preparing for continued large-scale arrivals of invasive Japanese brown algae (Rugulopteryx okamurae) along the Andalucía coastline in 2026. Aggregated regional reporting indicates that around 40 municipalities may be affected to varying degrees, as marine currents continue to transport significant volumes of algae onto beaches.

The species, commonly known as Japanese brown algae or Asian invasive seaweed, has spread rapidly since its arrival in waters linked to the Strait of Gibraltar. It is now established along much of the southern Spanish coast, creating persistent challenges for local authorities responsible for beach maintenance and environmental management.

Tens of thousands of tonnes expected annually

Regional estimates suggest that approximately 56,500 tonnes of invasive algae could be deposited on Andalucía’s beaches during 2026. The figure is based on accumulated removal data and observed seasonal patterns rather than a fixed scientific forecast.

The distribution is uneven, with the highest concentrations typically recorded in Cádiz and Málaga provinces, particularly in coastal areas closest to the Strait of Gibraltar. Smaller but persistent accumulations are also recorded in Huelva, Granada and Almería.

Authorities describe the situation as continuous rather than seasonal, as the algae is repeatedly reintroduced by marine currents rather than arriving in single isolated events.

Around 40 municipalities affected across the coastline

Aggregated regional monitoring indicates that around 40 municipalities across Andalucía are affected to varying degrees. These include both large urban coastal centres and smaller towns dependent on seasonal tourism.

In Cádiz province, municipalities such as Algeciras, Tarifa, La Línea de la Concepción, Barbate, Conil de la Frontera, Bolonia, Caños de Meca and Rota have reported repeated beach accumulations. These areas are among the most exposed due to their proximity to the Strait of Gibraltar.. 

In Málaga province, the impact is concentrated along the western Costa del Sol corridor. The most consistently affected areas include Manilva, Casares Costa, Estepona, Marbella, Mijas Costa and Fuengirola. Occasional lighter deposits have also been recorded further east in Torremolinos and parts of the western Málaga city coastline have also experienced regular deposits requiring mechanical removal  depending on seasonal current conditions. 

Additional lower-intensity impacts have been recorded along parts of Granada, Almería and Huelva.

How the algae affects beaches

The arrival of Japanese brown algae can significantly alter beach conditions. When large volumes accumulate on shorelines, the algae forms thick mats that cover sand surfaces and shoreline edges.

Key impacts include:

• Reduced usable beach area during peak accumulation periods 
• Changes to the appearance and texture of sand, as algae mixes with sediment 
• Odour issues as decomposing algae is exposed to heat and sunlight 
• Increased labour requirements for mechanical and manual beach cleaning 
• Temporary disruption to beach facilities in heavily affected zones 

While not structurally damaging to sand itself, repeated deposition can require frequent intervention to maintain safe and accessible beach environments.

What it means for beach goers

For visitors, the algae does not pose a direct health risk, but it can affect the overall beach experience.

In heavily affected areas, beachgoers may encounter:

• Sections of shoreline covered in decomposing seaweed 
• Reduced swimming and sunbathing space during peak accumulation 
• Strong organic odours in hot weather conditions 
• Increased presence of cleaning machinery during the day 

In many locations, municipalities prioritise clearing main swimming areas first, meaning conditions can vary significantly along the same stretch of coastline.

Despite these disruptions, beaches generally remain open, with local councils working to maintain accessibility throughout the tourist season.

Ongoing removal operations across Andalucía

Local authorities across Andalucía have implemented continuous removal programmes. These include mechanical beach cleaning, manual collection in environmentally sensitive areas, and transport of collected algae to authorised disposal sites.

In some municipalities, repeated interventions are required during peak accumulation periods. In more exposed locations, cleaning may take place daily in order to maintain beach usability.

The cost of these operations has placed pressure on municipal budgets, particularly in smaller coastal towns with limited seasonal revenue.

Environmental pressures and long-term management

Marine scientists continue to monitor the ecological impact of the Japanese brown algae.

Beyond its presence on beaches, Rugulopteryx okamurae has significant ecological consequences in coastal waters. The algae can form dense mats on the seabed, blocking light from reaching native marine vegetation and reducing the space available for local species to grow. This process can displace native algae and seagrass habitats, leading to reduced biodiversity in affected areas. Over time, the structure of local ecosystems may shift, with fewer native species able to compete for space and resources.

Marine scientists also note that the algae can alter seabed composition and simplify habitats used by fish and invertebrates. This reduces ecological complexity in nearshore waters and can affect local food chains. Once established, the species is extremely difficult to remove. Authorities and researchers generally agree that eradication is not currently feasible, and management efforts focus on containment and repeated removal rather than elimination.

Outlook for 2026

With continued inflows expected throughout 2026, municipalities across Andalucía’s coastline are likely to remain engaged in ongoing clean-up operations. While severity varies significantly by location, the overall trend indicates sustained pressure on coastal maintenance systems, particularly in the 40 municipalities identified as most affected.