Brown Water and Strange Algae Appear Around Lanzarote
Residents and visitors have been sharing photographs of unusually discoloured water at several locations around Lanzarote in recent days, prompting questions about what is happening beneath the island’s normally clear Atlantic waters.
Reports and photographs have emerged from the natural swimming pools at Punta Mujeres in Haría, the Charco de San Ginés in Arrecife and Playa Bastián in Costa Teguise.
The images show water ranging from murky brown to a more uniform, cloudy appearance. Understandably, many people seeing these photographs are wondering whether they are looking at natural algae, decaying seaweed or evidence of pollution.
While these phenomena can sometimes look remarkably similar, they do not necessarily have the same cause.
So, what do we know about these strange appearances in Lanzarote’s coastal waters, and how frequently do natural algae blooms occur in the Canary Islands?
Punta Mujeres: Brown Water in the Natural Swimming Pools
Photographs shared recently from Punta Mujeres show brownish water around the village’s popular natural swimming pools.
The appearance has prompted questions from residents and visitors who regularly enjoy swimming in this part of northern Lanzarote.
One possible explanation is the accumulation of naturally occurring marine microorganisms, including certain types of microalgae and cyanobacteria. The photographs alone cannot establish precisely what is responsible for the current discolouration.
Punta Mujeres has experienced similar concerns previously. In August 2025, following complaints about unusual water conditions and unpleasant smells, the Ayuntamiento de Haría and the island’s water authorities reported that inspections and analyses had attributed the episode to a natural proliferation of microalgae rather than a sewage discharge.
This demonstrates that natural algae can produce changes in the appearance of the water in this area. It does not, however, prove that every subsequent episode has the same cause.
The Charco de San Ginés: A Recurring Natural Phenomenon?
The photographs from Arrecife’s Charco de San Ginés have attracted particular attention because the lagoon has experienced similar appearances in previous years.
In March 2024, the Ayuntamiento de Arrecife released scientific information explaining the large floating patches that had appeared in the lagoon.
The organism identified was Trichodesmium erythraeum, a marine cyanobacterium commonly found in Canary Islands waters.
Although frequently referred to as a microalga in everyday language, it is technically a cyanobacterium.
According to the scientific information published at the time, the phenomenon had been observed repeatedly at the Charco since June 2022.
This means that the appearance of brown or floating patches in the Charco is not necessarily a new development.
However, the same scientific information also highlighted how the lagoon’s sheltered conditions, changing water circulation, sediment accumulation and human activities can influence the environment.
The important point is that a natural algae bloom and environmental problems can exist in the same location without necessarily being the same issue.
What Exactly Is Trichodesmium?
One of the most interesting explanations for brown or reddish water around the Canary Islands is a naturally occurring marine cyanobacterium called Trichodesmium erythraeum.
It is sometimes known as “marine sawdust” because of the appearance of its floating accumulations.
Unlike large seaweed that can be seen growing on rocks, Trichodesmium consists of microscopic organisms that live in the water.
Under suitable conditions, these organisms can multiply and gather together in large concentrations, creating visible patches on the sea surface.
The colour can vary considerably, ranging from brown and reddish tones to greenish, pinkish or whitish appearances as the colonies develop and break down.
According to information published by the Canary Islands Government and marine researchers, these blooms can form offshore before being carried towards the coast by currents and other ocean movements.
This is one reason why a patch of discoloured water can suddenly appear in a sheltered bay, harbour or natural swimming pool, even when the surrounding sea looks relatively clear.
Why Do Algae Blooms Happen in the Canary Islands?
The Canary Islands provide favourable conditions for several types of naturally occurring marine microorganisms.
Researchers have identified a number of environmental factors that can encourage Trichodesmium to become more abundant.
1. Warmer sea temperatures
Warmer water can encourage the growth of certain marine microorganisms.
Trichodesmium is particularly associated with relatively warm waters, and blooms can become more noticeable during warmer periods.
2. Calima and Saharan dust
Calima brings mineral-rich Saharan dust across the Atlantic.
Some of the iron contained in this dust can provide an important nutrient for Trichodesmium, helping it grow under suitable conditions.
3. Calm weather and reduced wind
When winds are weaker and the sea is relatively calm, floating organisms can become concentrated in particular areas.
This can make a naturally occurring organism much more visible than it would be when dispersed throughout the ocean.
4. Ocean currents and sheltered coastal areas
Currents can transport blooms towards the coast, where they may become trapped in sheltered bays, harbours and natural swimming pools.
The Charco de San Ginés is particularly interesting because its sheltered nature can encourage the accumulation of floating material.
These factors help explain why algae blooms can appear suddenly and why their location and intensity can change considerably.
How Often Does This Happen in Lanzarote?
Natural algae blooms are not an entirely unusual occurrence in the Canary Islands.
The archipelago has experienced notable episodes of marine microorganism proliferation in previous years, including 2004, 2011 and 2017.
More recently, Trichodesmium has been documented in Lanzarote, including the Charco de San Ginés in 2024 and the Los Pocillos area of Puerto del Carmen in April 2024.
However, there is no simple annual timetable for these events.
They depend on a combination of sea temperatures, wind, currents, nutrient availability and other environmental conditions.
Some locations may experience recurring accumulations, while other areas may go for long periods without any visible discolouration.
It is therefore more accurate to describe these events as naturally recurring but irregular, rather than suggesting that they happen at a fixed time every year.
Costa Teguise: A Different Situation at Playa Bastián
The recent situation at Playa Bastián in Costa Teguise requires a slightly different explanation.
On 31 October 2026, the Ayuntamiento de Teguise closed the beach to swimming after a large discoloured patch was detected in the water.
According to reporting by La Voz de Lanzarote, the council said the substance did not appear to originate from the local sewage network and that investigations were continuing.
Two possible explanations were being considered: material originating from a vessel or the presence of dead algae.
At the time of the report, the exact cause had not been established.
This is an important distinction.
Although dead algae can accumulate in coastal waters and create unpleasant appearances or smells, a suspected contamination incident should not automatically be described as a natural algae bloom.
Testing and investigation are needed before the cause can be confirmed.
Is Brown Water Dangerous? Can You Still Swim?
Not every algae bloom is harmful, but that does not mean every discoloured patch of water should be considered safe.
The Canary Islands Government advises that people should avoid swimming in areas affected by visible blooms until appropriate guidance is available.
Certain marine microorganisms can cause skin or eye irritation, particularly when they accumulate in large quantities or begin to break down.
For Trichodesmium erythraeum, researchers have not classified it as one of the toxic species listed by the IOC-UNESCO. Nevertheless, irritation can occur, and avoiding direct contact with visible accumulations is recommended.
For visitors and residents, the safest approach is straightforward:
- Avoid swimming directly through visible brown, green or reddish patches.
- Follow any local swimming restrictions or warning signs.
- Avoid touching or collecting unidentified floating material.
- Check with local authorities if the water has an unusual smell or appearance.
- Remember that clear-looking water is not necessarily proof of good water quality.
If a beach or swimming pool has been closed by authorities, it should remain out of use until it is officially reopened.
What Happens Next?
The recent photographs from Punta Mujeres and the Charco de San Ginés raise understandable questions about the condition of Lanzarote’s coastal waters.
Natural algae blooms are a recognised feature of the marine environment around the Canary Islands, and previous scientific investigations have confirmed that they can produce dramatic changes in the appearance of the water.
At the same time, the recent incident at Playa Bastián demonstrates why it is important not to assume that every brown patch has a natural explanation.
The cause of each incident needs to be assessed individually.
For Lanzarote, where natural swimming pools, sheltered lagoons and clear Atlantic waters are such an important part of island life and tourism, reliable monitoring and clear communication from local authorities remain essential.
