The news and social media has been buzzing with speculation and theories about the algal (or algae) bloom that has formed in Fethiye Bay in recent weeks.

Fethiye Times has taken a closer look at algal blooms and what causes them and pulled together an update on the bloom in Fethiye from official statements and news articles.

What is an algal bloom?

An algal bloom is a rapid increase in the population of algae in an aquatic system and may occur in freshwater as well as marine environments.

They’re natural occurrences triggered by increased water temperature and sunlight that provide perfect growing conditions for the algae.

Many scientific organisations, such as the National Oceanic and Atmospheric Administration, are now looking more closely at the types of human activity that has contributed to the significant increase in recent algae blooms, worldwide.

Rain washes the fertilisers into water systems where they feed different species of algae. Waste water from leeching septic systems and municipal sewage plants also release excess nutrients into waterways that can stimulate algal growth.

Scientists with the international environmental organization, Sea Web, suspect climate change also may be playing a role in algal blooms.

Every year in May, June, and July an algal bloom turns Turkey’s Salt Lake in central Anatolia red.

Are algal blooms harmful?

Not all algal blooms are harmful, some can actually be beneficial. Phytoplankton are found at the base of the marine food chain therefore all other life in the ocean relies on phytoplankton. 

Less than one percent of algal blooms actually produce toxins. Harmful algal blooms are blooms of species of algae that can have negative impacts on humans, marine and freshwater environments, and coastal economies. 

Environmental Problems

A bloom does not have to produce toxins in order to be harmful to the environment. 

Excessive growth of algae can block sunlight and stunt the growth of other plants, which may provide important habitats for aquatic animals. Algae also can collect in the gills of fish and other animals and choke off their breathing.

When significant algal blooms die and decompose, they can deplete most of the available oxygen within an area or aquatic system making it uninhabitable for other forms of life.

Dead zones

Less oxygen dissolved in the water is often referred to as a “dead zone” because most marine life either dies, or, if they are mobile such as fish, leave the area. Habitats that would normally be teeming with life become, essentially, biological deserts. 

Hypoxic zones can occur naturally, but scientists are concerned about the areas created or enhanced by human activity. There are many physical, chemical, and biological factors that combine to create dead zones, but nutrient pollution is the primary cause of those zones created by humans.

Excess nutrients that run off land or are piped as wastewater into rivers and coasts can stimulate an overgrowth of algae, which then sinks and decomposes in the water. The decomposition process consumes oxygen and depletes the supply available to healthy marine life. 

Fethiye’s algal bloom

Extensive research is being carried out to understand the reason for the algal bloom that has turned an area of Fethiye Bay an unusual shade of green.

The bloom is concentrated in the shallower area of the bay and there is a clear demarcation line where it mainly ends. There are still a few patches as you approach the harbour mouth.

Algal bloom in Fethiye
You can clearly see the line in this image taken on 30 July 2019.
Algal bloom in Fethiye
You can just see the last of the bloom as you approach the harbour mouth. 30 July 2019.

Once you get out of the harbour, the sea is crystal clear and a perfect blue.

Algal bloom in Fethiye
Beyond the green the sea is perfectly clear and as blue as ever. 30 July 2019.

What’s the official stance?

In an interview with Beşkaza (Fethiye) TV, Muğla Metropolitan Municipality Mayor Osman Gürün stated that one of the contributory factors is agricultural chemicals and fertilizers that reach the rivers and flow into the sea causing pollution.

He went on to suggest that the *wastewater treatment plant in Fethiye has sufficient capacity, a claim that was challenged by Muğla Environment and Urbanism Manager Ömür Özdil after an investigation and inspection of the plant was carried out.

*Wastewater treatment is a process used to remove contaminants from wastewater or sewage and convert it into an effluent that can be returned to the water cycle with minimum impact on the environment, or directly reused.

In a statement to Anadolu Agency, Özdil pointed out that the wastewater treatment plant is working over capacity.

Algal bloom in Fethiye
Fethiye wastewater treatment plant is working over capacity.

“In 2103, 23 thousand 500 cubic meters of wastewater and sewage were processed”, Özdil said, “However, as of today (31 July 2019), it is working with a capacity of 33 thousand cubic meters.”

Özdil expressed that there is detergent-like household waste in the wastewaters that are not treated sufficiently and this has raised the nitrogen and phosphate ratio in the sea to very high levels. This situation, along with the high temperatures, causes pollution and colour changes in marine environments.

An inspection of the wastewater treatment plant in 2017 found that it was exceeding capacity however, the required investment has not been made. The results of the recent investigation will be reported back to the Ministry of Environment and Urbanism as there is no way to improve the situation without investment.

Muğla Agriculture and Forestry Director Şakir Fırat Erkal said that the color change and pollution in the bay does not stem from the use of pesticides.

The use of pesticide for crops leads to serious environmental pollution, therefore, it is essential to monitor water samples for pesticide residues.

The water from the rivers that feed the Gulf, including Fethiye Bay, is tested every month by Muğla according to the strict guidelines issued by the Ministry. The results from the analysis of samples taken from 39 above ground water sources and 31 underground water sources indicate there is no pesticide pollution in the Gulf.

Is the bloom harmful to humans?

There have been no official reports that the algal bloom in Fethiye is harmful to humans.

Is there a swimming ban?

Last week there was a report that if the sea quality at Calış Beach, Küçük Samanlık and Letoonia Bay continued to deteriorate, the Ministry of Health would consider a swimming ban in these areas. To date, there has been no further update on the situation.

Algal bloom in Fethiye
Çalış from the sea on 30 July 2019.

Sources: Wikipedia/Popular Science/şkaza TV/


  1. If the nitrogen and phosphate are at high levels and the treatment plant is at capacity then this is clearly a problem for the waters environment. This is fact.

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