Sea mucilage is an increasingly common phenomenon in the waters of the Mediterranean Sea, raising concern among experts, environmentalists and professionals in the tourism industry. But what exactly is that we’re talking about? Mucilage refers to the formation of gelatinous masses that cover the surface of the sea, causing disruptions for both the marine life inhabiting these environments and the human activities connected to them. In this article we will take a closer look at the mucilage phenomenon, examining what it is made of and why it forms, while exploring the main causes behind its spread. We’ll also analyze its impact on marine ecosystems and local economies, and consider what solutions might help reduce its effects.
What is sea mucilage?
Mucilage is a viscous, gelatinous substance that forms in certain parts of the sea, particularly during the summer months. This phenomenon has become more frequent over the past few decades, raising ecological and economic concerns, especially in countries bordering the Mediterranean.
Mucilage is primarily composed of a mix of organic and inorganic substances produced by marine microorganisms such as bacteria and phytoplankton, which thrive under particularly favorable conditions. This base often includes material from algae and other marine biomass. Its composition can vary depending on the region and the origin of the substances involved, but it typically contains polysaccharides, proteins, and lipids, components that give mucilage its well-known sticky, gelatinous consistency. In fact, it usually appears as a thick, slimy mass, with a color that can range from white to yellowish, sometimes even green or brown, depending on the organisms involved in its formation. It is most commonly found on the sea surface or along coastlines, where it can accumulate into large patches or even form “beaches” of mucus, ranging in size from small clumps to vast areas covering entire stretches of shoreline. This phenomenon is often accompanied by a foul odor caused by the decomposition of organic matter.
Why do mucilage form?
Marine mucilage is the result of a complex mix of environmental and biological factors that create the right conditions for its development. The phenomenon mainly stems from the interaction between marine ecosystems and human activity, but is also influenced by natural dynamics that, when combined, lead to the accumulation of mucilaginous material capable of disrupting marine ecosystems.
Due to global warming sea waters are becoming increasingly warm, creating an ideal environment for the proliferation of marine microorganisms such as algae and bacteria that produce mucilaginous substances. Higher temperatures promote the rapid growth of algae, which in turn contributes to the production of mucilage, accumulating along the coasts and in open waters.
Another key factor in the formation of mucilage is eutrophication, the excessive enrichment of water with nutrients (primarily nitrogen and phosphorus). These nutrients mostly come from agricultural runoff, industrial waste, and sewage discharge, leading to abnormal growth in phytoplankton populations. The overabundance of nutrients stimulates an uncontrolled bloom of plankton, creating the ideal conditions for the release of mucilaginous substances that clump together into gelatinous masses.
In addition, when ocean currents are weak or absent, water becomes stagnant, preventing the natural dispersion of substances and nutrients. In such conditions, mucilage-producing plankton remains concentrated in a specific area, supporting the formation of persisting mucus masses. It’s also worth noting that the introduction of non-native plankton species, or the alteration of native populations due to climate change and pollution, is disrupting the marine ecological balance. Certain species of plankton, particularly those in the dinoflagellate and diatom groups, are especially prone to producing mucilaginous substances, further contributing to the accumulation of these gelatinous formations.
Mucilage effects
Although marine mucilage does not pose a direct threat to humans, it has a significant impact on the marine environment, local economies and fishing activities, contributing to numerous ecological and economic issues.
In terms of the marine environment, mucilage can have devastating effects on aquatic ecosystems. The gelatinous masses that accumulate on the water’s surface and on the seabed can suffocate corals and other forms of marine life, such as certain bivalves, which rely on proper water oxygenation. The mucilage covers the seabed disrupting the normal circulation of water, reducing the amount of oxygen available for marine fauna and compromising aquatic plants’ ability to carry out photosynthesis. If persistent, this phenomenon can lead to a significant decline in marine biodiversity, disrupt ecological balances and threaten native species.
In fishing, mucilage can clog fishing nets, trapping catches or making it difficult to retrieve them. Fishing gear, such as nets and holding tanks, can be damaged by the sticky nature of mucilage, which easily adheres to surfaces. Additionally, the buildup of mucilage on fishing gear can affect the quality of the catch, making it harder for fishermen to harvest healthy, marketable fish. Lastly, mucilage directly impacts local economies, especially in the tourism sector. The unpleasant appearance and smell of mucilage often deter tourists, who may choose to avoid beaches where the phenomenon occurs. This inevitably leads to a decline in tourist numbers and, consequently, a loss of revenue for local businesses.
How to reduce this phenomenon
To tackle and reduce the occurrence of marine mucilage, a multi-level approach involving local, national, and global strategies is required. One of the most effective solutions to limit the spread of mucilage is reducing pollution, especially through an improved management of agricultural and industrial discharges. The excessive release of nutrients such as nitrogen and phosphorus into coastal waters (from fertilizers, pesticides, and industrial runoff) is a key driver of eutrophication, which promotes the uncontrolled growth of algae and microorganisms responsible for mucilage formation. Implementing sustainable waste management policies, improving water treatment systems, and promoting eco-friendly farming practices can significantly reduce pollutant loads in marine environments and limit the conditions that lead to mucilage outbreaks.
Monitoring environmental conditions and the chemical composition of seawater can help predict mucilage proliferation periods. Tracking water temperature, nutrient concentrations, and shifts in plankton populations allows for early identification of vulnerable areas and helps prevent the problem before it escalates.
During periods of high proliferation, the use of pumps and specialized machinery can help collect floating mucilage masses, preventing them from accumulating along the coastlines and on beaches. This type of intervention is particularly useful to limitate the inconvenience to tourism and local businesses . While it doesn’t address the root causes of the phenomenon, it does offer an immediate solution to contain the issue and reduce its impact.
Each of us, in our own way, can contribute to reduce the impact of mucilage and preserve the health of the sea. For example, avoiding the excessive use of fertilizers and chemicals in agricultural and household activities helps limit the surplus of nutrients that fuels the spread of these gelatinous aggregates. Even reducing plastic consumption and properly disposing of waste helps prevent pollutants from entering the water and worsening the situation. Remember: even the smallest actions, when multiplied on a large scale, can have a meaningful impact in fighting the spread of mucilage and protecting our seas.
