Lake Ichkeul, which has a unique ecosystem in northern Tunisia, and one of the most important wetlands in the region, is under pressure due to human activities and climatic changes, but measures to mitigate these effects are still possible in light of a new scientific study recently released.

The study was prepared by an international team of researchers under the supervision of the National Institute for Marine Science and Technology in Tunisia as part of an international research project to protect the lake.

Fresh lake, salty winter, summer

Wetlands are important ecosystems with abundant habitats and high productivity that play a distinctive and unique role on a global scale, particularly in relation to climate regulation, biodiversity and food security.

These systems are experiencing a reduction in their area and a deterioration in their environmental condition in semi-arid regions, especially in North Africa, due to human and climatic pressures.

Lake Ichkeul is no exception to this rule, although it is considered one of the most important wetlands in the Mediterranean region and an important wintering site for migratory birds between Africa and Europe.

Lake Ichkeul receives fresh water from the valleys in winter and salt water from Lake Bizerte in summer (Nature)

The lake is characterized by a unique hydrological performance, which is reflected in a seasonal reversal of water exchange with the neighboring Lake Bizerte, which in turn is connected to the Mediterranean Sea, so it is fresh in winter and salty in summer.

The lake receives fresh water from rain and from the valleys that pour into it during the winter, and in the summer, salty water flows into it from the neighboring Lake Bizerte through the “Tinga” channel linking them as a result of the decline in fresh water quantities, says Dr. Laila Al-Basti, professor of marine environment and water resources at Tokyo University of Science and Marine Technology (Tokyo University of Marine Science and Technology), in an interview with Al Jazeera Net via social media.

Thanks to its high environmental value and its unique hydrological performance, Lake Ichkeul and its surroundings, according to the authors of the study, are among the few sites listed since the 1970s under 3 international conventions at the same time: the Convention on Biosphere Reserves, the World Heritage Convention, and the Convention on Wetlands with International importance "Ramsar", in addition to being certified as a national park since 1980.

In the opinion of Dr. Al-Basti, "The decline in the quantities of water flowing from the valleys as a result of the construction of dams, drought, and the significant and tangible rise in temperatures in the Mediterranean basin, as a hot spot for climate change in the past years, has led to an imbalance in the vital balance of the lake."

The study showed that the increase in salinity in the lake is associated with a disruption of the nitrogen cycle in it (National Institute of Oceanography in Tunisia)

Model used for the first time

In the new study, recently published on the "Nature Scientific Reports" website, the researchers applied a numerical model used for the first time in the southern Mediterranean to assess the performance of the lake in order to enhance its water management.

The model is based on “calculating the difference between the quantities of materials entering and leaving the lake to estimate the balance at the water and nutrients balance in the lake, in addition to evaluating seasonal changes to the availability of nutrients using field data,” according to Dr. Al Jazeera Net over the phone.

To ensure the accuracy of the results, long-term data on water variables in the lake were entered, such as rainfall amounts, temperatures and salinity, and the quantities of water flowing into and out of the lake.

Bedjawi, the lead author of the scientific paper, explains the biological balance within the lake's water, saying that "the food web within Lake Ichkeul consists of nutrients, phytoplankton, the nitrogen cycle and the phosphorous cycle, and the disruption of the balance of these cycles leads to what is called nutritional enrichment."

This process is manifested in an increase in nutrients rich in compounds containing nitrogen and phosphorous, which leads to suffocation of the system and a lack of oxygen.

The lack of water flowing from the valleys led to the imbalance of the lake's vitality (National Institute of Marine Science and Technology in Tunisia)

The role of the model, according to Dr. Bedjaoui, is "to determine the balance of the nitrogen and phosphorous cycles or not, while measuring the ratios of nitrogen and phosphorous - which are nutrients for marine plankton - in the system."

High salinity and nitrogen emission

The results of the study showed that the salinity rate in some areas of the lake reached about 40 grams per liter during summer and 30 grams per liter in winter, compared to about 5 grams per liter a few decades ago in the rainy season.

This rise "can result in changes in the vital system of the lake, and it also has effects on living organisms within it, such as herbs, algae and fish," says Bedjawi.

The model used revealed an imbalance in the nitrogen and phosphorous cycles inside the lake, which led to the emission of quantities of nitrogen into the air, which indicates the presence of pollution in the lake and that marine plankton is exposed to the effects of human activity and climate changes.

Nitrogen is also emitted in part in the form of nitrous oxide (two nitrogen atoms with one oxygen atom), a greenhouse gas 300 times more potent than carbon dioxide.

Dr. Laila Al-Basti, a participant in the study, confirms that the phenomenon of emission of this compound has also been observed in many global lakes and wet areas that are subject to similar pressures due to human activities and climatic changes.

The model used could be an effective tool in the future for the management of water in the lake (Institut National de la Marinerciennes Tunis)

Possible solutions - according to the Tunisian researcher - are to "develop a national strategy for the management and protection of wetlands, which includes water management and the reduction of chemical and organic pollution within the framework of the national plan to adapt to climate changes, and rely on sustainable management and the use of nature in addressing the environmental challenges of the lake."

Dr. Bashir Al-Bjawi concludes that the model used can be an effective tool in the future in managing water and monitoring changes that occur on the lake and the future impacts of each project that will be established in the lake or its surroundings.