A newly formed lagoon under eutrophication on the coast of Kumlubent-Gelibolu, Çanakkale Strait (Dardanelles), Sea of Marmara

Lagoons are semi-enclosed and dynamic water bodies that are highly vulnerable to coastal dynamics and environmental stressors associated with anthropogenic activities and climate change. We investigated a pristine lagoon, hereafter referred to as Kumlubent Lagoon, located on the coast of Gelibolu in the Çanakkale Strait in the Sea of Marmara. The evolution of coastal morphology and Kumlubent Lagoon’s formation was investigated by using satellite images collected between 2006 and 2020. In addition, water samples were collected from the lagoon and the shore on April 15 and 16, 2022 for nutrient (NO3, NO2, NH4, PO4, and Si), chlorophyll-a (chl-a) and total organic carbon (TOC) analyses in order to determine the trophic status of the lagoon. Our results showed that the nearshore deposition of coastal sediments gradually formed a sand barrier that isolated the lagoon from the sea in the year 2013. The nutrient analyses showed a clear indication of eutrophication of the lagoon. Accordingly, 29.784 µm/L of NH4, 1.168 µm/L of PO4, 34.15 (±1.54) µg/L of chl-a and 40.50 mg/L of TOC were measured in the water samples from the Kumlubent Lagoon. Our study suggests that the deposition of longshore drifted sediments in a southwesterly direction along the Çanakkale Strait plays a dramatic role in the development of coastal morphology in the Gelibolu-Kumlubent region. The rapid eutrophication of the Kumlubent Lagoon may be related to the high nutrient input from agricultural activities in the region.