Large‐Scale Pandemic: Ichthyological, Microbiological and Ichthyopathological Symptoms After the Massive Mucilage Aggregate Phenomenon in the Sea of Marmara

ABSTRACT The Sea of Marmara, connecting the Black Sea and the Aegean Sea, experiences a two‐layer current system due to density disparities. Unfortunately, pollution has emerged as a significant problem, resulting in diseases and abnormalities in animals, particularly fish. Monitoring studies have uncovered a significant deterioration in the environmental conditions of the Sea of Marmara. This study presents a multidisciplinary assessment of the Sea of Marmara conducted between August 2021 and August 2022. In this study, the cases that develop after the massive mucilage phenomenon due to plankton blooms observed throughout the Sea of Marmara are discussed. The study identified predominant bacterial species in mucilage aggregate, seawater, sediment and fish samples, emphasising Vibrio spp., focusing on Merluccius merluccius and Trachurus trachurus . The examination involved a total of 7392 samples, with detailed analyses of length–weight relationships, condition factors, gonadosomatic and viscerosomatic indices and microbiological and ichthyopathologycal aspects. Non‐alcoholic fatty liver disease (NAFLD) was observed at various stages in almost all of the species sampled within the scope of the study. Depending on this, T. trachurus exhibited negative allometric growth ( b = 2.8288), with males ( b = 2.7948) and females ( b = 2.8538) following this trend. M. merluccius also showed negative allometric growth ( b = 3.0696), with males ( b = 2.9755) and females ( b = 3.2829) displaying growth types. Pollution from various wastewater sources poses a substantial threat to the biodiversity and water quality of the Sea of Marmara. This situation has been further exacerbated by the occurrence of the massive mucilage phenomenon, which consists of organic components. Understanding the pathogenesis processes of marine organisms and their responses to external factors, such as pollution and changes in environmental conditions, is crucial for preserving biodiversity and ensuring the well‐being of widely consumed species.