# Google Earth Engine for Monitoring Marine Mucilage: Izmit Bay in Spring Bay in Spring 2021
###### Abstract
The Sea of Marmara (11,350 km\({}^{2}\)) connecting the Black Sea with the Aegean Sea through the Straits of Bosporus and Dardanelles has an exceptional two-layer circulation system [18]. The hydrodynamics of the Sea of Marmara is much more complex than that of other seas in the world [19]. Its complex structure is caused by the water bodies moving in layers within the system. Since the salinity in the Black Sea is lower compared to the Aegean Sea, an upper stream of water with low salinity (\(\sim\)0-25 m) is formed from the Black Sea towards the North Aegean Sea. Similarly, a high salinity bottom water flow is observed in the opposite direction from the Mediterranean Sea to the Sea of Marmara. In addition to the salinity layers, there are also temperature layers that show seasonal changes due to the heating under the influence of solar radiation. It should be pointed out that its eutrophic-mesotrophic upper layer is highly prone to anthropogenic and natural disturbances [20]. Many anthropogenic activities including heavy industrialization, urbanization and intense fishing activities take place around the Sea of Marmara, which is surrounded by mega cities including Istanbul, Kocaeli, Bursa, and Canakkale. These activities certainly have harmful effects on the welfare of the ecosystem. According to the official statistics provided by The Turkish State Meteorological Service, while the mean water temperature in the Sea of Marmara was 15 \({}^{\circ}\)C, it increased to 16.8 \({}^{\circ}\)C in the last decade ([[https://mgm.gov.tr](https://mgm.gov.tr)]([https://mgm.gov.tr](https://mgm.gov.tr)), accessed on 10 March 2021). Considering the monthly mean temperatures between 1970 and 2021, the hottest May was in 2021 at 19 \({}^{\circ}\)C ([[https://mgm.gov.tr](https://mgm.gov.tr)]([https://mgm.gov.tr](https://mgm.gov.tr)), accessed on 10 March 2021). Ref. [20] underline the potential risk of an increase in the number and extent of the phytoplankton blooms that may result in a total collapse of the water ecosystem. To protect and improve the ecosystem in the Sea of Marmara, TMEUCC declared a conservation action plan including 22 governmental actions. In the case of Izmit Bay, which is selected for this study, heavy industrialization and urbanization have taken place during the past several decades [21]. The coast of the study site is full of industrial factories and facilities, including petroleum refineries, cement, fertilizer, metal, pesticides, detergent, and dye factories. The area is also subject to intense shipping activities all year round [14; 22]. All these activities cause water pollution, resulting in frequent eutrophication events after the observation of potentially harmful species that have a tendency for blooming [23; 24; 25; 26; 27]. In fact, a series of red tides were observed in the Bay in 2015. Monitoring sea surface mucilage and mapping its spatial distributions provide valuable information to the local authorities and decision-makers in developing prevention and rehabilitation strategies. Since the 1970s, remote sensing has been the most effective approach for detecting and monitoring water quality and water pollution. Spectral, spatial, temporal, and polarization signatures are major characteristics of the remote sensing sensors, helping to measure water characteristics [28]. Marine remote sensing is a subfield of remote sensing with a continuously expanding agenda. Various studies include ecosystem characterization, biodiversity assessment, oil spill detection, monitoring algal blooms, and modeling seasonal and annual ocean circulation patterns. With recently launched sensors, finer spatial resolutions, more spectral bands, higher radiometric resolutions, and shorter temporal resolutions can be achieved, opening new horizons for researchers to investigate biophysical aspects of the oceanic and nearshore environments.