Turkish seas, like all other marine environments, are affected by chronic pollution. Household waste and land-based pollution are important factors in this. Most coasts are affected by the discharge of untreated waste into marine environments. Advanced treatment of wastewater, removing nitrogen and phosphorus after dissolving solid waste, is necessary for discharging wastewater into marine environments. Advanced treatment facilities for wastewater is around an insufficient 20%. Land-based pollution is most frequent in the Marmara Sea. All the coastal municipalities must invest in proper treatment technology and protect the already small Marmara Sea from further pollution (Table 1). It’s important to prevent the northern Aegean and Istanbul strait from being polluted, as this small sea is refreshed by the undercurrents from the Aegean Sea. It’s also important to monitor the pollutants flowing in from the Black Sea. In this way, pollution budgets of the Marmara Sea and Black Sea will be kept updated.

Table 1. Wastewater indicators for municipalities, 2001-2018 (TUİK 2018)

Treatment deficiencies also cause bacterial pollution. Many beaches see a rise in Escherichia coli from time to time. Discharge of gray and black waters and insufficient inspection in terms of MARPOL 73/78 also causes marine pollution. Before discharge, treated wastewater must be considered for other uses such as irrigation and industrial cooling. In short, Turkish coasts and seas are threatened by heavy household waste and new approaches are necessary towards modern, advanced treatment. Little data exists on sound and acoustic pollution, a relatively recent and popular topic of high importance.


One of the worst marine pollutants, oil is drawn from the ground in land and sea. Oil tankers are the main source of pollution. Others are organic (pesticides, polychlorinated aromatic hydrocarbons, polychlorinated biphenyls, dioxins, furans etc.) and inorganic (heavy metals, detergent components, etc.) pollutants from household, agricultural and industrial discharges. These pollutants can pile up inside marine organisms and not only cause their deaths but also harm human health through the ingestion of marine life as food. Another negative consequence of these pollutants is the loss of biodiversity.

Research has shown that highest numbers in terms of oil observed in the nearby seas are Sevastapol, Black Sea – 540 µg/L, Caspian Sea – 230 µg/L, Marmara Sea – 148 µg/L, İstanbul Strait – 1100 µg/L, Çanakkale Strait – 592 µg/L. Acceptable levels of marine and pollution in the international literature is maximum 30 µg/L in the sea and 10 µg/L in the sediment. Oil pollution in marine environments is far above acceptable levels according to recent studies. Marine organisms also have various oil components and pollution in their bodies.

On a national scale, oil pollution is infamous for damages to marine environments and the fisheries sector due to accidents in the Turkish Straits. For this reason, proper preparations, realistic drills and efficiency is necessary in terms of emergency action. 2016 and 2017 accidents in Çeşme and Izmit Bay failed spectacularly, with inadequate response from relevant organizations. More than 90 tons of oil was reported as spilled in Izmit Bay, carried out over dozens of kilometers by the currents (Ergül et al. 2017) (Figure 1). Spilled oil doesn’t just affect the surface waters. It’s absorbed by the water particles and binds to sediment, affecting the environment for years. It’s important to monitor the situation regularly and share the data with international organizations like IMO.

Figure 1. Oil Pollution


There is little data on eutrophication related pollution in Turkish seas. Use of cleaning products without phosphate is decreasing the ecological damage to marine environments. Use of phosphate compounds increases the amount of phosphate in water and this, coupled with other nutritional factors, leads to a process called eutrophication, and an eventual decrease in oxygen levels affects marine organisms negatively. Eutrophication from increasing phosphate cause a sharp increase in algae, limited by transparency, organic sedimentation and oxygen depletion, resulting in fish mortalities. Careful choosing of raw materials is important not only for the protection of our seas and environment, but also for limiting our water consumption. At this point it’s important to save our seas from pollution (Figure 2). Especially on the coasts of Mediterranean, Posidonia oceanica, the endemic seagrass meadows, are withdrawing due to habitat loss from household waste. Seagrass meadows (also known as lungs of the sea thanks to their oxygen production capacity, erosion prevention capability and CO2 sequestration abilities) are being threatened despite having been placed under protection.

Figure 2. Seagrass meadows

Heavy metals in Turkish waters have been the subject of many studies. Heavy metals transferred to marine organisms may end up in humans through the food chain. Studies on Marmara and Black Sea commercial species’ consumable tissues showed that derivatives of elements such as As and Cu do rise above levels determined to be safe by the Turkish Food Codex occasionally (Ergül and Aksan 2013). Industrial regions such as Izmit Bay and heavily residential areas are also quiet high in heavy metal derivatives compared to other seas (Ergül et al. 2013). Research shows that its heavy metal derivatives in consumable tissues do not present an immediate danger within normal consumer levels but monitoring studies are necessary on the subject.


Plankton blooms, an important indicator of eutrophication, are observed frequently and over a wide area in spring, and lately, in fall (Figure 3).

Figure 3. Red tide in the Marmara Sea

Plankton blooms can be observed in most of our seas including the Marmara Sea. It usually begins in spring and ends around June. Last decade has seen a sharp increase in plankton blooms (about five times more) likely due to an inflow of a large amount of nutrients. This nutritional intake causes an overproduction of the single-celled phytoplankton, observed as red and sometimes white water on the surface (Figure 4). If the oxygen-consuming blooms las long, they can cause the death of fish and invertebrate species (Ergül et al. 2018) (Figure 5, Figure 6). Dynamics of these blooming planktons, phytoplankton and coccolithophores, must be monitored, especially in the Turkish Straits system. Our foundation provides occasional press releases about these species.

Figure 4. Some red-tide causing phytoplankton species in the Marmara Sea (Prorocentrum micans)

Figure 5. One of the millions of amphipodes dead as a result of the bloom (Prorocentrum micans) on May 2015, Izmit Bay (Ergül et al. 2018)

Figure 6. Some phytoplankton blooms between 2000 and 2015 at the Marmara Sea.


Ergül, H.A, Aksan, S. (2013) Evaluation of non-essential element and micronutrient concentrations in seafood from the Marmara and Black Seas. J. Black Sea/Mediterranean Environment 19 (3): 312˗330.

Ergül, H.A, Aksan, S., İşpiroğlu, M. (2018) Assessment of the consecutive harmful dinoflagellate blooms during 2015 in the Izmit Bay (the Marmara Sea). Acta Oceanologica Sinica 37(8): 91-101 doi: 10.1007/s13131-018-1191-7.

Ergül, H.A., Pelin, E. G., Erdem, T., Aksan, S. (2017) Assessment of Total PAH Concentrations in Mussel Tissue After the Largest Oil Spill in İzmit Bay (the Marmara Sea) ISEEP-2017, VIII. International Symposium on Ecology and Environmental Problems Abstract Book, 4-7 October 2017, Çanakkale.

Ergül, H.A., Varol, T., Ay, Ü. (2013) Investigation of heavy metal pollutants at various depths in the Gulfof Izmit. Marine Pollution Bulletin 73: 389-393.