Posted on October 16, 2024
Experts emphasize that cleaning the water column is crucial for restoring the sediment’s natural filtration role and improving overall marine health in Izmir Bay
In Izmir, on the western coast of Türkiye, pollution mixed with seawater has been accumulating on the sediment at the seabed for many years, causing its structure to deteriorate. Professor Ebru Yeşim Özkan, a member of the Izmir Bay Scientific Board and a faculty member at the Faculty of Fisheries at Izmir Katip Çelebi University (IKÇÜ), stated: “Dredging the inner bay is the best method, but it’s important to conduct feasibility studies on the dredged sediment and dispose of it properly, Simply moving the sediment elsewhere has no significance, transferring degraded sediment to another marine environment will also damage that habitat.”
Pollution that mixes with seawater in Izmir Bay has been accumulating on the seabed sediment for many years, leading to the deterioration of its structure. Professor Özkan, who examined the sediment at the bottom of Izmir Bay through studies conducted between 2008 and 2018, noted: “In 2008, sediment was a natural filtration system. It was composed of sand, silt, and clay. However, in our TÜBITAK project in 2018, we found that the structure of the sediment had changed significantly. By 2018, it no longer behaved like a natural filtration system; instead, it returned contaminated material back into the seawater column.”
Özkan indicated that there is a substantial amount of external materials entering the inner bay of Izmir, which can come from atmospheric sources, natural processes or agricultural activities. She added that during this period of increased urbanization and population, household and industrial waste also contributes to the bay.
“Unfiltered materials alter the sediment structure once they enter the water column. We need to maintain balance here, if we clean the water column and prevent excessive accumulation in the sediment, the sediment can perform its filtration role much more effectively,” she said.
Özkan expressed concern about the rapid changes in sediment structures over the 10 years between 2008 and 2018. “In a normal marine environment, sediment thickness changes by 1 centimeter (0.39 inches) in 100 years, while this can vary due to global and climatic processes, such a drastic change in just 10 years is alarming.”
“You see less than 2-3 centimeters of sediment, but the accumulation of sludge or mud on top creates issues for the underlying structure, leading to pollution, areas where fish deaths occur are typically shallow, where the interaction between sediment and water is significant. Because the sediment isn’t performing its filtration role, an oxygen-deficient environment forms in the water column, leading to sudden fish deaths,” she explained.
Dredging the sediment is part of the short-term emergency action plan, especially in shallow areas where polluted materials are located on the sediment surface. She added, “If too much load comes from the water column to the sediment, the underwater structure will gradually change due to currents and winds. However, the existing sludge won’t disappear overnight, and restoring the sediment to its former state will not happen quickly.”
She continued: “Therefore, I advocate for the immediate removal of this sludge, if the 1-2 centimeters of sludge are dredged, the underlying sediment, which is composed of clay and silt, can again provide healthy nutrients and organic matter to the water column through its chemical and biological processes.”
She noted that the maximum depth in the inner bay is 13 meters (42.65 feet), “Dredging the inner bay is the best approach, but it’s important to conduct feasibility studies on the dredged sediment and dispose of it properly, simply moving the degraded sediment to another location serves no purpose.”
“Transferring degraded sediment in the marine environment will also disrupt the habitat there. Therefore, it is necessary to create large areas on land to transport it. The transported sediment may be cleaned and used for different purposes, there is currently a very deep sediment structure at the bottom of the sea. With the removal of the degraded sludge over a 15-20 year period and treatment of the additional waters entering the bay, Izmir Bay can return to its former state,” she concluded.
On Sept. 9, numerous dead fish were observed floating on the surface in the Aksoy neighborhood of the Karşıyaka district, where the seawater had turned green and brown.
