Red tide poses risk for sea ecosystem

ISTANBUL - Hürriyet Daily News

An unusual red strip has emerged on some coastal parts of the Marmara Sea, which might be due to an increase in the population of some types of plankton. DHA Photo

The extreme change of color in the Marmara Sea off of the Thracian province of Tekirdağ could pose a potential threat to the region’s ecosystem, according to marine science experts.

The red layers formed over the surface of the water are huge masses of certain types of plankton, Istanbul University Melek İşinibilir Okyar told the Hürriyet Daily News, adding that such formations carry severe risks for the fish population living in the area.

The plankton stick to fish gills, hampering the animals’ breathing and subsequently causing mass deaths in the area, İşinibilir said. They also release toxic substances which could result in further fish deaths. “They clog up the gills of fish because of their extreme quantity, and the fish can’t breathe,” İşinibilir Okyar said. “And the toxic substances can also kill the animals.”

The redness lasts several days until the plankton masses die, resulting in large quantities of the dead plankton sinking to the depths of the sea and depleting oxygen levels due to their decomposition, she said.

The red tide not only carries future ecological risks, but is also a sign of existing pollution in the water, with substance-rich waters becoming likelier targets for plankton populations.

“These changes happen in polluted waters,” İşinibilir Okyar said. “The water that flows is rich in food for planktons, containing chemicals like phosphate and ammonia, and the nitrogen-based substances cause the extreme multiplication of such organisms,” the professor said.

Further analysis needed

Middle East Technical University Institute of Marine Sciences Director Professor Ahmet Kıdeyş also said the overabundance of one or more species of certain phytoplankton could have caused the red tide off Tekirdağ but added that only an analysis of samples could confirm the hypothesis.

Red tide was seen in the Marmara Sea near Istanbul yesterday. The tide has been spotted in Tekirdağ, near the small shore town of Şarköy, as well as the Büyükçekmece bay area west of Istanbul.

A small, enclosed basin between two straits, the Marmara Sea is home to the most industrialized regions in Turkey and also lies on the route of hundreds of oil tankers that cross it every day.