Marine mucilage in the Sea of Marmara and its effects on the marine ecosystem: Mass deaths

Abstract

In April of 2021, there was a massive explosion of marine mucilage in the Sea of Marmara, as a result, many invertebrates of marine communities suffered mass mortality. We summarize our results about the devastating effect of mucilage bloom on mass deaths in the Sea of Marmara. The phenomena were lethal to the pelagic fishes and crustaceans, and individuals were impacted severely smothered by mucilage or anoxia. Mucilage accumulations have shown their effectiveness in many areas around the Kapıdağ Peninsula. Misakça, Şirinçavuş, Narlı, and Tatlısu regions, where mass death cases occurred, were selected as study areas, and these areas are characterized as shallow and calm waters. In total, 10164 dead individuals belonging to eighteen families were observed in the coastal area. Atherina sp. was the most affected species with an abundance of 3040 dead ind∙100 m-2, because of the spawning period in the coastal zone. Most of the species that died were pelagic, and Engraulis encrasicolus, Spicara sp., Trachurus trachurus, and Sardina pilchardus also suffered massive mortality. Due to insufficient wave action and tidal currents, mucilage was also identified at depths 5-30 m. In the following years to come, mass deaths in the Sea of Marmara are likely to have adverse effects, particularly on the food web.