Zooplankton Composition in the Southwestern Sea of Marmara During the Summer Season

Abstract

The Sea of Marmara (SoM) is a highly sensitive semi-enclosed marine ecosystem that has been undergoing considerable ecological changes in the recent decades. This study aimed to evaluate the summer zooplankton community structure via vertical hauls at 0-20 m depth in Erdek Bay, located in the southwestern part of the SoM, during two consecutive years, 2019 and 2020. The results revealed marked year-to-year shifts. In 2020, total zooplankton abundance declined markedly compared to 2019, primarily due to a sharp decrease in the abundance of Penilia avirostris, which was dominant in the community during 2019. Despite the higher abundance observed in 2019, diversity indices were lower, indicating that the community structure was largely shaped by the dominance of a single species. In contrast, unlike the Cladocera group, Copepoda abundance increased in 2020 compared to 2019. As the most recent data for this region date back to the early 2010s, this research provides an updated contribution to the understanding of summer zooplankton composition in Erdek Bay. The findings highlight the necessity for long-term zooplankton monitoring with high temporal resolution to better understand zooplankton dynamics in response to environmental changes in the southwestern part of the Sea of Marmara.

Keywords

• Mesozooplankton
• diversity indices
• abundance
• Erdek Bay

Marmara Denizi’nin Güneybatısında Yaz Dönemi Zooplankton Kompozisyonu

Abstract

Marmara Denizi, son yıllarda önemli ekolojik değişimlerin yaşandığı, oldukça hassas yarı kapalı bir denizel ekosistemdir. Bu çalışma, Marmara Denizi’nin güneybatısında yer alan Erdek Körfezi'nde yaz dönemi zooplankton topluluk yapısını, iki farklı yıl olan 2019 ve 2020’de 0-20 m derinlikte yapılan dikey çekimler ile değerlendirmeyi amaçlamıştır. Elde edilen sonuçlar yıllar arası belirgin farklılıkları ortaya koymuştur. 2020 yılında, zooplanktonun toplam bolluğu 2019 yılına kıyasla önemli ölçüde azalmıştır. Bu düşüşün başlıca nedeni, 2019 yılında toplulukta baskın olan Penilia avirostris türünün bolluğundaki keskin azalmadır. 2019 yılında yüksek bolluk gözlemlenmesine rağmen, çeşitlilik indekslerinin daha düşük olması, topluluk yapısının büyük ölçüde tek bir türün baskınlığıyla şekillendiğini göstermektedir. Buna karşılık, Cladocera grubunun aksine, Copepoda bolluğu 2020 yılında 2019’a göre artış göstermiştir. Bölgeye ait en güncel veriler 2010’lu yılların başına dayandığından, bu çalışma Erdek Körfezi'ndeki yaz dönemi zooplankton bileşimine ilişkin güncel bir katkı sunmaktadır. Elde edilen bulgular, Marmara Denizi’nin güneybatı kesiminde çevresel değişimlere bağlı olarak zooplankton dinamiklerini daha iyi anlayabilmek için yüksek zaman çözünürlüğüne sahip uzun dönemli zooplankton izleme çalışmalarının gerekliliğini vurgulamaktadır.

Keywords

• Mesozooplankton
• çeşitlilik indeksleri
• bolluk
• Erdek Körfezi

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