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Microbial response to the presence of invasive ctenophore Mnemiopsis leidyi in the coastal waters of the Northeastern Adriatic

Paliaga, Paolo; Budiša, Andrea; Dautović, Jelena; Đakovac, Tamara; Dutour-Sikirić, Mathieu Andre; Mihanović, Hrvoje; Supić, Nastjenjka; Celić, Igor; Iveša, Neven; Buršić, Moira; Balković, Ivan; Jurković, Lara; Ciglenečki-Jušić, Irena (2021) Microbial response to the presence of invasive ctenophore Mnemiopsis leidyi in the coastal waters of the Northeastern Adriatic. Estuarine, coastal and shelf science, 259 . ISSN 0272-7714

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Seasonal blooms of the invasive ctenophore Mnemiopsis leidyi have been recorded throughout the Adriatic Sea, affecting the ecosystem and its pelagic resources. Gelatinous organisms such as M. leidyi release significant quantities of excreta as labile and surface active dissolved organic carbon (DOC) that supports the microbial activity. The effects of M. leidyi’s presence on heterotrophic prokaryotes (HP), cyanobacteria (CB) and heterotrophic nanoflagellates (HNF) were investigated at five locations in the coastal waters of Rovinj- Rovigno (northern Adriatic) during intensive blooms in September 2019. Additionally, circulation in the study area was examined using available current measurements and a hydrodynamic model. In September, low-pass filtered currents near the surface were mostly directed toward S-SE reaching 25 cm/s, indicating the presence of the Istrian Coastal Countercurrent (ICCC). Ctenophores displayed a patchy spatial distribution from 0.05 to 100 M. leidyi individuals per m3. When ctenophore density in the swarms surpassed 1 individual per m3, the change in the abundances of microbial groups became evident. The lowest microbial densities and lowest concentrations of dissolved and particulate organic carbon (DOC and POC) and surface-active substances occurred in the absence of M. leidyi, while the highest were within the swarms. We hypothesise that HP utilises the available DOC enhancing the remineralisation of organic matter. Finally, greater availability of HNF’s prey (HP and CB) leads to an increase in their abundance. This study illustrates how the release of surface-active DOC during intensive M. leidyi’s blooms can stimulate the microbial loop. The current system with the ICCC prevailing in September enables the spreading of M. leidyi from its hypothetic origin in an open sea gyre towards the coast. Bora wind episodes may initiate and favour this type of circulation. In these conditions, M. leidyi agglomerates in large numbers along the coast, enabling the accumulation of organic matter and altering the abundance of pico- and nanoplankton.

Item Type: Article
Uncontrolled Keywords: Heterotrophic prokaryotes ; Cyanobacteria ; Heterotrophic nanoflagellates ; Surface active DOC ; Istrian Coastal Countercurrent
Subjects: NATURAL SCIENCES > Interdisciplinary Natural Sciences
Divisions: Center for Marine Research
Division for Marine and Enviromental Research
Project titleProject leaderProject codeProject type
Ekološki odziv sjevernog Jadrana na klimatske promjene i antropogeni učinakSupić, NastenjkaIP-2016-06-4764HRZZ
Rogozničko morsko jezero kao model odziva ekosustava na promjene u okolišuCiglenečki-Jušić, IrenaIP-2018-01-1717HRZZ
Depositing User: Jelena Dautović
Date Deposited: 03 Aug 2021 13:35
DOI: 10.1016/j.ecss.2021.107459

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