Preprints
https://doi.org/10.5194/egusphere-2022-393
https://doi.org/10.5194/egusphere-2022-393
 
31 May 2022
31 May 2022
Status: this preprint is open for discussion.

Multi-platform study of the extreme bloom of the barrel jellyfish Rhizostoma pulmo (Cnidaria: Scyphozoa) in the northernmost gulf of the Mediterranean Sea (Gulf of Trieste) in April 2021

Nydia Catalina Reyes Suàrez1, Valentina Tirelli1, Laura Ursella1, Matjaž Ličer2,3, Massimo Celio4, and Vanessa Cardin1 Nydia Catalina Reyes Suàrez et al.
  • 1National Institute of Oceanography and Applied Geophysics - OGS, Trieste, Italy
  • 2Slovenian Environment Agency, Ljubljana, Slovenia
  • 3National Institute of Biology, Marine Biology Station, Piran, Slovenia
  • 4Regional Environmental Protection Agency of Friuli Venezia Giulia - FVG, Palmanova, Udine, Italy

Abstract. On 7 April 2021, an exceptional bloom of the scyphomedusa Rhizostoma pulmo was observed in the Gulf of Trieste (Italy). Blooms of this species in the northern Adriatic Sea have been reported since the late 1800s, however, the density of jellyfish observed in 2021 reached more than 10 specimens per square metre. In this work, we analyse the bloom from a multiplatform approach using observations and model data at different time scales. We attempt to explain the intensity of the bloom as a consequence of thermohaline and hydrodynamical conditions in the gulf. Meteo-oceanographic conditions that may have contributed to the exceptional aggregation of jellyfish observed along the northernmost coast of the Adriatic Sea are discussed in detail. Specifically, our results indicate that this bloom was enabled by 1) the presence of a high number of jellyfish in the Gulf probably linked to the anomalously warm sea conditions in spring 2020 and winter 2021 which may have favoured a longer reproductive period and enhanced survival of adult R. pulmo respectively; 2) strong wind events, such as the Bora wind for the Gulf of Trieste, which enhanced upwelling and mixing processes in the Gulf bringing the jellyfish from the deeper waters to the surface and clustering them along the coast.

Nydia Catalina Reyes Suàrez et al.

Status: open (until 02 Aug 2022)

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Nydia Catalina Reyes Suàrez et al.

Nydia Catalina Reyes Suàrez et al.

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Short summary
On 7 April 2021, an exceptional bloom of barrel jellyfish was observed in the Gulf of Trieste (Italy), where the observed density reached more than 10 jellyfish per square metre. In this paper, we analyse the bloom using observations and model data to try to explain the intensity of the bloom as a consequence of oceanographic conditions in the gulf and how these may have contributed to the exceptional jellyfish aggregation observed.