Original scientific paper

https://doi.org/10.32582/aa.63.2.4

The occurrence of the jellyfish Aequorea cf. forskalea in the Adriatic Sea: comparison of historical and recent data

Alenka Malej ; National Institute of Biology, Marine Biology Station Piran, Fornače 43, 6330 Piran, Slovenia
Davor Lučić ; University of Dubrovnik, Institute for Marine and Coastal Research, 20000 Dubrovnik, Croatia
Natalia Bojanić ; Institute of Oceanography and Fisheries, Šetalište Ivana Meštrovića 63, 21000 Split, Croatia
Martin Vodopivec ; National Institute of Biology, Marine Biology Station Piran, Fornače 43, 6330 Piran, Slovenia
Paolo Paliaga ; Juraj Dobrila University of Pula, Zagrebačka 30, Pula, Croatia
Branka Pestorić ; Institute of Marine Biology, University of Montenegro, 85330 Kotor, Montenegro
Ivana Violić ; University of Dubrovnik, Institute for Marine and Coastal Research, 20000 Dubrovnik, Croatia
Nastjenjka Supić ; University of Dubrovnik, Institute for Marine and Coastal Research, 20000 Dubrovnik, Croatia

Abstract

Jellyfish are becoming an increasingly important component of studies of the global marine environment,
as their frequent mass phenomena affect ecosystem performance and have economic and
health consequences. Recent research has focused primarily on mass occurrences of scyphozoans
and ctenophores, while less attention has been paid to hydromedusae blooms, which can also have
significant impacts on the marine ecosystem with economic consequences. Like many members of
the Scyphozoa and Ctenophora, Aequorea species can be numerous and form blooms. Based on surveys
from 2000 to 2020 and information provided by marine professionals, we examine the (multiannual)
variability, seasonality, and spatial distribution patterns of the poorly studied temperate species Aequorea
cf. forskalea (Hydrozoa: Leptothecata). We hypothesized that this macrogelatinous
jellyfish with a bipartite life cycle (benthic polyps and planktonic medusae) is sensitive to seasonal
and long-term temperature fluctuations, particularly because temperature has been shown to play
a critical role in mediating transitions in the life cycle of cnidarians. The cold-water affinity of A.
cf. forskalea was confirmed by a significant negative correlation with temperature and the most frequent
occurrence during the winter-spring period. For the northern Adriatic (Gulf of Trieste), sea
temperature data and semi-quantitative plankton data are available for the first decade of the 20th
century, allowing comparison of the historical data (1900-1911) with our current data set. Compared
to historical records, the current occurrence of A. cf. forskalea differs significantly. With the
warming of the northern Adriatic Sea since the beginning of the 20th century, the current phenology
of A. cf. forskalea has changed, probably related to the delayed production of medusae by hydroids
in autumn, the absence of medusae in this season and their less frequent occurrence in winter

Keywords

hydromedusae; blooms; long-term monitoring; multiannual variability; Mediterranean Sea

Hrčak ID:

289609

URI

https://hrcak.srce.hr/289609

Publication date:

30.12.2022.

Article data in other languages: croatian

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