Scyphomedusae and Ctenophora of the Eastern Adriatic: Historical Overview and New Data

Branka Pestorić,Tjaša Kogovšek,Ivana Violić,Martin Vodopivec,Paolo Paliaga,Alenka Malej,Davor Lučić,Natalia Bojanić

doi:10.3390/d13050186

Abstract

One of the obstacles to detecting regional trends in jellyfish populations is the lack of a defined baseline. In the Adriatic Sea, the jellyfish fauna (Scyphozoa and Ctenophora) is poorly studied compared to other taxa. Therefore, our goal was to collect and systematize all available data and provide a baseline for future studies. Here we present phenological data and relative abundances of jellyfish based on 2010–2019 scientific surveys and a “citizen science” sighting program along the eastern Adriatic. Inter-annual variability, seasonality and spatial distribution patterns of Scyphomedusae and Ctenophore species were described and compared with existing historical literature. Mass occurrences with a clear seasonal pattern and related to the geographical location were observed for meroplanktonic Scyphomedusae Aurelia solida, Rhizostoma pulmo, and to a lesser extent Chrysaora hysoscella, Cotylorhiza tuberculata and Discomedusa lobata. Holoplanktonic Pelagia noctiluca also formed large aggregations, which were seasonally less predictable and restricted to the central and southern Adriatic. Four species of Ctenophora produced blooms limited to a few areas: Bolinopsis vitrea, Leucothea multicornis, Cestum veneris and the non-native Mnemiopsis leidyi. However, differences between Adriatic subregions have become less pronounced since 2014. Our results suggest that gelatinous organisms are assuming an increasingly important role in the Adriatic ecosystem, which may alter the balance of the food web and lead to harmful and undesirable effects.

Highlights

IntroductionVariability in jellyfish abundance, phenology, population density, and geographic distribution has been reported for many marine ecosystems worldwide [1,2,3,4,5]
Among other Scyphozoa, seven species previously documented in the study area and two non-native species (Aurelia solida and Mawia benovici) were confirmed
Aurelia aurita was recorded in the Adriatic Sea as early as the beginning of the nineteenth century [for references, see 67]

Summary

Introduction

Variability in jellyfish abundance, phenology, population density, and geographic distribution has been reported for many marine ecosystems worldwide [1,2,3,4,5]. The proliferation of gelatinous macroplankton has various ecological impacts which can affect ecosystem services [15,16]. They can pose a threat to human health [17] and affect the economy. Many authors reported an increasing frequency and severity of negative impacts on marine fisheries and aquaculture over the last 50 years [18,19,20]. Fourteen species of Scyphomedusae and two species of Ctenophora have been associated with these adverse impacts worldwide [21]; approximately one-third of these species are present in the Adriatic Sea

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