Biogeography and phenology of the jellyfish Rhizostoma pulmo (Cnidaria: Scyphozoa) in southern European seas

Abstract

Aim Global anthropogenic changes have altered biogeography and phenology of marine populations, thereby promoting a spatial reconfiguration in the functioning of marine ecosystems. Among these changes, massive proliferations of jellyfish in temperate latitudes warn of potential alterations in biogeochemical fluxes, ecosystems’ structure and assets, and the services they provide to human welfare. Understanding driving factors shaping large‐scale patterns of jellyfish proliferations is a pressing need in global ecology and sustainability science. Using a comprehensive dataset of the largest blooming scyphomedusae in southern European seas we test, over broad space–time scales, current hypotheses relating jellyfish dynamics to warming and eutrophication. Location Southern European seas. Time period 1875–2019. Major taxa studied Rhizostoma pulmo. Methods We have gathered historical and contemporaneous records of R. pulmo from the Mediterranean and Black Seas over the last two centuries (7,359 records). Generalized statistical models were used to assess the influence of thermal (latitudinal) and productivity (longitudinal) gradients on the biogeographical patterns, and the species’ phenology at large and regional scales. Results Rhizostoma pulmo abundance exhibited an enhanced magnitude and frequency in recent decades, concurrently with positive temperature anomalies. We found that the latitudinal temperature gradient, but not productivity, shaped long‐term bloom intensity and biogeographical patterns of the species. Our analysis further uncovered a significant effect of the interannual variability of spring temperature on the species’ phenology over the period 2008–2018, with warmer springs favouring an earlier start (c. 3 months) and a longer duration (from 5 to 7 months) of jellyfish season. Main conclusions Among the current hypotheses linking jellyfish changes with anthropogenic disturbances, only the warming‐based hypothesis gained support over wide space–time scales, while the eutrophication‐based hypothesis mainly applied at local scales. Hence, biogeographical patterns of R. pulmo are shaped by the latitudinal temperature gradient, while the species bloom dynamics echo variations in ecoregion thermal regimes.

Unfolding Jellyfish Bloom Dynamics along the Mediterranean Basin by Transnational Citizen Science Initiatives

“…In the Ligurian Sea, P. noctiluca has been reported as present along most of the coastline but exhibiting alternating years of presence and absence [3,28], in full agreement with data collected in the current study. Regarding R. pulmo, the general distribution pattern shown in the present study is consistent with that reported by Boero et al [15] and Leoni et al [93]. For P. noctiluca, one of the environmental variables with highest importance was salinity, which is in agreement with Piccinetti Manfrin and Piccinetti [94] and Canepa et al [30].…”

“…In the same study, the authors indicated that, by 2010, important impacts caused by this species had been reported by fishermen as a result of more frequent and intense blooms. Within our temporal dynamics analysis, a notable increase in R. pulmo records was observed from the year 2010 to 2013, with a considerable peak in 2012, agreeing also with the results shown in Leoni et al [93]. The spatial distribution observed in this study is also in agreement with Fuentes et al [102], showing the occurrence of this species along the entire Catalan coast, with the highest concentration in the central area around the Barcelona province.…”

“…R. pulmo is a characteristic species of Tunisian coasts [106], and blooms are described under conditions of high temperature and coastal eutrophication [107]. However, there is no ample information about the spatio-temporal distribution of this species in Tunisian waters, except from the recent work by Leoni et al [93] that documents a year-round presence and large blooms for this species, neither of the key environmental variables that determine its presence, elevating the current study to the first one of its kind on R. pulmo within these waters.…”

Long-term Monitoring of Carnivorous Gelatinous Macrozooplankton in the Area of Dubrovnik-Neretva County (Croatia)

“…Values represent the highest frequency of jellyfi sh occurrence in a given month, regardless of the number of reports received. Several authors have already used similar methods to present the results of macrozooplankton research [27,43,16,48,62,79,54].…”

A novel endocast technique providing a 3D quantitative analysis of the gastrovascular system in Rhizostoma pulmo: An unexpected through-gut in cnidaria

“…Rhizostoma pulmo ( S1 Fig ) is one of the first jellyfish species formally described in history [ 27 ], however, up to now, a complete description of its gastrovascular system is still missing, despite being a rather common jellyfish along the coasts of the Mediterranean Sea [ 28 , 29 ]. As part of a research on defining the phylogenetic pattern of the Rhizostoma genus, the morphology and functional anatomy of the species R .…”