Jellyfish diversity, trends and patterns in Southwestern Mediterranean Sea: a citizen science and field monitoring alliance

Abstract

Jellyfish (Cnidaria and Ctenophora) are an essential component of marine ecosystems and represent a potential effect, positive or negative, for several economic activities. Jellyfish blooms and non-indigenous species (NIS) introduction can shift ecological community structure and energy transfer. Despite their importance in ecosystem function and services, knowledge of jellyfish fauna diversity and phenology are largely lacking for the southern Mediterranean Sea. Here, we present an overview of the current state of jellyfish biodiversity in Tunisia. Based on a comprehensive literature survey, historical records and unpublished data, 66 jellyfish species, including 11 non-indigenous species, have been recorded in Tunisia between 1994 and 2020. Additionally, based on field surveys and a citizen science sighting program between 2004 and 2020, we present data on the spatial distribution of 13 conspicuous jellyfish taxa and the phenology of the eight most frequently detected species (Aurelia solida, Cotylorhiza tuberculata, Pelagia noctiluca, Phyllorhiza punctata, Rhizostoma pulmo, Rhopilema nomadica, Olindias muelleri and Velella velella) in Tunisian two ecoregions, the Western Mediterranean and the Tunisian Plateau. The 17 year survey showed a shift in R. pulmo, A. solida and P. noctiluca phenology. Additionally, citizen science revealed an increase in the spatial range of P. punctata (NIS) and the distinct phenologies of populations in the two ecoregions.

Distribution and species composition of planktonic cnidarians in the Algerian coastal waters (SW Mediterranean Sea)

“…The recorded hydrozoans account for 12.47% of the hydrozoan diversity in the Mediterranean, while the scyphozoans account for 15%. A similar pattern of hydrozoan biodiversity (12.7% or 57 species) was recorded in Tunisian waters (Gueroun et al, 2022). The diversity of scyphozoans is greater in Tunisian waters, with only seven species accounting for 30% of the scyphozoan diversity in the Mediterranean Sea (Gueroun et al, 2022).…”

“…These various studies show that the inventory conducted on the eastern Algerian coast is far from complete, as a small number of samplings cannot represent the entire diversity of planktonic cnidarians in this region. The specific taxonomic composition of this group revealed the presence of meroplanktonic hydrozoans (15 Anthoathecata and eight Leptothecata), and the variability that characterizes the hydromedusae fauna of the western Mediterranean (Bouillon et al, 2004;Sabatés et al, 2010;Kherchouche and Hafferssas, 2020;Gueroun et al, 2022). The coastal location of the sampling stations could explain the diversity of meroplanktonic taxa observed.…”

“…Along the Tunisian coast, more than 20 species of medusae and 11 species of Siphonophorae have been identified (Daly Yahia et al, 2003;Touzri et al, 2010Touzri et al, , 2012. Gueroun et al (2022) recently reported a significantly greater species richness (66 species) in Tunisian coastal waters. These various studies show that the inventory conducted on the eastern Algerian coast is far from complete, as a small number of samplings cannot represent the entire diversity of planktonic cnidarians in this region.…”

“…The Mediterranean Sea has been designated a hotspot for marine biodiversity (Coll et al, 2010). Overall, there is significant heterogeneity in the distribution of species richness in the Mediterranean Sea (Gueroun et al, 2022). The uneven distribution of research efforts could explain this.…”

Blue button (Cnidaria: Hydrozoa) distribution and trends in the Mexican Atlantic, based on field surveys and open-access data

“…The technology and software of our days have allowed the generation of a significant amount of biodiversity data, helpful to biological sciences (Dickinson et al 2012, Ivanova & Shashkov 2021, Gueroun et al 2022). Data about observations of organisms recorded by citizens is of immense value to ecological, evolutionary, and conservation research (Tiago et al 2017, Petrovan et al 2020, Robinson et al 2020.…”