Trophic ecology of a blooming jellyfish (Aurelia coerulea) in a Mediterranean coastal lagoon

Abstract

The current lack of knowledge on the trophic ecology of scyphozoans, particularly at the benthic stage, prevents a full understanding of the controls on many jellyfish blooms. The blooming scyphozoan (Aurelia coerulea) completes its entire life cycle in the Thau lagoon (southern France), where the annual population dynamics of both its benthic and pelagic stages have been described. This offered an exceptional framework to investigate the trophic processes regulating jellyfish populations over time. To this aim, stable isotopic signature analysis (δ 13 C and δ 15 N) was used to infer the diet of both A. coerulea scyphistomae and medusae over 1 year. These results were matched with medusae gut content analysis and with the monthly abundances of local plankton groups. Lastly, the isotopic signatures of A. coerulea scyphistomae and medusae were compared with those of the oysters (Crassostrea gigas) cultivated in the lagoon to evaluate the potential interspecific trophic competition. The results revealed two seasonal shifts in the trophic niche of A. coerulea and substantial overlap between the diets of its benthic and pelagic stages. Conversely, trophic niche overlaps with the oysters were restricted, suggesting a limited impact of the local jellyfish bloom on shellfish production. Phytoplankton, microzooplankton, mesozooplankton, and sedimentary organic matter were all important food sources during critical periods of A. coerulea life-cycle. However, microzooplankton abundance was found to be key for the production of buds by the scyphistomae and, therefore it is likely to control the benthic population size and, thereby, to modulate the intensity of its annual bloom in Thau.

Size‐based changes in trophic ecology and nutritional quality of moon jellyfish (Aurelia labiata)

“…Additionally, A. labiata collected in the current study in September spanned the size range of 25-225 mm, so variability in trophic levels and resource competition likely also exists at any given time. Size-based diet shifts have also been documented for other species of jellyfish (used here to mean medusozoans; Graham & Kroutil, 2001;Marques et al, 2021;Nagata & Morandini, 2018;Sullivan et al, 1994). A positive relationship between bell diameter and δ 15 N is commonly seen in jellyfish (Fleming et al, 2015;Malej et al, 1993;Nagata et al, 2015), and qualitative assessments have indicated a shift in prey from seston to zooplankton (Wang et al, 2020;Ying et al, 2012), similar to what was found here.…”

Bayesian Network Analysis reveals resilience of the jellyfish Aurelia aurita to an Irish Sea regime shift

“…Aurelia spp. are known to be able to thrive on very small zooplankton 75 and indeed feeding experiments on Aurelia aurita from the Black Sea suggest that food items overlooked by researchers appraising prey visually may provide ten times the energy for Aurelia than that obtained from mesozooplankton 76 : it is possible that Aurelia medusa could be sustained by cyphonautes. Another possibility is that environmental conditions that favour strobilation (asexual reproduction) of Aurelia benthic phases also favour bryozoan reproduction.…”

Intra- and Inter-Specific Variation in Edible Jellyfish Biomarkers and Implications for Origin Traceability and Authentication

“…This may be explained by the intraguild predation of C. nozakii that N. nomurai and small medusae were the main prey items of this species (Wang et al, 2020), and N. nomurai was found to have higher δ 13 C and δ 15 N values (-16.80 ± 1.28 and 8.11 ± 1.45 , respectively) than R. esculentum in our study (as discussed below). On the other hand, the differences in the sampling year might also lead to different δ 13 C and δ 15 N values between R. esculentum and C. nozakii since temporal variations of δ 13 C and δ 15 N values have been reported in several previous studies performed on jellyfish (Fleming et al, 2015;Javidpour et al, 2016;Marques et al, 2020). Significant spatial variations were found in δ 13 C and δ 15 N values among origins (ANOVA, δ 13 C: F 2,65 = 66.66, p < 0.01; δ 15 N: F 2,65 = 255.17, p < 0.01, Figure 2).…”