Dynamics and asexual reproduction of the jellyfish Aurelia coerulea benthic life stage in the Thau lagoon (northwestern Mediterranean)

Abstract

For many jellyfish, the magnitude and timing of medusae blooms are recognized to result from the benthic stage dynamics. However, information on the scyphistomae of jellyfish populations in the wild remains scarce. Here, bi-mensual underwater photoquadrat surveys were combined with scyphistomae sampling and observation to describe the annual (February 2017-January 2018) benthic stage dynamics and asexual reproduction strategy of Aurelia coerulea in the Thau lagoon (43°25′31.1″N; 03°42′0.9″E). Our results revealed unexpected seasonal patterns of variation: scyphistoma coverage peaked in the spring (11.6 ± 3.7% on 21st April) and was minimal in the summer and autumn (1.4 ± 1.3% on 10th October). The increase in scyphistoma coverage mainly resulted from an intense production of buds between February and April during the spring rise in water temperature (peak of 12,800 buds m−2 on 21st April), but scyphistoma coverage appeared to be negatively influenced by the interaction of high summer temperatures and salinities. Strobilation was observed from November to April. It peaked on 17th November, with 33.1% of the scyphistomae strobilating and an average production of 19,100 strobila disks m−2. However, the low scyphistoma coverage at this time of the year (< 2%) likely limited the intensity of ephyrae liberation and the subsequent medusae bloom. The final population size of A. coerulea thus results from a complex interaction of abiotic and biotic factors. Our results bring into question how the different populations of Aurelia spp. will respond to the predicted global warming scenarios.

Insights on Bloom Forming Jellyfish (Class: Scyphozoa) in the Gulf of Mexico: Environmental Tolerance Ranges and Limits Suggest Differences in Habitat Preference and Resistance to Climate Change Among Congeners

“…9 and sp. new, polyps of A. coerulea have been found in the wild (Ishii and Katsukoshi, 2010;Marques et al, 2019). Interestingly, the experimentally resolved temperature range where polyps of A. coerulea maintained minimal signs of stress (response scores of 4 or above) determined in this study align well with published reports of the habitat temperatures for this species derived from field surveys of wild populations.…”

“…Interestingly, the experimentally resolved temperature range where polyps of A. coerulea maintained minimal signs of stress (response scores of 4 or above) determined in this study align well with published reports of the habitat temperatures for this species derived from field surveys of wild populations. According to our experiments, A. coerulea polyps experienced minimal stress from 6.5 • C to 27 • C, whereas natural polyp habitats in the Thau Lagoon (northwestern Mediterranean) range from 7.6 • C to 25.8 • C (Marques et al, 2019), 6 • C to 30 • C for polyps in Lake Verano, Italy (Belmonte et al, 2011), and 9 • C to 29 • C for A. coerulea in Tokyo Bay, Japan (Ishii and Katsukoshi, 2010). These are the minimum and maximum recorded water temperatures of wild populations surveyed over the span of approximately 1 year (Ishii and Katsukoshi, 2010;Marques et al, 2019).…”

“…Field and laboratory studies demonstrate Aurelia congeners to have differing responses to salinity variation (Spangenberg, 1964;Purcell et al, 2009;Marques et al, 2019). The size of wild populations of A. coerulea polyps appeared to be negatively impacted by high salinities especially in combination with high temperatures (Marques et al, 2019). Low salinity retarded growth of wild A. labiata (Purcell et al, 2009), while varying the salinity within the range of local environmental fluctuation was found to have no significant effect on polyp growth in Aurelia sp.…”

“…Many past studies were also confounded by the presence of multiple cryptic species within the Aurelia genus (Dawson and Martin, 2001;Scorrano et al, 2017). Field and laboratory studies demonstrate Aurelia congeners to have differing responses to salinity variation (Spangenberg, 1964;Purcell et al, 2009;Marques et al, 2019). The size of wild populations of A. coerulea polyps appeared to be negatively impacted by high salinities especially in combination with high temperatures (Marques et al, 2019).…”

“…Only a few natural polyp habitats of Aurelia spp. have been studied (Gröndahl, 1988;Purcell et al, 2009;Malej et al, 2012;Marques et al, 2015Marques et al, , 2019Hoèvar et al, 2018), thus information on the diversity of salinity tolerances within the genus is limited. Many past studies were also confounded by the presence of multiple cryptic species within the Aurelia genus (Dawson and Martin, 2001;Scorrano et al, 2017).…”