ASSESSMENT OF OPTIMAL TEMPERATURE AND SALINITY CONDITIONS TO CULTURE Aurelia solida

Introduction

Jellyfish blooms and their consequences have been of increasing interest over the last decades, often highlighting challenges for local economies (Purcell et al., 2015). More recently, studies started investigating new opportunities and the potential use of jellyfish for a great variety of purposes such as human consumption, aquaculture feed, cosmetics, or microplastic filter (Torri et al., 2020; Prieto et al., 2018). For example, Aurelia aurita, has been presented as a crispy product with a potential gastronomic interest (Pedersen et al., 2017). This new marketing of jellyfish drives the interest in jellyfish culture and the possibility to produce fast-growing biomass for economic purposes. Understanding jellyfish ecology is crucial to determine optimal culture conditions as studies have shown that there are differences between closely related species (Hubot et al., 2017). In this context, the present study tested the effect of different temperature and salinity regimes on the rearing success of Aurelia solida.

Material and Methods

Mesocosm experiments investigated the simultaneous effects of temperature and salinity on the rearing of the jellyfish Aurelia solida. Experiments were performed on two different life stages, polyps and ephyra, at the mesocosm system (MOSS) and laboratory facilities at the Madeira research unit of MARE – Marine and Environmental Research Centre, located at Quinta do Lorde Marina, Madeira, Portugal. Temperature and salinity (S) levels represented values typically found for the species across their distributional range and covered temperatures between 10 and 28°C and salinities of 20 up to 40. Survival, asexual reproduction of polyps and growth of ephyra were monitored for several weeks to determine successful rearing conditions for A. solida.

Results

Survival of the A. solida polyps was generally high (83-100%) in almost all treatments. Only the combination of the highest temperature (28°C) and lowest salinity (20), resulted in 0% survival. Polyps showed asexual reproduction in all combinations but produced the most at 20°C and 30S (Figure 1). Strobilation occurred mainly at 16°C and 35S.

Ephyrae kept at lower temperatures (10 and 15°C) showed the highest survival rates. However, preliminary results suggest that the highest growth rates were reached at 20°C in combination with 20 and 35S.

Discussion and Conclusion

The best conditions for asexual reproduction in A. solida polyps was at intermediate temperatures (20°C) and lower than marine salinities (25 and 30). In contrast, although ephyrae growth was highest at intermediate temperatures as well (20°C), it increased at lower salinities (20). Comparing these results to studies on other Aurelia species, we can see differences in optimal rearing conditions regarding temperature and salinity depending on species: Aurelia aurita showed highest budding rates at higher temperatures (28°C; Pascual et al., 2015), and Aurelia labiata showed higher budding rates at lower temperatures (7 and 10°C; Purcell, 2007). These comparisons highlight the need for laboratory studies for individual species to advance our current understanding on best rearing conditions for the particular species in order to optimize jellyfish culture.

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