How Much Recurrent Outbreaks of the Moon Jellyfish May Impact the Dynamics of Bacterial Assemblages in Coastal Lagoons?

The moon jellyfish Aurelia coerulea (Scyphozoa) is one of the most common and largestjellyfish inhabiting coastal lagoons, confined bays, and marinas of temperate and subtropical coastalwaters. The annual population dynamics of A. coerulea along with some bacterial parameters (bacterialsize and biomass, total coliforms, faecal coliforms, intestinal enterococci, culturable Vibrio spp., andculturable bacteria at 37 oC), sea surface temperature (SST), salinity, and an array of nutrients(ammonia, nitrites, nitrates, phosphates, silicates, total nitrogen, and total phosphorus) were assessedin the Varano lagoon (Adriatic Sea) that is subject to anthropogenic pollution. Statistical analysesrevealed that jellyfish outbreaks and their consequent biomass deposition significantly correlatedto seawater temperature, total nitrogen, phosphates, and ammonia concentrations while negativecorrelations appeared with nitrite and nitrate concentrations. In addition, bacterial biomass andVibrio abundance correlated with each other and temperature, jellyfish density, and total nitrogen.These findings suggest that environmental changes could trigger the occurrence of jellyfish bursts inthe lagoon which, in turn, may act as one of the central drivers of processes regulating some bacterialcomponents. The positive relationship between jellyfish flush-and-crash dynamics and SST suggeststhat ongoing global warming will seemingly increase jellyfish outbreaks.