Boom and Bust: Life History, Environmental Noise, and the (un)Predictability of Jellyfish Blooms

Abstract

Jellyfish (pelagic Cnidarians and Ctenophores) form erratic and seemingly unpredictable blooms with often large, transient effects on ecosystem structure. To rapidly capitalize on favorable conditions, jellyfish can employ different life histories, which are either a life cycle with one annual sexual reproduction event and an overwintering benthic stage (metagenic life cycle), or continuous reproduction and a holoplanktonic life cycle. However, the links between life history, blooms, and environmental variability are unclear. Here, we examine how environmental variability can drive the bloom dynamics of typical jellyfish in coastal enclosed or semi-enclosed temperate ecosystems. With a simple community model, we reproduce typical seasonalities of the two strategies and trophic cascades triggered by abundant jellyfish, demonstrating how erratic blooms can be generated by irregular changes in the environment. Consistent with literature observations, we predict that metagenic jellyfish dominate early in the season, compared to holoplanktonic organisms, and are favored by increased seasonality. Our results reveal possible mechanisms driving coastal patterns of jellyfish blooms, and factors that are important for the outcome of competition between jellyfish with different life cycles. Such knowledge is important for our understanding of jellyfish blooms, which have large consequences for human activities and well-being, and may improve our ability to predict and manage local ecosystems.

Major Shifts in Pelagic Micronekton and Macrozooplankton Community Structure in an Upwelling Ecosystem Related to an Unprecedented Marine Heatwave

“…During warm years such as El Niños, food webs tend to be more elongated with additional intermediate trophic levels compared to cool years, leading to less trophic efficiency in the system (Brodeur and Pearcy, 1992;Ruiz-Cooley et al, 2017). The increased densities of these gelatinous microcarnivorous predators such as Aequorea victoria may have depressed populations of grazing copepods, thus creating a trophic cascade typical of many jellyfish blooms (Schnedler-Meyer et al, 2018), leading to the high chlorophyll levels we observed in 2015. In contrast, pelagic tunicates such as pyrosomes feed on smaller particles including phytoplankton (Perissinotto et al, 2007, but see Pakhomov et al, 2019), which may have depressed chlorophyll a levels as seen in 2016.…”

Ecological drivers of jellyfish blooms – The complex life history of a ‘well‐known’ medusa (Aurelia aurita)

“…Bordehore et al, ) to quantify and evaluate the development of jellyfish blooms from a food web perspective (cf. Schnedler‐Meyer, Kiørbøe, & Mariani, ). Although the temporal and spatial patterns of abundance in each life stage may vary according to jellyfish species (Lucas et al, ; Scorrano, Aglieri, Boero, Dawson, & Piraino, ) and even across populations of the same species (Dawson et al, ), our observations on the moon jellyfish are likely describing general trends.…”

Unique role of jellyfish in the plankton ecosystem revealed using a global ocean biogeochemical model

“…Data on the polyp stage of jellyfish is largely focussed on common species and almost exclusively lab-based, with the patterns observed being locale-and species-dependant. Modelling of jellyfish life cycles is still relatively new, with the focus of previous modelling studies also being locale-and species-dependant (Henschke et al, 2018;Schnedler-Meyer et al, 2018). Higher temperature within PlankTOM11 increases the growth rate, which translates into increased biomass if there is sufficient food, thus providing a representation of an increasing medusa population.…”