A matter of tolerance: Distribution potential of scyphozoan polyps in a changing environment

Abstract

Jellyfish blooms are unpredictable, unsustainable events, frequently affecting aquatic ecosystems severely. Of particular interest are the consequences of environmental change for jellyfish populations, especially in semi‐enclosed habitats. Regional and seasonal changes in water chemistry and physics may control the distribution of sessile polyps in the Baltic Sea, hence potentially driving the population dynamics of the two abundant medusa species Aurelia aurita and Cyanea capillata (Scyphozoa, Cnidaria). In laboratory experiments, settlement, growth, survival and physiological condition of A. aurita polyps were investigated at different levels of water temperature, pH and salinity. Survival and physiological condition of C. capillata polyps were examined after exposure to low salinity levels. Increased settlement of A. aurita planula larvae was observed on substrate plates at low temperature (4°C), low pH (7.4) and low salinity (7.5 psu), whereas early polyp growth was constrained by salinity ≤10 psu. Aurelia aurita polyps were in good physiological condition over the whole temperature range, while exposure to pH <6.5 led to stepwise tissue degradation. Salinity reduction to ≤5 and ≤8 psu caused irreversible degeneration of A. aurita and C. capillata polyps, respectively. Observed physiological limits suggest distribution of polyp populations of A. aurita in central and of C. capillata in western parts of the Baltic Sea, while future climate changes may particularly restrict occurrence of the less tolerant C. capillata.

Impact of ocean warming and ocean acidification on asexual reproduction and statolith formation of the symbiotic jellyfish Cotylorhiza tuberculata

“…The influence of pH on asexual reproduction by budding was negligible ( p = 0.297), indicating that the OA scenario expected under the RCP8.5 will not lead to massive disappearance of polyps, at least under tested temperatures (18, 24 and, 30°C). This response coincides with previous findings [ 15 , 33 , 60 , 61 ]. Winans & Purcell [ 19 ] observed no effect of acidification (pH 7.2) on asexual reproduction of polyps of the scyphozoan jellyfish A .…”

“…High tolerance to elevated P CO2 has also been described for A . aurita polyps [ 33 , 61 ], which survived even to extreme acidification conditions (pH 4.5) [ 33 ]. In contrast, a decrease in the asexual reproduction by budding under future temperatures and pH levels (pH 7.6) has been reported in the Irukandji jellyfish A .…”

“…Similar results regarding asexual reproduction of scyphozoan polyps were obtained when combining reduced pH with low oxygen concentrations [ 31 , 32 ]. Recent laboratory studies have tested the effects of OA on other jellyfish life stages, from planula larvae [ 33 , 34 ] to ephyrae [ 31 , 32 , 35 ] and even on adult medusae [ 36 – 38 ]. The differential responses reported seem to be related to the magnitude of the stressors, life stage, and species-specific tolerance limits.…”

Ocean acidification causes mortality in the medusa stage of the cubozoan Carybdea xaymacana

“…using alkaline pH treatments), these few studies found positive and negative non-lethal effects of pH on jellyfishes, depending on life stages and species, and have led to the general perception that jellyfish are relatively resilient to OA 13 . Thus far, only a pH below 4.5 (far more acidic than OA projections) led to mortality in polyps of the moon jellyfish Aurelia aurita 14 . Only one study investigated the reproductive life stage of jellyfish (i.e.…”

“…46 Scyphozoa Aurelia aurita Ephyra7.6Smaller size and lower pulsation rateGoldstein et al . 14 Scyphozoa Aurelia aurita Planula larva; polyp7.4 (larva) 2 (polyp)Increased larvae settlement and tissue degradation (pH < 6.5) and mortality (pH < 4.5) of polypsKlein et al . 24 Cubozoa Alatina alata Polyp7.55Reproductive and protein content resilience, and increased early respiration rate under predicted temperature increase.…”