The effect of freshwater pulse on Aurelia aurita (Linnaeus 1758) (Cnidaria: Scyphozoa): an ecohydrological solution for controlling jellyfish blooms

Amorim, Katherine

http://hdl.handle.net/10400.1/7805

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Authors

Amorim, Katherine

Advisor(s)

Teodósio, Maria Alexandra

Abstract(s)

Jellyfish blooms are increasingly being reported in coastal areas and have been related to both climate changes and anthropogenic impacts. However, several questions underlying such blooms remain understudied, particularly during their benthic phase (polyps). Salinity is one of the environmental variables that has been linked with blooms occurrence. Reports in Guadiana estuary have correlated high precipitation and high freshwater input to low medusa occurrence. Therefore, we hypothesize that using freshwater pulses from a hydrotechnical structure (Dam) could be a promising ecohydrological approach for controlling jellyfish blooms. To explore this idea, the present study aimed to assess different short term salinity concentrations effects on benthic stages and ephyrae larvae of Aurelia aurita. It also explored the feeding ecology of such stages. It had two set of experiment designs. The first set of experiments focuses on responses of scyphistomae (Experiment I, II ) and ephyrae larvae (Experiment III) under low salinity treatments (3,10,17 and 35(control)). The analyzed variables were survival, asexual reproduction and ecophysiological response (feeding rate and number of swimming pulses). It was found significant difference on scyphistomae survival between control and salinity 3 treatment (p-value < 0,05); on budding reproduction, number of scyphistoma actively budding and feeding response between control and salinity 10; on ephyrae survival between control and salinities 3 and 10 ; and ephyrae swimming pulses between control and salinity 17. It did not present significant difference on the number of strobilating scyphistoma and produced medusa. The second set of experiments investigated diet and feeding strategy of scyphistomae (Experiment IV) and ephyrae (Experiment V). It was used Costello plot method. The present study concluded that short term freshwater pulse may control jellyfish blooms by affecting jellyfish early phases survival, their ecophysiological response, and scyphistomae budding reproduction. It was also concluded that ephyrae and scyphistomae feeding strategy are generalists.