The larval and benthic stages of the scyphozoan medusa Chrysaora plocamia under El Niño-La Niña thermal regimes

article i nfo Jellyfish particularly scyphozoan population blooms appear to be increasing in strength and frequency in re- cent decades but efforts to understand drivers of population variability are hampered by the limited under- standing of the ecology of the larval and benthic stages of the majority of species which may ultimately determine the abundance of the pelagic phase. Planula larvae and polyps of the large scyphomedusa Chrysaora plocamia inhabiting the Humboldt Current Upwelling System of Chile and Peru were experimental- ly exposed to temperature regimes representing El Nino-La Nina and Neutral conditions. Settlement of plan- ulae was significantly affected only by El Nino temperature whereas survivorship of polyps was affected by both El Nino and La Nina temperatures. Somatic growth of polyps was negatively affected by both La Nina and El Nino temperatures although responses changed over the course of the experiment: whereas La Nina caused a longer term effect on the growth of polyps, under El Nino this showed a rapid recovery after an ini- tial decrease in somatic growth. Therefore we concluded that increased abundances of the pelagic phase of C. plocamia observed during El Nino cannot be attributed to improved conditions for settlement of larvae growth or survivorship of the benthic stage. A comparative analysis of the effects of temperature on settle- ment and metamorphosis of larvae and survivorship of polyps of scyphozoans showed that the performance of animals in these stages is higher within a species-specific thermal range which reflects seasonal tempera- ture variability of their environment.