Effects of environmental variables on the distribution of juvenile cubomedusaeCarybdea marsupialisin the coastal Western Mediterranean

AbstractRelationships between environmental factors and oscillations in jellyfish abundance, especially in the early life stages, could help to interpret past increases and also predict scenarios in a changing future. For the first time, we present cubozoan spatial and temporal distributions in the earliest stages and their relationships with different factors. Abundances ofCarybdea marsupialismedusae showed high interannual variability from 2008 to 2014 along the Dénia coast (SE Spain, W Mediterranean). During 2015, samples were collected from 11 beaches along 17 km of coastline, 8 times from January to November in order to determine the effects of environmental factors on the distribution of juvenileC. marsupialis. Juveniles (≤ 15 mm diagonal bell width) were present from May to July, with more sampled near shore (0 – 15 m). Most of them occurred in June when their numbers were unequal among beaches (average 0.05 ind m−3, maximum 6.71 ind m−3). We tested distributions of juveniles over time and space versus temperature, salinity, nutrients (N, P and Si), chlorophyll-a(Chl-a), and zooplankton abundance. Temperature and cladocerans (zooplankton group) were significantly positively correlated with juvenile distribution, whereas Chl-aconcentration was weakly negative. By contrast, in 2014, high productivity areas (Chl-aand zooplankton) overlapped the maximum adult abundance (5.2 ind m−3). The distribution of juveniles during 2015 did not spatially coincide with the areas where ripe adults were located the previous year, suggesting that juveniles drift with the currents upon release from the cubopolyps. Our results yield important insights into the complexity of cubozoan distributions.