Environmental factors influencing the spatio-temporal distribution of Carybdea marsupialis (Lineo, 1978, Cubozoa) in South-Western Mediterranean coasts

Abstract

Jellyfish blooms cause important ecological and socio-economic problems. Among jellyfish, cubozoans are infamous for their painful, sometimes deadly, stings and are a major public concern in tropical to subtropical areas; however, there is little information about the possible causes of their outbreaks. After a bloom of the cubomedusa Carybdea marsupialis (Carybdeidae) along the coast of Denia (SW Mediterranean, Spain) in 2008 with negative consequences for local tourism, the necessity to understand the ecological restrictions on medusae abundance was evident. Here we use different models (GAM and zero-inflated models) to understand the environmental and human related factors influencing the abundance and distribution of C. marsupialis along the coast of Denia. Selected variables differed among medusae size classes, showing different environmental restriction associated to the developmental stages of the species. Variables implicated with dispersion (e.g. wind and current) affected mostly small and medium size classes. Sea surface temperature, salinity and proxies of primary production (chl a, phosphates, nitrates) were related to the abundances of small and large size classes, highlighting the roles of springtime salinity changes and increased primary production that may promote and maintain high densities of this species. The increased primary (and secondary) production due to anthropogenic impact is implicated as the factor enabling high numbers of C. marsupialis to thrive. Recommendations for monitoring blooms of this species along the study area and applicable to Mediterranean Sea include focus effort in coastal waters where productivity have been enriched by anthropogenic activities.

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

“…The cubomedusae were captured using plankton nets dragged parallel to the coastline. In order to detect the first appearance of new cubomedusae, coastal sampling started in January and used a 500-μm-mesh net to collect them, as suggested by Canepa et al [12].…”

“…After 2008, abundances of cubomedusae in this area have shown high inter-annual variability. For instance, the mean density of C. marsupialis in 2010-2011 was 0.8 ind m −3 [12], but 0.17 ind m −3 in 2013 [13]. More recently, this species has been found in Malta [14] and off the east coast of Tunisia, with an average of 1.1 ind m −3 and a maximum of 1.8 ind m −3 [15].…”

“…The seasonality and lifecycle of C. marsupialis have been studied in the scope of the LIFE CUBOMED Project on the Spanish Mediterranean coast [12,13,16]. The life cycle of this cubozoan alternates between a planktonic stage as a sexually-reproductive cubomedusa and an asexually-reproductive benthic stage as a cubopolyp.…”

“…Previous analyses of the abundance and distribution of C. marsupialis at 0.5-1 m depth off Dénia showed an inverse relationship between medusa abundance and salinity [16] and occurrence of this species in conditions of low salinity, high coastal productivity (Chl- a and phosphate) and optimal physical conditions (wind current speed and direction) [12]. Medusa outbreaks also were linked with anthropogenic nutrient inputs (N, P and Si) and high productivity [13].…”

“…Medusa outbreaks also were linked with anthropogenic nutrient inputs (N, P and Si) and high productivity [13]. We built on these earlier works to focus on the distribution of juvenile C. marsupialis , by use of a more detailed sampling grid that included points at different depths in the water column and three distances from the coast to overcome the spatial restrictions pointed out by Canepa et al [12]. Our main objective in 2015 was to determine the relationships between the abundance of juvenile C. marsupialis and the environmental variables: temperature, salinity, nutrients (N, P and Si), Chl- a and zooplankton.…”