Carybdea marsupialis (Cubozoa) at a shallow beach in West Mediterranean: are they where they want to be? Cesar Bordehore 1 , Elia Durá 1 , Antonio Ortiz 1 , Isidro Rico 1 , Melissa J. Acevedo 1,2 , Antonio Canepa and Verónica L. Fuentes 2 Fourth International Jellyfish Bloom Symposium, 5-7 June 2013 – Hiroshima, Japan 1, Department of Ecology and IMEM Ramon Margalef, University of Alicante, Spain. 2, Institute of Marine Sciences, Spanish Research Council, Barcelona, Spain. . INTRODUCTIONION Scyphozoan and cubozoan jellyfish are unevenly distributed. Differences in spatial distribution of adult jellyfish have been correlated with water temperature (1) or salinity and river run-off (2). Densities of cubozoans are generally low, with values of <3 medusae per 100m 3 (Great Barrier Reef, Australia , 3). In the studied area (W Mediterranean, SE Spain) we detected high densities of C. marsupialis in shallow waters (0 to 1,5 m depth) during Summer and Autumn 2008 (4). This high density of individuals in shallow waters resulted in a high number of stung bathers (3.330 people between 16 th July to 15 th September 2008). The next year (2009), we quantified densities and sizes of box jellyfish in order to compare them with the previous data collected in 2008, and we also measured other environmental variables to elucidate how this species interact with the environment. We analyze the correlation of C. marsupialis presence and densities with different parameters such as temperature, salinity, sea bottom, visibility, sea and sky condition. ISTUDY AREA Denia is a coastal city where sun-and-beach tourism is the main item on its economy. Each summer about 30.000-50.000 tourists are added to the permanent population of 45.000 inhabitants. There is intensive watered agriculture in the surroundings, which uses a high quantity of fertilizers rich in nitrate and phosphate. Rainfall range from 600 and 800mm per year, being mid-late autumn when rain is more abundant. Low salinity close to the shore was originated to by sub-surface aquifer discharge (~6· 10 6 m 3 ·y -1 , 120-170mg NO 3 = ·l -1 ). The study area comprises 17km along the coastline with a low underwater slope and a variety of sea bottoms: sand, Posidonia oceanica, boulders, and mud. We sampled at 8 beaches (organized into 5 groups) as in Bordehore et al (4) (Fig. 1). At each sampling point we took different number of samples, depending mainly on swell and accumulations of Posidonia oceanica death leaves in the sampling areas – net towing is impossible in such conditions-. IMATERIALS & METHODS Sampling We sampled from 1 th October to 15 th November 2009 performing net trawlings parallel to the coastline, by walking at 2-3 km·h -1 .We towed plankton nets of 4mm mesh, squared shape, 0.1256 m 2 of mouth area. We used a set of 4 nets in a row, approximately 1m apart each other. At each sampling site we sampled from 2 to 5 transects of 30 meters, leaving 30m of separation between each transect. At each transect we recorded environmental variables such as: substrate type (sand, mud, boulder, rocky), visibility (Sechhi disk in horizontal), sky conditions (sunny/cloudy), sea state (categorical scale:1-6, where 1 is calm and 6 is rough sea), and water temperature and salinity using a compact Infinity-CT attached to one of the nets (sensor depth at 0.4m – 0.6m). Data treatment We used Simple Generalized Linear Model (GLM) and Mixed (GLMM) to elucidate how Carybdea marsupialis distribution was correlated to the measured environmental factors. RESULTSION Different densities among sampling sites (fig 4) and before vs after a storm occurred at the middle of the period. Transects from 15 th October only captured 16 individuals in 2165,31 m 3 , being this amount of individuals not enough to perform any correlation analysis. We only used for analysis data from 2 th September to 14 th October to correlate densities of C. marsupialis with independent environmental values. C. marsupialis maximum density was recorded at Raset beach on 8th October (249,43 indv/100m 3 ). Comparing densities and individuals size (fig 5) structure between 2008 and 2009 data were similar at each beach. Environmental variables (fig 6): The variable that better explained the spatial distribution of C. marsupialis was low salinity (GLM, p-valor<0.001), with some values under 222 psu. We also obtained a significative correlation with low visibility (GLM, p- valor<0.001) and sunny days (GLM, p_valor<0.001). The other variables ȋwater temperatura, depth, and sea bottomȌ didn’t show positive correlation. CONCLUSIONSON Carybdea marsupialis at the sampling site shows patchy distribution (hundreds of meters) and high densities. We find that low salinity is positively correlated to C. marsupialis distribution as showed by other authors (Gordon et al 2004; Cutress and Studebaker, 1973). Low salinity in the study area was not due to any river runoff but to sub-surface aquifer discharge (~6 10 6 m 3 ·y -1 , and about 120-170mg NO 3 = ·l -1 ), and seems that the response of the cubomedusae to low salinity is the same independently of the low salinity origin. We also detect a positive correlation with low visibility and sunny days. Sea bottom had no any influence on C. marsupialis distribution, in contrast to other authors that stated that this species was associated with sandy bottoms (Di Camilo et al 2006). References: [1] Bettoso, N., 2002. First record of Carybdea marsupialis (L., 1758) (Cnidaria: Cubozoa) in the Gulf of Trieste. Periodicum Biologorum, 104, 233. [2] Gordon, M. R., C. Hatcher & J. E. Seymour, 2004. Growth and age determination of the tropical Australian cubozoan Chiropsalmus sp. Hydrobiologia 530: 339–345. [3] Hartwick, R. F., 1991. Distributional ecology and behavior of the early life stages of the box-jellyfish Chironex fleckeri. Hydrobiologia 216: 181–188. [4] Bordehore, C., Fuentes, V. L., Atienza, D., Barberá, C., Fernandez-Jover, D., Roig, M., Acevedo-Dudley, M. J., et al. (2011). Detection of an unusual presence of the cubozoan Carybdea marsupialis at shallow beaches located near Denia, Spain (south- western Mediterranean). Marine Biodiversity Records, 4(5), 1–6. This research was carried out under contract LIFE 08 NAT ES 0064 (to VF and CB) co- financed by the European Union, the Ministerio de Agricultura, Alimentación y Medio Ambiente, Fundación Biodiversidad, and the Dirección General del Agua of the Regional Government of Valencia. We also thank the collaboration of Balearia Foundation (www.balearia.com ), the Real Club Nautico Denia (www.cndenia.es ) and el Portet (www.elportetdedenia.es ). . 5km 1 2 3 4 5 Fig.1 Sampling sites. SE Spain. Beach names: 1: Deveses+Almadrava 2: Molins 3: Bovetes 4: Raset 5: Marineta Fig 2. Sampling with a set of 4 nets in a row. Fig 3. Measuring an individual of Carybdea marsupialis (distance between rhopalias). 0 10 20 30 40 50 before after before after before after before after before after Dev+Alm Molins Bov+Bris+Mar Raset Marineta indvs /100m3 +SE ND ND Figure 4. Density (Indv/100m 3 ) of Carybdea marsupialis adults at each group of adjacent beaches, grouped in two sets of data: before and after storm. Mean +SE. ND: No data. Before: samples from 2 nd to 14 th October 2009. After: samples from 20 th October to 2 nd November 2009. Storm began 15 th October, waves disappeared on 20 th October. Table 1. Number of transects done at each group of beaches, meters towed, m 3 of sea water filtered and densities (invds/100m 3 ) of Carybdea marsupialis and SE of the density. Figure 6. Carybdea marsupialis response to environmental factors Figure 5. Size histograms (in mm) at three periods. See how sizes are increasing from August to the end of October. www.cubomed.eu Transects number M towed M 3 filtered Indv. Captured Dens/ 100m 3 SE Deveses+Almadrava before 4 240 35,28 15 42,52 7,13 after 216 6480 952,56 2 0,21 0,01 Molins before 0 ND ND ND ND ND after 138 4140 608,58 0 0,00 0,00 Bovetes+Brisas+M.Reig before 56 3360 493,92 55 13,82 2,71 after 99 2970 436,59 0 0,00 0,00 Raset before 134 6690 983,43 305 31,48 15,92 after 38 1140 167,58 14 8,35 2,48 Marineta before 56 1680 246,96 0 0,00 0,00 after 0 ND ND ND ND ND Before storm 250 11970 1759,59 375 20.05 8.58 After storm 491 14730 2165,31 16 0.73 0.22 Total 741 26700 3924,9 391 7.25 2.91 View publication stats View publication stats