The Mediterranean Sea is a region threatened by fast environmental changes and high coastal human impacts. Over the last decade, recurrent blooms of the harmful dinoflagellate Ostreopsis cf. ovata have been recorded in many Mediterranean beaches. Here we investigate whether the spatial-temporal distribution of this microalga and the frequency of its blooms could be altered in future regional climate change scenarios, with a special focus in the Western basin. An ecological niche model forced by physical and biogeochemical high-resolution climate change simulations under the strong greenhouse gas emission trajectory (RCP8.5) was used to characterize how O. cf. ovata may respond to projected conditions and how its distribution could shift in this plausible future. Before being applied to the niche model, the future climate change simulations are further refined by using a statistical adaptation method (Cumulative Distribution Function transform) to improve the representativity of the environmental parameters. Our results depict that O. cf. ovata abundances are driven by temperature (optimum 23-26 °C), high salinity (> 38 psu) and high inorganic nutrient concentrations (nitrate > 0.25 mmol N·m-3 and phosphate > 0.035 mmol P·m-3). Future projections suggest no changes in bloom intensity for mid- and end-century. Nevertheless high spatial disparities in future abundances are observed.. Namely, O. cf. ovata abundances could increase in the Mediterranean coasts of France, Spain and the Adriatic Sea while a decrease is expected in the Tyrrhenian Sea. The bloom period could also be enlarged, starting earlier and extending later in the year, which could have important consequences on marine ecosystems, human health and economy. From a methodological point of view, this study highlights good practices of ecological niche models in the context of climate change to identify sensitive areas for current and future harmful algal blooms.
Caulerpa taxifolia (Vahl) C. Agardh (Ulvophyceae, Caulerpales) is an algae of tropical origin that was accidentally introduced into the Mediterranean in 1984. Caulerpenyne (Cau) is the major metabolite present in Caulerpa taxifolia. This metabolite has previously been shown to be cytotoxic against cell lines in culture as in KB cells and fibroblasts from hamsters. Cau along with 6 other drugs representative of the major classes of anticancer products was tested against 8 cancer cell lines of human origin. Cau demonstrated growth-inhibitory effects in all cases with some variability between cell lines; this inter-cell variability was, however, less marked than that observed with the anticancer drug tested. Cells of colorectal cancer origin were the most sensitive to the presence of Cau with IC50 values of 6.1 and 7.7 microM. Increasing the duration of contact between Cau and the cells from 75 min to 29.5 hr did not improve the cytotoxic efficacy of this compound. When Cau was pre-incubated in the culture medium for from 7 to 83 min before being exposed to CAL 27 cells (head and neck cancer origin), there was a constant loss of cytostatic action of Cau as a function of Cau pre-incubation time. As the bovine serum albumin concentration increased in the culture medium, the concentration-response curves showed a constant shift towards the right, indicating a loss of cytostatic activity of Cau. In the presence of Cau, cells in culture clearly exhibited an early and marked shift into S phase followed by a blockade into the premitotic G2 M phase. Possible targets for CAU remain to be identified. Cau needs to be tested on tumor bearing animals to confirm this promising antiproliferative activity.
Ostreopsis cf. ovata development in relation with depth, biotic substrate and environmental factors in the North Western Mediterranean Sea in 2008 and 2009 years - MediOs 2 program.
