Digestion and predation rates of zooplankton by the pleustonic hydrozoanVelella velellaand widespread blooms in 2013 and 2014

Surface-dwelling colonies ofVelella velellaoccur throughout tropical to cold-temperate oceans of the world and some-times are stranded in masses along hundreds of kilometers of beaches. Large-scale blooms in the WesternMediterranean Sea in 2013 and 2014 allowed the study of diet, prey digestion times and predation rates. Gastrozooidcontent analyses showed that 59% of the 769 identified prey were euphausiid larvae (calytopsis and furcilia) capturedat night. Copepods (41%), fish eggs (2.2%) and larvae (0.5%) were captured both at day and night. Digestion times atambient temperature (178C) of calytopsis, furcilia and copepods were estimated to be.6.5, 4.4 and 3.9 h, respect-ively. Estimated prey consumption was substantially lower in 2014 than in 2013 (41 vs. 75 prey day21colony21).Velella velellaand other gelatinous species bloomed in the Mediterranean Sea and the northeastern Atlantic and Pacificoceans in 2013 and 2014. Because of the wide distribution ofV. velellacolonies, their mass occurrences, potential im-portance as predators and competitors of fish, additional production from symbiotic zooxanthellae and stranding onbeaches, they could be important in open-ocean carbon cycling and in transport of pelagic production to landmasses.