MEPS 591:241-251 (2018)  -  DOI: https://doi.org/10.3354/meps12266

ABSTRACT: Velella velella is a pleustonic colonial organism found in temperate and tropical oceanic waters worldwide. During certain periods of the year, large numbers of the species can wash up on coastal beaches. However, little information exists on the ecology and dispersal patterns of this cosmopolitan species, especially on their distribution at sea. How V. velella’s at-sea distribution changes with respect to local oceanographic conditions is important to determine their impact on zooplankton communities and the entire marine food web. Zooplankton samples collected off the northwestern Portuguese shelf during a spring oceanographic survey revealed considerable abundance of V. velella specimens, mostly in the pelagic phase. Drifters released in the sampling area were remotely followed to examine surface currents, and current velocities were registered, allowing the characterization of the oceanic conditions in the region. Sightings of V. velella collected through the ‘GelAvista’ program, a Portuguese citizen science initiative, were used complementarily, and provided important indications on periods of high abundance and probable areas of occurrence. Local wind regimes were the main driver of V. velella distribution and onshore transport, taking into account the direct exposure to the wind and surface circulation variability. The observed occurrences followed the predominant local alongshore currents and are discussed according to local ocean dynamics, enhancing the knowledge on the at-sea ecology of these organisms.

KEY WORDS: Jellyfish · Zooplankton · Transport · Distribution · Upwelling · Portugal