Vanesa Raya

Contrasting diel vertical migration patterns in Salpa fusiformis populations

Vertically stratified zooplankton sampling at three locations in the Catalan Sea demonstrated that the coexistence of two diel vertical migration patterns in Salpa fusiformis populations. Salps migrated to the surface during the day (reverse migration) at one station while they swam to surface layers at night (nocturnal migration) at the other two stations. While nocturnal migration was significant at the deepest station, reverse and nocturnal migrations at shallow stations were weak. Our data support the idea of reproductive, surface aggregation in this species, with a possibility that the larger individuals hit the bottom at the shallower stations, resulting in an apparently random migration pattern.

Long-term changes in the planktonic cnidarian community in a mesoscale area of the NW Mediterranean

In the present work, possible long-term changes in the planktonic cnidarian community were investigated by analyzing (1) species and community spatial distribution patterns, (2) variations in abundance and (3) changes in species richness during three mesoscale surveys representative of the climatic and anthropogenic changes that have occurred during the last three decades (years: 1983, 2004 and 2011) in the NW Mediterranean. These surveys were conducted during the summer (June) along the Catalan coast. All surveys covered the same area, used the same sampling methodology, and taxonomic identification was conducted by the same team of experts. An increase in the abundance of total cnidaria was found from 1983 to 2011. The siphonophore Muggiaea atlantica and the hydromedusa Aglaura hemistoma were the most abundant species, while Muggiaea kochii presented the largest abundance increment over time. Temperature was the main environmental parameter driving significant differences in the cnidarian community composition, abundance and spatial distribution patterns among the surveys. Our results suggest that in the current climate change scenario, warm-water species abundances will be positively favored, and the community will suffer changes in their latitudinal distribution patterns. We consider it extremely important to study and monitor gelatinous zooplankton in mesoscale spatial areas to understand not only long-term changes in abundances but also changes in their spatial distributions since spatial changes are sensitive indicators of climate change.