Spatial distribution of salps in the Catalan Sea, Northwestern Mediterranean

Abstract

Salps are pelagic tunicates with high feeding, growth and fecal pellet production rates. These features allow them to efficiently graze on algal blooms, rapidly developing dense populations which mediate significant fluxes of organic matter to the bottom. Their complex life cycle, ephemeral appearance and patchy distribution make them difficult to study, which explains why they have been barely investigated in the Northwestern Mediterranean Sea. Our study analyzes the specific composition and the mesoscale distribution of salps in the Catalan Sea. The aim was to investigate how the spatial patterns are structured by local physical (temperature, salinity) and biological (chlorophyll-a and zooplankton concentrations) conditions. Salps were sampled by oblique bongo tows in 70 stations along the Catalan Sea during the FishJelly cruise in June 2011. The two species found had distinct distributions with Thalia democratica occupying shelf areas while Salpa fusiformis had an offshore distribution. Although salp blooms naturally occur every year in the Catalan coast, changes in environmental factors such as temperature or chlorophyll due to anthropogenic activities could lengthen their presence and might have an effect on the ecosystem