Ecological Role of Common Appendicularian Species from Shelf Waters Off Argentina

Abstract

Appendicularians generally comprise a significant fraction of mesozooplanktonic tunicates in marine environments. Their eggs, trunks, and houses are important food supply to large copepods, chaetognaths, ctenophores, and larvae and adults of engraulids. They are semelparous and hermaphrodites (except O. dioica) organisms, with a short and temperature-dependent life cycle. In this chapter, we discuss the seasonal dynamics of appendicularians, comparing life strategies of dominant species at distinct coastal environments of the Southwest Atlantic Ocean. O. dioica, O. fusiformis, Appendicularia sicula, and Fritillaria borealis are common coastal species in the southwestern Atlantic. Total abundance, biomass, and house production of O. dioica and A. sicula were higher during spring and summer. O. dioica and A. sicula bloomed during summer with temperatures between 17 and 20 °C. O. fusiformis appeared occasionally during summer and fall but in very low densities. Fritillaria borealis prefers subantarctic and Antarctic cold (<11 °C) and salty waters. The contribution of appendicularians to the zooplankton secondary production had been underestimated. Here we emphasized the role of appendicularians as extraordinary producers of carbon and macroscopic aggregates in planktonic ecosystems, as it has been shown by several studies at the northern hemisphere and herein for the southern SW Atlantic Ocean.