Ecological rol of common appendicularian species from coastal South West Atlantic Ocean

PRESTA MARIA LAURA; PAJARO, M; CAPITANIO, F; AGUIRRE, G.; DERISIO, C; SPINELLI, M; CERVETTO, G

Plankton ecology from the Southwestern Atlantic- From the tropical to subantarctic realm

SPRINGER

Lugar: Berlin; Año: 2018; p. 201 - 218

Among tunicates, appendicularians generally comprise a significant fraction of mesozooplankton in marine environments. Oikopleura dioica. Oikopleura fusiformis, Appendicularia sicula and Fritillaria borealis are common coastal Southwestern Atlantic species. They are semelparous organisms with short life cycle-strongly temperature dependent, being all hermaphrodites, excepting O. dioica. A comparison of life strategies of these species at distinct coastal environments of the South West Atlantic Ocean is provided using available literature. At the EPEA temperate coastal station (38°28´S-57°41´W), a seasonal succession of appendicularians was investigated. Total abundances, biomasses and secondary and house productions were higher during spring and summer. Oikopleura dioica and A. sicula bloomed during summer with temperatures between 17°-20°C. Oikopleura fusiformis appeared occasionally during summer and fall but in very low densities. Fritillaria borealis was more abundant during winter associated with temperatures below 11°C. This species prefers Subantarctic and Antarctic waters such as those of the Beagle Channel (ca 55°S - 68°W), where it can bloom. At the Río de La Plata estuary, the variability of river discharges is reflected on the species spatial distribution. Oikopleura fusiformis and F. borealis are better represented at high salinity waters. Particularly, the contribution of appendicularians to the carbon flux is enhanced in this estuary during El Niño events due to higher biomasses, higher pellet production and higher houses renewal. In the Valdés Peninsula front, high abundance of O. dioica was found in transitional and stratified areas. This species performs diel vertical migration, whether for feeding, avoiding predators and/or spawning their gametes. It is well known that appendicularians are important food supply worldwide; being their eggs, trunks and houses commonly preyed by large copepods, chaetognaths, ctenophores and larvae and adults of Engraulis spp. A top down control of O. dioica population is speculate to occur at this system being retained through their diel vertical migration.