Resumen de Seasonal Cycle of Appendicularians at a Coastal Station (38°28's, 57°4'w) of the SW Atlantic Ocean
F.L. Capitanio, Jessica Curelovich, Martín Tresguerres, R.M. Negri, María Delia Viñas, Graciela B. Esnal
Temporal fluctuations in appendicularian species composition, abundance, size structure, and biomass, and their relationships with physical and biological factors were studied biweekly to monthly from March 2000 to April 2001 at a coastal station (38°28's, 57°4'w) off Argentina, SW Atlantic Ocean. The highest abundances and biomasses were recorded during spring-summer with a maximum in early January (4369 ind m-3 = 2321 [micro]g C m-3). Secondary production was 76 mg C m-3 yr-1 and house production was 123 mg C m-3 yr-1 Abundance of Fritillaria borealis Lohmann, 1896 was related to temperature changes, being more abundant during fall-winter; however, we measured only low biomasses. Appendicularia sicula Fol, 1874 and Oikopleura fusiformis Fol, 1872 appeared during summer and autumn, but their abundances were low. Oikopleura dioica Fol, 1872 was present all year and was the dominant species. When chlorophyll-a concentration was high, and copepod abundance was low (fall-winter period), both juvenile and adult O. dioica were abundant in all of the samples. During the spring-summer period (low chlorophyll-a concentration) a high predominance of adult animals (up to 1400 [micro]m TL) was observed, suggesting a strong predation by copepods upon O. dioica eggs and juveniles. However, further field evidence is needed to test this hypothesis.
