Seasonal succession of gelatinous zooplankton (medusae and ctenophores) from Buenos Aires coast, Argentina (SW Atlantic Ocean).

PUENTE TAPIA; GENZANO

Ecología Austral

Ecologia austral

Año: 2019 vol. 29 p. 339 - 351

1667-7838

ABSTRACT. Temporal variation of the population dynamics of the medusae and ctenophores (gelatinouszooplankton) is described over an annual cycle in the Mar del Plata Harbor, Argentina. A total of 18 specieswere identified, 3 of which were ctenophores (2 of Class Tentaculata and 1 of Nuda) and 15 medusae (14 ofClass Hydrozoa and 1 of Scyphozoa). A species of hydromedusae, Annatiara affinis, was observed for thefirst time in the Argentine Sea. In both groups, species richness and abundances showed the lowest valuesin the cold period (austral autumn-winter) and the highest values in the warm period (spring-summer). Themeroplanktonic medusae Obelia sp. and Eucheilota ventricularis as well as the holoplanktonic Liriope tetraphyllarepresented 94.2% of the total abundances of this group (classified as dominant). In the ctenophores, thedominant species were Pleurobrachia pileus and Mnemiopsis leidyi, which accounted for 99.3% of the ctenophores.Monthly medusae succession indicated that holoplanktonic species were dominant over practically all theannual cycle in terms of abundance, while considering species richness values, meroplanktonic speciesshowed highest values. Ctenophores (considering abundance values) was displayed alternating periods ofapproximately three months of dominance between P. pileus and M. leidyi. The Bray-Curtis similarity indexperformed on medusae identified two groups of seasons with faunal affinity, the 1) cold and 2) warm periods,with the water temperature and non-gelatinous zooplankton abundances as the environmental factors thatbest explained this variability (BIO-ENV analysis), while for ctenophores, temporal faunal homogeneity wasobserved and a single group with faunal affinity was identified.