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Volume 44 - Number 2 - 2009


Interannual changes in biomass and diversity of the gelatinous zooplankton in the interior waters of Chiloé, southern Chile (Springs 2004 and 2005)

Francisco Villenas1, Daniela Soto1 y Sergio Palma1


1Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, Casilla 1020, Valparaíso, Chile




Zooplankton biomass was compared between the fraction of chitinous and gelatinous organisms from the southern region of Chile between Puerto Montt and Boca del Guafo, in the springs of 2004 and 2005. The biomass
values were higher in 2004, being mainly composed by chitinous fraction, particularly in the north microbasin. Conversely, during 2005, a sharp increase of the gelatinous fraction was observed reaching 60% of the total biomass in the northern microbasin, and gradually decreasing into the Boca del Guafo. The increase in biomass seemed to be a result of the explosive
proliferation of the siphonophore Muggiaea atlantica, whose densities increased 5.6 folds in 2005, triggering a drastic decrease
in diversity of the gelatinous zooplankters. In both springs, 34 species of semi- and gelatinous organisms were identified, distributed in six chaetognaths, six siphonophores and 22 hydromedusae. Chaetognaths and siphonophores had previously been registered for the study area, but all hydromedusae encompass new records for the area
between Puerto Montt and Boca del Guafo


Key words: Zooplankton biomass, chaetognaths, siphonophores, hydromedusae, Chiloé Island



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