Horizontal and vertical distributions of siphonophores in relation to oceanographic conditions in Chilean Patagonian fjords

Abstract

Siphonophores collected in Chilean Patagonian fjords, between the Gulf of Penas and the Trinidad Channel in 2008 were analysed. A total of 12 species were recorded, of which Muggiaea bargmannae, Lensia subtilis, Praya dubia and Sphaeronectes fragilis were identified for the first time in this sector of the Patagonian fjords. M. bargmannae represents a new record for the southeastern Pacific. The most abundant species were Muggiaea atlantica (78.6%), Lensia conoidea (8.7%) and Dimophyes arctica (8.5%). M. atlantica, the dominant species, showed high densities in both oceanic and interior waters. L. conoidea and D. arctica, on the other hand, were principally collected in interior waters. M. atlantica was collected in less saline (< 30), more oxygenated (6-7 mL L–1) shallow strata (0-50 m), while L. conoidea and D. arctica were collected below 50 m depth in more saline (30-33) and less oxygenated (4-6 mL L–1) waters. The eudoxids of these species followed the same horizontal and vertical distribution patterns as their polygastric stages. These results confirm the success of M. atlantica in the colonization of all the southern fjords and document an increase with respect to the results obtained for the same geographical area in the spring of 1996. They also allowed us to infer that salinity and dissolved oxygen vertical gradients play an important role in determining the depth distribution patterns of these species.

Keywords

• siphonophores
• gelatinous zooplankton
• horizontal distribution
• vertical distribution
• chilean patagonian fjords