Contrasting structural patterns of the mesozooplankton community result from the development of a frontal system in San José Gulf, Patagonia

HERNÁNDEZ-MORESINO, RODRIGO D.; VILLANUEVA-GOMILA, GABRIELA L.; HERNÁNDEZ-MORESINO, RODRIGO D.; VILLANUEVA-GOMILA, GABRIELA L.; CRESPI-ABRIL, AUGUSTO C.; BARÓN, PEDRO J.; CRESPI-ABRIL, AUGUSTO C.; BARÓN, PEDRO J.; DI MAURO, ROSANA; COMPAIRE, JESUS C.; DI MAURO, ROSANA; COMPAIRE, JESUS C.

ESTUARINE COASTAL AND SHELF SCIENCE

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 2017 vol. 193 p. 1 - 11

0272-7714

The structural patterns of the mesozooplankton community of San José Gulf (SJG), a semi-enclosed basin located in the northern margin of the Valdés Peninsula (Argentinian Patagonia) were studied by means of semi-automatic image analysis. Samples were obtained bimonthly during the warm season (October-April) at stations distributed on a regular grid. Cluster analyses rendered two spatiallyconsistent groups of stations, showing perfect match when based on physical variables (SST and Chl-a) and on community structure descriptors (abundance, biomass, size spectra and evenness index), each distributed on one of two previously described hydrographic domains generated by the interaction of tidal circulation, coastal morphology and bottom topography. Examination of size spectra revealed that the stratified waters of the East domain sustain higher proportions of small organisms than its vertically mixed West counterpart. Dominance of cladocerans in the former and of large copepods in the later imply the occurrence of contrasting trophic cascades that could result in different secondary productivities. Three-clustering analyses resulted in still spatially consistent groups of stations when based on the community descriptors, revealing the existence of a transition zone, presumably resulting from intermediate hydrodynamic conditions. Principal component analysis revealed that biomasses ofthe main taxonomic groups relates to the velocity of horizontal tidal circulation, while the size spectra and evenness indexes relate to the longitude of sampling stations, given support to the hypothesis that in SJG the vertical stratification of the water column, determined by the tidal circulation, and thestructure of the mesozooplankton community are strongly related.