The seasonal dynamics of plankton communities relative to the foraging of the southern right whale ( Eubalaena australis ) in northern Patagonian gulfs, Península Valdés, Argentina

D'AGOSTINO, VALERIA C.; DEGRATI, MARIANA; SANTINELLI, NORMA; SASTRE, VIVIANA; DANS, SILVANA L.; HOFFMEYER, MÓNICA S.

CONTINENTAL SHELF RESEARCH

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2018 vol. 164 p. 45 - 57

0278-4343

This is the first exploratory study that addresses simultaneously the phytoplankton and mesozooplankton seasonaldynamics associated with some environmental factors in the northern Patagonian gulfs: Golfo Nuevo (GN)and Golfo San José GSJ), Argentina, during an annual cycle (December 2014?2015 and January 2015?2016,respectively). It also reports data on mesozooplankton composition and abundance in a sample collected whilesouthern right whales (Eubalaena australis) were feeding at the sea surface in Bahía Pirámide (GN). The phytoplanktoncommunity was represented by 69 taxa in GN and by 83 taxa in GSJ. In GN, phytoplankton wasmainly dominated by diatoms and dinoflagellates whereas in GSJ diatoms dominated the phytoplankton communitythroughout the year. In GN, the highest phytoplankton biomass and density values were registeredduring austral spring, 2015 which coincided with a Pseudo-nitzschia australis bloom. In contrast, the lowestbiomass values, which were associated with elevated abundances of dinoflagellates, were observed in late spring2014. In GSJ, the highest biomass values showed two equal peaks in austral autumn and spring 2015. The latterwas associated with the maximum cell density recorded in this gulf during a Chaetoceros debilis bloom. Incontrast, the lowest biomass values were recorded in winter 2015. Mesozooplankton was represented by 63 taxain GN and by 61 taxa in GSJ. In GN, this community was mainly represented by cladocerans and copepods,whereas it was dominated by copepods in GSJ. The lowest mesozooplankton abundances were recorded inaustral winter in both gulfs. In GN, the highest abundances were recorded in austral summer and spring 2015,whereas in GSJ, the maximum mesozooplankton abundances were observed during austral summer and autumn2015. The major prey items for E. australis were the copepods Calanoides carinatus, Ctenocalanus vanus, Calanusaustralis, and Paracalanus parvus, zoeae of the squat lobster Munida gregaria, calyptopis and furcilia of Euphausialucens, and fish eggs and larvae. In both gulfs, the warm seasons were mainly characterized by higher relativeabundances of diatoms, while the cold seasons were mostly associated with higher abundances of dinoflagellatesand Dictyochophyceae. Salinity and phaeopigments were related with copepod and appendicularian abundances,whereas surface sea water temperature seemed to modulate the seasonal distribution pattern of cladoceransand decapods.