Plankton dynamics and marine biotoxin transfer to the southern right whale Eubalaena australis through feeding in Nuevo and San José gulfs, Península Valdés, Chubut, Argentina

D'AGOSTINO, VALERIA C.

MASTOZOOLOGíA NEOTROPICAL

UNIDAD DE ZOOLOGÍA Y ECOLOGÍA ANIMAL, INSTITUTO ARGENTINO DE INVESTIGACIÓN DE LAS ZONAS ARIDAS, CRICYT, CONICET

Lugar: Mendoza; Año: 2017 vol. 24

0327-9383

Phytoplankton community in Nuevo (GN) and San José (GSJ) Gulfs is dominated by diatoms and dinoflagellates. Species that are potential producers of domoic acid (DA) of the genus Pseudo-nitzschia are frequent components of phytoplankton in these gulfs. The dinoflagellate Alexandrium tamarense, a producer of paralytic shellfish poisoning (PSP) toxins, has been found in this area showing a tendency to produce blooms in spring. Copepods are the most abundant group in the mesozooplankton community both in GN and GSJ, its maximum densities occurring during spring after the spring phytoplankton bloom. Recent studies have demonstrated that the southern right whale Eubalaena australis feeds during its stay in GN and GSJ. Still, feeding in these gulfs could be dangerous for the whales due to the recurrent toxic phytoplankton blooms in this area during spring. The effect of toxins on whales? health has been postulated to be one of the causes of the calves? mortality observed in Península Valdés in the last years. The aims of this Ph. D. Thesis were i) to study seasonal variations in food availability in qualitative and quantitative terms for individuals of E. australis, and ii) to analyze biotoxin transfer from phytoplankton-producing species to vectors in mesozooplankton and from them to whales. During the annual cycle studied (December 2014-December 2015 in GN and January 2015-January 2016 in GSJ) phytoplankton in GN as well as in GSJ was dominated by diatoms and dinoflagellates. Toxic microalgae species were more frequent during spring, including a bloom of Pseudo-nitzschia australis in October in GN. Mesozooplankton in GN was dominated by copepods and cladocerans while in GSJ it was dominated by copepods. In both gulfs copepods were associated to phaeopigments and salinity whereas cladocerans were positively correlated to temperature. Mesozooplankton abundance and biomass were in general low during the season of whales (winter and spring). Interestingly, a remarkable mesozooplankton biomass was observed towards the end of winter in GN, a total of ~17-20 whales being recorded filtrating seawater. The main prey for E. australis were calanoid copepods, Munida gregaria zoea larvae, Euphausia lucens caliptopis, furcilia, juveniles and adults as well as several ichthyoplankton organisms. DA was also detected in the water column, in the plankton samples and in faecal material from live specimens of E. australis. This study demonstrates for the first time that the southern right whale is exposed to DA through feeding in Península Valdés and that copepods could be the principal vector of this toxin. It was nonetheless not possible to verify the transfer of PSP toxins through the food web nor was it possible to show that this transfer could affect whales.