Phytoplankton and zooplankton structure in lakes of the Patagonian steppe: the influence of the fish introduction

JULIO, LANCELOTTI; PORCEL, MARÍA SOL; INÉS, O?FARRELL; IRINA, IZAGUIRRE; MARINONE, M. C.; SAAD, J. F.

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Workshop; 18th WORKSHOP OF THE INTERNATIONAL ASSOCIATION OF PHYTOPLANKTON TAXONOMY AND ECOLOGY (IAP); 2017

INTERNATIONAL ASSOCIATION OF PHYTOPLANKTON TAXONOMY AND ECOLOGY

Most lakes of the basaltic plateaus of Patagoniaare naturally fishless, but during the last decade many of thoselocated at the Strobel Plateau have been stocked with rainbow trout(Oncorhynchus mykiss).Fish introductions have been identified among the main causes ofalterations in lakes, and studying the effects caused by exotic fishin lakes of this region is relevant because they constitute the mainfeeding and breeding habitat for several waterbird species, includingendemic threatened species such as the hooded grebe (Podicepsgallardoi). We surveyed differentfishless and fish stocked lakes of the Strobel Plateau in successivefield trips, and we analyzed the structure of phytoplankton andzooplankton. Our study revealed that phytoplankton was affected bythe presence of fish, probably due to a trophic cascade effect,registering the lowest phytoplankton biomass in fishless lakes.Phytoplankton assemblages also differed between both lake types:fishless lakes exhibited a higher proportion of nanoplanktonic taxa,many of them mixotrophic, belonging to functional groups X1, X2, Y, Dand MP; fish stocked lakes showed a higher proportion of species >20 µm, higher abundance of cyanobacteria in some of them, and themain functional groups were K, F, Lm, P, MP together with X1 and X2.We also found differences in the zooplankton structure betweenfishless and fish stocked lakes, with ahigher abundance of macrozooplanktonand Crustacea in fishless ones. On the other hand, we found that theeffect of fish introductions on planktonic communities seems to bepotentiated by a decrease in the water level of the lakes that istaken place in the region, as a consequence of lower precipitation.p { margin-bottom: 0.25cm; direction: ltr; line-height: 120%; text-align: left; }