Stoichiometric constraints in plankton communities of Patagonian lakes. Implications for Parabroteas sarsi distribution and conservation

BALSEIRO, ESTEBAN; MODENUTTI, BEATRIZ; LASPOUMADERES, CECILIA; SCHENONE, LUCA; BASTIDAS NAVARRO, MARCELA; MARTYNIUK, NICOLÁS

ECOLOGÍA AUSTRAL

ASOCIACIÓN ARGENTINA DE ECOLOGÍA

Año: 2022 vol. 32 p. 638 - 649

0327-5477

The Patagonian region, from the Andes to the steppe, includes a profuse hydrographic networkwith deep and shallow lakes. Here, we analyze the stoichiometric constraints for the large predaceouscopepod Parabroteas sarsi in fish and fishless lakes. For this purpose, we examined previous literature data onthe composition of the zooplankton community in different Patagonian lakes with and without fish (mainlyintroduced in the XX century) and own laboratory and field experiments. The ecological stoichiometrytheory predicts that consumers need to a􀄴ain specific elemental ratios to achieve maximum growth, and thegeometric framework of nutrition proposes that consumers may need to combine food items to fulfill nutrientrequirements. We show that the predaceous copepod does not necessarily encounter prey that fulfills theirstoichiometric requirements, thus growth is impaired. However, through the combination of different prey,this predator can fulfill its requirements. In the presence of fishes, food webs change towards smaller-sizedzooplankton species with the loss of low C:nutrient ratio species. In this sense, we demonstrate the direct andindirect impact of fish introduction on the stoichiometric balances and the disappearance of this invertebratepredator in lacustrine food webs.