Stoichiometric constraints in plankton communities of Patagonian lakes: implications for Parabroteas sarsi distribution and conservation

BALSEIRO, E. G.; MODENUTTI, B. E.; LASPOUMADERES, C.; BASTIDAS NAVARRO, M.; MARTYNIUK, N.

ECOLOGÍA AUSTRAL

ASOCIACIÓN ARGENTINA DE ECOLOGÍA

Lugar: Buenos Aires; Año: 2022

0327-5477

The Patagonian region, from the Andes to the steppe,includes a profuse hydrographic network with deep and shallow lakes.  Here, we analyze the stoichiometricconstraints for the large predaceous copepod Parabroteas sarsi in fish and fishless lakes.For this purpose, we examined previous literature data on the composition ofthe zooplankton community in different Patagonian lakes with and without fish(introduced mainly in the XX century) and own laboratory and field experiments.The ecological stoichiometry theory predicts that consumers need to attainspecific elemental ratios to achieve maximum growth, and the geometricframework of nutrition proposes that consumers may need to combine food itemsto fulfill nutrient requirements. We show that the predaceous copepod does notnecessarily encounter prey that fulfills their stoichiometric requirements,thus growth is impaired. However, through the combination of different prey,this predator can fulfill its requirements. In the presence of fishes, foodwebs change towards smaller-sized zooplankton species with the loss of lowC:nutrient ratio species. In this sense, we demonstrate the direct and indirectimpact of fish introduction on the stoichiometric balances and the disappearanceof this invertebrate predator in lacustrine food webs.