BALSEIRO esteban Gabriel
Glacier melting and stoichiometric implications for lake community structure: zooplankton species distributions across a natural light gradient
LASPOUMADERES, C.; MODENUTTI, B.E.; SOUZA, M.S.; BASTIDAS NAVARRO, M.; BALSEIRO, E.G
GLOBAL CHANGE BIOLOGY
WILEY-BLACKWELL PUBLISHING, INC
Lugar: Londres; Año: 2013 vol. 19 p. 316 - 326
Glaciers around the globe are melting rapidly, threatening the receiving environments of the worlds fresh water reservoirswith significant changes. The meltwater, carried by rivers, contains large amounts of suspended sedimentparticles, producing longitudinal gradients in the receiving lakes. These gradients may result in changes in thelight : nutrient ratio that affect grazer performance by altering elemental food quality. Thus, glacial melting mayinduce a shift in the phytoplankton carbon : nutrient ratio and hence influence the dominance of herbivorous zooplanktonthrough stoichiometric mechanisms. To test this hypothesis, we combined field and experimental data, takingadvantage of a natural light intensity gradient caused by glacial clay input in a deep oligotrophic Patagonianlake. Across this gradient, we evaluated the abundances of two consumer taxa with different phosphorus requirements,the copepod Boeckella gracilipes and the cladoceran Daphnia commutata, using a six-station transect along thelake. We found significant differences in light : nutrient ratio and stoichiometric food quality of the seston, togetherwith a switch from dominance of P-rich Daphnia in low carbon : nutrient stations to dominance of low-P copepods inhigh carbon : nutrient stations. The laboratory experiments confirmed that the difference in the carbon : nutrientratio across the gradient is sufficient to impair Daphnia growth. The overall patterns are consistent with our predictionthat shifts in the environmental light : nutrient ratio as a result of glacial melting would contribute to shifts in thedominance of stoichiometrically contrasting taxa in consumer guilds.