GLACIER MELTING AND STOICHIOMETRIC IMPLICATIONS IN LAKE COMMUNITY STRUCTURE: ZOOPLANKTON SPECIES DISTRIBUTIONS IN A NATURAL LIGHT-GRADIENT

CECILIA LASPOUMADERES; BEATRIZ MODENUTTI; MARIA S. SOUZA; MARCELA BASTIDAS NAVARRO; FLORENCIA CUASSOLO; ESTEBAN BALSEIRO

Congreso; ASLO 2012, Aquatic Sciences Meeting; 2012

Glaciers around the world are melting rapidly, threatening the world fresh water reservoirs with significant changes in the receiving environments. Meltwater, carried by rivers, contains high amounts of suspended sediment particles producing longitudinal gradients in the receiving lakes. The supply gradients of light and nutrients affect grazer performance by altering elemental food-quality. We evaluated the relative abundance of two consumer taxa with differing phosphorus requirements, across a lake with a strong longitudinal increase in transparency due to inputs of glacial flour at one end of the lake. We quantified variations in light:nutrient ratio, in stoichiometric food quality of the seston, and zooplankton distributions across a six-station transect. We found differences in optical properties and nutrients across the lake, together with a switch from dominance of P-rich Daphnia in low-light regions to dominance of low-P copepods in clearer waters. Thus, the overall patterns are consistent with predictions of the stoichiometric light:nutrient hypothesis and indicate that shifts in environmental light:nutrient ratio as a result of glacial melting may contribute to shifts in the relative abundance of stoichiometrically contrasting taxa in consumer guilds.