Glacier melting and stoichiometric implications for lake community structure: zooplankton species distributions across a natural light gradient

Abstract

Glaciers around the globe are melting rapidly, threatening the receiving environments of the world's fresh water reservoirs with significant changes. The meltwater, carried by rivers, contains large amounts of suspended sediment particles, producing longitudinal gradients in the receiving lakes. These gradients may result in changes in the light : nutrient ratio that affect grazer performance by altering elemental food quality. Thus, glacial melting may induce a shift in the phytoplankton carbon : nutrient ratio and hence influence the dominance of herbivorous zooplankton through stoichiometric mechanisms. To test this hypothesis, we combined field and experimental data, taking advantage of a natural light intensity gradient caused by glacial clay input in a deep oligotrophic Patagonian lake. 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 the lake. We found significant differences in light : nutrient ratio and stoichiometric food quality of the seston, together with a switch from dominance of P-rich Daphnia in low carbon : nutrient stations to dominance of low-P copepods in high carbon : nutrient stations. The laboratory experiments confirmed that the difference in the carbon : nutrient ratio across the gradient is sufficient to impair Daphnia growth. The overall patterns are consistent with our prediction that shifts in the environmental light : nutrient ratio as a result of glacial melting would contribute to shifts in the dominance of stoichiometrically contrasting taxa in consumer guilds.

Rapid decline of snow and ice in the tropical Andes – Impacts, uncertainties and challenges ahead

“…When the glacier has vanished, this habitat may disappear, nutrient levels will shift and food resources increase. Hence, glacier melting will probably have profound effects on both species composition and behavior of several planktonic taxa with potential effects on the food web (Hylander et al, 2011;Laspoumaderes et al, 2013).…”

First Observations of Boeckella michaelseni Mrázek 1901 in and Optical Properties of a Central Patagonian Lake

“…In marine environments zooplankton mortality, mainly associated with the chemical properties of the ice, has been found in areas close to ice fields [11,12]. For Patagonian lakes the glacial influence is water turbidity due to glacier sediments and dissolved organic matter, which prevents light penetration into the water column [13,14], with the consequences in photosynthesis activity that involve the biogeochemical process of nutrient input from phytoplankton that are grazed by zooplankton, such as was observed in Argentinean Patagonian lakes [14].…”

Spectral Properties Observations in Lakes of a Chilean National Park

“…denoted using remote sensing techniques determined for Patagonian lakes with marked environmental heterogeneity such as were observed for Tagua Tagua and General Carrera lakes [4][5][6]. The environmental heterogeneity for Patagonian lakes has been described with details mainly in trophic status and associated basins [7][8][9], but recently optical properties associated with ecological implicances due to the presence of associated glaciers with consequent changes in water coloration properties, light absorption, and changes in associated trophic webs have been studied [10][11][12], and these results can be associated with optical properties obtained from satellite images [4][5][6]. Many of these lakes are located in zones with serious accessibility issues, and only a few of them are not accessible by mountain paths [1,3].…”