Climate-induced input of turbid glacial meltwater affects vertical distribution and community composition of phyto- and zooplankton
SAMUEL HYLANDER; THERESE JEPHSON; KAREN LEBRET; JESSICA VON EINEM; TONY FAGERBERG; ESTEBAN BALSEIRO; BEATRIZ MODENUTTI; MARÍA SOL SOUZA; CECILIA LASPOUMADERES; MIKAEL JONSSON; PETER LJUNGBERG; ALICE NICOLLE; PER ANDERS NILSSON; LYNN RANNAKER; LARS-ANDERS HANSSON
JOURNAL OF PLANKTON RESEARCH
OXFORD UNIV PRESS
Año: 2011 vol. 33 p. 1239 - 1239
Receding glaciers are among the most obvious changes caused by global warming, and glacial meltwater entering lakes generally forms plumes of particles. By taking vertical samples along a horizontal gradient from such a particle source, we found that photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) attenuated 2025% faster close to the inflow of suspended particles compared with the more transparent part of the gradient. All sampled stations had a deep chlorophyll a (Chl a) maximum at 1520 m which was more distinct in the transparent part of the horizontal gradient. Picocyanobacteria increased in abundance in more transparent water and their numbers were tightly correlated with the intensity of the deep Chl a maxima. Motile species of phytoplankton had a deeper depth distribution in transparent versus less transparent water. Yet other species, like Chrysochromulina parva, that can withstand high PAR intensities and low nutrient concentrations, increased in abundance as the water became more transparent. Also copepods increased in abundance, indicating that they are more successful in transparent water. We conclude that sediment input into lakes creates horizontal gradients in PAR and UVR attenuation which strongly affect both distribution and behavior of phyto- and zooplankton. The input of glacial flour creates a subhabitat that can function as a refuge for species that are sensitive to high PAR and UVR exposure. When the glacier has vanished, this habitat may disappear. During the melting period, with heavy sediment input, we predict that competitive species in transparent waters, like Chrysocromulina, picocyanobacteria and copepods, will become less common. The deep Chl a maxima is also likely to become less developed. 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.