Climate-induced input of turbid glacial meltwater affects vertical distribution and community composition of phyto- and zooplankton.

HYLANDER, S.; JEPHSON, T; LEBRET, K.; VON EINEM, J.; FAGERBERG, T.; BALSEIRO, E.G; MODENUTTI, B.E.; SOUZA, M.S.; LASPOUMADERES, C.; JÖNSSON, M.,; LJUNGBERG, P; NICOLLE, A.; NILSSON, A.; RANÅKER, L.; HANSSON, L-A.

JOURNAL OF PLANKTON RESEARCH

OXFORD UNIV PRESS

Año: 2011 vol. 33 p. 1239 - 1248

0142-7873

Receding glaciers are among the most obvious changes caused by global warming,and glacial meltwater entering lakes generally forms plumes of particles. By takingvertical samples along a horizontal gradient from such a particle source, we foundthat photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) attenuated20–25% faster close to the inflow of suspended particles compared withthe more transparent part of the gradient. All sampled stations had a deep chlorophylla (Chl a) maximum at 15–20 m which was more distinct in the transparentpart of the horizontal gradient. Picocyanobacteria increased in abundance inmore transparent water and their numbers were tightly correlated with the intensityof the deep Chl a maxima. Motile species of phytoplankton had a deeperdepth distribution in transparent versus less transparent water. Yet other species,like Chrysochromulina parva, that can withstand high PAR intensities and low nutrientconcentrations, increased in abundance as the water became more transparent.Also copepods increased in abundance, indicating that they are more successful intransparent water. We conclude that sediment input into lakes creates horizontalgradients in PAR and UVR attenuation which strongly affect both distributionand behavior of phyto- and zooplankton. The input of glacial flour creates a subhabitatthat can function as a refuge for species that are sensitive to high PAR andUVR exposure. When the glacier has vanished, this habitat may disappear.During the melting period, with heavy sediment input, we predict that competitivespecies in transparent waters, like Chrysocromulina, picocyanobacteria and copepods,will become less common. The deep Chl a maxima is also likely to become lessdeveloped. Hence, glacier melting will probably have profound effects on bothspecies composition and behavior of several planktonic taxa with potential effectson the food web.