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345 results on '"Köster, O."'

101. Auftreten von Mikroorganismen in Grundwasser

Author

Pronk, M., Sinreich, M., Guhl, F., Egli, T., Kötsch, S., Felleisen, R., Koch, M., Köster, O., Raetz, E., Ramseier, C., Rossi, P., and Schürch, N.

Subjects
bacteria, Groundwater, water quality

149. The Red Harmful Plague in Times of Climate Change: Blooms of the Cyanobacterium Planktothrix rubescens Triggered by Stratification Dynamics and Irradiance.

Author

Knapp D, Fernández Castro B, Marty D, Loher E, Köster O, Wüest A, and Posch T

Abstract

Planktothrix rubescens is a harmful planktonic cyanobacterium, forming concentrated metalimnetic populations in deep oligo- and mesotrophic lakes, even after successful restoration. In Lake Zurich (Switzerland), P. rubescens emerged as a keystone species with annual mass developments since the 1970s. Its success was partly attributed to effects of lake warming, such as changes in thermal stratification and seasonal deep mixing. However, recent observations based on a biweekly monitoring campaign (2009-2020) revealed two massive breakdowns and striking seasonal oscillations of the population. Here, we disentangle positive from negative consequences of secular lake warming and annual variations in weather conditions on P. rubescens dynamics: (i) despite the high survival rates of overwintering populations (up to 25%) during three consecutive winters (2014-2016) of incomplete deep convective mixing, cyanobacterial regrowth during the following stratified season was moderate and not overshooting a distinct standing stock threshold. Moreover, we recorded a negative trend for annual population maxima and total population size, pointing to a potential nutrient limitation after a series of incomplete winter mixing. Thus, the predication of steadily increasing blooms of P. rubescens could not be confirmed for the last decade. (ii) The seasonal reestablishment of P. rubescens was strongly coupled with a timely formation of a stable metalimnion structure, where the first positive net growth in the following productive summer season was observed. The trigger for the vertical positioning of filaments within the metalimnion was irradiance and not maximal water column stability. Repetitive disruptions of the vernal metalimnion owing to unstable weather conditions, as in spring 2019, went in parallel with a massive breakdown of the standing stock and marginal regrowth during thermal stratification. (iii) Driven by light intensity, P. rubescens was entrained into the turbulent epilimnion in autumn, followed by a second peak in population growth. Thus, the typical bimodal growth pattern was still intact during the last decade. Our long-term study highlights the finely tuned interplay between climate-induced changes and variability of thermal stratification dynamics and physiological traits of P. rubescens , determining its survival in a mesotrophic temperate lake., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Knapp, Fernández Castro, Marty, Loher, Köster, Wüest and Posch.)

Published
2021
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150. Global data set of long-term summertime vertical temperature profiles in 153 lakes.

Author

Pilla RM, Mette EM, Williamson CE, Adamovich BV, Adrian R, Anneville O, Balseiro E, Ban S, Chandra S, Colom-Montero W, Devlin SP, Dix MA, Dokulil MT, Feldsine NA, Feuchtmayr H, Fogarty NK, Gaiser EE, Girdner SF, González MJ, Hambright KD, Hamilton DP, Havens K, Hessen DO, Hetzenauer H, Higgins SN, Huttula TH, Huuskonen H, Isles PDF, Joehnk KD, Keller WB, Klug J, Knoll LB, Korhonen J, Korovchinsky NM, Köster O, Kraemer BM, Leavitt PR, Leoni B, Lepori F, Lepskaya EV, Lottig NR, Luger MS, Maberly SC, MacIntyre S, McBride C, McIntyre P, Melles SJ, Modenutti B, Müller-Navarra DC, Pacholski L, Paterson AM, Pierson DC, Pislegina HV, Plisnier PD, Richardson DC, Rimmer A, Rogora M, Rogozin DY, Rusak JA, Rusanovskaya OO, Sadro S, Salmaso N, Saros JE, Sarvala J, Saulnier-Talbot É, Schindler DE, Shimaraeva SV, Silow EA, Sitoki LM, Sommaruga R, Straile D, Strock KE, Swain H, Tallant JM, Thiery W, Timofeyev MA, Tolomeev AP, Tominaga K, Vanni MJ, Verburg P, Vinebrooke RD, Wanzenböck J, Weathers K, Weyhenmeyer GA, Zadereev ES, and Zhukova TV

Abstract

Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change., (© 2021. The Author(s).)

Published
2021
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