@article{238a406a69eb468faa92ca8a48c01a68,
title = "Lake browning counteracts cyanobacteria responses to nutrients: Evidence from phytoplankton dynamics in large enclosure experiments and comprehensive observational data",
abstract = "Lakes worldwide are affected by multiple stressors, including climate change. This includes massive loading of both nutrients and humic substances to lakes during extreme weather events, which also may disrupt thermal stratification. Since multi-stressor effects vary widely in space and time, their combined ecological impacts remain difficult to predict. Therefore, we combined two consecutive large enclosure experiments with a comprehensive time-series and a broad-scale field survey to unravel the combined effects of storm-induced lake browning, nutrient enrichment and deep mixing on phytoplankton communities, focusing particularly on potentially toxic cyanobacterial blooms. The experimental results revealed that browning counteracted the stimulating effect of nutrients on phytoplankton and caused a shift from phototrophic cyanobacteria and chlorophytes to mixotrophic cryptophytes. Light limitation by browning was identified as the likely mechanism underlying this response. Deep-mixing increased microcystin concentrations in clear nutrient-enriched enclosures, caused by upwelling of a metalimnetic Planktothrix rubescens population. Monitoring data from a 25-year time-series of a eutrophic lake and from 588 northern European lakes corroborate the experimental results: Browning suppresses cyanobacteria in terms of both biovolume and proportion of the total phytoplankton biovolume. Both the experimental and observational results indicated a lower total phosphorus threshold for cyanobacterial bloom development in clearwater lakes (10–20 μg P L−1) than in humic lakes (20–30 μg P L−1). This finding provides management guidance for lakes receiving more nutrients and humic substances due to more frequent extreme weather events.",
keywords = "climate change, deep-mixing, harmful algal blooms, lake browning, large-scale lake survey, long-term monitoring, mesocosm, multiple stressors, nutrient gradient",
author = "Anne Lyche Solheim and Hege Gundersen and Ute Mischke and Birger Skjelbred and Nejstgaard, {Jens C.} and Guislain, {Alexis L.N.} and Erik Sperfeld and Giling, {Darren P.} and Sigrid Haande and Andreas Ballot and Moe, {S. Jannicke} and Susanne Stephan and Walles, {Tim J.W.} and Andreas Jechow and Laetitia Minguez and Lars Ganzert and Thomas Hornick and Hansson, {Truls Hveem} and Stratmann, {Cleo N.} and Marko J{\"a}rvinen and Stina Drakare and Laurence Carvalho and Grossart, {Hans Peter} and Gessner, {Mark O.} and Berger, {Stella A.}",
note = "Funding Information: We are grateful for assistance during the LakeLab experiment to Armin Penske, Maren Lentz, Gonzalo Idoate Santaolalla, Anatole Boich{\'e}, Michael Sachtleben, Max Schnittger, Solvig Pinnow, Elke Mach, Reingard Ro{\ss}berg, Uta Mallok, Monika Degebrodt, Monika Papke, Elfi Huth, Ute Beyer, Carola Kasprzak, Gabriele Mohr, Sebastian Beeske (technicians); Katharina G{\"o}rden, Jennifer Klein, Katharina L{\"o}rsch, Malte Zamzow (students); Maia R{\o}st Kile, Lise Tveiten, Hartvig Christie (divers); and Peter Casper, Silke van den Wyngaert, Maria Belyaeva, Armando Sepulveda-Jauregui, Karla Martinez-Cruz, Manja Saebelfeld, Takeshi Miki, Nina Pansch, Hua Ma, Jeremy Fonvielle, Werner Eckert, Jan K{\"o}hler, Sabine Hilt, Gabriel A. Singer and Franz H{\"o}lker (scientists). We thank D.P. Hamilton and S.E. Bunn at the Australian Rivers Institute of Griffith University for hosting Mark Gessner during the finalization of the manuscript. We further thank Vansj{\o} Vannverk for kindly providing water color data on Lake Vansj{\o} for the period from 1999 to 2004, and Knut Bj{\o}rndalen at the local environmental authority of Moss municipality, Norway, for phytoplankton composition data for Lake Vansj{\o} (Vanemfjorden basin) for the period from 1996 to 2004. Furthermore, we are grateful to Heleen de Wit from NIVA, Nina Kotam{\"a}ki from SYKE and Jessica Richardson from NERC-CEH for contributing initial ideas on data analyses during a drafting workshop. We also thank all providers of data on the 588 lakes analyzed in the present study, including the UK Environment Agency. We thank two anonymous reviewers for their constructive comments on a previous version of the manuscript. Open Access funding enabled and organized by Projekt DEAL. Funding Information: This work was supported by the following funding sources: MARS project (Managing Aquatic ecosystems and water Resources under multiple Stress) funded under the 7th EU Framework Programme, Theme 6 (Environment including Climate Change), No. 603378 ( http://www.mars‐project.eu ). ILES project (Illuminating Lake Ecosystems) funded by the Leibniz Association within the Collaborative Excellence programme, No. SAW‐2015‐IGB‐1 ( https://www.igb‐berlin.de/en/project/iles ). BIBS project (Bridging in Biodiversity Science) funded by the German Federal Ministry of Education and Research (BMBF), No. 01LC1501 ( https://www.bbib.org/bibs‐project.html ). BMBF grant (No. 033L041B) enabling the construction of the enclosure facility ( https://www.igb‐berlin.de/en/infrastructure/lakelab ). Core Facility grant by the German Research Foundation (DFG, No. GE 1775/2‐1) supporting the operation of the enclosure facility. AQUACOSM project (Network of Leading European AQUAtic MesoCOSMFacilities Connecting Mountains to Oceans from the Arctic to the Mediterranean) funded by the EU Horizon 2020 INFRAIA programme, No. 731065 ( https://www.aquacosm.eu ). CONNECT project (Connectivity and synchronisation of lake ecosystems in space and time) funded by the Leibniz Association within the Collaborative Excellence programme, No. K45/2017 ( https://www.igb‐berlin.de/en/projekt/connect ). Lake Vansj{\o} annual monitoring funded by the Morsa River Basin authority, Norway. WISER project (Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery), which facilitated the large data compilation for northern lakes, funded by the EU Commission under the 7th Framework Programme, Theme 6 (Environment including Climate Change), No. 226273 ( http://www.wiser.eu ). Publisher Copyright: {\textcopyright} 2023 The Authors. Global Change Biology published by John Wiley & Sons Ltd.",
year = "2023",
month = nov,
day = "22",
doi = "10.1111/gcb.17013",
language = "English",
volume = "30",
pages = "1--23",
journal = "Global Change Biology",
issn = "1354-1013",
publisher = "Wiley-Blackwell",
number = "1",
}