Effects of DOC addition from different sources on phytoplankton community in a temperate eutrophic lake: An experimental study exploring lake compartments

Bárbara Medeiros Fonseca; Eti Ester Levi; Lea Westphalen Jensen; Daniel Graeber; Martin Søndergaard; Torben Linding Lauridsen; Erik Jeppesen; Thomas Alexander Davidson

doi:10.1016/j.scitotenv.2021.150049

Effects of DOC addition from different sources on phytoplankton community in a temperate eutrophic lake: An experimental study exploring lake compartments

Sci Total Environ. 2022 Jan 10:803:150049. doi: 10.1016/j.scitotenv.2021.150049. Epub 2021 Sep 2.

Authors

Bárbara Medeiros Fonseca¹, Eti Ester Levi², Lea Westphalen Jensen³, Daniel Graeber⁴, Martin Søndergaard⁵, Torben Linding Lauridsen⁶, Erik Jeppesen⁷, Thomas Alexander Davidson⁸

Affiliations

¹ Lake Ecology Section, Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark. Electronic address: barbara.fonseca0603@gmail.com.
² Lake Ecology Section, Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; WATEC Aarhus University Centre for Water Technology, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark. Electronic address: eel@bios.au.dk.
³ Lake Ecology Section, Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark.
⁴ Dep. Aquatic Ecosystem Analysis, Helmholtz Centre for Environmental Research - UFZ, Brückstraße 3a, 39114 Magdeburg, Germany. Electronic address: daniel.graeber@ufz.de.
⁵ Lake Ecology Section, Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; WATEC Aarhus University Centre for Water Technology, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; Sino-Danish Centre for Education and Research (SDC), Beijing, China. Electronic address: ms@bios.au.dk.
⁶ Lake Ecology Section, Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; WATEC Aarhus University Centre for Water Technology, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; Sino-Danish Centre for Education and Research (SDC), Beijing, China. Electronic address: tll@bios.au.dk.
⁷ Lake Ecology Section, Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; WATEC Aarhus University Centre for Water Technology, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; Sino-Danish Centre for Education and Research (SDC), Beijing, China; Limnology Laboratory, Department of Biological Sciences and Centre for Ecosystem Research and Implementation, Middle East Technical University, Ankara, Turkey; Institute of Marine Sciences, Middle East Technical University, Mersin, Turkey. Electronic address: ej@bios.au.dk.
⁸ Lake Ecology Section, Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark; WATEC Aarhus University Centre for Water Technology, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark. Electronic address: thd@bios.au.dk.

PMID: 34500271
DOI: 10.1016/j.scitotenv.2021.150049

Abstract

A mesocosm experiment was conducted in a temperate eutrophic lake with the hypotheses: 1) the addition of a labile form of DOC would trigger a more pronounced response in phytoplankton biomass and composition compared with a non-labile form; 2) DOC addition would increase phytoplankton biomass by co-inserting organic nutrients for phytoplankton growth; 3) DOC addition would change phytoplankton composition, in particular towards mixotrophic taxa due to higher DOC availability; and that 4) there would be differences in phytoplankton responses to DOC addition, depending on whether sediment was included or not. We used two types of mesocosms: pelagic mesocosms with closed bottom, and benthic mesocosms open to the sediment. The experiment ran for 29 days in total. The DOC addition occurred once, at Day 1. Besides the control, there were two treatments: HuminFeed® (non-labile DOC) at a concentration of 2 mg L^-1, and a combination of 2 mg L^-1 HuminFeed® and 2 mg L^-1 DOC from alder leaf leachate (labile). Responses were detected only in the treatment with alder leaf extract. Ecosystem processes responded immediately to DOC addition, with the fall in dissolved oxygen and pH indicating an increase in respiration, relative to primary production (Day 2). In contrast, there was a delay of a few days in structural responses in the phytoplankton community (Day 6). Phytoplankton biomass increased after DOC addition, probably boosted by the phosphorus released from alder leaf extract. Changes in phytoplankton composition towards mixotrophic taxa were not as strong as changes in biomass, and happened only in the pelagic mesocosms. With the DOC addition, diatoms prevailed in benthic mesocosms, while the contribution of colonial buoyant cyanobacteria increased in the pelagic ones. This study points towards the necessity to look in greater detail at specific responses of phytoplankton to DOC concentration increases considering lake-habitat and sediment influence.

Keywords: Leaf leachate; Low-level brownification; Mesocosm experiment; Primary production; Pulse disturbance.

MeSH terms

Biomass
Ecosystem
Lakes*
Phosphorus
Phytoplankton*

Substances

Phosphorus