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Contrasting impacts of warming and browning on periphyton
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.ORCID iD: 0000-0003-0291-2639
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.ORCID iD: 0000-0001-5102-4289
(English)Manuscript (preprint) (Other academic)
National Category
Climate Research Environmental Sciences Physical Geography Geochemistry
Research subject
environmental science
Identifiers
URN: urn:nbn:se:umu:diva-194520OAI: oai:DiVA.org:umu-194520DiVA, id: diva2:1656921
Available from: 2022-05-09 Created: 2022-05-09 Last updated: 2022-05-09
In thesis
1. Impacts of global change on primary production in northern lakes
Open this publication in new window or tab >>Impacts of global change on primary production in northern lakes
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Globala förändringars påverkan på primärproduktionen i nordliga sjöar
Abstract [en]

Algae are primary producers, a major component of the aquatic foodweb, and changes in primary production affect aquatic ecology in general. Global changes such as warming, recovery of acidification and changes in land-use have caused warming and browning of northern lakes. Warming is a direct effect of increasing air temperatures, whereas browning is mainly caused by increasing amounts of terrestrially derived colored dissolved organic carbon (DOC). Altogether, such global changes impact important environmental drivers for aquatic gross primary production (GPP). Increased temperatures and nutrient supplementation by DOC at low concentrations enhance GPP, but the browning by DOC at high concentrations inhibits GPP by light reduction, resulting in contrasting controls of global changes on primary production in northern lakes. Primary producers grow in two distinct habitats; free-floating algae (phytoplankton) and stationary periphytic (attached) algae that are restricted to use the light that reaches them. Periphyton includes algae growing on submerged surfaces ranging from nutrient-poor rocks to nutrient-rich sediments (here: benthic algae), and both often exceed pelagic GPP but are overlooked and often simply excluded from algal biomass estimates.

In this thesis, I investigate how global change influences key environmental drivers of GPP, and how those changes impact GPP in the benthic and pelagic habitat, and the sum and partitioning of GPP between these habitats (the autrotrophic structuring). I do this by interpreting a dataset with GPP measurements in several lakes over the Swedish Arctic, subarctic and boreal landscape that representa wide range of DOC concentrations. I also assess to what extent temperature and DOC impact periphytic algae growth on plastic strips in an experimental study where DOC and temperature are manipulated in 20 ponds. Besides assessing the direct impacts of changes in nutrients and light climate associated with changes in DOC, I assess indirect impacts of global changes on primary production, e.g., through intensified warming, CO2 supersaturation, changes in pH, and the role of landscape processes and properties.

Results confirm that DOC is dominant in structuring GPP in northern lakes by light inhibition, nutrient supplementation, indirect warming of surface waters, and additionally by CO2 fertilization. In addition, warming can enhance growth rates, but thermal compensation can also lead to reduced algae growth. Moreover, periphytic GPP of algae growing on both soft nutrient-rich sediments and nutrient-poor plastic strips GPP was generally much higher than pelagic GPP, and should thus not be excluded in studies assessing global change impacts on GPP. DOC affects the total GPP, as well as the autotrophic structuring in northern lakes, and likely also higher trophic levels productivity and community composition.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2022. p. 30
Keywords
Primary production, global change, warming, browning, lake, carbon dioxide, organic carbon, inorganic carbon, boreal, arctic, DOC, DIC, CO2, allochthonous organic carbon, benthic, periphyton
National Category
Physical Geography Ecology
Research subject
environmental change; environmental science; biology; climate change
Identifiers
urn:nbn:se:umu:diva-194523 (URN)978-91-7855-813-1 (ISBN)978-91-7855-812-4 (ISBN)
Public defence
2022-06-03, S205, Samhällsvetarhuset, Umeå, 09:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation, 2016.0083
Available from: 2022-05-13 Created: 2022-05-09 Last updated: 2022-05-24Bibliographically approved

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Puts, Isolde C.Ask, JennyBergström, Ann-Kristin

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