caa a22 4500 605517207 CHVBK 20210128100718.0 cr unu---uuuuu 210128e20150301xx s 000 0 eng 10.1007/s10533-014-0053-4 doi (NATIONALLICENCE)springer-10.1007/s10533-014-0053-4 Late Holocene changes in the humic state of a boreal lake and their associations with organic matter transport and climate dynamics [Elektronische Daten] [Marttiina Rantala, Tomi Luoto, Liisa Nevalainen] An important factor in the ontogeny of boreal lakes is the development of their humic state through terrigenous input of organic matter (carbon) that affects strongly the functioning and structure of these ecosystems. The long-term dynamics and role of humic substances for these systems in relation to climate are not clear. In this study, a boreal lake from southern Finland was investigated using paleolimnological methods, including diatom, chironomid and geochemical analyses, for Late Holocene changes in the humic state. The aim was to examine the relationship between sediment biogeochemistry and climate variation. Consistent trends were found in diatom-inferred total lake-water organic carbon (TOC) and in the ratio of humic/oligohumic chironomids. Sediment geochemistry provided further evidence for the limnological development of the lake and related long-term climate trends in the region. The results indicated three distinct phases with differing humic state; the beginning of the record at ca. 4,500calyear BP was characterized by extremely humic conditions coinciding with warm and dry climatic conditions, a meso-oligohumic period between ca. 3,000-500calyear BP with increasing allochthonous organic matter transport and cooler and wetter climate, and recent period with polyhumic (TOC >10mgL−1) lake status and warming climate. This study shows that instead of straightforward linear development, boreal lakes evolve through dynamic humic stages related to climate and lake-catchment coupling processes. As the changes in the humic state are ultimately climate-driven, the ongoing climate change probably has a major influence on boreal lakes through direct and indirect effects on organic carbon transport, utilization and accumulation. Springer International Publishing Switzerland, 2014 Dystrophy nationallicence Environmental change nationallicence Lake-catchment coupling nationallicence Organic carbon nationallicence Paleolimnology nationallicence Rantala Marttiina Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland aut Luoto Tomi Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland aut Nevalainen Liisa Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland aut Biogeochemistry Springer International Publishing 123/1-2(2015-03-01), 63-82 0168-2563 123:1-2<63 2015 123 10533 https://doi.org/10.1007/s10533-014-0053-4 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10533-014-0053-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rantala Marttiina Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland aut NATIONALLICENCE 700 1- Luoto Tomi Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland aut NATIONALLICENCE 700 1- Nevalainen Liisa Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland aut NATIONALLICENCE 773 0- Biogeochemistry Springer International Publishing 123/1-2(2015-03-01), 63-82 0168-2563 123:1-2<63 2015 123 10533