Terrestrial organic matter reverses competition between aquatic primary producers by altering within-lake, cross-habitat resource fluxes
(English)Manuscript (preprint) (Other academic)
Flows of energy and matter across habitat boundaries can be major determinants of the functioning of recipient ecosystems. It is currently debated whether terrestrial dissolved organic matter (tDOM) is a resource subsidy or a resource subtraction in recipient lakes. In a long-term field experiment, pelagic phosphorus concentration and aquatic primary production increased with increasing tDOM input, suggesting that tDOM acted primarily as a direct nutrient subsidy. Piecewise structural equation modeling supports, however, an approximately equally important role for a second mechanism: colored tDOM acted also as a resource subtraction by shading benthic algae, preventing them from intercepting nutrients released across the sediment-water interface. Inhibition of benthic algae by colored tDOM thus indirectly promoted pelagic algae and whole-ecosystem primary production. We conclude that cross-ecosystem terrestrial DOM inputs can modify light and nutrient flows between aquatic habitats and alter the outcome of resource competition between benthic and pelagic producers. These results are particularly relevant for shallow northern lakes, which are facing increased tDOM runoff with climate change.
IdentifiersURN: urn:nbn:se:umu:diva-133325OAI: oai:DiVA.org:umu-133325DiVA: diva2:1086972
FunderKnut and Alice Wallenberg FoundationSwedish Research Council, 621-2011-3908Swedish Research Council, 621-2014-5238Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGEThe Kempe Foundations