Allochthonous carbon is a major driver of the microbial food web - A mesocosm study simulating elevated terrestrial matter runoffShow others and affiliations
2017 (English)In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 129, p. 236-244Article in journal (Refereed) Published
Abstract [en]
Climate change predictions indicate that coastal and estuarine environments will receive increased terrestrial runoff via increased river discharge. This discharge transports allochthonous material, containing bioavailable nutrients and light attenuating matter. Since light and nutrients are important drivers ofbasal production, their relative and absolute availability have important consequences for the base of the aquatic food web, with potential ramifications for higher trophic levels. Here, we investigated the effects of shifts in terrestrial organic matter and light availability on basal producers and their grazers. In twelve Baltic Sea mesocosms, we simulated the effects of increased river runoff alone and in combination. We manipulated light (clear/shade) and carbon (added/not added) in a fully factorial design, with three replicates. We assessed microzooplankton grazing preferences in each treatment to assess whether increased terrestrial organic matter input would: (1) decrease the phytoplankton to bacterial biomass ratio, (2) shift microzooplanlcton diet from phytoplankton to bacteria, and (3) affect microzooplankton biomass. We found that carbon addition, but not reduced light levels per se resulted in lower phytoplanlcton to bacteria biomass ratios. Microzooplankton generally showed a strong feeding preference for phytoplanlcton over bacteria, but, in carbon-amended mesocosms which favored bacteria, microzooplankton shifted their diet towards bacteria. Furthermore, low total prey availability corresponded with low microzooplankton biomass and the highest bacteria/phytoplankton ratio. Overall our results suggest that in shallow coastal waters, modified with allochthonous matter from river discharge, light attenuation may be inconsequential for the basal producer balance, whereas increased allochthonous carbon, especially if readily bioavailable, favors bacteria over phytoplankton. We conclude that climate change induced shifts at the base of the food web may alter energy mobilization to and thebiomass of microzooplankton grazers. (C) 2017 Elsevier Ltd. All rights reserved.
Place, publisher, year, edition, pages
2017. Vol. 129, p. 236-244
Keywords [en]
Trophic interactions, Food quality, Phytoplankton, Bacteria, Competition, Microzooplaktion
National Category
Oceanography, Hydrology and Water Resources
Identifiers
URN: urn:nbn:se:hh:diva-35038DOI: 10.1016/j.marenvres.2017.06.008ISI: 000407981500021PubMedID: 28645656Scopus ID: 2-s2.0-85021065789OAI: oai:DiVA.org:hh-35038DiVA, id: diva2:1143104
Funder
Swedish Research Council Formas
Note
CLM was financed by the Young Researchers Award from Umeå University to AL and AA, JP, SB and OR were financed by the EcoChange project. This study was supported by the Lars Hierta Memorial Foundation and the Strategic Marine Environmental Research program Ecosystem dynamics in the Baltic Sea in a changing climate perspective (EcoChange), a FORMAS funded initiative. This study was also partially supported by a grant from the Oscar and Lilli Lamms foundation (FO2011-0095) to Carolyn Faithfull.
2017-09-202017-09-202018-01-13Bibliographically approved