Differences in the sensitivity of fungi and bacteria to season and invertebrates affect leaf litter decomposition in a Mediterranean stream.
Microorganisms are key drivers of leaf litter decomposition; however, the mechanisms underlying the dynamics of different microbial groups are poorly understood. We investigated the effects of seasonal variation and invertebrates on fungal and bacterial dynamics, and on leaf litter decomposition. We followed the decomposition of Populus nigra litter in a Mediterranean stream through an annual cycle, using fine and coarse mesh bags. Irrespective of the season, microbial decomposition followed two stages. Initially, bacterial contribution to total microbial biomass was higher compared to later stages, and it was related to disaccharide and lignin degradation; in a later stage, bacteria were less important and were associated with hemicellulose and cellulose degradation, while fungi were related to lignin decomposition. The relevance of microbial groups in decomposition differed among seasons: fungi were more important in spring, whereas in summer, water quality changes seemed to favour bacteria and slowed down lignin and hemicellulose degradation. Invertebrates influenced litter-associated microbial assemblages (especially bacteria), stimulated enzyme efficiencies and reduced fungal biomass. We conclude that bacterial and fungal assemblages play distinctive roles in microbial decomposition and differ in their sensitivity to environmental changes, ultimately affecting litter decomposition, which might be particularly relevant in highly seasonal ecosystems, such as intermittent streams.
GRECO, Institute of Aquatic Ecology, University of Girona, Campus Montilivi, 17071 Girona, Spain juanita.mora@udg.edu.
Juanita
J
Mora-Gómez
Faculty of Science and Technology, University of the Basque Country, UPV/EHU, PO Box 644, 48080 Bilbao, Spain.
Arturo
A
Elosegi
CBMA-Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Sofia
S
Duarte
CBMA-Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Fernanda
F
Cássio
CBMA-Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Cláudia
C
Pascoal
GRECO, Institute of Aquatic Ecology, University of Girona, Campus Montilivi, 17071 Girona, Spain.
Anna M
AM
Romaní
D000818:Animals; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism*; D001673:Biodegradation, Environmental; D018533:Biomass; D002980:Climate; D017753:Ecosystem; D005658:Fungi / Q000254:growth & development / Q000378:metabolism*; D007448:Invertebrates / Q000254:growth & development / Q000378:metabolism*; D008031:Lignin / Q000378:metabolism*; D019083:Mediterranean Region; D018515:Plant Leaves / Q000378:metabolism* / Q000382:microbiology; D032107:Populus / Q000378:metabolism* / Q000382:microbiology; D045483:Rivers / Q000382:microbiology*; D012621:Seasons; D013030:Spain
D008031:Lignin
Populus nigra; enzyme efficiency; extracellular enzymes; litter breakdown; microbial assemblages