Sediment anoxia limits microbial-driven seagrass carbon remineralization under warming conditions.
Seagrass ecosystems are significant carbon sinks, and their resident microbial communities ultimately determine the quantity and quality of carbon sequestered. However, environmental perturbations have been predicted to affect microbial-driven seagrass decomposition and subsequent carbon sequestration. Utilizing techniques including 16S-rDNA sequencing, solid-state NMR and microsensor profiling, we tested the hypothesis that elevated seawater temperatures and eutrophication enhance the microbial decomposition of seagrass leaf detritus and rhizome/root tissues. Nutrient additions had a negligible effect on seagrass decomposition, indicating an absence of nutrient limitation. Elevated temperatures caused a 19% higher biomass loss for aerobically decaying leaf detritus, coinciding with changes in bacterial community structure and enhanced lignocellulose degradation. Although, community shifts and lignocellulose degradation were also observed for rhizome/root decomposition, anaerobic decay was unaffected by temperature. These observations suggest that oxygen availability constrains the stimulatory effects of temperature increases on bacterial carbon remineralization, possibly through differential temperature effects on bacterial functional groups, including putative aerobic heterotrophs (e.g. Erythrobacteraceae, Hyphomicrobiaceae) and sulfate reducers (e.g. Desulfobacteraceae). Consequently, under elevated seawater temperatures, carbon accumulation rates may diminish due to higher remineralization rates at the sediment surface. Nonetheless, the anoxic conditions ubiquitous to seagrass sediments can provide a degree of carbon protection under warming seawater temperatures.
Climate Change Cluster, University of Technology Sydney, NSW 2007, Australia.
Stacey M
SM
Trevathan-Tackett
Climate Change Cluster, University of Technology Sydney, NSW 2007, Australia.
Justin R
JR
Seymour
Climate Change Cluster, University of Technology Sydney, NSW 2007, Australia.
Daniel A
DA
Nielsen
Climate Change Cluster, University of Technology Sydney, NSW 2007, Australia.|School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University, Burwood, VIC 3125, Australia.
Peter I
PI
Macreadie
Climate Change Cluster, University of Technology Sydney, NSW 2007, Australia.|Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW 2750, Australia.
Thomas C
TC
Jeffries
CSIRO Agriculture and Food, Glen Osmond, SA 5064, Australia.|Woods Hole Research Center, Falmouth, MA 02540, USA.
Jonathan
J
Sanderman
CSIRO Agriculture and Food, Glen Osmond, SA 5064, Australia.
Jeff
J
Baldock
Climate Change Cluster, University of Technology Sydney, NSW 2007, Australia.
Johanna M
JM
Howes
CSIRO Ocean and Atmosphere, Dutton Park, QLD 4102, Australia.
Andrew D L
ADL
Steven
Climate Change Cluster, University of Technology Sydney, NSW 2007, Australia.
Peter J
PJ
Ralph
D035961:Alismatales / Q000378:metabolism* / Q000382:microbiology; D000693:Anaerobiosis / Q000502:physiology*; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D057965:Carbon Sequestration; D017753:Ecosystem; D005068:Eutrophication / Q000502:physiology; D019015:Geologic Sediments / Q000382:microbiology*; D006358:Hot Temperature; D010100:Oxygen / Q000378:metabolism; D020560:Proteobacteria / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012623:Seawater / Q000382:microbiology*
D012336:RNA, Ribosomal, 16S; D002244:Carbon; D010100:Oxygen
bacterial remineralization; carbon cycling; oxygen availability; seagrass microbiology; succession; temperature