Effects of nutrient load on microbial activities within a seagrass-dominated ecosystem: Implications of changes in seagrass blue carbon.
Nutrient loading is a leading cause of global seagrass decline, triggering shifts from seagrass- to macroalgal-dominance. Within seagrass meadows of Xincun Bay (South China Sea), we found that nutrient loading (due to fish farming) increased sediment microbial biomass and extracellular enzyme activity associated with carbon cycling (polyphenol oxidase, invertase and cellulase), with a corresponding decrease in percent sediment organic carbon (SOC), suggesting that nutrients primed microorganism and stimulated SOC remineralization. Surpisingly, however, the relative contribution of seagrass-derived carbon to bacteria (δ13Cbacteria) increased with nutrient loading, despite popular theory being that microbes switch to consuming macroalgae which are assumed to provide a more labile carbon source. Organic carbon sources of fungi were unaffected by nutrient loading. Overall, this study suggests that nutrient loading changes the relative contribution of seagrass and algal sources to SOC pools, boosting sediment microbial biomass and extracellular enzyme activity, thereby possibly changing seagrass blue carbon.
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Songlin
S
Liu
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China.
Zhijian
Z
Jiang
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Yunchao
Y
Wu
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China.
Jingping
J
Zhang
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Iman
I
Arbi
Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
Feng
F
Ye
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: xphuang@scsio.ac.cn.
Xiaoping
X
Huang
Blue Carbon Lab, Centre for Integrative Ecology, School of Life and Environmental Sciences, Faculty of Science Engineering & Built Environment, Burwood, Deakin University, Victoria 3125, Australia.
Peter Ian
PI
Macreadie
D000818:Animals; D017756:Aquaculture; D001419:Bacteria / Q000378:metabolism*; D018533:Biomass; D002244:Carbon; D002681:China; D017753:Ecosystem; D019015:Geologic Sediments; D009792:Oceans and Seas; D006109:Poaceae; D014871:Water Microbiology
D002244:Carbon
Extracellular enzymes activities; Microbial community structure; PLFA; Seagrass bed; Sediment organic carbon; δ(13)C