Warming and organic matter sources impact the proportion of dissolved to total activities in marine extracellular enzymatic rates

Baltar, Federico; Moran, Xose Anxelu G.; Lønborg, Christian

Warming and organic matter sources impact the proportion of dissolved to total activities in marine extracellular enzymatic rates

Files

Baltar et al 2017 BGC accepted ms.pdf (4 MB)

Type

Article

Authors

Baltar, Federico
Moran, Xose Anxelu G.

Lønborg, Christian

KAUST Department

Biological and Environmental Sciences and Engineering (BESE) Division
Marine Science Program
Red Sea Research Center (RSRC)

Online Publication Date

2017-04-19

Print Publication Date

2017-05

Date

2017-04-19

Abstract

Extracellular enzymatic activities (EEAs) are the rate-limiting step in the degradation of organic matter. Extracellular enzymes can be found associated to cells or dissolved in the surrounding water. The proportion of cell-free EEA constitutes in many marine environments more than half of the total activity. This high proportion causes an uncoupling between hydrolysis rates and the actual bacterial activity. However, we do not know what factors control the proportion of dissolved relative to total EEA, nor how this may change in the future ocean. To resolve this, we performed laboratory experiments with water from the Great Barrier Reef (Australia) to study the effects of temperature and dissolved organic matter sources on EEA and the proportion of dissolved EEA. We found that warming increases the rates of organic matter hydrolysis and reduces the proportion of dissolved relative to total EEA. This suggests a potential increase of the coupling between organic matter hydrolysis and heterotrophic activities with increasing ocean temperatures, although strongly dependent on the organic matter substrates available. Our study suggests that local differences in the organic matter composition in tropical coastal ecosystems will strongly affect the proportion of dissolved EEA in response to ocean warming.

Citation

Baltar F, Morán XAG, Lønborg C (2017) Warming and organic matter sources impact the proportion of dissolved to total activities in marine extracellular enzymatic rates. Biogeochemistry 133: 307–316. Available: http://dx.doi.org/10.1007/s10533-017-0334-9.

Acknowledgements

The authors would like to thank the SeaSim team at AIMS for the help with setting up the experiments. The study was co-financed by the AIMS visiting fellowship program as part of the capability development fund (CDF). F. Baltar was supported by a University of Otago Research Grant.