Heterotrophic bacterial production and extracellular enzymatic activity in sinking particulate matter in the western North Pacific Ocean

• Published in: Frontiers in Microbiology
• Main Authors: Namiha eYamada, Hideki eFukuda, Hiroshi eOgawa, Hiroaki eSaito, Masahiro eSuzumura
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2012
• Subjects: extracellular enzyme activity; sinking particulate matter; sediment trap; heterotrophic bacterial activity; the western North Pacific; western North Pacific; Microbiology; QR1-502; Pacific; Subarctic
• Online Access: https://doi.org/10.3389/fmicb.2012.00379; https://doaj.org/article/5a1f557edd3547e792e138485e92cc40

Heterotrophic activities on sinking particulate matter (SPM) play an important role in SPM fluxes in the ocean. To demonstrate regional differences in heterotrophic activities on SPM, we measured heterotrophic bacterial production (HBP) in seawater and SPM as well as potential extracellular enzyme activity (EEA) in SPM on a transect along 155°E in the western North Pacific Ocean in the subarctic (44°N), the Kuroshio Extension area (35°N), and the subtropical gyre (20°N). Depth-integrated HBP in seawater from the surface to 500 m was comparable between the locations, whereas HBP in SPM at 44°N was substantially lower than at the other sites. We found the highest particulate organic carbon (POC) export flux and export efficiency to bathypelagic depths, and the lowest water temperatures, at 44°N. We found significant correlations between leucine aminopeptidase (LAPase) activity, ß-glucosidase (BGase) activity, POC flux and particulate organic nitrogen flux. LAPase activity was two orders of magnitude higher than BGase activity, with a BGase:LAPase activity ratio of 0.027. There were no significant correlations between HBP and EEA in SPM except for lipase, and lipase activity was significantly correlated with temperature. We propose that hydrographic conditions are an important factor controlling heterotrophic bacterial activity and export efficiency of organic carbon to the deep ocean, as are the sources and abundance of SPM produced in the euphotic zone via primary production.