Teasing apart the different size pools of extracellular enzymatic activity in the ocean

Author(s)
Federico Baltar, Daniele De Corte, Blair Thomson, Taichi Yokokawa
Abstract

Extracellular enzymatic activity (EEA) is performed by cell-associated and cell-free (i.e., “dissolved”) enzymes. This cell-free fraction is operationally defined as passing through a 0.22 μm filter. The contribution of cell-free to total EEA is comparable to the cell-associated counterpart, so it is critical to understand what controls the relative importance of cell-free versus cell-associated EEA. However, attempts to tease apart the contribution of EEAs in the so-called dissolved fraction (<0.22 μm) in general, and of the nanoparticle size fraction (0.020–0.20 μm) in particular, to the total EEA pool are lacking. Here we performed experiments with Northern and Southern Hemisphere coastal waters to characterize the potential contribution of that nanoparticle fraction to the total EEA fraction of alkaline phosphatase, beta-glucosidase and leucine aminopeptidase. We found a significant contribution (in both hemispheres) of the nanoparticle fraction to the total EEA pool (up to 53%) that differed depending on the enzyme type and location. Collectively, our results indicate that a significant fraction of the so-called “dissolved EEA” is not really dissolved but associated to nanoparticles, colloidal nanogels and/or viruses. Thus, the total marine EEA pool can actually be divided into a cell-associated, undissolved-cell-free (associated to nano-particle of different origins such as viruses and nanogels) and a dissolved-cell-free pools. Our results also imply that the dissolved EEA pool is more complex than thus far anticipated. Future research will be now needed to further characterize the factors controlling the relative importance of these different pools of EEA, which are key in the recycling of organic matter in the ocean.

Organisation(s)
Department of Limnology and Bio-Oceanography
Journal
Science of the Total Environment
Volume
660
Pages
690-696
No. of pages
7
ISSN
0048-9697
DOI
https://doi.org/10.1016/j.scitotenv.2019.01.083
Publication date
04-2019
Publication status
Published
Peer reviewed
Yes
Austrian Fields of Science 2012
106021 Marine biology
Keywords
Cell-free enzymatic activity, Extracellular enzymatic activity, Marine environment, Organic matter remineralization
ASJC Scopus subject areas
Environmental Engineering, Environmental Chemistry, Waste Management and Disposal, Pollution
Portal url
https://ucris.univie.ac.at/portal/en/publications/teasing-apart-the-different-size-pools-of-extracellular-enzymatic-activity-in-the-ocean(879b01d3-6491-495a-9e64-d30b21a57cc6).html