Please use this identifier to cite or link to this item: http://hdl.handle.net/10553/122932
Title: Extracellular enzyme activity in the coastal upwelling system off Peru: A mesocosm experiment
Authors: Spilling, Kristian
Piiparinen, Jonna
Achterberg, Eric P.
Arístegui Ruiz, Javier 
Bach, Lennart T.
Camarena-Gómez, Maria T.
Von Der Esch, Elisabeth
Fischer, Martin A.
Gómez Letona, Markel 
Hernández Hernández, Nauzet 
Meyer, Judith
Schmitz, Ruth A.
Riebesell ,Ulf 
UNESCO Clasification: 251007 Oceanografía física
251001 Oceanografía biológica
Issue Date: 2023
Journal: Biogeosciences 
Abstract: The Peruvian upwelling system is a highly productive ecosystem with a large oxygen minimum zone (OMZ) close to the surface. In this work, we carried out a mesocosm experiment off Callao, Peru, with the addition of water masses from the regional OMZ collected at two different sites simulating two different upwelling scenarios. Here, we focus on the pelagic remineralization of organic matter by the extracellular enzyme activity of leucine aminopeptidase (LAP) and alkaline phosphatase activity (APA). After the addition of the OMZ water, dissolved inorganic nitrogen (N) was depleted, but the standing stock of phytoplankton was relatively high, even after N depletion (mostly >g€¯4g€¯μg chlorophyll ag€¯L-1). During the initial phase of the experiment, APA was 0.6g€¯nmolg€¯L-1g€¯h-1 even though the PO43- concentration was >g€¯0.5g€¯μmolg€¯L-1. Initially, the dissolved organic phosphorus (DOP) decreased, coinciding with an increase in the PO43- concentration that was probably linked to the APA. The LAP activity was very high, with most of the measurements in the range of 200-800g€¯nmolg€¯L-1g€¯h-1. This enzyme hydrolyzes terminal amino acids from larger molecules (e.g., peptides or proteins), and these high values are probably linked to the highly productive but N-limited coastal ecosystem. Moreover, the experiment took place during a rare coastal El Niño event with higher than normal surface temperatures, which could have affected enzyme activity. Using a nonparametric multidimensional scaling analysis (NMDS) with a generalized additive model (GAM), we found that biogeochemical variables (e.g., nutrient and chlorophyll-a concentrations) and phytoplankton and bacterial communities explained up to 64g€¯% of the variability in APA. The bacterial community best explained the variability (34g€¯%) in LAP. The high hydrolysis rates for this enzyme suggest that pelagic N remineralization, likely driven by the bacterial community, supported the high standing stock of primary producers in the mesocosms after N depletion.
URI: http://hdl.handle.net/10553/122932
ISSN: 1726-4170
DOI: 10.5194/bg-20-1605-2023
Source: Biogeosciences [ISSN 1726-4170], v. 20 (8), p. 1605-1619, (Abril 2023)
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