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Assessing the contribution of euphausiids’ fecal pellets to greenhouse gas inventories in the Eastern South Pacific
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DOI：10.3389/fmars.2026.1743607.png)
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Abstract
En 中文
The Eastern South Pacific (ESP) is a highly heterogeneous environment; characterized by a productivity gradient that goes from eutrophic waters in the coastal zone to ultraoligotrophic waters in the center of the South Pacific Gyre. Its coastal region is a significant source of CO2; CH4; and N2O to the atmosphere; mainly due to upwelled subsurface waters high in greenhouse gases (GHGs); where microbial processes produce these gases through the remineralization of organic matter. Few studies have assessed the contribution that microbial processes within particles; especially those rich in organic matter such as fecal pellets; could make to GHG inventories. We aimed to evaluate whether krill fecal pellets generated in the surface layer contribute to GHG inventories (CO2; N2O; and CH4) in the mixed layer. Experiments were conducted at four stations along a zonal transect near 27° S on board the CIMAR 26 Oceanic Island Expedition (June-July; 2022). The estimated contribution of a krill assemblage was less than 1% of the excess/deficit of each GHG; which; due to experimental limitations that introduced uncertainties; rather than providing absolute values for contribution or consumption; our results should be viewed as a potential range; indicating that krill fecal pellets can act as both sources and sinks of GHGs. Still; this contribution also depends on fecal pellet production rates and the abundance of krill assemblages; suggesting that large krill aggregations can contribute to changes in local GHG concentrations. This study represents the first effort to simultaneously quantify CO2; N2O; and CH4 production in zooplankton fecal pellets and assess their contribution to GHG inventories in the ESP; providing a baseline for quantifying future changes in GHG production in upwelling ecosystems and the open ocean under a climate change scenario.
Keywords:
methane
greenhouse gases
nitrous oxide
carbon dioxide
krill
Eastern South Pacific
fecal pellets
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