Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions.

Kiko, Rainer, Hauss, Helena , Buchholz, Friedrich and Melzner, Frank (2016) Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions. Open Access Biogeosciences (BG), 13 (8). pp. 2241-2255. DOI 10.5194/bg-13-2241-2016.

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Abstract

Calanoid copepods and euphausiids are key components of marine zooplankton communities worldwide. Most euphausiids and several copepod species perform diel vertical migrations (DVMs) that contribute to the export of particulate and dissolved matter to midwater depths. In vast areas of the global ocean, and in particular in the eastern tropical Atlantic and Pacific, the daytime distribution depth of many migrating organisms corresponds to the core of the oxygen minimum zone (OMZ). At depth, the animals experience reduced temperature and oxygen partial pressure (pO2) and an increased carbon dioxide partial pressure (pCO2) compared to their near-surface nighttime habitat. Although it is well known that low oxygen levels can inhibit respiratory activity, the respiration response of tropical copepods and euphausiids to relevant pCO2, pO2 and temperature conditions remains poorly parameterized. Further, the regulation of ammonium excretion at OMZ conditions is generally not well understood. It was recently estimated that DVM-mediated ammonium supply considerably fuels bacterial anaerobic ammonium oxidation – a major loss process for fixed nitrogen in the ocean. These estimates were based on the implicit assumption that hypoxia or anoxia in combination with hypercapnia (elevated pCO2) does not result in a downregulation of ammonium excretion. Here we show that exposure to OMZ conditions can result in strong depression of respiration and ammonium excretion in calanoid copepods and euphausiids from the Eastern Tropical North Atlantic and the Eastern Tropical South Pacific. These physiological responses need to be taken into account when estimating DVM-mediated fluxes of carbon and nitrogen into OMZs.

Document Type: Article
Additional Information: WOS:000377276700002
Keywords: Animalia; Bacteria (microorganisms); Calanoida; Copepoda; Euphausia gibboides; Euphausia mucronata; Euphausiidae; Galatheidae; Pleuromamma abdominalis; Undinula vulgaris
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-N Experimental Ecology - Food Webs
OceanRep > SFB 754
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-B Experimental Ecology - Benthic Ecology
AWI
OceanRep > SFB 754 > B8
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-13-2241-2016
ISSN: 1726-4170
Projects: SFB754
Expeditions/Models/Experiments:
Date Deposited: 30 Oct 2015 13:47
Last Modified: 01 Feb 2019 15:09
URI: http://oceanrep.geomar.de/id/eprint/30126

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