Evidence of nitrification associated with globally distributed pelagic jellyfish

Abstract

Bioavailable nitrogen is a scarce resource in most of the surface ocean
and often limits primary productivity. Although Pelagic jellyfish excrete
substantial amounts of ammonia (the preferred form of nitrogen for
most phytoplankton), they are overlooked players in marine nitrogen
cycling. Here, we observed high rates of nitrification (NH4+ → NO3-, 5.7
– 40.8 nM gWW-1 (wet weight) h-1) associated with the scyphomedusae
Aurelia aurita, Chrysaora hysoscella and Chrysaora pacifica and low rates
of incomplete nitrification (NH4+ → NO2-, 1-2.7 nM gWW-1 h-1)
associated with Chrysaora fulgida, Chrysaora hysoscella and Chrysaora
pacifica. These observations indicate that microbes living in association
with the jellyfish thrive by oxidizing the readily available ammonia to
nitrite and nitrate. The four studied species are abundant over a large
geographic distribution and exhibit frequent population outbreaks. We
show that, during such outbreaks, jellyfish-associated release of nitrogen
can provide more than 100% of the nitrogen required for primary
production. These findings reveal a so far overlooked pathway when
assessing pelagic nitrification rates that might be of particular relevance
in nitrogen depleted surface waters and at high jellyfish population
densities.

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Identifiers

ORCID for Nathan Damien Hubot: orcid.org/0000-0001-6917-2255

ORCID for Catherine Lucas: orcid.org/0000-0002-5929-7481

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