Evidence of nitrification associated with globally distributed pelagic jellyfish

Nathan D Hubot,Cathy H Lucas,Julie Robidart,Cynthia Dumousseaud,Jessika Füssel,Mark Stinchcombe,Antony Birchill,Sarah L C Giering

doi:10.1002/lno.11736

Abstract

AbstractOften considered detrimental to the environment and human activities, jellyfish blooms are increasing in several coastal regions worldwide. Yet, the overall effect of these outbreaks on ecosystem productivity and structure are not fully understood. Here we provide evidence for a so far unanticipated role of jellyfish in marine nitrogen cycling. Pelagic jellyfish release nitrogen as a metabolic waste product in form of ammonium. Yet, 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−, 1.0–2.8 nM gWW−1 h−1) associated with Chrysaora fulgida, C. hysoscella, and C. pacifica. These observations indicate that microbes living in association with these jellyfish thrive by oxidizing the readily available ammonia to nitrite and nitrate. The four studied species have 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.

Highlights

We measured the release rates of ammonium, nitrite, nitrate and phosphate in association with all four jellyfish species in order to assess the global prevalence of an association between nitrifiers and jellyfish as well as its potential role in the marine nitrogen cycle
Nutrient excretion and nitrification To determine rates of nitrification catalyzed by members of the jellyfish microbiome, we performed incubation experiments with four species of non-zooxanthellate scyphozoan jellyfish, A. aurita, C. hysoscella, C. fulgida, and C. pacifica
Mass-specific release rates of ammonium ranged from 22.8 to 86.2 nmol NH4+ gWW−1 h−1 at experimental temperatures (27.9–86.1 nmol NH4+ gWW−1 h−1 when normalized to 16C), which falls within the range of previous observations (2–111 nmol NH4+ gWW−1 h−1: Pitt et al 2013)

Summary

Introduction

We measured the release rates of ammonium, nitrite, nitrate and phosphate in association with all four jellyfish species in order to assess the global prevalence of an association between nitrifiers and jellyfish as well as its potential role in the marine nitrogen cycle. The rates of nutrient (ammonium, phosphate, nitrite, and nitrate) release per incubator (or per jellyfish for the jellyfish treatment) were calculated using linear regression for each replicate.

Results

Conclusion