High rates of nitrogen fixation (acetylene reduction) on coral skeletons following bleaching mortality

Davey, Madeline; Holmes, Glen; Johnstone, Ron

doi:10.1007/s00338-007-0316-9

Cited by 38 publications

(47 citation statements)

References 46 publications

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“…Another hot spot of N 2 fixation in reefs is represented by microbial mats (where N 2 fixation can be as high as 3.2 nmol N cm −2 h −1 or a mean of 1.66 nmol N cm −2 h −1 ) with beach-rock showing the highest rates (Charpy-Roubaud and Larkum, 2005). Compared to the above substrates, N 2 fixation is much lower when diazotrophs are associated to sponges (Shashar et al, 1994;Rix et al, 2015) and soft coral species (0.001 to 0.205 nmol C 2 H 4 cm −2 h −1 or maximum of 0.07 nmol N cm −2 h −1 ; Bednarz et al, 2015a), but can increase in the presence of scleractinian coral species up to 8.7 nmol C 2 H 4 cm −2 h −1 (Davey et al, 2008;or 2.8 nmol N cm −2 h −1 ; Shashar et al, 1994;Lesser et al, 2007), as well as in turf algae (Haan et al, 2014;Rix et al, 2015). The dominance of BOX 1 | Methodological considerations for N 2 fixation measurements N 2 fixation rates can be assessed through different methods, mainly the acetylene (C 2 H 2 ) reduction assay (ARA; Capone, 1993) and the 15 N 2 enrichment technique (Montoya et al, 1996).…”

Section: N 2 Fixation In Coral Reef Ecosystems Description Of N 2 Fixmentioning

confidence: 95%

“…In this area, high light and temperature in summer enhance coral photosynthesis and thereby the release of organic matter in addition to the fact that high temperature per se enhances pelagic N 2 fixation too (Böttjer et al, 2016). Likewise, Davey et al (2008) showed that coral death as a result of thermal bleaching enhanced N 2 fixation through production of organic matter followed by the decay of coral tissue, which induced an increase in the development of microbial epiphytic and epilithic communities on coral skeletons. Finally, a recent study showed that low pH (decreased pCO 2 ) significantly decreased N 2 fixation associated with some coral species, likely due to a competition for energy between coral calcification or photosynthesis and N 2 fixation (Rädecker et al, 2014).…”

Section: N 2 Fixation In Coral Reef Ecosystems Description Of N 2 Fixmentioning

confidence: 97%

“…High rates of N 2 fixation have been measured in reefs sediments, rocks and dead coral skeletons, as well as related to several benthic (cyanobacterial mats, macroalgae, sponges, corals) and pelagic (unicellular cyanobacteria, Trichodesmium species) organisms (reviewed by Davey et al, 2008;O'Neil and Capone, 2008;Cardini et al, 2014). Rates of N 2 fixation can either be expressed indirectly as ethylene (C 2 H 4 ) produced from acetylene (C 2 H 2 ) using the acetylene reduction assay (ARA), or directly as the amount of nitrogen assimilated using 15 N 2 tracer experiments (see Box 1).…”

Section: N 2 Fixation In Coral Reef Ecosystems Description Of N 2 Fixmentioning

confidence: 99%

“…Rates of N 2 fixation can either be expressed indirectly as ethylene (C 2 H 4 ) produced from acetylene (C 2 H 2 ) using the acetylene reduction assay (ARA), or directly as the amount of nitrogen assimilated using 15 N 2 tracer experiments (see Box 1). The lowest rates have been recorded in the water column (Capone, 2001;Foster et al, 2009;Knapp et al, 2016), compared to benthic environments such as reef sediments and hard substrates which often present high N 2 fixation activities (Davey et al, 2008;O'Neil and Capone, 2008;Bednarz et al, 2015b;Rix et al, 2015). Epilithic communities recovering coral rubbles or dead coral skeletons can indeed fix up to 12 and 27 nmol N cm −2 h −1 , respectively (Davey et al, 2008).…”

Section: N 2 Fixation In Coral Reef Ecosystems Description Of N 2 Fixmentioning

confidence: 99%

“…diazotrophs have colonized a wide range of habitats, such as the water column (Riemann et al, 2010;Turk-Kubo et al, 2015), the sediments and dead coral surfaces (Davey et al, 2008;Bednarz et al, 2015b), the algal turfs (Rohwer et al, 2001;Haan et al, 2014;Rix et al, 2015), microbial mats and seagrass meadows (Rohwer et al, 2001(Rohwer et al, , 2002Charpy et al, 2012;Cardini et al, 2014), as well as sponge and coral tissue (Rohwer et al, 2002;Lema et al, 2014a,b). Still, their contribution to nitrogen cycling in the coral reef ecosystem as a whole, their spatial-temporal variability, level of activity and dependence on environmental factors, are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

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Diazotrophs: Overlooked Key Players within the Coral Symbiosis and Tropical Reef Ecosystems?

2017

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Coral reefs are highly productive ecosystems thriving in nutrient-poor waters. Their productivity depends largely on the availability of nitrogen, the proximate limiting nutrient for primary production. In reefs, the major nitrogen pathways include regeneration, nitrification, ammonification and dinitrogen (N 2 ) fixation. N 2 fixation is performed by prokaryotes called "diazotrophs" that abound in coral rubbles, sandy bottoms, microbial mats, or seagrass meadows. Corals, which are the main reef builders, have developed a partnership with dinoflagellates which transform dissolved inorganic nitrogen into amino acids and protein, and with diazotrophs to gain diazotrophically-derived nitrogen (DDN). Pioneering studies found active diazotrophic cyanobacteria in the corals' mucus and/or tissue, and later high throughput sequencing efforts have described diverse communities of non-cyanobacterial diazotrophs associated with scleractinian corals. Yet, the metabolic processes behind these associations and how they benefit corals are currently not well understood. While genomic studies describe the diversity of diazotrophs and isotopic tracer experiments quantify N 2 fixation rates, combined advanced methods are needed to elucidate the mechanisms behind the transfer of DDN to the coral holobiont and whether these mechanisms change according to the identity of the diazotrophs or coral species. Here we review our current knowledge on N 2 fixation in corals: the diversity and localization of diazotrophs in the coral holobiont, the environmental factors controlling N 2 fixation, the fate of DDN within the coral symbiosis as well as its potential role in coral resilience. We finally summarize the unknowns: are the diversity, abundance and localization of diazotrophs within the holobiont species-and/or site-specific? Do they have an impact on DDN production? What are the metabolic mechanisms implicated? Do they change spatially, temporally or according to environmental factors? We encourage scientists to undertake research efforts to tackle these questions in order to shed light on nitrogen cycling in reef ecosystems and to understand if coral-associated N 2 fixation can improve coral's resilience in the face of climate change.

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Section: N 2 Fixation In Coral Reef Ecosystems Description Of N 2 Fixmentioning

confidence: 95%

Section: N 2 Fixation In Coral Reef Ecosystems Description Of N 2 Fixmentioning

confidence: 97%

Section: N 2 Fixation In Coral Reef Ecosystems Description Of N 2 Fixmentioning

confidence: 99%

Section: N 2 Fixation In Coral Reef Ecosystems Description Of N 2 Fixmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Diazotrophs: Overlooked Key Players within the Coral Symbiosis and Tropical Reef Ecosystems?

2017

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Benthic N₂ fixation in coral reefs and the potential effects of human‐induced environmental change

Cardini

Bednarz

Foster

et al. 2014

Ecology and Evolution

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Tropical coral reefs are among the most productive and diverse ecosystems, despite being surrounded by ocean waters where nutrients are in short supply. Benthic dinitrogen (N2) fixation is a significant internal source of “new” nitrogen (N) in reef ecosystems, but related information appears to be sparse. Here, we review the current state (and gaps) of knowledge on N2 fixation associated with coral reef organisms and their ecosystems. By summarizing the existing literature, we show that benthic N2 fixation is an omnipresent process in tropical reef environments. Highest N2 fixation rates are detected in reef-associated cyanobacterial mats and sea grass meadows, clearly showing the significance of these functional groups, if present, to the input of new N in reef ecosystems. Nonetheless, key benthic organisms such as hard corals also importantly contribute to benthic N2 fixation in the reef. Given the usually high coral coverage of healthy reef systems, these results indicate that benthic symbiotic associations may be more important than previously thought. In fact, mutualisms between carbon (C) and N2 fixers have likely evolved that may enable reef communities to mitigate N limitation. We then explore the potential effects of the increasing human interferences on the process of benthic reef N2 fixation via changes in diazotrophic populations, enzymatic activities, or availability of benthic substrates favorable to these microorganisms. Current knowledge indicates positive effects of ocean acidification, warming, and deoxygenation and negative effects of increased ultraviolet radiation on the amount of N fixed in coral reefs. Eutrophication may either boost or suppress N2 fixation, depending on the nutrient becoming limiting. As N2 fixation appears to play a fundamental role in nutrient-limited reef ecosystems, these assumptions need to be expanded and confirmed by future research efforts addressing the knowledge gaps identified in this review.

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Dynamics of Coral Reef Communities in the Sekisei Lagoon, Japan, Following the Severe Mass Bleaching Event of 2016

Afzal

Ikeda

Ueno³

et al. 2023

Coral Reefs of the World

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High rates of nitrogen fixation (acetylene reduction) on coral skeletons following bleaching mortality

Cited by 38 publications

References 46 publications

Diazotrophs: Overlooked Key Players within the Coral Symbiosis and Tropical Reef Ecosystems?

Diazotrophs: Overlooked Key Players within the Coral Symbiosis and Tropical Reef Ecosystems?

Benthic N₂ fixation in coral reefs and the potential effects of human‐induced environmental change

Dynamics of Coral Reef Communities in the Sekisei Lagoon, Japan, Following the Severe Mass Bleaching Event of 2016

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High rates of nitrogen fixation (acetylene reduction) on coral skeletons following bleaching mortality

Cited by 38 publications

References 46 publications

Diazotrophs: Overlooked Key Players within the Coral Symbiosis and Tropical Reef Ecosystems?

Diazotrophs: Overlooked Key Players within the Coral Symbiosis and Tropical Reef Ecosystems?

Benthic N2 fixation in coral reefs and the potential effects of human‐induced environmental change

Dynamics of Coral Reef Communities in the Sekisei Lagoon, Japan, Following the Severe Mass Bleaching Event of 2016

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Benthic N₂ fixation in coral reefs and the potential effects of human‐induced environmental change