1
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Dellisanti W, Zhang Q, Ferrier-Pagès C, Kühl M. Contrasting effects of increasing dissolved iron on photosynthesis and O 2 availability in the gastric cavity of two Mediterranean corals. PeerJ 2024; 12:e17259. [PMID: 38699194 PMCID: PMC11064864 DOI: 10.7717/peerj.17259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 03/27/2024] [Indexed: 05/05/2024] Open
Abstract
Iron (Fe) plays a fundamental role in coral symbiosis, supporting photosynthesis, respiration, and many important enzymatic reactions. However, the extent to which corals are limited by Fe and their metabolic responses to inorganic Fe enrichment remains to be understood. We used respirometry, variable chlorophyll fluorescence, and O2 microsensors to investigate the impact of increasing Fe(III) concentrations (20, 50, and 100 nM) on the photosynthetic capacity of two Mediterranean coral species, Cladocora caespitosa and Oculina patagonica. While the bioavailability of inorganic Fe can rapidly decrease, we nevertheless observed significant physiological effects at all Fe concentrations. In C. caespitosa, exposure to 50 nM Fe(III) increased rates of respiration and photosynthesis, while the relative electron transport rate (rETR(II)) decreased at higher Fe(III) exposure (100 nM). In contrast, O. patagonica reduced respiration, photosynthesis rates, and maximum PSII quantum yield (Fv/Fm) across all iron enrichments. Both corals exhibited increased hypoxia (<50 µmol O2 L-1) within their gastric cavity at night when exposed to 50 and 100 nM Fe(III), leading to increased polyp contraction time and reduced O2 exchange with the surrounding water. Our results indicate that C. caespitosa, but not O. patagonica, might be limited in Fe for achieving maximal photosynthetic efficiency. Understanding the multifaceted role of iron in corals' health and their response to environmental change is crucial for effective coral conservation.
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Affiliation(s)
- Walter Dellisanti
- Department of Biology, Marine Biology Section, University of Copenhagen, Helsingør, Denmark
| | - Qingfeng Zhang
- Department of Biology, Marine Biology Section, University of Copenhagen, Helsingør, Denmark
| | - Christine Ferrier-Pagès
- Coral Ecophysiology Laboratory, Center Scientifique de Monaco, Principality of Monaco, Monaco
| | - Michael Kühl
- Department of Biology, Marine Biology Section, University of Copenhagen, Helsingør, Denmark
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2
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Glaze TD, Erler DV, Siljanen HMP. Microbially facilitated nitrogen cycling in tropical corals. THE ISME JOURNAL 2022; 16:68-77. [PMID: 34226659 PMCID: PMC8692614 DOI: 10.1038/s41396-021-01038-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 06/04/2021] [Accepted: 06/08/2021] [Indexed: 02/06/2023]
Abstract
Tropical scleractinian corals support a diverse assemblage of microbial symbionts. This 'microbiome' possesses the requisite functional diversity to conduct a range of nitrogen (N) transformations including denitrification, nitrification, nitrogen fixation and dissimilatory nitrate reduction to ammonium (DNRA). Very little direct evidence has been presented to date verifying that these processes are active within tropical corals. Here we use a combination of stable isotope techniques, nutrient uptake calculations and captured metagenomics to quantify rates of nitrogen cycling processes in a selection of tropical scleractinian corals. Denitrification activity was detected in all species, albeit with very low rates, signifying limited importance in holobiont N removal. Relatively greater nitrogen fixation activity confirms that corals are net N importers to reef systems. Low net nitrification activity suggests limited N regeneration capacity; however substantial gross nitrification activity may be concealed through nitrate consumption. Based on nrfA gene abundance and measured inorganic N fluxes, we calculated significant DNRA activity in the studied corals, which has important implications for coral reef N cycling and warrants more targeted investigation. Through the quantification and characterisation of all relevant N-cycling processes, this study provides clarity on the subject of tropical coral-associated biogeochemical N-cycling.
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Affiliation(s)
- Thomas D Glaze
- Centre for Coastal Biogeochemistry Research, School of Environment Science and Engineering, Southern Cross University, Lismore, NSW, Australia.
| | - Dirk V Erler
- Centre for Coastal Biogeochemistry Research, School of Environment Science and Engineering, Southern Cross University, Lismore, NSW, Australia
| | - Henri M P Siljanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland
- Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
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3
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Rädecker N, Pogoreutz C, Gegner HM, Cárdenas A, Perna G, Geißler L, Roth F, Bougoure J, Guagliardo P, Struck U, Wild C, Pernice M, Raina JB, Meibom A, Voolstra CR. Heat stress reduces the contribution of diazotrophs to coral holobiont nitrogen cycling. THE ISME JOURNAL 2021; 16:1110-1118. [PMID: 34857934 PMCID: PMC8941099 DOI: 10.1038/s41396-021-01158-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 11/11/2021] [Accepted: 11/16/2021] [Indexed: 12/22/2022]
Abstract
Efficient nutrient cycling in the coral-algal symbiosis requires constant but limited nitrogen availability. Coral-associated diazotrophs, i.e., prokaryotes capable of fixing dinitrogen, may thus support productivity in a stable coral-algal symbiosis but could contribute to its breakdown when overstimulated. However, the effects of environmental conditions on diazotroph communities and their interaction with other members of the coral holobiont remain poorly understood. Here we assessed the effects of heat stress on diazotroph diversity and their contribution to holobiont nutrient cycling in the reef-building coral Stylophora pistillata from the central Red Sea. In a stable symbiotic state, we found that nitrogen fixation by coral-associated diazotrophs constitutes a source of nitrogen to the algal symbionts. Heat stress caused an increase in nitrogen fixation concomitant with a change in diazotroph communities. Yet, this additional fixed nitrogen was not assimilated by the coral tissue or the algal symbionts. We conclude that although diazotrophs may support coral holobiont functioning under low nitrogen availability, altered nutrient cycling during heat stress abates the dependence of the coral host and its algal symbionts on diazotroph-derived nitrogen. Consequently, the role of nitrogen fixation in the coral holobiont is strongly dependent on its nutritional status and varies dynamically with environmental conditions.
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Affiliation(s)
- Nils Rädecker
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia. .,Department of Biology, University of Konstanz, Konstanz, Germany. .,Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
| | - Claudia Pogoreutz
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.,Department of Biology, University of Konstanz, Konstanz, Germany
| | - Hagen M Gegner
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.,Metabolomics Core Technology Platform, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Anny Cárdenas
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.,Department of Biology, University of Konstanz, Konstanz, Germany
| | - Gabriela Perna
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.,Department of Biology, University of Konstanz, Konstanz, Germany
| | - Laura Geißler
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Florian Roth
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.,Baltic Sea Centre, Stockholm University, Stockholm, Sweden.,Faculty of Biological and Environmental Sciences, Tvärminne Zoological Station, University of Helsinki, Helsinki, Finland
| | - Jeremy Bougoure
- Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Perth, WA, Australia
| | - Paul Guagliardo
- Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Perth, WA, Australia
| | - Ulrich Struck
- Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany.,Department of Earth Sciences, Freie Universität Berlin, Berlin, Germany
| | - Christian Wild
- Faculty of Biology and Chemistry, Marine Ecology Department, University of Bremen, Bremen, Germany
| | - Mathieu Pernice
- Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Jean-Baptiste Raina
- Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
| | - Anders Meibom
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,Center for Advanced Surface Analysis, Institute of Earth Sciences, Université de Lausanne, Lausanne, Switzerland
| | - Christian R Voolstra
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.,Department of Biology, University of Konstanz, Konstanz, Germany
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4
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Yang F, Long C, Wei Z, Long L. Optimization of medium using response surface methodology to enhance the growth of Effrenium voratum (Symbiodiniaceae, Dinophyceae). JOURNAL OF PHYCOLOGY 2020; 56:1208-1215. [PMID: 32306387 DOI: 10.1111/jpy.13007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 03/27/2020] [Indexed: 06/11/2023]
Abstract
Survival of coral reef-associated Symbiodiniaceae is vital to maintain the healthy coral community in coral reefs. However, knowledge about cultivation of free-living or symbiotic Symbiodiniaceae has been limited. In this study, the response surface methodology was applied to optimize the medium for Effrenium voratum. The results showed that the impacts of nutrient components on algal growth were: FeCl3 > NaH2 PO4 >MnSO4 > MgSO4 /CoSO4 > KCl>ZnSO4 > CaCl2 /NaNO3 , among which NaH2 PO4 and FeCl3 significantly affected algal growth. The optimal medium was: natural seawater supplemented with NaH2 PO4 ·2H2 O 0.25 mM,FeCl3 ·6H2 O 14.24 μM, NaNO3 0.94 mM, MgSO4 ·7H2 O 40.63 mM, KCl 5.37 mM, CaCl2 ·2H2 O 4.08 mM, ZnSO4 ·7H2 O 0.35 μM, MnSO4 9.93 μM, and CoSO4 0.36 μM. The use of the optimized medium resulted in an increase of biomass yield (0.76 g dry weight · L-1 ) by 46% over that using the initial medium, which agreed with the predicted value (0.71 g · L-1 ). Additionally, fatty acids, mainly consisting of palmitic acid (C16:0) and ethyl carbonate (C20:0), accounted for approximately 50% of the total fatty acids in E. voratum. Interestingly, docosahexaenoic acid (DHA) accounted for 6% of total fatty acids, a high proportion that makes E. voratum a potential candidate feedstock in aquaculture for DHA production.
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Affiliation(s)
- Fangfang Yang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Chao Long
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Zhangliang Wei
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Lijuan Long
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
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5
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Liu YC, Huang RM, Bao J, Wu KY, Wu HY, Gao XY, Zhang XY. The unexpected diversity of microbial communities associated with black corals revealed by high-throughput Illumina sequencing. FEMS Microbiol Lett 2019; 365:5047306. [PMID: 29982506 DOI: 10.1093/femsle/fny167] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 06/28/2018] [Indexed: 12/16/2022] Open
Abstract
The microbes associated with black corals remain poorly studied. The present study is the first attempt to investigate microbial community structure in the black corals Antipathes ceylonensis and A. dichotoma from the South China Sea by using high-throughput Illumina sequencing. A total of 52 bacterial and 3 archaeal phyla were recovered in this study, suggesting the black corals harboured highly diverse microbial communities. Among the 55 microbial phyla, Proteobacteria, Firmicutes, Bacteroidetes, Chloroflexi, Acidobacteria and Actinobacteria dominated in the two black corals from the South China Sea. Although most of the microbial phyla recovered from the two black corals have been reported in previous studies on coral-associated microbes, eight bacterial phyla including Synergistetes, Thermi, AncK6, GNO2, NKB19, NC10, WWE1 and GAL15, and the archaeal phylum Parvarchaeota are reported for the first time from corals in this study, which expands our knowledge about the diversity of coral-associated microbes. The comparison of microbial communities in the different black coral species indicated that A. ceylonensis harboured few abundant bacterial genera such as Citrobacter and Pseudomonas, whereas a high diversity of rare bacterial genera (<1% abundance), such as Winogradskyella and Rubricoccus, was detected only in A. dichotoma. These results suggested that the microbial community in black corals exhibited species-specific variation.
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Affiliation(s)
- Yong-Chun Liu
- College of Marine Sciences, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China
| | - Ri-Ming Huang
- College of Food Science, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China
| | - Jie Bao
- School of Biological Science and Technology, University of Jinan, 336 West Road of Nan Xinzhuang, Jinan 250022, China
| | - Ke-Yue Wu
- College of Marine Sciences, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China
| | - Heng-Yu Wu
- College of Marine Sciences, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China
| | - Xiang-Yang Gao
- College of Food Science, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China
| | - Xiao-Yong Zhang
- College of Marine Sciences, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China
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6
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Teng Z, Zhang Y, Zhang W, Pan H, Xu J, Huang H, Xiao T, Wu LF. Diversity and Characterization of Multicellular Magnetotactic Prokaryotes From Coral Reef Habitats of the Paracel Islands, South China Sea. Front Microbiol 2018; 9:2135. [PMID: 30271390 PMCID: PMC6142882 DOI: 10.3389/fmicb.2018.02135] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 08/21/2018] [Indexed: 02/01/2023] Open
Abstract
While multicellular magnetotactic prokaryotes (MMPs) are ubiquitous in marine environments, the diversity of MMPs in sediments of coral reef ecosystems has rarely been reported. In this study, we made an investigation on the diversity and characteristics of MMPs in sediments at 11 stations in coral reef habitats of the Paracel Islands. The results showed that MMPs were present at nine stations, with spherical mulberry-like MMPs (s-MMPs) found at all stations and ellipsoidal pineapple-like MMPs (e-MMPs) found at seven stations. The maximum abundance of MMPs was 6 ind./cm3. Phylogenetic analysis revealed the presence of one e-MMP species and five s-MMP species including two species of a new genus. The results indicate that coral reef habitats of the Paracel Islands have a high diversity of MMPs that bio-mineralize multiple intracellular chains of iron crystals and play important role in iron cycling in such oligotrophic environment. These observations provide new perspective of the diversity of MMPs in general and expand knowledge of the occurrence of MMPs in coral reef habitats.
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Affiliation(s)
- Zhaojie Teng
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yuyang Zhang
- Key Laboratory of Marine Bio-resources Sustainable Utilization, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
| | - Wenyan Zhang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.,International Associated Laboratory of Evolution and Development of Magnetotactic Multicellular Organisms (LIA-MagMC), CNRS-CAS, Qingdao, China
| | - Hongmiao Pan
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.,International Associated Laboratory of Evolution and Development of Magnetotactic Multicellular Organisms (LIA-MagMC), CNRS-CAS, Qingdao, China
| | - Jianhong Xu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Hui Huang
- Key Laboratory of Marine Bio-resources Sustainable Utilization, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
| | - Tian Xiao
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.,International Associated Laboratory of Evolution and Development of Magnetotactic Multicellular Organisms (LIA-MagMC), CNRS-CAS, Qingdao, China
| | - Long-Fei Wu
- Aix Marseille University, CNRS, LCB, Marseille, France.,International Associated Laboratory of Evolution and Development of Magnetotactic Multicellular Organisms (LIA-MagMC), CNRS-CAS, Qingdao, China
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7
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Pogoreutz C, Rädecker N, Cárdenas A, Gärdes A, Wild C, Voolstra CR. Dominance of Endozoicomonas bacteria throughout coral bleaching and mortality suggests structural inflexibility of the Pocillopora verrucosa microbiome. Ecol Evol 2018; 8:2240-2252. [PMID: 29468040 PMCID: PMC5817147 DOI: 10.1002/ece3.3830] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 12/11/2017] [Accepted: 12/17/2017] [Indexed: 01/04/2023] Open
Abstract
The importance of Symbiodinium algal endosymbionts and a diverse suite of bacteria for coral holobiont health and functioning are widely acknowledged. Yet, we know surprisingly little about microbial community dynamics and the stability of host-microbe associations under adverse environmental conditions. To gain insight into the stability of coral host-microbe associations and holobiont structure, we assessed changes in the community structure of Symbiodinium and bacteria associated with the coral Pocillopora verrucosa under excess organic nutrient conditions. Pocillopora-associated microbial communities were monitored over 14 days in two independent experiments. We assessed the effect of excess dissolved organic nitrogen (DON) and excess dissolved organic carbon (DOC). Exposure to excess nutrients rapidly affected coral health, resulting in two distinct stress phenotypes: coral bleaching under excess DOC and severe tissue sloughing (>90% tissue loss resulting in host mortality) under excess DON. These phenotypes were accompanied by structural changes in the Symbiodinium community. In contrast, the associated bacterial community remained remarkably stable and was dominated by two Endozoicomonas phylotypes, comprising on average 90% of 16S rRNA gene sequences. This dominance of Endozoicomonas even under conditions of coral bleaching and mortality suggests the bacterial community of P. verrucosa may be rather inflexible and thereby unable to respond or acclimatize to rapid changes in the environment, contrary to what was previously observed in other corals. In this light, our results suggest that coral holobionts might occupy structural landscapes ranging from a highly flexible to a rather inflexible composition with consequences for their ability to respond to environmental change.
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Affiliation(s)
- Claudia Pogoreutz
- Red Sea Research Center, Biological and Environment Science and Engineering Division (BESE)King Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia
- Marine Ecology GroupFaculty of Biology and ChemistryUniversity of BremenBremenGermany
- Coral Reef Ecology GroupLeibniz Center for Tropical Marine Research (ZMT)BremenGermany
| | - Nils Rädecker
- Red Sea Research Center, Biological and Environment Science and Engineering Division (BESE)King Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia
| | - Anny Cárdenas
- Red Sea Research Center, Biological and Environment Science and Engineering Division (BESE)King Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia
- Tropical Marine Microbiology GroupLeibniz Center for Tropical Marine Research (ZMT)BremenGermany
| | - Astrid Gärdes
- Tropical Marine Microbiology GroupLeibniz Center for Tropical Marine Research (ZMT)BremenGermany
| | - Christian Wild
- Marine Ecology GroupFaculty of Biology and ChemistryUniversity of BremenBremenGermany
- Coral Reef Ecology GroupLeibniz Center for Tropical Marine Research (ZMT)BremenGermany
| | - Christian R. Voolstra
- Red Sea Research Center, Biological and Environment Science and Engineering Division (BESE)King Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia
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8
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Rädecker N, Pogoreutz C, Ziegler M, Ashok A, Barreto MM, Chaidez V, Grupstra CGB, Ng YM, Perna G, Aranda M, Voolstra CR. Assessing the effects of iron enrichment across holobiont compartments reveals reduced microbial nitrogen fixation in the Red Sea coral Pocillopora verrucosa. Ecol Evol 2017; 7:6614-6621. [PMID: 28861262 PMCID: PMC5574852 DOI: 10.1002/ece3.3293] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 07/07/2017] [Accepted: 07/09/2017] [Indexed: 11/09/2022] Open
Abstract
The productivity of coral reefs in oligotrophic tropical waters is sustained by an efficient uptake and recycling of nutrients. In reef-building corals, the engineers of these ecosystems, this nutrient recycling is facilitated by a constant exchange of nutrients between the animal host and endosymbiotic photosynthetic dinoflagellates (zooxanthellae), bacteria, and other microbes. Due to the complex interactions in this so-called coral holobiont, it has proven difficult to understand the environmental limitations of productivity in corals. Among others, the micronutrient iron has been proposed to limit primary productivity due to its essential role in photosynthesis and bacterial processes. Here, we tested the effect of iron enrichment on the physiology of the coral Pocillopora verrucosa from the central Red Sea during a 12-day experiment. Contrary to previous reports, we did not see an increase in zooxanthellae population density or gross photosynthesis. Conversely, respiration rates were significantly increased, and microbial nitrogen fixation was significantly decreased. Taken together, our data suggest that iron is not a limiting factor of primary productivity in Red Sea corals. Rather, increased metabolic demands in response to iron enrichment, as evidenced by increased respiration rates, may reduce carbon (i.e., energy) availability in the coral holobiont, resulting in reduced microbial nitrogen fixation. This decrease in nitrogen supply in turn may exacerbate the limitation of other nutrients, creating a negative feedback loop. Thereby, our results highlight that the effects of iron enrichment appear to be strongly dependent on local environmental conditions and ultimately may depend on the availability of other nutrients.
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Affiliation(s)
- Nils Rädecker
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Claudia Pogoreutz
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Maren Ziegler
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Ananya Ashok
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Marcelle M Barreto
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Veronica Chaidez
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Carsten G B Grupstra
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Yi Mei Ng
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Gabriela Perna
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Manuel Aranda
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
| | - Christian R Voolstra
- Red Sea Research Center Division of Biological and Environmental Science and Engineering (BESE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia
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