1
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Archibald KM, Dutkiewicz S, Laufkötter C, Moeller HV. Emergent trade-offs among plasticity strategies in mixotrophs. J Theor Biol 2024; 590:111854. [PMID: 38763324 DOI: 10.1016/j.jtbi.2024.111854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 03/14/2024] [Accepted: 05/14/2024] [Indexed: 05/21/2024]
Abstract
Marine mixotrophs combine phagotrophy and phototrophy to acquire the resources they need for growth. Metabolic plasticity, the ability for individuals to dynamically alter their relative investment between different metabolic processes, allows mixotrophs to efficiently exploit variable environmental conditions. Different mixotrophs may vary in how quickly they respond to environmental stimuli, with slow-responding mixotrophs exhibiting a significant lag between a change in the environment and the resulting change metabolic strategy. In this study, we develop a model of mixotroph metabolic strategy and explore how the rate of the plastic response affects the seasonality, competitive fitness, and biogeochemical role of mixotroph populations. Fast-responding mixotrophs are characterized by more efficient resource use and higher average growth rates than slow-responding mixotrophs because any lag in the plastic response following a change in environmental conditions creates a mismatch between the mixotroph's metabolic requirements and their resource acquisition. However, this mismatch also results in increased storage of unused resources that support growth under future nutrient-limited conditions. As a result of this trade-off, mixotroph biomass and productivity are maximized at intermediate plastic response rates. Furthermore, the trade-off represents a mechanism for coexistence between fast-responding and slow-responding mixotrophs. In mixed communities, fast-responding mixotrophs are numerically dominant, but slow-responding mixotrophs persist at low abundance due to the provisioning effect that emerges as a result of their less efficient resource acquisition strategy. In addition to increased competitive ability, fast-responding mixotrophs are, on average, more autotrophic than slow-responding mixotrophs. Notably, these trade-offs associated with mixotroph response rate arise without including an explicit physiological cost associated with plasticity, a conclusion that may provide insight into evolutionary constraints of metabolic plasticity in mixotrophic organisms. When an explicit cost is added to the model, it alters the competitive relationships between fast- and slow-responding mixotrophs. Faster plastic response rates are favored by lower physiological costs as well as higher amplitude seasonal cycles.
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Affiliation(s)
- Kevin M Archibald
- Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA.
| | - Stephanie Dutkiewicz
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA; Center for Global Change Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Charlotte Laufkötter
- Climate and Environmental Physics, University of Bern, Bern, Switzerland; Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
| | - Holly V Moeller
- Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA
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2
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Mak EWK, Turk‐Kubo KA, Caron DA, Harbeitner RC, Magasin JD, Coale TH, Hagino K, Takano Y, Nishimura T, Adachi M, Zehr JP. Phagotrophy in the nitrogen-fixing haptophyte Braarudosphaera bigelowii. ENVIRONMENTAL MICROBIOLOGY REPORTS 2024; 16:e13312. [PMID: 39049182 PMCID: PMC11269211 DOI: 10.1111/1758-2229.13312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Accepted: 06/26/2024] [Indexed: 07/27/2024]
Abstract
Biological nitrogen fixation provides fixed nitrogen for microbes living in the oligotrophic open ocean. UCYN-A2, the previously known symbiont of Braarudosphaera bigelowii, now believed to be an early-stage B. bigelowii organelle that exchanges fixed nitrogen for fixed carbon, is globally distributed. Indirect evidence suggested that B. bigelowii might be a mixotrophic (phagotrophic) phototrophic flagellate. The goal of this study was to determine if B. bigelowii can graze on bacteria using several independent approaches. The results showed that B. bigelowii grazed on co-occurring bacteria at a rate of 5-7 cells/h/B. bigelowii and that the overall grazing rate was significantly higher at nighttime than at daytime. Bacterial abundance changes, assessed with 16S rRNA gene amplicon sequencing analysis, may have indicated preferential grazing by B. bigelowii on specific bacterial genotypes. In addition, Lysotracker™ staining of B. bigelowii suggested digestive activity inside B. bigelowii. Carbon and nitrogen fixation measurements revealed that the carbon demand of B. bigelowii could not be fulfilled by photosynthesis alone, implying supplementation by heterotrophy. These independent lines of evidence together revealed that B. bigelowii engages in phagotrophy, which, beyond serving as a supplementary source of carbon and energy, may also facilitate the indirect assimilation of inorganic nutrients.
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Affiliation(s)
| | | | - David A. Caron
- Department of Biological SciencesUniversity of Southern CaliforniaLos AngelesCaliforniaUSA
| | | | | | - Tyler H. Coale
- Department of Ocean SciencesUniversity of CaliforniaSanta CruzCaliforniaUSA
| | - Kyoko Hagino
- Marine Core Research InstituteKochi UniversityNankokuJapan
| | | | - Tomohiro Nishimura
- Faculty of Agriculture and Marine ScienceKochi UniversityNankokuJapan
- Fisheries Technology Institute, Japan Fisheries Research and Education AgencyHiroshimaJapan
| | - Masao Adachi
- Faculty of Agriculture and Marine ScienceKochi UniversityNankokuJapan
| | - Jonathan P. Zehr
- Department of Ocean SciencesUniversity of CaliforniaSanta CruzCaliforniaUSA
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3
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Li J, Xiang S, Li Y, Cheng R, Lai Q, Wang L, Li G, Dong C, Shao Z. Arcobacteraceae are ubiquitous mixotrophic bacteria playing important roles in carbon, nitrogen, and sulfur cycling in global oceans. mSystems 2024; 9:e0051324. [PMID: 38904399 PMCID: PMC11265409 DOI: 10.1128/msystems.00513-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Accepted: 05/14/2024] [Indexed: 06/22/2024] Open
Abstract
Mixotrophy is an important trophic strategy for bacterial survival in the ocean. However, the global relevance and identity of the major mixotrophic taxa remain largely elusive. Here, we combined phylogenetic, metagenomic, and metatranscriptomic analyses to characterize ubiquitous Arcobacteraceae based on our deep-sea in situ incubations and the global data. The phylogenomic tree of Arcobacteraceae is divided into three large clades, among which members of clades A and B are almost all from terrestrial environments, while those of clade C are widely distributed in various marine habitats in addition to some terrestrial origins. All clades harbor genes putatively involved in chitin degradation, sulfide oxidation, hydrogen oxidation, thiosulfate oxidation, denitrification, dissimilatory nitrate reduction to ammonium, microaerophilic respiration, and metal (iron/manganese) reduction. Additionally, in clade C, more unique pathways were retrieved, including thiosulfate disproportionation, ethanol fermentation, methane oxidation, fatty acid oxidation, cobalamin synthesis, and dissimilatory reductions of sulfate, perchlorate, and arsenate. Within this clade, two mixotrophic Candidatus genera represented by UBA6211 and CAIJNA01 harbor genes putatively involved in the reverse tricarboxylic acid pathway for carbon fixation. Moreover, the metatranscriptomic data in deep-sea in situ incubations indicated that the latter genus is a mixotroph that conducts carbon fixation by coupling sulfur oxidation and denitrification and metabolizing organic matter. Furthermore, global metatranscriptomic data confirmed the ubiquitous distribution and global relevance of Arcobacteraceae in the expression of those corresponding genes across all oceanic regions and depths. Overall, these results highlight the contribution of previously unrecognized Arcobacteraceae to carbon, nitrogen, and sulfur cycling in global oceans.IMPORTANCEMarine microorganisms exert a profound influence on global carbon cycling and ecological relationships. Mixotrophy, characterized by the simultaneous utilization of both autotrophic and heterotrophic nutrition, has a significant impact on the global carbon cycling. This report characterizes a group of uncultivated bacteria Arcobacteraceae that thrived on the "hot time" of bulky particulate organic matter and exhibited mixotrophic strategy during the in situ organic mineralization. Compared with clades A and B, more unique metabolic pathways were retrieved in clade C, including the reverse tricarboxylic acid pathway for carbon fixation, thiosulfate disproportionation, methane oxidation, and fatty acid oxidation. Global metatranscriptomic data from the Tara Oceans expeditions confirmed the ubiquitous distribution and extensive transcriptional activity of Arcobacteraceae with the expression of genes putatively involved in carbon fixation, methane oxidation, multiple sulfur compound oxidation, and denitrification across all oceanic regions and depths.
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Affiliation(s)
- Jianyang Li
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
| | - Shizheng Xiang
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
| | - Yufei Li
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
| | - Ruolin Cheng
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
| | - Qiliang Lai
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
| | - Liping Wang
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
| | - Guizhen Li
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
| | - Chunming Dong
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
| | - Zongze Shao
- Key Laboratory of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Third Institute of Oceanography, Ministry of Natural Resources of PR China, Xiamen, China
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
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4
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Princiotta SD, VanKuren A, Williamson CE, Sanders RW, Valiñas MS. Disentangling the role of light and nutrient limitation on bacterivory by mixotrophic nanoflagellates. JOURNAL OF PHYCOLOGY 2023; 59:785-790. [PMID: 37379435 DOI: 10.1111/jpy.13358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 05/15/2023] [Accepted: 05/27/2023] [Indexed: 06/30/2023]
Abstract
Many phytoplankton taxa function on multiple trophic levels by combining photosynthesis and ingestion of bacteria, termed mixotrophy. Despite the recognition of mixotrophy as a universal functional trait, we have yet to fully resolve how environmental conditions influence community grazing rates in situ. A microcosm study was used to assess bacterivory by mixotrophic nanoflagellates following nutrient enrichment and light attenuation in a temperate lake. We found contrasting results based on assessment of mixotroph abundance or bacterivory. Despite an interactive effect of nutrient enrichment and light attenuation on mixotroph abundance, significant differences within light treatments were observed only after enrichment with P or N + P. The greatest abundance of mixotrophs across treatments occurred under co-nutrient enrichment with full exposure to irradiance. However, bacterivory by mixotrophic nanoflagellates was greatest under shaded conditions after either N or P enrichment. We suggest that PAR availability dampened the stimulatory effect of nutrient limitation, and bacterivory supplemented a suboptimal photosynthetic environment. In a saturating light regime, the mixotrophic community was less driven to ingest bacteria because photosynthesis was able to satisfy energetic demands. These findings quantify community bacterivory in response to environmental drivers that may characterize future ecosystem conditions and highlight the importance of considering grazing rates in conjunction with abundance of mixotrophic protists.
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Affiliation(s)
| | - Andrew VanKuren
- Department of Biology, Temple University, Philadelphia, Pennsylvania, USA
| | | | - Robert W Sanders
- Department of Biology, Temple University, Philadelphia, Pennsylvania, USA
| | - Macarena S Valiñas
- Estación de Fotobiología Playa Unión, Rawson, Chubut, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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5
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Schenone L, Balseiro E, Modenutti B. Light dependence in the phototrophy-phagotrophy balance of constitutive and non-constitutive mixotrophic protists. Oecologia 2022; 200:295-306. [PMID: 35962828 DOI: 10.1007/s00442-022-05226-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 07/20/2022] [Indexed: 11/28/2022]
Abstract
Mixotrophic protists display contrasting nutritional strategies and are key groups connecting planktonic food webs. They comprise constitutive mixotrophs (CMs) that have an innate photosynthetic ability and non-constitutive mixotrophs (NCMs) that acquire it from their prey. We modelled phototrophy and phagotrophy of two mixotrophic protists as a function of irradiance and prey abundance. We hypothesised that differences in their physiology (constitutive versus non-constitutive mixotrophy) can result in different responses to light gradients. We fitted the models with primary production and bacterivory data from laboratory and field experiments with the nanoflagellate Chrysochromulina parva (CM) and the ciliate Ophrydium naumanni (NCM) from north Andean Patagonian lakes. We found a non-monotonic response of phototrophy and phagotrophy to irradiance in both mixotrophs, which was successfully represented by our models. Maximum values for phototrophy and phagotrophy were found at intermediate irradiance coinciding with the light at the deep chlorophyll maxima in these lakes. At lower and higher irradiances, we found a decoupling between phototrophy and phagotrophy in the NCM while these functions were more coupled in the CM. Our modelling approach revealed the difference between both mixotrophic functional types on the balance between their nutritional strategies under different light scenarios. Thus, our proposed models can be applied to account how changing environmental conditions affect both primary and secondary production within the planktonic microbial food web.
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Affiliation(s)
- Luca Schenone
- Laboratorio de Limnología, INIBIOMA-CONICET, Universidad Nacional del Comahue. Quintral 1250, 8400, San Carlos de Bariloche, Río Negro, Argentina.
| | - Esteban Balseiro
- Laboratorio de Limnología, INIBIOMA-CONICET, Universidad Nacional del Comahue. Quintral 1250, 8400, San Carlos de Bariloche, Río Negro, Argentina
| | - Beatriz Modenutti
- Laboratorio de Limnología, INIBIOMA-CONICET, Universidad Nacional del Comahue. Quintral 1250, 8400, San Carlos de Bariloche, Río Negro, Argentina
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6
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Fischer R, Kitzwögerer J, Ptacnik R. Light-dependent niche differentiation in two mixotrophic bacterivores. ENVIRONMENTAL MICROBIOLOGY REPORTS 2022; 14:530-537. [PMID: 35509225 PMCID: PMC9541266 DOI: 10.1111/1758-2229.13071] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 04/07/2022] [Accepted: 04/07/2022] [Indexed: 05/13/2023]
Abstract
Mixotrophy usually is considered with respect to the advantages gained and the associated trade-offs of this form of nutrition, compared to specialized competitors, strict photoautotrophs and heterotrophs. However, we currently have an incomplete understanding of the functional diversity of mixotrophs and the factors controlling niche differentiation in different mixotrophic species. Here we experimentally studied the light-dependent niche differentiation in two chrysophyte species. We show that the newly isolated Ochromonas sp. is an obligate phototroph and possibly an obligate mixotroph. In contrast, Poterioochromonas malhamensis is a facultative mixotroph; photosynthesis and heterotrophy in this species represent substitutable routes of resource acquisition. We further hypothesize that the variable plasticity in the considered traits of the here tested species may result in different niche differentiation with regard to a vertical light gradient. Ochromonas sp. should perform better in stable stratified surface water layers, where light is available, but prey abundances might be low. However, P. malhamensis should be able to also successfully grow in deeper water layers, benefiting from higher bacterial production. This study represents a first step towards understanding competition between mixotrophs engaging in different physiological strategies, and consequently their potential co-occurrence due to niche differentiation.
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Affiliation(s)
- Robert Fischer
- AquaScale, WasserCluster Lunz Biologische Station GmbHLunz am SeeAustria
| | - Julia Kitzwögerer
- Austrian Biotech University of Applied Sciences, Biotech Campus TullnTulln an der DonauAustria
| | - Robert Ptacnik
- AquaScale, WasserCluster Lunz Biologische Station GmbHLunz am SeeAustria
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7
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Protist Diversity and Metabolic Strategy in Freshwater Lakes Are Shaped by Trophic State and Watershed Land Use on a Continental Scale. mSystems 2022; 7:e0031622. [PMID: 35730947 PMCID: PMC9426515 DOI: 10.1128/msystems.00316-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Protists play key roles in aquatic food webs as primary producers, predators, nutrient recyclers, and symbionts. However, a comprehensive view of protist diversity in freshwaters has been challenged by the immense environmental heterogeneity among lakes worldwide. We assessed protist diversity in the surface waters of 366 freshwater lakes across a north temperate to subarctic range covering nearly 8.4 million km2 of Canada. Sampled lakes represented broad gradients in size, trophic state, and watershed land use. Hypereutrophic lakes contained the least diverse and most distinct protist communities relative to nutrient-poor lakes. Greater taxonomic variation among eutrophic lakes was mainly a product of heterotroph and mixotroph diversity, whereas phototroph assemblages were more similar under high-nutrient conditions. Overall, local physicochemical factors, particularly ion and nutrient concentrations, elicited the strongest responses in community structure, far outweighing the effects of geographic gradients. Despite their contrasting distribution patterns, obligate phototroph and heterotroph turnover was predicted by an overlapping set of environmental factors, while the metabolic plasticity of mixotrophs may have made them less predictable. Notably, protist diversity was associated with variation in watershed soil pH and agricultural crop coverage, pointing to human impact on the land-water interface that has not been previously identified in studies on smaller scales. Our study exposes the importance of both within-lake and external watershed characteristics in explaining protist diversity and biogeography, critical information for further developing an understanding of how freshwater lakes and their watersheds are impacted by anthropogenic stressors. IMPORTANCE Freshwater lakes are experiencing rapid changes under accelerated anthropogenic stress and a warming climate. Microorganisms underpin aquatic food webs, yet little is known about how freshwater microbial communities are responding to human impact. Here, we assessed the diversity of protists and their myriad ecological roles in lakes varying in size across watersheds experiencing a range of land use pressures by leveraging data from a continental-scale survey of Canadian lakes. We found evidence of human impact on protist assemblages through an association with lake trophic state and extending to agricultural activity and soil characteristics in the surrounding watershed. Furthermore, trophic state appeared to explain the distributions of phototrophic and heterotrophic protists in contrasting ways. Our findings highlight the vulnerability of lake ecosystems to increased land use and the importance of assessing terrestrial interfaces to elucidate freshwater ecosystem dynamics.
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8
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González-Olalla JM, Medina-Sánchez JM, Norici A, Carrillo P. Regulation of Phagotrophy by Prey, Low Nutrients, and Low Light in the Mixotrophic Haptophyte Isochrysis galbana. MICROBIAL ECOLOGY 2021; 82:981-993. [PMID: 33661311 DOI: 10.1007/s00248-021-01723-w] [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: 11/24/2020] [Accepted: 02/16/2021] [Indexed: 06/12/2023]
Abstract
Mixotrophy combines autotrophy and phagotrophy in the same cell. However, it is not known to what extent the phagotrophy influences metabolism, cell composition, and growth. In this work, we assess, on the one hand (first test), the role of phagotrophy on the elemental and biochemical composition, cell metabolism, and enzymes related to C, N, and S metabolism of Isochrysis galbana Parke, 1949. On the other hand, we study how a predicted increase of phagotrophy under environmental conditions of low nutrients (second test) and low light (third test) can affect its metabolism and growth. Our results for the first test revealed that bacterivory increased the phosphorous and iron content per cell, accelerating cell division and improving the cell fitness; in addition, the stimulation of some C and N enzymatic routes help to maintain, to some degree, compositional homeostasis. Under nutrient or light scarcity, I. galbana grew more slowly despite greater bacterial consumption, and the activities of key enzymes involved in C, N, and S metabolism changed according to a predominantly phototrophic strategy of nutrition in this alga. Contrary to recent studies, the stimulation of phagotrophy under low nutrient and low irradiance did not imply greater and more efficient C flux.
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Affiliation(s)
- Juan Manuel González-Olalla
- Laboratory of Algal and Plant Physiology, Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, 60131, Ancona, Italy.
- University Institute of Water research, University of Granada, C/Ramón y Cajal, 4, 18071, Granada, Spain.
| | - Juan Manuel Medina-Sánchez
- University Institute of Water research, University of Granada, C/Ramón y Cajal, 4, 18071, Granada, Spain
- Department of Ecology, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, 18071, Granada, Spain
| | - Alessandra Norici
- Laboratory of Algal and Plant Physiology, Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, 60131, Ancona, Italy
| | - Presentación Carrillo
- University Institute of Water research, University of Granada, C/Ramón y Cajal, 4, 18071, Granada, Spain
- Department of Ecology, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, 18071, Granada, Spain
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9
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Schenone L, Balseiro EG, Bastidas Navarro M, Modenutti BE. Modelling the consequence of glacier retreat on mixotrophic nanoflagellate bacterivory: a Bayesian approach. OIKOS 2020. [DOI: 10.1111/oik.07170] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Luca Schenone
- Laboratorio de Limnología, INIBIOMA (CONICET‐UNCo), Quintral 1250 San Carlos de Bariloche (8400) Río Negro Argentina
| | - Esteban G. Balseiro
- Laboratorio de Limnología, INIBIOMA (CONICET‐UNCo), Quintral 1250 San Carlos de Bariloche (8400) Río Negro Argentina
| | - Marcela Bastidas Navarro
- Laboratorio de Limnología, INIBIOMA (CONICET‐UNCo), Quintral 1250 San Carlos de Bariloche (8400) Río Negro Argentina
| | - Beatriz E. Modenutti
- Laboratorio de Limnología, INIBIOMA (CONICET‐UNCo), Quintral 1250 San Carlos de Bariloche (8400) Río Negro Argentina
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10
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Grazing resistance and poor food quality of a widespread mixotroph impair zooplankton secondary production. Oecologia 2020; 193:489-502. [PMID: 32504109 PMCID: PMC7320944 DOI: 10.1007/s00442-020-04677-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 05/28/2020] [Indexed: 12/03/2022]
Abstract
Growing evidence suggests that global climate change promotes the dominance of mixotrophic algae especially in oligotrophic aquatic ecosystems. While theory predicts that mixotrophy increases trophic transfer efficiency in aquatic food webs, deleterious effects of some mixotrophs on consumers have also been reported. Here, using a widespread mixotrophic algal genus Dinobryon, we aimed to quantify how colonial taxa contribute to secondary production in lakes. We, therefore, studied the dietary effects of Dinobryon divergens on Cladocera (Daphnia longispina) and Copepoda (Eudiaptomus gracilis), representing two main taxonomic and functional groups of zooplankton. In feeding experiments, we showed that Dinobryon was largely grazing resistant and even inhibited the uptake of the high-quality reference food in Daphnia. Eudiaptomus could to some extent compensate with selective feeding, but a negative long-term food quality effect was also evident. Besides, Eudiaptomus was more sensitive to the pure diet of Dinobryon than Daphnia. Low lipid content and high C:P elemental ratio further supported the low nutritional value of the mixotroph. In a stable isotope approach analysing a natural plankton community, we found further evidence that carbon of Dinobryon was not conveyed efficiently to zooplankton. Our results show that the increasing dominance of colonial mixotrophs can result in reduced dietary energy transfer to consumers at higher trophic levels. In a wider perspective, global climate change favours the dominance of some detrimental mixotrophic algae which may constrain pelagic trophic transfer efficiency in oligotrophic systems, similarly to cyanobacteria in eutrophic lakes.
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11
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Wilken S, Choi CJ, Worden AZ. Contrasting Mixotrophic Lifestyles Reveal Different Ecological Niches in Two Closely Related Marine Protists. JOURNAL OF PHYCOLOGY 2020; 56:52-67. [PMID: 31529498 PMCID: PMC7065223 DOI: 10.1111/jpy.12920] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 08/13/2019] [Indexed: 05/13/2023]
Abstract
Many marine microbial eukaryotes combine photosynthetic with phagotrophic nutrition, but incomplete understanding of such mixotrophic protists, their functional diversity, and underlying physiological mechanisms limits the assessment and modeling of their roles in present and future ocean ecosystems. We developed an experimental system to study responses of mixotrophic protists to availability of living prey and light, and used it to characterize contrasting physiological strategies in two stramenopiles in the genus Ochromonas. We show that oceanic isolate CCMP1393 is an obligate mixotroph, requiring both light and prey as complementary resources. Interdependence of photosynthesis and heterotrophy in CCMP1393 comprises a significant role of mitochondrial respiration in photosynthetic electron transport. In contrast, coastal isolate CCMP2951 is a facultative mixotroph that can substitute photosynthesis by phagotrophy and hence grow purely heterotrophically in darkness. In contrast to CCMP1393, CCMP2951 also exhibits a marked photoprotection response that integrates non-photochemical quenching and mitochondrial respiration as electron sink for photosynthetically produced reducing equivalents. Facultative mixotrophs similar to CCMP2951 might be well adapted to variable environments, while obligate mixotrophs similar to CCMP1393 appear capable of resource efficient growth in oligotrophic ocean environments. Thus, the responses of these phylogenetically close protists to the availability of different resources reveals niche differentiation that influences impacts in food webs and leads to opposing carbon cycle roles.
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Affiliation(s)
- Susanne Wilken
- Monterey Bay Aquarium Research Institute7700 Sandholdt RoadMoss LandingCalifornia95039USA
- Department of Freshwater and Marine EcologyInstitute for Biodiversity and Ecosystem DynamicsUniversity of AmsterdamScience Park 904Amsterdam1098 XHThe Netherlands
| | - Chang Jae Choi
- Monterey Bay Aquarium Research Institute7700 Sandholdt RoadMoss LandingCalifornia95039USA
- Ocean EcoSystems Biology UnitGEOMAR Helmholtz Centre for Ocean ResearchDüsternbrooker Weg 20Kiel24105Germany
| | - Alexandra Z. Worden
- Monterey Bay Aquarium Research Institute7700 Sandholdt RoadMoss LandingCalifornia95039USA
- Ocean EcoSystems Biology UnitGEOMAR Helmholtz Centre for Ocean ResearchDüsternbrooker Weg 20Kiel24105Germany
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12
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Wilken S, Yung CCM, Hamilton M, Hoadley K, Nzongo J, Eckmann C, Corrochano-Luque M, Poirier C, Worden AZ. The need to account for cell biology in characterizing predatory mixotrophs in aquatic environments. Philos Trans R Soc Lond B Biol Sci 2019; 374:20190090. [PMID: 31587652 PMCID: PMC6792458 DOI: 10.1098/rstb.2019.0090] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/24/2019] [Indexed: 12/16/2022] Open
Abstract
Photosynthesis in eukaryotes first arose through phagocytotic processes wherein an engulfed cyanobacterium was not digested, but instead became a permanent organelle. Other photosynthetic lineages then arose when eukaryotic cells engulfed other already photosynthetic eukaryotic cells. Some of the resulting lineages subsequently lost their ability for phagocytosis, while many others maintained the ability to do both processes. These mixotrophic taxa have more complicated ecological roles, in that they are both primary producers and consumers that can shift more towards producing the organic matter that forms the base of aquatic food chains, or towards respiring and releasing CO2. We still have much to learn about which taxa are predatory mixotrophs as well as about the physiological consequences of this lifestyle, in part, because much of the diversity of unicellular eukaryotes in aquatic ecosystems remains uncultured. Here, we discuss existing methods for studying predatory mixotrophs, their individual biases, and how single-cell approaches can enhance knowledge of these important taxa. The question remains what the gold standard should be for assigning a mixotrophic status to ill-characterized or uncultured taxa-a status that dictates how organisms are incorporated into carbon cycle models and how their ecosystem roles may shift in future lakes and oceans. This article is part of a discussion meeting issue 'Single cell ecology'.
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Affiliation(s)
- Susanne Wilken
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, 1090GE Amsterdam, Noord-Holland, The Netherlands
- Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
- Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM)-CSIC, 08003 Barcelona, Catalunya, Spain
| | - Charmaine C. M. Yung
- Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
- Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Schleswig-Holstein, Germany
| | - Maria Hamilton
- Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
- Division of Physical and Biological Sciences, UC Santa Cruz, Santa Cruz, CA 95064, USA
| | - Kenneth Hoadley
- Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Schleswig-Holstein, Germany
| | - Juliana Nzongo
- Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
- Division of Physical and Biological Sciences, UC Santa Cruz, Santa Cruz, CA 95064, USA
| | - Charlotte Eckmann
- Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
- Division of Physical and Biological Sciences, UC Santa Cruz, Santa Cruz, CA 95064, USA
| | | | - Camille Poirier
- Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
- Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Schleswig-Holstein, Germany
| | - Alexandra Z. Worden
- Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
- Ocean EcoSystems Biology Unit, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Schleswig-Holstein, Germany
- Division of Physical and Biological Sciences, UC Santa Cruz, Santa Cruz, CA 95064, USA
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Waibel A, Peter H, Sommaruga R. Importance of mixotrophic flagellates during the ice-free season in lakes located along an elevational gradient. AQUATIC SCIENCES 2019; 81:45. [PMID: 31057304 PMCID: PMC6469636 DOI: 10.1007/s00027-019-0643-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 04/13/2019] [Indexed: 06/09/2023]
Abstract
Mixotrophy seems to be widespread among phytoplankton, but whether this strategy is more relevant in oligotrophic lakes remains unclear. Here, we tested the hypothesis that the relative abundance of mixotrophic flagellates in lakes increases along an elevational gradient paralleling increasingly oligotrophic conditions. For this purpose, 12 lakes located between 575 and 2796 m above sea level were sampled in summer and fall to include two different seasonal windows in phytoplankton dynamics and environmental conditions. The degree of mixotrophy in phytoplankton was estimated in tracer experiments using fluorescently-labeled bacteria and done with composite samples collected in the euphotic zone and in samples obtained from the chlorophyll-a maximum. The results indicated the existence of a positive trend particularly in summer in the relative abundance of mixotrophic flagellates with elevation, however, this trend was not linear, and exceptions along the elevational gradient were found. Changes in the relative abundance of mixotrophic flagellates were related with significant changes in water transparency, DOC and phosphorus concentrations, as well as in bacterial and flagellate abundance. Overall, our results reveal that the harsh growth conditions found in oligotrophic high mountain lakes favor a mixotrophic trophic strategy among phytoplankton.
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Affiliation(s)
- Anna Waibel
- Department of Ecology, Lake and Glacier Research Group, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
| | - Hannes Peter
- Department of Ecology, Lake and Glacier Research Group, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
- Present Address: Stream Biofilm and Ecosystem Research Laboratory, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne, Switzerland
| | - Ruben Sommaruga
- Department of Ecology, Lake and Glacier Research Group, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
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14
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Mixotrophy in nanoflagellates across environmental gradients in the ocean. Proc Natl Acad Sci U S A 2019; 116:6211-6220. [PMID: 30760589 DOI: 10.1073/pnas.1814860116] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Mixotrophy, the combination of autotrophic and heterotrophic nutrition, is a common trophic strategy among unicellular eukaryotes in the ocean. There are a number of hypotheses about the conditions that select for mixotrophy, and field studies have documented the prevalence of mixotrophy in a range of environments. However, there is currently little evidence for how mixotrophy varies across environmental gradients, and whether empirical patterns support theoretical predictions. Here I synthesize experiments that have quantified the abundance of phototrophic, mixotrophic, and heterotrophic nanoflagellates, to ask whether there are broad patterns in the prevalence of mixotrophy (relative to pure autotrophy and heterotrophy), and to ask whether observed patterns are consistent with a trait-based model of trophic strategies. The data suggest that mixotrophs increase in abundance at lower latitudes, while autotrophs and heterotrophs do not, and that this may be driven by increased light availability. Both mixotrophs and autotrophs increase greatly in productive coastal environments, while heterotrophs increase only slightly. These patterns are consistent with a model of resource competition in which nutrients and carbon can both limit growth and mixotrophs experience a trade-off in allocating biomass to phagotrophy vs. autotrophic functions. Importantly, mixotrophy is selected for under a range of conditions even when mixotrophs experience a penalty for using a generalist trophic strategy, due to the synergy between photosynthetically derived carbon and prey-derived nutrients. For this reason mixotrophy is favored relative to specialist strategies by increased irradiance, while at the same time increased nutrient supply increases the competitive ability of mixotrophs against heterotrophs.
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15
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Stibor H, Stockenreiter M, Nejstgaard JC, Ptacnik R, Sommer U. Trophic switches in pelagic systems. CURRENT OPINION IN SYSTEMS BIOLOGY 2019; 13:108-114. [PMID: 32984659 PMCID: PMC7493431 DOI: 10.1016/j.coisb.2018.11.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ecological studies need experimentation to test concepts and to disentangle causality in community dynamics. While simple models have given substantial insights into population and community dynamics, recent ecological concepts become increasingly complex. The globally important pelagic food web dynamics are well suited to test complex ecological concepts. For instance, trophic switches of individual organisms within pelagic food webs can elongate food webs or shift the balance between autotroph and heterotroph carbon fluxes. Here, we summarize results from mesocosm experiments demonstrating how environmental drivers result in trophic switches of marine phytoplankton and zooplankton communities. Such mesocosm experiments are useful to develop and test complex ecological concepts going beyond trophic level-based analyses, including diversity, individual behavior, and environmental stochasticity.
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Affiliation(s)
- Herwig Stibor
- Department Biology II, Experimental Aquatic Ecology, Ludwig-Maximilians-Universität München, Großhaderner Str. 2, 82152, Planegg-Martinsried, Germany
| | - Maria Stockenreiter
- Department Biology II, Experimental Aquatic Ecology, Ludwig-Maximilians-Universität München, Großhaderner Str. 2, 82152, Planegg-Martinsried, Germany
| | - Jens Christian Nejstgaard
- Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Alte Fischerhtute 2, D-16775, Stechlin, Germany
| | - Robert Ptacnik
- WasserCluster Lunz – Biologische Station GmbH, Seehof 4, 3293, Lunz Am See, Austria
| | - Ulrich Sommer
- Helmholtz Centre for Ocean Research (GEOMAR), Düsternbrooker Weg 20, 24105, Kiel, Germany
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16
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Rising nutrient-pulse frequency and high UVR strengthen microbial interactions. Sci Rep 2017; 7:43615. [PMID: 28252666 PMCID: PMC5333626 DOI: 10.1038/srep43615] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 01/26/2017] [Indexed: 01/13/2023] Open
Abstract
Solar radiation and nutrient pulses regulate the ecosystem’s functioning. However, little is known about how a greater frequency of pulsed nutrients under high ultraviolet radiation (UVR) levels, as expected in the near future, could alter the responses and interaction between primary producers and decomposers. In this report, we demonstrate through a mesocosm study in lake La Caldera (Spain) that a repeated (press) compared to a one-time (pulse) schedule under UVR prompted higher increases in primary (PP) than in bacterial production (BP) coupled with a replacement of photoautotrophs by mixotrophic nanoflagellates (MNFs). The mechanism underlying these amplified phytoplanktonic responses was a dual control by MNFs on bacteria through the excretion of organic carbon and an increased top-down control by bacterivory. We also show across a 6-year whole-lake study that the changes from photoautotrophs to MNFs were related mainly to the frequency of pulsed nutrients (e.g. desert dust inputs). Our results underscore how an improved understanding of the interaction between chronic and stochastic environmental factors is critical for predicting ongoing changes in ecosystem functioning and its responses to climatically driven changes.
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