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Abdelrazek HM, Shams El-Din NG, Ghozlan HA, Sabry SA, Abouelkheir SS. Distribution and functional perspective analysis of epiphytic and endophytic bacterial communities associated with marine seaweeds, Alexandria shores, Egypt. BMC Microbiol 2024; 24:293. [PMID: 39107684 PMCID: PMC11302221 DOI: 10.1186/s12866-024-03426-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 07/15/2024] [Indexed: 08/10/2024] Open
Abstract
There is an enormous diversity of life forms present in the extremely intricate marine environment. The growth and development of seaweeds in this particular environment are controlled by the bacteria that settle on their surfaces and generate a diverse range of inorganic and organic chemicals. The purpose of this work was to identify epiphytic and endophytic bacterial populations associated with ten common marine macroalgae from various areas along the Mediterranean Sea coast in Alexandria. This was done to target their distribution and possible functional aspects. Examine the effects of the algal habitat on the counting and phenotypic characterization of bacteria, which involves grouping bacteria based on characteristics such as shape, colour, mucoid nature, type of Gram stain, and their ability to generate spores. Furthermore, studying the physiological traits of the isolates under exploration provides insight into the optimum environmental circumstances for bacteria associated with the formation of algae. The majority of the bacterial isolates exhibited a wide range of enzyme activities, with cellulase, alginase, and caseinase being the most prevalent, according to the data. Nevertheless, 26% of the isolates displayed amylolytic activity, while certain isolates from Miami, Eastern Harbor, and Montaza lacked catalase activity. Geographical variations with the addition of algal extract may impact on the enumeration of the bacterial population, and this might have a relationship with host phylogeny. The most significant observation was that endophytic bacteria associated with green algae increased in all sites, while those associated with red algae increased in Abu Qir and Miami sites and decreased in Eastern Harbor. At the species level, the addition of algal extract led to a ninefold increase in the estimated number of epiphytic bacteria for Cladophora pellucida in Montaza. Notably, after adding algal extract, the number of presented endophytic bacteria associated with Codium sp. increased in Abu Qir while decreasing with the same species in Montaza. In addition to having the most different varieties of algae, Abu Qir has the most different bacterial isolates.
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Affiliation(s)
- Hanan M Abdelrazek
- Faculty of Science, Alexandria University, Moharrem Bey, Alexandria, 21511, Egypt
| | | | - Hanan A Ghozlan
- Faculty of Science, Alexandria University, Moharrem Bey, Alexandria, 21511, Egypt
| | - Soraya A Sabry
- Faculty of Science, Alexandria University, Moharrem Bey, Alexandria, 21511, Egypt
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Brodersen KE, Mosshammer M, Bittner MJ, Hallstrøm S, Santner J, Riemann L, Kühl M. Seagrass-mediated rhizosphere redox gradients are linked with ammonium accumulation driven by diazotrophs. Microbiol Spectr 2024; 12:e0333523. [PMID: 38426746 PMCID: PMC10986515 DOI: 10.1128/spectrum.03335-23] [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: 09/11/2023] [Accepted: 01/24/2024] [Indexed: 03/02/2024] Open
Abstract
Seagrasses can enhance nutrient mobilization in their rhizosphere via complex interactions with sediment redox conditions and microbial populations. Yet, limited knowledge exists on how seagrass-derived rhizosphere dynamics affect nitrogen cycling. Using optode and gel-sampler-based chemical imaging, we show that radial O2 loss (ROL) from rhizomes and roots leads to the formation of redox gradients around below-ground tissues of seagrass (Zostera marina), which are co-localized with regions of high ammonium concentrations in the rhizosphere. Combining such chemical imaging with fine-scale sampling for microbial community and gene expression analyses indicated that multiple biogeochemical pathways and microbial players can lead to high ammonium concentration within the oxidized regions of the seagrass rhizosphere. Symbiotic N2-fixing bacteria (Bradyrhizobium) were particularly abundant and expressed the diazotroph functional marker gene nifH in Z. marina rhizosphere areas with high ammonium concentrations. Such an association between Z. marina and Bradyrhizobium can facilitate ammonium mobilization, the preferred nitrogen source for seagrasses, enhancing seagrass productivity within nitrogen-limited environments. ROL also caused strong gradients of sulfide at anoxic/oxic interfaces in rhizosphere areas, where we found enhanced nifH transcription by sulfate-reducing bacteria. Furthermore, we found a high abundance of methylotrophic and sulfide-oxidizing bacteria in rhizosphere areas, where O2 was released from seagrass rhizomes and roots. These bacteria could play a beneficial role for the plants in terms of their methane and sulfide oxidation, as well as their formation of growth factors and phytohormones. ROL from below-ground tissues of seagrass, thus, seems crucial for ammonium production in the rhizosphere via stimulation of multiple diazotrophic associations. IMPORTANCE Seagrasses are important marine habitats providing several ecosystem services in coastal waters worldwide, such as enhancing marine biodiversity and mitigating climate change through efficient carbon sequestration. Notably, the fitness of seagrasses is affected by plant-microbe interactions. However, these microscale interactions are challenging to study and large knowledge gaps prevail. Our study shows that redox microgradients in the rhizosphere of seagrass select for a unique microbial community that can enhance the ammonium availability for seagrass. We provide first experimental evidence that Rhizobia, including the symbiotic N2-fixing bacteria Bradyrhizobium, can contribute to the bacterial ammonium production in the seagrass rhizosphere. The release of O2 from rhizomes and roots also caused gradients of sulfide in rhizosphere areas with enhanced nifH transcription by sulfate-reducing bacteria. O2 release from seagrass root systems thus seems crucial for ammonium production in the rhizosphere via stimulation of multiple diazotrophic associations.
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Affiliation(s)
| | - Maria Mosshammer
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Meriel J. Bittner
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Søren Hallstrøm
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Jakob Santner
- Department of Crop Sciences, Institute of Agronomy, University of Natural Resources and Life Sciences Vienna, Tulln an der Donau, Austria
| | - Lasse Riemann
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
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Peralta Ogorek LL, Takahashi H, Nakazono M, Pedersen O. The barrier to radial oxygen loss protects roots against hydrogen sulphide intrusion and its toxic effect. THE NEW PHYTOLOGIST 2023; 238:1825-1837. [PMID: 36928886 DOI: 10.1111/nph.18883] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 03/06/2023] [Indexed: 05/04/2023]
Abstract
The root barrier to radial O2 loss (ROL) is a key root trait preventing O2 loss from roots to anoxic soils, thereby enabling root growth into anoxic, flooded soils. We hypothesized that the ROL barrier can also prevent intrusion of hydrogen sulphide (H2 S), a potent phytotoxin in flooded soils. Using H2 S- and O2 -sensitive microsensors, we measured the apparent permeance to H2 S of rice roots, tested whether restricted H2 S intrusion reduced its adverse effects on root respiration, and whether H2 S could induce the formation of a ROL barrier. The ROL barrier reduced apparent permeance to H2 S by almost 99%, greatly restricting H2 S intrusion. The ROL barrier acted as a shield towards H2 S; O2 consumption in roots with a ROL barrier remained unaffected at high H2 S concentration (500 μM), compared to a 67% decline in roots without a barrier. Importantly, low H2 S concentrations induced the formation of a ROL barrier. In conclusion, the ROL barrier plays a key role in protecting against H2 S intrusion, and H2 S can act as an environmental signalling molecule for the induction of the barrier. This study demonstrates the multiple functions of the suberized/lignified outer part of the rice root beyond that of restricting ROL.
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Affiliation(s)
- Lucas León Peralta Ogorek
- The Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd Floor, Copenhagen, 2100, Denmark
| | - Hirokazu Takahashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8601, Japan
| | - Mikio Nakazono
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8601, Japan
- School of Agriculture and Environment, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Ole Pedersen
- The Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd Floor, Copenhagen, 2100, Denmark
- School of Agriculture and Environment, The University of Western Australia, Crawley, WA, 6009, Australia
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Pascal L, Chaillou G, Nozais C, Cool J, Bernatchez P, Letourneux K, Archambault P. Benthos response to nutrient enrichment and functional consequences in coastal ecosystems. MARINE ENVIRONMENTAL RESEARCH 2022; 175:105584. [PMID: 35168006 DOI: 10.1016/j.marenvres.2022.105584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 02/05/2022] [Accepted: 02/08/2022] [Indexed: 06/14/2023]
Abstract
As land use intensifies, many coastal waters are becoming enriched with otherwise limiting nutrients, leading to eutrophication. While the extreme effects of eutrophication on benthic communities are well documented, there is still a lack of knowledge about how nutrient enrichment alters biogeochemical interactions occurring at the sediment-water interface. Using ex-situ experiments, this study explores the consequences of nutrient enrichment on sediment characteristics, macrofauna community and benthic fluxes. The quantity of sedimentary organic matter and porewater concentration of NH4+, NOx and PO43- increased in enriched treatments. These changes did not affect the macrobenthic community structure. However, macroinfauna buried less deep and increased their ventilation activity. As consequences, nutrient efflux increased, thereby favouring eutrophication processes. These effects were reduced in presence of seagrass, thus illustrating the buffering capacity of seagrass in the context of environmental changes, and particularly, of eutrophication. Overall, this study highlights that the functional consequences of nutrient enrichment involve interconnected processes that are variable in space and time.
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Affiliation(s)
- Ludovic Pascal
- Institut des Sciences de la Mer de Rimouski, Québec-Océan, Canada Research Chair in Geochemistry of Coastal Hydrogeosystems, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada.
| | - Gwénaëlle Chaillou
- Institut des Sciences de la Mer de Rimouski, Québec-Océan, Canada Research Chair in Geochemistry of Coastal Hydrogeosystems, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada
| | - Christian Nozais
- Département de biologie, chimie et géographie, Québec-Océan, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
| | - Joannie Cool
- Institut des Sciences de la Mer de Rimouski, Québec-Océan, Canada Research Chair in Geochemistry of Coastal Hydrogeosystems, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada
| | - Pascal Bernatchez
- Research Chair in Coastal Geoscience, Québec-Océan, Département de biologie, chimie et géographie, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
| | - Kevin Letourneux
- Institut des Sciences de la Mer de Rimouski, Québec-Océan, Canada Research Chair in Geochemistry of Coastal Hydrogeosystems, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada
| | - Philippe Archambault
- ArcticNet, Québec-Océan, Département de biologie, Université Laval, 2325 Rue de l'Université, Québec, QC, G1V 0A6, Canada
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Abstract
Drought and waterlogging seriously affect the growth of plants and are considered severe constraints on agricultural and forestry productivity; their frequency and degree have increased over time due to global climate change. The morphology, photosynthetic activity, antioxidant enzyme system and hormone levels of plants could change in response to water stress. The mechanisms of these changes are introduced in this review, along with research on key transcription factors and genes. Both drought and waterlogging stress similarly impact leaf morphology (such as wilting and crimping) and inhibit photosynthesis. The former affects the absorption and transportation mechanisms of plants, and the lack of water and nutrients inhibits the formation of chlorophyll, which leads to reduced photosynthetic capacity. Constitutive overexpression of 9-cis-epoxydioxygenase (NCED) and acetaldehyde dehydrogenase (ALDH), key enzymes in abscisic acid (ABA) biosynthesis, increases drought resistance. The latter forces leaf stomata to close in response to chemical signals, which are produced by the roots and transferred aboveground, affecting the absorption capacity of CO2, and reducing photosynthetic substrates. The root system produces adventitious roots and forms aerenchymal to adapt the stresses. Ethylene (ETH) is the main response hormone of plants to waterlogging stress, and is a member of the ERFVII subfamily, which includes response factors involved in hypoxia-induced gene expression, and responds to energy expenditure through anaerobic respiration. There are two potential adaptation mechanisms of plants (“static” or “escape”) through ETH-mediated gibberellin (GA) dynamic equilibrium to waterlogging stress in the present studies. Plant signal transduction pathways, after receiving stress stimulus signals as well as the regulatory mechanism of the subsequent synthesis of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) enzymes to produce ethanol under a hypoxic environment caused by waterlogging, should be considered. This review provides a theoretical basis for plants to improve water stress tolerance and water-resistant breeding.
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Soonthornkalump S, Ow YX, Saewong C, Buapet P. Comparative study on anatomical traits and gas exchange responses due to belowground hypoxic stress and thermal stress in three tropical seagrasses. PeerJ 2022; 10:e12899. [PMID: 35186485 PMCID: PMC8840093 DOI: 10.7717/peerj.12899] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 01/17/2022] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The ability to maintain sufficient oxygen levels in the belowground tissues and the rhizosphere is crucial for the growth and survival of seagrasses in habitats with highly reduced sediment. Such ability varies depending on plant anatomical features and environmental conditions. METHODS In the present study, we compared anatomical structures of roots, rhizomes and leaves of the tropical intertidal seagrasses, Cymodocea rotundata, Thalassia hemprichii and Halophila ovalis, followed by an investigation of their gas exchange both in the belowground and aboveground tissues and photosynthetic electron transport rates (ETR) in response to experimental manipulations of O2 level (normoxia and root hypoxia) and temperature (30 °C and 40 °C). RESULTS We found that C. rotundata and T. hemprichii displayed mostly comparable anatomical structures, whereas H. ovalis displayed various distinctive features, including leaf porosity, number and size of lacunae in roots and rhizomes and structure of radial O2 loss (ROL) barrier. H. ovalis also showed unique responses to root hypoxia and heat stress. Root hypoxia increased O2 release from belowground tissues and overall photosynthetic activity of H. ovalis but did not affect the other two seagrasses. More pronounced warming effects were detected in H. ovalis, measured as lower O2 release in the belowground tissues and overall photosynthetic capacity (O2 release and dissolved inorganic carbon uptake in the light and ETR). High temperature inhibited photosynthesis of C. rotundata and T. hemprichii but did not affect their O2 release in belowground tissues. Our data show that seagrasses inhabiting the same area respond differently to root hypoxia and temperature, possibly due to their differences in anatomical and physiological attributes. Halophila ovalis is highly dependent on photosynthesis and appears to be the most sensitive species with the highest tendency of O2 loss in hypoxic sediment. At the same time, its root oxidation capacity may be compromised under warming scenarios.
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Affiliation(s)
- Sutthinut Soonthornkalump
- Division of Biological Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, Thailand,Coastal Oceanography and Climate Change Research Center, Prince of Songkla University, Hat Yai, Songkhla, Thailand
| | - Yan Xiang Ow
- St John’s Island National Marine Laboratory, Tropical Marine Science Institute, National University of Singapore, Singapore, Singapore
| | - Chanida Saewong
- Division of Biological Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, Thailand,Coastal Oceanography and Climate Change Research Center, Prince of Songkla University, Hat Yai, Songkhla, Thailand
| | - Pimchanok Buapet
- Division of Biological Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, Thailand,Coastal Oceanography and Climate Change Research Center, Prince of Songkla University, Hat Yai, Songkhla, Thailand
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Sfriso A, Buosi A, Facca C, Sfriso AA, Tomio Y, Juhmani AS, Wolf MA, Franzoi P, Scapin L, Ponis E, Cornello M, Rampazzo F, Berto D, Gion C, Oselladore F, Boscolo Brusà R, Bonometto A. Environmental restoration by aquatic angiosperm transplants in transitional water systems: The Venice Lagoon as a case study. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 795:148859. [PMID: 34328918 DOI: 10.1016/j.scitotenv.2021.148859] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 06/30/2021] [Accepted: 07/01/2021] [Indexed: 06/13/2023]
Abstract
The paper reports the results obtained after 4 years of aquatic angiosperm transplants in areas of the Venice Lagoon (North Adriatic Sea, Mediterranean) where meadows almost disappeared due to eutrophication, pollution and overexploitation of clam resources. The project LIFE12 NAT/IT/000331-SeResto, funded by the European Union, allowed to recolonize the Habitat 1150* (coastal lagoons) in the northernmost part of the lagoon, by extensive manual transplants of small sods or single rhizomes of Zostera marina, Zostera noltei, Ruppia cirrhosa and, in some stations also of Cymodocea nodosa. Over the 4 years of the project more than 75,000 rhizomes were transplanted in 35 stations with the support of local stakeholders (fishermen, hunters and sport clubs). Plants took root in 32 stations forming extensive meadows on a surface of approx. 10 km2 even if some failures were recorded in areas affected by outflows of freshwater rich in nutrients and suspended particulate matter. The rapid recovery of the ecological status of the involved areas was the result of this meadow restoration, which was in compliance with Water Framework Directive (WFD 2000/60/EC) objectives. Moreover, the monitoring of environmental parameters in the water column and in surface sediments allowed to identify the best conditions for successful transplants. Small, widespread interventions and the participation of local stakeholders in the environmental recovery, make this action economically cheap and easily transposable in other similar environments.
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Affiliation(s)
- Adriano Sfriso
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Alessandro Buosi
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Chiara Facca
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Andrea Augusto Sfriso
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Yari Tomio
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Abdul-Salam Juhmani
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Marion Adelheid Wolf
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Piero Franzoi
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Luca Scapin
- Dipartimento di Scienze Ambientali, Informatica e Statistica (DAIS), Università Ca' Foscari Venezia, Via Torino 155, 30170 Mestre, Ve, Italy.
| | - Emanuele Ponis
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Loc. Brondolo, 30015 Chioggia, Ve, Italy.
| | - Michele Cornello
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Loc. Brondolo, 30015 Chioggia, Ve, Italy.
| | - Federico Rampazzo
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Loc. Brondolo, 30015 Chioggia, Ve, Italy.
| | - Daniela Berto
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Loc. Brondolo, 30015 Chioggia, Ve, Italy.
| | - Claudia Gion
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Loc. Brondolo, 30015 Chioggia, Ve, Italy.
| | - Federica Oselladore
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Loc. Brondolo, 30015 Chioggia, Ve, Italy.
| | - Rossella Boscolo Brusà
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Loc. Brondolo, 30015 Chioggia, Ve, Italy.
| | - Andrea Bonometto
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Loc. Brondolo, 30015 Chioggia, Ve, Italy.
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Zabarte-Maeztu I, Matheson FE, Manley-Harris M, Davies-Colley RJ, Hawes I. Fine sediment effects on seagrasses: A global review, quantitative synthesis and multi-stressor model. MARINE ENVIRONMENTAL RESEARCH 2021; 171:105480. [PMID: 34547500 DOI: 10.1016/j.marenvres.2021.105480] [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: 07/11/2021] [Revised: 09/06/2021] [Accepted: 09/12/2021] [Indexed: 06/13/2023]
Abstract
This review collates research into fine sediment as a stressor of seagrass and emphasizes the multiple modes of action of this contaminant. The article is based on a bibliographic database search that identified 201 articles describing sediment impacts on seagrasses. Articles were classified by one of three non-exclusive modes of action: 1) light reduction; 2) smothering (burial), and 3) effects via rhizosphere physico-chemistry. Most citations (104) investigated multi-mode impacts of sediments, but the most frequently investigated single mode was light reduction (57 citations), followed by substrate rhizosphere chemistry (31) then smothering effects (6). Mud with high organic content is particularly problematic and smaller seagrasses are particularly vulnerable. Research gaps include polyphasic approaches, and studies of interactions between smothering, rhizosphere biogeochemistry and light climate. Identifying the thresholds of seagrass health indicators under mud stress should benefit coastal resource management, enabling improved decision-making and implementation of protective actions.
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Affiliation(s)
- Iñigo Zabarte-Maeztu
- National Institute of Water & Atmospheric Research, Hamilton, 3216, New Zealand; School of Science, University of Waikato, Hamilton, 3240, New Zealand.
| | - Fleur E Matheson
- National Institute of Water & Atmospheric Research, Hamilton, 3216, New Zealand
| | | | | | - Ian Hawes
- Coastal Marine Field Station, University of Waikato, Tauranga, 3110, New Zealand
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Resilience of Tropical Ecosystems to Ocean Deoxygenation. Trends Ecol Evol 2021; 36:227-238. [PMID: 33419595 DOI: 10.1016/j.tree.2020.11.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 11/03/2020] [Accepted: 11/10/2020] [Indexed: 01/18/2023]
Abstract
The impacts of ocean deoxygenation on biodiversity and ecosystem function are well established in temperate regions, and here we illustrate how the study of hypoxia in tropical ecosystems can offer insights of general importance. We first describe how mechanisms of resilience have developed in response to naturally occurring hypoxia across three tropical ecosystems: coral reefs, seagrass beds, and mangrove forests. We then suggest that the vulnerability of these systems to deoxygenation lies in interactions with other stressors that are increasing rapidly in the Anthropocene. Finally, we advocate for the adoption of a broader community- and ecosystem-level perspective that incorporates mutualisms, feedbacks, and mechanisms of self-rescue and recovery to develop a better predictive understanding of the effects of deoxygenation in coastal ecosystems.
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Krause-Jensen D, Duarte CM, Sand-Jensen K, Carstensen J. Century-long records reveal shifting challenges to seagrass recovery. GLOBAL CHANGE BIOLOGY 2021; 27:563-575. [PMID: 33241657 DOI: 10.1111/gcb.15440] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/11/2020] [Accepted: 10/29/2020] [Indexed: 05/28/2023]
Abstract
Global losses over the 20th century placed seagrass ecosystems among the most threatened ecosystems in the world, with eutrophication, and associated deterioration of the submarine light environment identified as the main driver. Growing appreciation of the ecological and societal benefits of healthy seagrass meadows has stimulated efforts to protect and restore them, largely focused on reducing nutrient input to coastal waters. Here we analyze a unique data set spanning 135 years on eelgrass (Zostera marina), the dominant seagrass of the northern hemisphere. We show that meadows in the Western Baltic Sea exhibited major declines relative to historic (1890-1910) reference due to the wasting disease in the 1930s followed by eutrophication peaking in the 1980s, but have only shown modest improvement despite major eutrophication mitigation, halving nitrogen input since the 1980s. Across the past century, we identified generally shallower colonization depths of eelgrass for a given submarine light penetration and, hence, increased apparent light requirements. This suggests that eelgrass recovery is limited by additional stressors. Our study indicates that bottom trawling and intense recent warming (0.5°C per decade, 1985-2018), which impact on deeper and shallower meadows, respectively, suppress eelgrass from fully recovering from eutrophication. Warming is most severe in shallow turbid waters, while clear-water areas offer eelgrass refugia from warming in deeper, cooler waters; but trawling can prevent eelgrass from reaching these refugia. Efforts to reduce nutrient input and thereby improve water clarity have been instrumental in avoiding a catastrophic loss of eelgrass ecosystems. However, local-scale future management must, in addition, reduce bottom trawling to facilitate eelgrass reaching deeper, cooler refugia, and increase resilience toward realized and further warming. Warming needs to be limited by meeting global climate change mitigation goals.
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Affiliation(s)
- Dorte Krause-Jensen
- Department of Bioscience, Aarhus University, Silkeborg, Denmark
- Arctic Research Centre, Aarhus University, Århus, Denmark
| | - Carlos M Duarte
- Arctic Research Centre, Aarhus University, Århus, Denmark
- Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Kaj Sand-Jensen
- Freshwater Biological Laboratory, Biological Institute, University of Copenhagen, Copenhagen, Denmark
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El-Hacen EHM, Sidi Cheikh MA, Bouma TJ, Olff H, Piersma T. Long-term changes in seagrass and benthos at Banc d’Arguin, Mauritania, the premier intertidal system along the East Atlantic Flyway. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2020.e01364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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12
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Egea LG, Jiménez-Ramos R, Hernández I, Brun FG. Differential effects of nutrient enrichment on carbon metabolism and dissolved organic carbon (DOC) fluxes in macrophytic benthic communities. MARINE ENVIRONMENTAL RESEARCH 2020; 162:105179. [PMID: 33065520 DOI: 10.1016/j.marenvres.2020.105179] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 10/06/2020] [Accepted: 10/06/2020] [Indexed: 06/11/2023]
Abstract
Nutrient enrichment can alter negatively benthic communities and reduce their ecological services. This study explores in two contrasting seasons (winter and summer), the effects of in situ nutrient enrichment at the community level on carbon metabolism and dissolved organic carbon (DOC) fluxes in two benthic communities dominated by the seagrass Cymodocea nodosa and by the macroalga Caulerpa prolifera. Under nutrient enrichment, C. nodosa increased total community biomass and diversity in summer, while net community production shifted from net autotrophic to net heterotrophic in winter. In contrast, C. prolifera became heterotrophic in summer, while no significant effects were found in winter. Regarding DOC fluxes, nutrient enrichment shifted C. nodosa from net DOC consumer in winter to a strong net DOC producer in summer, while C. prolifera seemed unaffected. Therefore, nutrient enrichment can promote conditional effects (positive, negative or neutral) in coastal areas depending both on macrophyte assemblages and season.
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Affiliation(s)
- Luis G Egea
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cadiz, International Campus of Excellence of the Sea (CEIMAR), 11510, Puerto Real (Cádiz), Spain.
| | - Rocío Jiménez-Ramos
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cadiz, International Campus of Excellence of the Sea (CEIMAR), 11510, Puerto Real (Cádiz), Spain; Mediterranean Institute for Advanced Studies (UIB-CSIC), C/ Miquel Marquès, 21 07190, Esporles Illes Balears, Spain
| | - Ignacio Hernández
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cadiz, International Campus of Excellence of the Sea (CEIMAR), 11510, Puerto Real (Cádiz), Spain
| | - Fernando G Brun
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cadiz, International Campus of Excellence of the Sea (CEIMAR), 11510, Puerto Real (Cádiz), Spain
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13
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Elgetti Brodersen K, Kühl M, Trampe E, Koren K. Imaging O 2 dynamics and microenvironments in the seagrass leaf phyllosphere with magnetic optical sensor nanoparticles. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 104:1504-1519. [PMID: 33037691 DOI: 10.1111/tpj.15017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 09/17/2020] [Accepted: 09/23/2020] [Indexed: 06/11/2023]
Abstract
Eutrophication leads to epiphyte blooms on seagrass leaves that strongly affect plant health, yet the actual mechanisms of such epiphyte-induced plant stress remain poorly understood. We used magnetic optical sensor nanoparticles in combination with luminescence lifetime imaging to map the O2 concentration and dynamics in the heterogeneous seagrass phyllosphere under changing light conditions. By incorporating magnetite into the sensor nanoparticles, it was possible to image the spatial O2 distribution under flow over seagrass leaf segments in the presence of a strong magnetic field. Local microniches with low leaf surface O2 concentrations were found under thick epiphytic biofilms, often leading to anoxic microhabitats in darkness. High irradiance led to O2 supersaturation across most of the seagrass phyllosphere, whereas leaf microenvironments with reduced O2 conditions were found under epiphytic biofilms at low irradiance, probably driven by self-shading. Horizontal micro-profiles extracted from the O2 images revealed pronounced heterogeneities in local O2 concentration over the base of the epiphytic biofilm, with up to 52% reduction in O2 concentrations in areas with relatively thick (>2 mm), compared with thin (≤1 mm), epiphyte layers in darkness. We also present evidence of enhanced relative internal O2 transport within leaves with epiphyte overgrowth, compared with bare seagrass leaves, in light as a result of limited mass transfer across thick outward diffusion pathways. The local availability of O2 was still markedly reduced in the epiphyte-covered leaves, however. The leaf phyllosphere is thus characterized by a complex microlandscape of O2 availability that strongly affects microbial processes occurring within the epiphytic biofilm, which may have implications for seagrass health, as anoxic microhabitats have been shown to promote the microbiological production of reduced toxic compounds, such as nitric oxide.
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Affiliation(s)
- Kasper Elgetti Brodersen
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, Helsingør, 3000, Denmark
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, Helsingør, 3000, Denmark
| | - Erik Trampe
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, Helsingør, 3000, Denmark
| | - Klaus Koren
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, Helsingør, 3000, Denmark
- Department of Biology, Section for Microbiology, Aarhus University Centre for Water Technology, Ny Munkegade 114, Aarhus C, 8000, Denmark
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14
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Xu S, Wang P, Zhou Y, Wang F, Zhang X, Gu R, Xu S, Yue S, Zhang Y, Suonan Z. Sheaths of Zostera marina L. as ecological indicators of shoot length and the elemental stoichiometry of aboveground tissues. MARINE POLLUTION BULLETIN 2020; 160:111545. [PMID: 32891962 DOI: 10.1016/j.marpolbul.2020.111545] [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: 12/19/2019] [Revised: 07/27/2020] [Accepted: 07/31/2020] [Indexed: 06/11/2023]
Abstract
Given a large quantity of epiphytes and other material attached on eelgrass leaf blades, we explored the relationship between eelgrass sheaths and different-aged leaf blades (1st, 2nd, 3rd, and 4th leaf blade) on nutrient content and their ratios (C, N, P, C/N, C/P, and N/P) to identify whether eelgrass sheaths could be used to instead of leaf blades in terms of nutrient content. In addition, we explored the relationship between eelgrass sheath length and shoot length. Results showed that there were significant relationships between the sheath and leaf blades in terms of N and P content and their ratios. For length analysis, there was a significant relationship between sheath length and shoot length, and shoot length was approximately four to five times (mean 4.4659) longer than sheath length, such that shoot length can be estimated by sheath length. These significant relationships suggest that eelgrass sheath could be used as a suitable predictor of leaf blade in length and nutrient stoichiometry, thus eelgrass sheath could be used as an indicator for further eelgrass nutrient monitoring and research.
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Affiliation(s)
- Shaochun Xu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pengmei Wang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi Zhou
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China.
| | - Feng Wang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaomei Zhang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China
| | - Ruiting Gu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shuai Xu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shidong Yue
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Zhang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhaxi Suonan
- Department of Biological Sciences, Pusan National University, Buson 46241, Republic of Korea
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15
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Noisette F, Depetris A, Kühl M, Brodersen KE. Flow and epiphyte growth effects on the thermal, optical and chemical microenvironment in the leaf phyllosphere of seagrass ( Zostera marina). J R Soc Interface 2020; 17:20200485. [PMID: 33050780 DOI: 10.1098/rsif.2020.0485] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Intensified coastal eutrophication can result in an overgrowth of seagrass leaves by epiphytes, which is a major threat to seagrass habitats worldwide, but little is known about how epiphytic biofilms affect the seagrass phyllosphere. The physico-chemical microenvironment of Zostera marina L. leaves with and without epiphytes was mapped with electrochemical, thermocouple and scalar irradiance microsensors as a function of four irradiance conditions (dark, low, saturating and high light) and two water flow velocities (approx. 0.5 and 5 cm s-1), which resemble field conditions. The presence of epiphytes led to the build up of a diffusive boundary layer and a thermal boundary layer which impeded O2 and heat transfer between the leaf surface and the surrounding water, resulting in a maximum increase of 0.8°C relative to leaves with no epiphytes. Epiphytes also reduced the quantity and quality of light reaching the leaf, decreasing plant photosynthesis. In darkness, epiphyte respiration exacerbated hypoxic conditions, which can lead to anoxia and the production of potential phytotoxic nitric oxide in the seagrass phyllosphere. Epiphytic biofilm affects the local phyllosphere physico-chemistry both because of its metabolic activity (i.e. photosynthesis/respiration) and its physical properties (i.e. thickness, roughness, density and back-scattering properties). Leaf tissue warming can lead to thermal stress in seagrasses living close to their thermal stress threshold, and thus potentially aggravate negative effects of global warming.
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Affiliation(s)
- Fanny Noisette
- Department of Marine Ecology, GEOMAR Helmholtz Centre for Ocean Research, Hohenbergstraße 2, 24105 Kiel, Germany.,Institute for Marine and Antarctic Studies, University of Tasmania, 20 Castray Esplanade, Battery Point, 7004 TAS Hobart, Australia
| | - Anna Depetris
- École Polytechnique Fédérale de Lausanne, Route Cantonale, 1015 Lausanne, Switzerland
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
| | - Kasper Elgetti Brodersen
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
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16
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Effects of Fine Sediment on Seagrass Meadows: A Case Study of Zostera muelleri in Pāuatahanui Inlet, New Zealand. JOURNAL OF MARINE SCIENCE AND ENGINEERING 2020. [DOI: 10.3390/jmse8090645] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Seagrass meadows are vulnerable to fine sediment (mud) pollution, with impacts usually attributed to reduction in submerged light. Here we tested two non-exclusive hypotheses, that mud particles (<63 µm) impact seagrasses through both (1) the light climate and (2) changes in substrate physico-chemistry. We tested these hypotheses in Pāuatahanui Inlet, New Zealand, by comparing seagrass presence, abundance, and health, together with light climate and substrate physico-chemistry at contrasting habitats where (1) seagrass used to thrive but no longer grows (historical seagrass), (2) seagrass still persists (existing seagrass) and (3) seagrass has been present recently, but not currently (potential seagrass). Historical seagrass substrate had significantly higher mud (35% average), bulk density (1.5 g cm−3), porewater ammonium concentration (65 µM), and a more reduced redox profile (negative redox at only 2 cm soil depth) as well as a lower light availability when submerged compared to other habitats, while total daily light exposure differed little between habitats. This suggests that failure of seagrass to recolonize historical seagrass habitat reflects substrate muddiness and consequent unfavorable rhizosphere conditions. Our results provide evidence for the multi-stressor effects of fine sediment on seagrasses, with substrate suitability for seagrass being detrimentally affected even where light exposure seems sufficient.
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17
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Pedersen O, Revsbech NP, Shabala S. Microsensors in plant biology: in vivo visualization of inorganic analytes with high spatial and/or temporal resolution. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:3941-3954. [PMID: 32253437 DOI: 10.1093/jxb/eraa175] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 04/04/2020] [Indexed: 06/11/2023]
Abstract
This Expert View provides an update on the recent development of new microsensors, and briefly summarizes some novel applications of existing microsensors, in plant biology research. Two major topics are covered: (i) sensors for gaseous analytes (O2, CO2, and H2S); and (ii) those for measuring concentrations and fluxes of ions (macro- and micronutrients and environmental pollutants such as heavy metals). We show that application of such microsensors may significantly advance understanding of mechanisms of plant-environmental interaction and regulation of plant developmental and adaptive responses under adverse environmental conditions via non-destructive visualization of key analytes with high spatial and/or temporal resolution. Examples included cover a broad range of environmental situations including hypoxia, salinity, and heavy metal toxicity. We highlight the power of combining microsensor technology with other advanced biophysical (patch-clamp, voltage-clamp, and single-cell pressure probe), imaging (MRI and fluorescent dyes), and genetic techniques and approaches. We conclude that future progress in the field may be achieved by applying existing microsensors for important signalling molecules such as NO and H2O2, by improving selectivity of existing microsensors for some key analytes (e.g. Na, Mg, and Zn), and by developing new microsensors for P.
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Affiliation(s)
- Ole Pedersen
- Department of Biology, University of Copenhagen, Denmark
- School of Agriculture and Environment, The University of Western Australia, Australia
| | - Niels Peter Revsbech
- Aarhus University Centre for Water Technology, Department of Bioscience, Aarhus University, Denmark
| | - Sergey Shabala
- School of Land and Food, University of Tasmania, Australia
- International Research Centre for Environmental Membrane Biology, Foshan University, China
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18
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Soler M, Colomer J, Folkard A, Serra T. Particle size segregation of turbidity current deposits in vegetated canopies. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 703:134784. [PMID: 31731162 DOI: 10.1016/j.scitotenv.2019.134784] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 09/09/2019] [Accepted: 10/01/2019] [Indexed: 06/10/2023]
Abstract
Interactions between ecology, hydrodynamics and sediments play central roles in the evolution of coastal and freshwater ecosystems. We set out to characterise interactions of a specific hydrodynamic phenomenon - turbidity currents - with vegetation and sediment dynamics. We measured hydrodynamics and sediment deposition rates when turbidity currents flowed into plant canopies in a lock-exchange flume experiment, using simulated vegetation and three real plant species, and varying the turbidity current's initial sediment concentration. The natural sediment used had an essentially bimodal size distribution, with coarse (6.2-104 μm) and fine (2.2-6.2 μm) fractions. In all cases, on entering the vegetation canopy, the turbidity current was initially inertially-dominated, but subsequently became drag-dominated. In the inertial regime, there was no size segregation in the deposited material. In the drag-dominated regime, the deposited material became increasingly dominated by fine sediment, at a rate dependent on the vegetation type. The transition between these two regimes occurred at a distance equivalent to 5.1-7.6 times the total water depth downstream of the lock gate. The size segregation of deposited sediment is posited to have consequences for substrate evolution, which in turn may affect vegetation growth. Thus, our findings point to a non-linear feedback mechanism between the spatial heterogeneity of vegetation canopies and that of the substrate they help to engineer.
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Affiliation(s)
- Marianna Soler
- Department of Physics, University of Girona, Universitat de Girona, 4, Campus Montilivi, 17003 Girona, Spain.
| | - Jordi Colomer
- Department of Physics, University of Girona, Universitat de Girona, 4, Campus Montilivi, 17003 Girona, Spain.
| | - Andrew Folkard
- Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
| | - Teresa Serra
- Department of Physics, University of Girona, Universitat de Girona, 4, Campus Montilivi, 17003 Girona, Spain.
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19
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Brodersen KE, Koren K, Revsbech NP, Kühl M. Strong leaf surface basification and CO 2 limitation of seagrass induced by epiphytic biofilm microenvironments. PLANT, CELL & ENVIRONMENT 2020; 43:174-187. [PMID: 31429088 DOI: 10.1111/pce.13645] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 08/07/2019] [Accepted: 08/09/2019] [Indexed: 06/10/2023]
Abstract
Coastal eutrophication is a growing problem worldwide, leading to increased epiphyte overgrowth of seagrass leaves. Yet little is known about how epiphytes affect key biogeochemical conditions and processes in the seagrass phyllosphere. We used electrochemical microsensors to measure microgradients of O2 , pH, and CO2 at the bare and epiphyte-covered leaf surface of seagrass (Zostera marina L.) to determine effects of epiphytes on the leaf chemical microenvironment. Epiphytes result in extreme daily fluctuations in pH, O2 , and inorganic carbon concentrations at the seagrass leaf surface severely hampering the plant's performance. In light, leaf epiphyte biofilms and their diffusive boundary layer lead to strong basification, markedly reducing the CO2 and HCO3- availability at the leaf surface, leading to reduced photosynthetic efficiency as a result of carbon limitation and enhanced photorespiration. With epiphytes, leaf surface pH increased to >10, thereby exceeding final pH levels (~9.62) and CO2 compensation points for active photosynthesis. In darkness, epiphyte biofilms resulted in increased CO2 and hypoxia at the leaf surface. Epiphytes can lead to severe carbon limitation in seagrasses owing to strong phyllosphere basification leading to CO2 depletion and costly, yet limiting, HCO3- utilization, increasing the risk of plant starvation.
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Affiliation(s)
| | - Klaus Koren
- Department of Bioscience, Aarhus University Centre for Water Technology, Aarhus C, Denmark
| | - Niels Peter Revsbech
- Department of Bioscience, Aarhus University Centre for Water Technology, Aarhus C, Denmark
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
- Climate Change Cluster, Faculty of Science, University of Technology Sydney, Sydney, Australia
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20
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Moßhammer M, Brodersen KE, Kühl M, Koren K. Nanoparticle- and microparticle-based luminescence imaging of chemical species and temperature in aquatic systems: a review. Mikrochim Acta 2019; 186:126. [PMID: 30680465 DOI: 10.1007/s00604-018-3202-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Accepted: 12/20/2018] [Indexed: 11/25/2022]
Abstract
Most aquatic systems rely on a multitude of biogeochemical processes that are coupled with each other in a complex and dynamic manner. To understand such processes, minimally invasive analytical tools are required that allow continuous, real-time measurements of individual reactions in these complex systems. Optical chemical sensors can be used in the form of fiber-optic sensors, planar sensors, or as micro- and nanoparticles (MPs and NPs). All have their specific merits, but only the latter allow for visualization and quantification of chemical gradients over 3D structures. This review (with 147 references) summarizes recent developments mainly in the field of optical NP sensors relevant for chemical imaging in aquatic science. The review encompasses methods for signal read-out and imaging, preparation of NPs and MPs, and an overview of relevant MP/NP-based sensors. Additionally, examples of MP/NP-based sensors in aquatic systems such as corals, plant tissue, biofilms, sediments and water-sediment interfaces, marine snow and in 3D bioprinting are given. We also address current challenges and future perspectives of NP-based sensing in aquatic systems in a concluding section. Graphical abstract ᅟ.
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Affiliation(s)
- Maria Moßhammer
- Marine Biological Section, Department of Biology, University of Copenhagen, 3000, Helsingør, Denmark
| | - Kasper Elgetti Brodersen
- Marine Biological Section, Department of Biology, University of Copenhagen, 3000, Helsingør, Denmark
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, 3000, Helsingør, Denmark.
- Climate Change Cluster, University of Technology Sydney, Ultimo, NSW, 2007, Australia.
| | - Klaus Koren
- Aarhus University Center for Water Technology, Department of Bioscience - Microbiology, Aarhus University, 8000, Aarhus, Denmark.
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21
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Bainbridge Z, Lewis S, Bartley R, Fabricius K, Collier C, Waterhouse J, Garzon-Garcia A, Robson B, Burton J, Wenger A, Brodie J. Fine sediment and particulate organic matter: A review and case study on ridge-to-reef transport, transformations, fates, and impacts on marine ecosystems. MARINE POLLUTION BULLETIN 2018; 135:1205-1220. [PMID: 30301020 DOI: 10.1016/j.marpolbul.2018.08.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Revised: 07/27/2018] [Accepted: 08/01/2018] [Indexed: 06/08/2023]
Abstract
Studies documenting the effects of land-derived suspended particulate matter (SPM, i.e., particulate organic matter and mineral sediment) on marine ecosystems are typically disconnected from terrestrial studies that determine their origin, transport and fate. This study reviews sources, transport, transformations, fate and effects of SPM along the 'ridge-to-reef' continuum. We show that some of the SPM can be transported over long distances and transformed into large and easily resuspendible organic-rich sediment flocs. These flocs may lead to prolonged reductions in water clarity, impacting upon coral reef, seagrass and fish communities. Using the Great Barrier Reef (NE Australia) as a case study, we identify the latest research tools to determine thresholds of SPM exposure, allowing for an improved appreciation of marine risk. These tools are used to determine ecologically-relevant end-of-basin load targets and reliable marine water quality guidelines, thereby enabling enhanced prioritisation and management of SPM export from ridge-to-reef.
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Affiliation(s)
- Z Bainbridge
- TropWATER, James Cook University, Townsville 4811, Australia.
| | - S Lewis
- TropWATER, James Cook University, Townsville 4811, Australia
| | - R Bartley
- CSIRO, Brisbane, Queensland 4068, Australia
| | - K Fabricius
- Australian Institute of Marine Science, PMB 3, Townsville MC, QLD 4810, Australia
| | - C Collier
- TropWATER, James Cook University, Townsville 4811, Australia
| | - J Waterhouse
- TropWATER, James Cook University, Townsville 4811, Australia
| | - A Garzon-Garcia
- Department of Environment and Science, GPO Box 5078, Brisbane 4001, Australia
| | - B Robson
- Australian Institute of Marine Science, PMB 3, Townsville MC, QLD 4810, Australia
| | - J Burton
- Department of Environment and Science, GPO Box 5078, Brisbane 4001, Australia
| | - A Wenger
- School of Earth and Environmental Sciences, University of Queensland, St. Lucia, QLD 4072, Australia
| | - J Brodie
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville 4811, Australia
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22
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Schrameyer V, York PH, Chartrand K, Ralph PJ, Kühl M, Brodersen KE, Rasheed MA. Contrasting impacts of light reduction on sediment biogeochemistry in deep- and shallow-water tropical seagrass assemblages (Green Island, Great Barrier Reef). MARINE ENVIRONMENTAL RESEARCH 2018; 136:38-47. [PMID: 29472034 DOI: 10.1016/j.marenvres.2018.02.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 01/31/2018] [Accepted: 02/11/2018] [Indexed: 06/08/2023]
Abstract
Seagrass meadows increasingly face reduced light availability as a consequence of coastal development, eutrophication, and climate-driven increases in rainfall leading to turbidity plumes. We examined the impact of reduced light on above-ground seagrass biomass and sediment biogeochemistry in tropical shallow- (∼2 m) and deep-water (∼17 m) seagrass meadows (Green Island, Australia). Artificial shading (transmitting ∼10-25% of incident solar irradiance) was applied to the shallow- and deep-water sites for up to two weeks. While above-ground biomass was unchanged, higher diffusive O2 uptake (DOU) rates, lower O2 penetration depths, and higher volume-specific O2 consumption (R) rates were found in seagrass-vegetated sediments as compared to adjacent bare sand (control) areas at the shallow-water sites. In contrast, deep-water sediment characteristics did not differ between bare sand and vegetated sites. At the vegetated shallow-water site, shading resulted in significantly lower hydrogen sulphide (H2S) levels in the sediment. No shading effects were found on sediment biogeochemistry at the deep-water site. Overall, our results show that the sediment biogeochemistry of shallow-water (Halodule uninervis, Syringodium isoetifolium, Cymodocea rotundata and C. serrulata) and deep-water (Halophila decipiens) seagrass meadows with different species differ in response to reduced light. The light-driven dynamics of the sediment biogeochemistry at the shallow-water site could suggest the presence of a microbial consortium, which might be stimulated by photosynthetically produced exudates from the seagrass, which becomes limited due to lower seagrass photosynthesis under shaded conditions.
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Affiliation(s)
- Verena Schrameyer
- Climate Change Cluster, School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia; Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Paul H York
- Centre for Tropical Water & Aquatic Ecosystem Research, James Cook University, Cairns, QLD, Australia
| | - Kathryn Chartrand
- Climate Change Cluster, School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia; Centre for Tropical Water & Aquatic Ecosystem Research, James Cook University, Cairns, QLD, Australia
| | - Peter J Ralph
- Climate Change Cluster, School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia
| | - Michael Kühl
- Climate Change Cluster, School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia; Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Kasper Elgetti Brodersen
- Climate Change Cluster, School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia; Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark.
| | - Michael A Rasheed
- Centre for Tropical Water & Aquatic Ecosystem Research, James Cook University, Cairns, QLD, Australia
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Kim M, Brodersen KE, Szabó M, Larkum AWD, Raven JA, Ralph PJ, Pernice M. Low oxygen affects photophysiology and the level of expression of two-carbon metabolism genes in the seagrass Zostera muelleri. PHOTOSYNTHESIS RESEARCH 2018; 136:147-160. [PMID: 0 DOI: 10.1007/s11120-017-0452-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 09/27/2017] [Indexed: 05/03/2023]
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Brodersen K, Koren K, Moßhammer M, Ralph PJ, Kühl M, Santner J. Seagrass-Mediated Phosphorus and Iron Solubilization in Tropical Sediments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:14155-14163. [PMID: 29149570 PMCID: PMC5738630 DOI: 10.1021/acs.est.7b03878] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 10/17/2017] [Accepted: 11/17/2017] [Indexed: 05/24/2023]
Abstract
Tropical seagrasses are nutrient-limited owing to the strong phosphorus fixation capacity of carbonate-rich sediments, yet they form densely vegetated, multispecies meadows in oligotrophic tropical waters. Using a novel combination of high-resolution, two-dimensional chemical imaging of O2, pH, iron, sulfide, calcium, and phosphorus, we found that tropical seagrasses are able to mobilize the essential nutrients iron and phosphorus in their rhizosphere via multiple biogeochemical pathways. We show that tropical seagrasses mobilize phosphorus and iron within their rhizosphere via plant-induced local acidification, leading to dissolution of carbonates and release of phosphate, and via local stimulation of microbial sulfide production, causing reduction of insoluble Fe(III) oxyhydroxides to dissolved Fe(II) with concomitant phosphate release into the rhizosphere porewater. These nutrient mobilization mechanisms have a direct link to seagrass-derived radial O2 loss and secretion of dissolved organic carbon from the below-ground tissue into the rhizosphere. Our demonstration of seagrass-derived rhizospheric phosphorus and iron mobilization explains why seagrasses are widely distributed in oligotrophic tropical waters.
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Affiliation(s)
- Kasper
Elgetti Brodersen
- Climate
Change Cluster, Faculty of Science, University
of Technology Sydney (UTS), Sydney 2007, New South Wales, Australia
- Marine
Biological Section, Department of Biology, University of Copenhagen, DK-3000 Helsingør, Denmark
| | - Klaus Koren
- Marine
Biological Section, Department of Biology, University of Copenhagen, DK-3000 Helsingør, Denmark
| | - Maria Moßhammer
- Marine
Biological Section, Department of Biology, University of Copenhagen, DK-3000 Helsingør, Denmark
| | - Peter J. Ralph
- Climate
Change Cluster, Faculty of Science, University
of Technology Sydney (UTS), Sydney 2007, New South Wales, Australia
| | - Michael Kühl
- Climate
Change Cluster, Faculty of Science, University
of Technology Sydney (UTS), Sydney 2007, New South Wales, Australia
- Marine
Biological Section, Department of Biology, University of Copenhagen, DK-3000 Helsingør, Denmark
| | - Jakob Santner
- Division
of Agronomy, Department of Crop SciencesUniversity of Natural Resources and Life Sciences, Vienna, 3430 Tulln an der Donau, Austria
- Rhizosphere
Ecology and Biogeochemistry Group, Institute of Soil Research, Department
of Forest and Soil Sciences, University
of Natural Resources and Life Sciences, Vienna, 3430 Tulln an der Donau, Austria
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