ORCID Profile
0000-0002-1792-4790
Current Organisations
IT University of Copenhagen
,
Københavns Universitet
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Plant Biology | Ecology | Microbial Ecology | Phycology | Marine And Estuarine Ecology (Incl. Marine Ichthyology) | Ecology | Microbiology | Invertebrate biology | Phycology (incl. Marine Grasses) | Genomics | Plant Physiology | Ecological Impacts of Climate Change | Invertebrate Biology | Plant Physiology | Invertebrate Biology | Ecological impacts of climate change and ecological adaptation | Ecological physiology | Conservation And Biodiversity | Ecological Physiology
ANZSRC Socio-Economic Objective (SEO)
Living resources (incl. impacts of fishing on non-target species) | Marine Flora, Fauna and Biodiversity | Ecosystem Assessment and Management of Coastal and Estuarine Environments | Ecosystem Adaptation to Climate Change | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Living resources (flora and fauna) | Living resources (flora and fauna) | Marine protected areas | Climate change | Physical and Chemical Conditions of Water in Marine Environments | Expanding Knowledge in the Biological Sciences | Ecosystem Assessment and Management of Marine Environments |
Related Links
Publications
Microplastic pollution associated with reduced respiration in seagrass (Zostera marina L.) and associated epiphytes
Publisher: Frontiers Media SA
Date: 03-08-2023
DOI: 10.3389/FMARS.2023.1216299
Abstract: Seagrasses provide crucial ecosystem services of relevance for the marine environment. However, anthropogenic activities are causing global seagrass decline. Increasing microplastic (MP) concentrations have been recognized as a novel threat to many marine organisms, but their effects on marine plants remain underexplored. Here, we investigate the effects of microplastic (polyethylene (PE) and polypropylene (PP)) exposure on the photosynthesis and respiration of the seagrass Zostera marina L. and its associated epiphytes. Measurements were conducted on seagrass leaves with and without epiphyte cover, as well as on epiphytes scraped off the leaf surface. Net gas exchange and pH drift measurements were used to determine rates of photosynthesis and respiration, as well as the ability of leaves and epiphytes to utilize bicarbonate. In addition, variable chlorophyll fluorescence imaging was employed to quantify the photosynthetic capacity of seagrass leaves. Our results show a limited effect of short-term (14 days) microplastic exposure on seagrass leaves and their associated epiphytes, although the photosynthetic activity and respiration rates were gradually reduced for bare seagrass leaves with increasing microplastic concentrations (25-1000 mg MP L -1 ). A & % reduction in dark respiration of bare leaves was found at the highest MP exposure, while respiration rates of leaves with epiphytes and separated epiphytes were reduced by maximally ~45 and 30% upon MP exposure, respectively. Short-term microplastic exposure did not alter i) the ability to utilize bicarbonate, ii) the maximum quantum yield of PSII ( F V / F M ), nor iii) the light utilization efficiency of Z. marina leaves and associated epiphytes. The compensation irradiance decreased for all investigated specimens, and seagrass leaves (with and without epiphytes) were able to retain a positive net oxygen balance throughout all treatments. We speculate that the observed decrease in photosynthetic activity and respiration was caused by leachates from microplastics. Our findings thus indicate that seagrass Z. marina largely possess resilience toward microplastic pollution at its current level.
Loss of Functional Photosystem II Reaction Centres in Zooxanthellae of Corals Exposed to Bleaching Conditions: Using Fluorescence Rise Kinetics
Publisher: Springer Science and Business Media LLC
Date: 2004
Strong leaf surface basification and CO2 limitation of seagrass induced by epiphytic biofilm microenvironments
Publisher: Wiley
Date: 09-09-2020
DOI: 10.1111/PCE.13645
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 O
Thermal effects of tissue optics in symbiont-bearing reef-building corals
Publisher: Wiley
Date: 11-2012
Inter-polyp genetic and physiological characterisation of Symbiodinium in an Acropora valida colony
Publisher: Springer Science and Business Media LLC
Date: 13-09-2007
Imaging O2 dynamics and microenvironments in the seagrass leaf phyllosphere with magnetic optical sensor nanoparticles
Publisher: Wiley
Date: 10-11-2020
DOI: 10.1111/TPJ.15017
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 O 2 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 O 2 distribution under flow over seagrass leaf segments in the presence of a strong magnetic field. Local microniches with low leaf surface O 2 concentrations were found under thick epiphytic biofilms, often leading to anoxic microhabitats in darkness. High irradiance led to O 2 supersaturation across most of the seagrass phyllosphere, whereas leaf microenvironments with reduced O 2 conditions were found under epiphytic biofilms at low irradiance, probably driven by self‐shading. Horizontal micro‐profiles extracted from the O 2 images revealed pronounced heterogeneities in local O 2 concentration over the base of the epiphytic biofilm, with up to 52% reduction in O 2 concentrations in areas with relatively thick ( mm), compared with thin (≤1 mm), epiphyte layers in darkness. We also present evidence of enhanced relative internal O 2 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 O 2 was still markedly reduced in the epiphyte‐covered leaves, however. The leaf phyllosphere is thus characterized by a complex microlandscape of O 2 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.
Flow and epiphyte growth effects on the thermal, optical and chemical microenvironment in the leaf phyllosphere of seagrass (Zostera marina)
Publisher: The Royal Society
Date: 10-2020
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 O 2 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.
Oxygen-sensitive nanoparticles reveal the spatiotemporal dynamics of oxygen reduction during magnesium implant biodegradation
Publisher: Springer Science and Business Media LLC
Date: 18-11-2022
DOI: 10.1038/S41529-022-00302-9
Abstract: Magnesium (Mg) alloys are becoming increasingly important in the biomedical field as temporary bone implants. However, the biodegradation process of Mg alloys is highly complex and recent findings suggest that oxygen (O 2 ) consumption is non-negligible. In this study, we give experimental proof of O 2 consumption during Mg degradation under physiological conditions. Specifically, we study pure Mg, Mg–6 wt%Ag and Mg–5 wt%Gd in Hanks’ balanced salt solution and Dulbecco’s modified Eagle’s medium. We show that O 2 consumption and hydrogen evolution are inversely correlated and that O 2 concentrations remain below 7.5% in certain cases, which could have significant implications for bone healing.
Epiphyte-cover on seagrass (Zostera marina L.) leaves impedes plant performance and radial O2 loss from the below-ground tissue
Publisher: Frontiers Media SA
Date: 20-08-2015
Endolithic chlorophyll d-containing phototrophs
Publisher: Springer Science and Business Media LLC
Date: 16-12-2010
Contrasting impacts of light reduction on sediment biogeochemistry in deep- and shallow-water tropical seagrass assemblages (Green Island, Great Barrier Reef)
Publisher: Elsevier BV
Date: 05-2018
DOI: 10.1016/J.MARENVRES.2018.02.008
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 O
CORAL PHOTOBIOLOGY STUDIED WITH A NEW IMAGING PULSE AMPLITUDE MODULATED FLUOROMETER1
Publisher: Wiley
Date: 08-03-2005
Spectral effects on Symbiodinium photobiology studied with a programmable light engine
Publisher: Public Library of Science (PLoS)
Date: 12-11-2014
Ocean acidification and warming alter photosynthesis and calcification of the symbiont-bearing foraminifera Marginopora vertebralis
Publisher: Springer Science and Business Media LLC
Date: 18-07-2014
Oxic microshield and local pH enhancement protects Z ostera muelleri from sediment derived hydrogen sulphide
Publisher: Wiley
Date: 03-11-2014
DOI: 10.1111/NPH.13124
Abstract: Seagrass is constantly challenged with transporting sufficient O 2 from above‐ to belowground tissue via aerenchyma in order to maintain aerobic metabolism and provide protection against phytotoxins. Electrochemical microsensors were used in combination with a custom‐made experimental chamber to analyse the belowground biogeochemical microenvironment of Z ostera muelleri under changing environmental conditions. Measurements revealed high radial O 2 release of up to 500 nmol O 2 cm −2 h −1 from the base of the leaf sheath, maintaining a c . 300‐μm‐wide plant‐mediated oxic microzone and thus protecting the vital meristematic regions of the rhizome from reduced phytotoxic metabolites such as hydrogen sulphide (H 2 S). H 2 S intrusion was prevented through passive diffusion of O 2 to belowground tissue from leaf photosynthesis in light, as well as from the surrounding water column into the flow‐exposed plant parts during darkness. Under water column hypoxia, high belowground H 2 S concentrations at the tissue surface correlated with the inability to sustain the protecting oxic microshield around the meristematic regions of the rhizome. We also found increased p H levels in the immediate rhizosphere of Z. muelleri , which may contribute to further detoxification of H 2 S through shifts in the chemical speciation of sulphide. Zostera muelleri can modify the geochemical conditions in its immediate rhizosphere, thereby reducing its exposure to H 2 S.
Seagrass rhizosphere microenvironment alters plant-associated microbial community composition.
Publisher: Wiley
Date: 21-05-2018
Abstract: The seagrass rhizosphere harbors dynamic microenvironments, where plant‐driven gradients of O 2 and dissolved organic carbon form microhabitats that select for distinct microbial communities. To examine how seagrass‐mediated alterations of rhizosphere geochemistry affect microbial communities at the microscale level, we applied 16S rRNA licon sequencing of artificial sediments surrounding the meristematic tissues of the seagrass Zostera muelleri together with microsensor measurements of the chemical conditions at the basal leaf meristem (BLM). Radial O 2 loss (ROL) from the BLM led to ∼ 300 µm thick oxic microzones, wherein pronounced decreases in H 2 S and pH occurred. Significantly higher relative abundances of sulphate‐reducing bacteria were observed around the meristematic tissues compared to the bulk sediment, especially around the root apical meristems (RAM ∼ 57% of sequences). Within oxic microniches, elevated abundances of sulphide‐oxidizing bacteria were observed compared to the bulk sediment and around the RAM. However, sulphide oxidisers within the oxic microzone did not enhance sediment detoxification, as rates of H 2 S re‐oxidation here were similar to those observed in a pre‐sterilized root/rhizome environment. Our results provide novel insights into how chemical and microbiological processes in the seagrass rhizosphere modulate plant‐microbe interactions potentially affecting seagrass health.
Disentangling compartment functions in sessile marine invertebrates
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.TREE.2022.04.008
Abstract: Sessile invertebrates are frequently s led and processed whole for downstream analyses. However, their apparent structural simplicity is deceptive as these organisms often harbour discrete compartments. These compartments have physicochemical conditions that differ markedly from neighbouring tissues, and that have likely evolved to support specific functions. Here, we argue that such compartments should be specifically targeted when characterising sessile invertebrate biology and we use the coral gastrovascular cavity to support our argument. This complex compartment displays steep and dynamic chemical gradients, harbours distinct microorganisms, and presumably plays a key role in coral biology. Disentangling the functions played by (and amongst) compartments will likely provide transformative insight into the biology of sessile invertebrates and their future under environmental change.
Spatial heterogeneity of photosynthesis and the effect of temperature-induced bleaching conditions in three species of corals
Publisher: Springer Science and Business Media LLC
Date: 04-2004
Fungi and viruses as important players in microbial mats
Publisher: Oxford University Press (OUP)
Date: 23-09-2020
Abstract: Microbial mats are compacted, surface-associated microbial ecosystems reminiscent of the first living communities on early Earth. While often considered predominantly prokaryotic, recent findings show that both fungi and viruses are ubiquitous in microbial mats, albeit their functional roles remain unknown. Fungal research has mostly focused on terrestrial and freshwater ecosystems where fungi are known as important recyclers of organic matter, whereas viruses are exceptionally abundant and important in aquatic ecosystems. Here, viruses have shown to affect organic matter cycling and the ersity of microbial communities by facilitating horizontal gene transfer and cell lysis. We hypothesise fungi and viruses to have similar roles in microbial mats. Based on the analysis of previous research in terrestrial and aquatic ecosystems, we outline novel hypotheses proposing strong impacts of fungi and viruses on element cycling, food web structure and function in microbial mats, and outline experimental approaches for studies needed to understand these interactions.
Radiative Energy Budgets in a Microbial Mat Under Different Irradiance and Tidal Conditions
Publisher: Springer Science and Business Media LLC
Date: 09-03-2019
DOI: 10.1007/S00248-019-01350-6
Abstract: Irradiance and temperature variations during tidal cycles modulate microphytobenthic primary production potentially by changing the radiative energy balance of photosynthetic mats between immersion and emersion and thus sediment daily net metabolism. To test the effect of tidal stages on the radiative energy budget, we used microsensor measurements of oxygen, temperature, and scalar irradiance to estimate the radiative energy budget in a coastal photosynthetic microbial mat during immersion (constant water column of 2 cm) and emersion under increasing irradiance. Total absorbed light energy was higher in immersion than emersion, due to a lower reflectance of the microbial mat, while most (> 97%) of the absorbed light energy was dissipated as heat irrespective of tidal conditions. During immersion, the upward heat flux was higher than the downward one, whereas the opposite occurred during emersion. At highest photon irradiance (800 μmol photon m
Divergent expression of hypoxia response systems under deoxygenation in reef‐forming corals aligns with bleaching susceptibility
Publisher: Wiley
Date: 16-11-2020
DOI: 10.1111/GCB.15436
Nanoparticle‐based measurements of pH and O2 dynamics in the rhizosphere of Zostera marina L.: effects of temperature elevation and light‐dark transitions
Publisher: Wiley
Date: 04-05-2016
DOI: 10.1111/PCE.12740
Abstract: Seagrasses can modulate the geochemical conditions in their immediate rhizosphere through the release of chemical compounds from their below‐ground tissue. This is a vital chemical defence mechanism, whereby the plants detoxify the surrounding sediment. Using novel nanoparticle‐based optical O 2 and pH sensors incorporated in reduced and transparent artificial sediment, we investigated the spatio‐temporal dynamics of pH and O 2 within the entire rhizosphere of Zostera marina L. during experimental manipulations of light and temperature. We combined such measurements with O 2 microsensor measurements of the photosynthetic productivity and respiration of seagrass leaves. We found pronounced pH and O 2 microheterogeneity within the immediate rhizosphere of Z . marina , with higher below‐ground tissue oxidation capability and rhizoplane pH levels during both light exposure of the leaf canopy and elevated temperature, where the temperature‐mediated stimuli of biogeochemical processes seemed to predominate. Low rhizosphere pH microenvironments appeared to correlate with plant‐derived oxic microzones stimulating local sulphide oxidation and thus driving local proton generation, although the rhizoplane pH levels generally where much higher than the bulk sediment pH. Our data show that Z . marina can actively alter its rhizosphere pH microenvironment alleviating the local H 2 S toxicity and enhancing nutrient availability in the adjacent sediment via geochemical speciation shift.
Microenvironment and phylogenetic diversity of P rochloron inhabiting the surface of crustose didemnid ascidians
Publisher: Wiley
Date: 11-08-2015
Abstract: The cyanobacterium Prochloron didemni is primarily found in symbiotic relationships with various marine hosts such as ascidians and sponges. Prochloron remains to be successfully cultivated outside of its host, which reflects a lack of knowledge of its unique ecophysiological requirements. We investigated the microenvironment and ersity of Prochloron inhabiting the upper, exposed surface of didemnid ascidians, providing the first insights into this microhabitat. The pH and O2 concentration in this Prochloron biofilm changes dynamically with irradiance, where photosynthetic activity measurements showed low light adaptation (Ek ∼ 80 ± 7 μmol photons m(-2) s(-1)) but high light tolerance. Surface Prochloron cells exhibited a different fine structure to Prochloron cells from cloacal cavities in other ascidians, the principle difference being a central area of many vacuoles dissected by single thylakoids in the surface Prochloron. Cyanobacterial 16S rDNA pyro-sequencing of the biofilm community on four ascidians resulted in 433 operational taxonomic units (OTUs) where on average -85% (65-99%) of all sequence reads, represented by 136 OTUs, were identified as Prochloron via blast search. All of the major Prochloron-OTUs clustered into independent, highly supported phylotypes separate from sequences reported for internal Prochloron, suggesting a hitherto unexplored genetic variability among Prochloron colonizing the outer surface of didemnids.
A Novel Epiphytic Chlorophyll d‐containing Cyanobacterium Isolated from a Mangrove‐associated Red Alga
Publisher: Wiley
Date: 16-10-2012
DOI: 10.1111/J.1529-8817.2012.01233.X
Abstract: A new habitat and a new chlorophyll (Chl) d-containing cyanobacterium belonging to the genus Acaryochloris are reported in this study. Hyperspectral microscopy showed the presence of Chl d-containing microorganisms in epiphytic biofilms on a red alga (Gelidium caulacantheum) colonizing the pneumato-phores of a temperate mangrove (Avicennia marina). The presence of Chl d was further proven by high performance liquid chromatography (HPLC)-based pigment analysis and by confocal imaging of cultured cells. Enrichment of mangrove biofilm s les under near-infrared radiation (NIR) yielded the new Acaryochloris sp. MPGRS1, which was closely related in terms of 16S rRNA gene sequence to an isolate from the hypertrophic Salton Sea, USA. The new isolate used Chl d as its major photopigment Chl d and Chl a contents were ~98% and 1%-2% of total cellular chlorophyll, respectively. These findings expand the variety of ecological niches known to harbor Chl d-containing cyanobacteria and support our working hypothesis that such oxyphototrophs may be ubiquitous in habitats depleted of visible light, but with sufficient NIR exposure.
Photosynthetic capacity in seagrass seeds and early-stage seedlings of Zostera marina
Publisher: Wiley
Date: 24-05-2023
DOI: 10.1111/NPH.18986
Abstract: In many terrestrial seeds, photosynthetic activity supplies O 2 to the developing plant embryo to sustain aerobic metabolism and enhance biosynthetic activity. However, whether seagrass seeds possess similar photosynthetic capacity to alleviate intra‐seed hypoxic stress conditions is unknown. We used a novel combination of microscale variable chlorophyll fluorescence imaging, a custom‐made O 2 optode microrespirometry system and planar optode O 2 imaging, to determine the O 2 microenvironment and photosynthetic activity in developing seeds and seedlings of seagrass ( Zostera marina ). Developing, sheath‐covered seeds exhibited high O 2 concentrations in the photosynthetic active seed sheath and low O 2 concentrations in the centre of the seed at the position of the embryo. In light, photosynthesis in the seed sheath increased O 2 availability in central parts of the seed enabling enhanced respiratory energy generation for biosynthetic activity. Early‐stage seedlings also displayed photosynthetic capacity in hypocotyl and cotyledonary tissues, which may be beneficial for seedling establishment. Sheath O 2 production is important for alleviating intra‐seed hypoxic stress, which might increase endosperm storage activity, improving the conditions for successful seed maturation and germination.
Photobiology of endolithic microorganisms in living coral skeletons: 1. Pigmentation, spectral reflectance and variable chlorophyll fluorescence analysis of endoliths in the massive corals Cyphastrea
Publisher: Springer Science and Business Media LLC
Date: 25-04-2007
Rhizome, Root/Sediment interactions, Aerenchyma and Internal Pressure Changes in Seagrasses
Publisher: Springer International Publishing
Date: 2018
Radiative energy budgets of phototrophic surface-associated microbial communities and their photosynthetic efficiency under diffuse and collimated light
Publisher: Cold Spring Harbor Laboratory
Date: 27-01-2017
DOI: 10.1101/103705
Abstract: We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O 2 , temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under light-limiting conditions and amounted to ~13% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis and light distribution. The light acclimation index, E k was times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident 45 irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. Our results suggest that the optical properties and the structural organization of phytoelements are important traits affecting the photosynthetic efficiency of biofilms and sediments.
Temporal patterns in effective quantum yield of individual zooxanthellae expelled during bleaching
Publisher: Elsevier BV
Date: 03-2005
In situ thermal dynamics of shallow water corals is affected by tidal patterns and irradiance
Publisher: Springer Science and Business Media LLC
Date: 29-05-2012
Genomic view of the diversity and functional role of archaea and bacteria in the skeleton of the reef-building corals Porites lutea and Isopora palifera
Publisher: Research Square Platform LLC
Date: 26-07-2022
DOI: 10.21203/RS.3.RS-1890655/V1
Abstract: At present our knowledge on the compartmentalization of coral holobiont microbiomes is highly skewed towards the millimetre-thin coral tissue, leaving the erse coral skeleton microbiome underexplored. Here, we present a genome-centric view of the skeleton of the reef-building corals' Porites lutea and Isopora palifera , through a compendium of ~ 400 high-quality bacterial and archaeal metagenome-assembled genomes (MAGs), spanning 34 phyla and 57 microbial classes. Skeletal microbiomes harboured a erse array of stress response genes, including dimethylsulfoniopropionate synthesis ( dsy B) and metabolism (DMSP lyase). Furthermore, skeletal MAGs encoded an average of 22 ± 15 genes in P. lutea and 28 ± 23 in I. palifera with eukaryotic-like motifs thought to be involved in maintaining host association. We provide comprehensive insights into the putative functional role of the skeletal microbiome on key metabolic processes such as nitrogen fixation, dissimilatory and assimilatory nitrate, and sulphate reduction. Our study provides critical genomic resources for a better understanding of the coral skeletal microbiome and its role in holobiont functioning.
Seagrass-mediated phosphorus and iron solubilization in tropical sediments
Publisher: American Chemical Society (ACS)
Date: 06-12-2017
Optical Sensor Nanoparticles in Artificial Sediments–A New Tool To Visualize O2 Dynamics around the Rhizome and Roots of Seagrasses
Publisher: American Chemical Society (ACS)
Date: 30-01-2015
DOI: 10.1021/ES505734B
Abstract: Seagrass communities provide important ecosystems services in coastal environments but are threatened by anthropogenic impacts. Especially the ability of seagrasses to aerate their below-ground tissue and immediate rhizosphere to prevent sulfide intrusion from the surrounding sediment is critical for their resilience to environmental disturbance. There is a need for chemical techniques that can map the O2 distribution and dynamics in the seagrass rhizosphere upon environmental changes and thereby identify critical stress thresholds of e.g. water flow, turbidity, and O2 conditions in the water phase. In a novel experimental approach, we incorporated optical O2 sensor nanoparticles into a transparent artificial sediment matrix consisting of pH-buffered deoxygenated sulfidic agar. Seagrass growth and photosynthesis was not inhibited in the experimental setup when the below-ground biomass was immobilized in the artificial sulfidic sediment with nanoparticles and showed root growth rates (∼ 5 mm day(-1)) and photosynthetic quantum yields (∼ 0.7) comparable to healthy seagrasses in their natural habitat. We mapped the real-time below ground O2 distribution and dynamics in the whole seagrass rhizosphere during experimental manipulation of light exposure and O2 content in the overlaying water. Those manipulations showed that oxygen release from the belowground tissue is much higher in light as compared to darkness and that water column hypoxia leads to diminished oxygen levels around the rhizome/roots. Oxygen release was visualized and analyzed on a whole rhizosphere level, which is a substantial improvement to existing methods relying on point measurements with O2 microsensors or partial mapping of the rhizosphere in close contact with a planar O2 optode. The combined use of optical nanoparticle-based sensors with artificial sediments enables imaging of chemical microenvironments in the rhizosphere of aquatic plants at high spatiotemporal resolution with a relatively simple experimental setup and thus represents a significant methodological advancement for studies of environmental impacts on aquatic plant ecophysiology.
Optical Properties of Corals Distort Variable Chlorophyll Fluorescence Measurements
Publisher: Oxford University Press (OUP)
Date: 28-01-2019
DOI: 10.1104/PP.18.01275
Genomic view of the diversity and functional role of archaea and bacteria in the skeleton of the reef-building corals Porites lutea and Isopora palifera
Publisher: Oxford University Press (OUP)
Date: 28-12-2022
DOI: 10.1093/GIGASCIENCE/GIAC127
Abstract: At present, our knowledge on the compartmentalization of coral holobiont microbiomes is highly skewed toward the millimeter-thin coral tissue, leaving the erse coral skeleton microbiome underexplored. Here, we present a genome-centric view of the skeleton of the reef-building corals Porites lutea and Isopora palifera, through a compendium of ∼400 high-quality bacterial and archaeal metagenome-assembled genomes (MAGs), spanning 34 phyla and 57 classes. Skeletal microbiomes harbored a erse array of stress response genes, including dimethylsulfoniopropionate synthesis (dsyB) and metabolism (DMSP lyase). Furthermore, skeletal MAGs encoded an average of 22 ± 15 genes in P. lutea and 28 ± 23 in I. palifera with eukaryotic-like motifs thought to be involved in maintaining host association. We provide comprehensive insights into the putative functional role of the skeletal microbiome on key metabolic processes such as nitrogen fixation, dissimilatory and assimilatory nitrate, and sulfate reduction. Our study provides critical genomic resources for a better understanding of the coral skeletal microbiome and its role in holobiont functioning.
Acute Tissue Death (white syndrome) Affects the Microenvironment of Tabular Acropora Corals
Publisher: Inter-Research Science Center
Date: 27-07-2010
DOI: 10.3354/AB00270
Beneath the surface: community assembly and functions of the coral skeleton microbiome
Publisher: Springer Science and Business Media LLC
Date: 12-2019
DOI: 10.1186/S40168-019-0762-Y
Abstract: Coral microbial ecology is a burgeoning field, driven by the urgency of understanding coral health and slowing reef loss due to climate change. Coral resilience depends on its microbiota, and both the tissue and the underlying skeleton are home to a rich bio ersity of eukaryotic, bacterial and archaeal species that form an integral part of the coral holobiont. New techniques now enable detailed studies of the endolithic habitat, and our knowledge of the skeletal microbial community and its eco-physiology is increasing rapidly, with multiple lines of evidence for the importance of the skeletal microbiota in coral health and functioning. Here, we review the roles these organisms play in the holobiont, including nutritional exchanges with the coral host and decalcification of the host skeleton. Microbial metabolism causes steep physico-chemical gradients in the skeleton, creating micro-niches that, along with dispersal limitation and priority effects, define the fine-scale microbial community assembly. Coral bleaching causes drastic changes in the skeletal microbiome, which can mitigate bleaching effects and promote coral survival during stress periods, but may also have detrimental effects. Finally, we discuss the idea that the skeleton may function as a microbial reservoir that can promote recolonization of the tissue microbiome following dysbiosis and help the coral holobiont return to homeostasis.
Effects of flow and colony morphology on the thermal boundary layer of corals
Publisher: The Royal Society
Date: 20-05-2011
Abstract: The thermal microenvironment of corals and the thermal effects of changing flow and radiation are critical to understanding heat-induced coral bleaching, a stress response resulting from the destruction of the symbiosis between corals and their photosynthetic microalgae. Temperature microsensor measurements at the surface of illuminated stony corals with uneven surface topography ( Leptastrea purpurea and Platygyra sinensis ) revealed millimetre-scale variations in surface temperature and thermal boundary layer (TBL) that may help understand the patchy nature of coral bleaching within single colonies. The effect of water flow on the thermal microenvironment was investigated in hemispherical and branching corals ( Porites lobata and Stylophora pistillata , respectively) in a flow chamber experiment. For both coral types, the thickness of the TBL decreased exponentially from 2.5 mm at quasi-stagnant flow (0.3 cm s −1 ), to 1 mm at 5 cm s −1 , with an exponent approximately 0.5 consistent with predictions from the heat transfer theory for simple geometrical objects and typical of laminar boundary layer processes. Measurements of mass transfer across the diffusive boundary layer using O 2 microelectrodes revealed a greater exponent for mass transfer when compared with heat transfer, indicating that heat and mass transfer at the surface of corals are not exactly analogous processes.
Lateral light transfer ensures efficient resource distribution in symbiont-bearing corals
Publisher: The Company of Biologists
Date: 15-02-2014
DOI: 10.1242/JEB.091116
Abstract: Coral tissue optics has received very little attention in the past, although the interaction between tissue and light is central to our basic understanding of coral physiology. Here we used fibre-optic and electrochemical microsensors along with variable chlorophyll fluorescence imaging to directly measure lateral light propagation within living coral tissues. Our results show that corals can transfer light laterally within their tissues to a distance of ~2 cm. Such light transport stimulates O2 evolution and photosystem II operating efficiency in areas & .5–1 cm away from direct illumination. Light is scattered strongly in both coral tissue and skeleton, leading to photon trapping and lateral redistribution within the tissue. Lateral light transfer in coral tissue is a new mechanism by which light is redistributed over the coral colony and we argue that tissue optical properties are one of the key factors in explaining the high photosynthetic efficiency of corals.
IMAGING OF OXYGEN DYNAMICS WITHIN THE ENDOLITHIC ALGAL COMMUNITY OF THE MASSIVE CORAL PORITES LOBATA1
Publisher: Wiley
Date: 07-05-2008
DOI: 10.1111/J.1529-8817.2008.00506.X
Abstract: We used transparent planar oxygen optodes and a luminescence lifetime imaging system to map (at a pixel resolution of <200 μm) the two-dimensional distribution of O2 within the skeleton of a Porites lobata colony. The O2 distribution was closely correlated to the distribution of the predominant endolithic microalga, Ostreobium quekettii Bornet et Flahault that formed a distinct green band inside the skeleton. Oxygen production followed the outline of the Ostreobium band, and photosynthetic O2 production was detected at only 0.2 μmol photons m(-2) · s(-1) , while saturation occurred at ∼37 μmol photons m(-2) · s(-1) . Oxygen levels varied from ∼60% to 0% air saturation in the illuminated section of the coral skeleton in comparison to the darkened section. The O2 production within the Ostreobium band was lower in the region below the upward facing surface of the coral and elevated on the sides. Oxygen consumption in darkness was also greatest within the Ostreobium zone, as well as in the white skeleton zone immediately below the corallites. The rate of O2 depletion was not constant within zones and between zones, showing pronounced heterogeneity in endolithic respiration. When the coral was placed in darkness after a period of illumination, O2 levels declined by 50% within 20 min and approached steady-state after 40-50 min in darkness. Our study demonstrates the use of an important new tool in endolith photobiology and presents the first data of spatially resolved O2 concentration and its correlation to the physical structures and specific zones responsible for O2 production and consumption within the coral skeleton.
Editorial: Ecophysiology and biogeochemistry of marine plants in the anthropocene
Publisher: Frontiers Media SA
Date: 18-08-2022
Hypoxia as a physiological cue and pathological stress for coral larvae
Publisher: Wiley
Date: 14-11-2021
DOI: 10.1111/MEC.16259
Abstract: Ocean deoxygenation events are intensifying worldwide and can rapidly drive adult corals into a state of metabolic crisis and bleaching‐induced mortality, but whether coral larvae are subject to similar stress remains untested. We experimentally exposed apo‐symbiotic coral larvae of Acropora selago to deoxygenation stress with subsequent reoxygenation aligned to their night‐day light cycle, and followed their gene expression using RNA‐Seq. After 12 h of deoxygenation stress (~2 mg O 2 /L), coral planulae demonstrated a low expression of HIF‐targeted hypoxia response genes concomitant with a significantly high expression of PHD2 (a promoter of HIFα proteasomal degradation), similar to corresponding adult corals. Despite exhibiting a consistent swimming phenotype compared to control s les, the differential gene expression observed in planulae exposed to deoxygenation‐reoxygenation suggests a disruption of pathways involved in developmental regulation, mitochondrial activity, lipid metabolism, and O 2 ‐sensitive epigenetic regulators. Importantly, we found that treated larvae exhibited a disruption in the expression of conserved HIF‐targeted developmental regulators, for ex le, Homeobox ( HOX ) genes, corroborating how changes in external oxygen levels can affect animal development. We discuss how the observed deoxygenation responses may be indicative of a possible acclimation response or alternatively may imply negative latent impacts for coral larval fitness.
Correlation of bio-optical properties with photosynthetic pigment and microorganism distribution in microbial mats from Hamelin Pool, Australia
Publisher: Oxford University Press (OUP)
Date: 31-10-2018
Abstract: Microbial mats and stromatolites are widespread in Hamelin Pool, Shark Bay, however the phototrophic capacity of these systems is unknown. This study has determined the optical properties and light-harvesting potential of these mats with light microsensors. These characteristics were linked via a combination of 16S rDNA sequencing, pigment analyses and hyperspectral imaging. Local scalar irradiance was elevated over the incident downwelling irradiance by 1.5-fold, suggesting light trapping and strong scattering by the mats. Visible light (400-700 nm) penetrated to a depth of 2 mm, whereas near-infrared light (700-800 nm) penetrated to at least 6 mm. Chlorophyll a and bacteriochlorophyll a (Bchl a) were found to be the dominant photosynthetic pigments present, with BChl a peaking at the subsurface (2-4 mm). Detailed 16S rDNA analyses revealed the presence of putative Chl f-containing Halomicronema sp. and photosynthetic members primarily decreased from the mat surface down to a depth of 6 mm. Data indicated high abundances of some pigments and phototrophic organisms in deeper layers of the mats (6-16 mm). It is proposed that the photosynthetic bacteria present in this system undergo unique adaptations to lower light conditions below the mat surface, and that phototrophic metabolisms are major contributors to ecosystem function.
Light Respiratory Processes and Gross Photosynthesis in Two Scleractinian Corals
Publisher: Public Library of Science (PLoS)
Date: 31-10-2014
Radiative energy budget reveals high photosynthetic efficiency in symbiont-bearing corals
Publisher: The Royal Society
Date: 06-04-2014
Abstract: The light field on coral reefs varies in intensity and spectral composition, and is the key regulating factor for phototrophic reef organisms, for ex le scleractinian corals harbouring microalgal symbionts. However, the actual efficiency of light utilization in corals and the mechanisms affecting the radiative energy budget of corals are underexplored. We present the first balanced light energy budget for a symbiont-bearing coral based on a fine-scale study of the microenvironmental photobiology of the massive coral Montastrea curta . The majority (more than 96%) of the absorbed light energy was dissipated as heat, whereas the proportion of the absorbed light energy used in photosynthesis was approximately 4.0% under an irradiance of 640 µmol photons m −2 s −1 . With increasing irradiance, the proportion of heat dissipation increased at the expense of photosynthesis. Despite such low energy efficiency, we found a high photosynthetic efficiency of the microalgal symbionts showing high gross photosynthesis rates and quantum efficiencies (QEs) of approximately 0.1 O 2 photon −1 approaching theoretical limits under moderate irradiance levels. Corals thus appear as highly efficient light collectors with optical properties enabling light distribution over the corallite/tissue microstructural canopy that enables a high photosynthetic QE of their photosynthetic microalgae in hospite .
Spatial heterogeneity in active chlorophyll fluorescence and PSII activity of coral tissues
Publisher: Springer Science and Business Media LLC
Date: 10-2002
Deoxygenation lowers the thermal threshold of coral bleaching
Publisher: Springer Science and Business Media LLC
Date: 31-10-2022
DOI: 10.1038/S41598-022-22604-3
Abstract: Exposure to deoxygenation from climate warming and pollution is emerging as a contributing factor of coral bleaching and mortality. However, the combined effects of heating and deoxygenation on bleaching susceptibility remain unknown. Here, we employed short-term thermal stress assays to show that deoxygenated seawater can lower the thermal limit of an Acropora coral by as much as 1 °C or 0.4 °C based on bleaching index scores or dark-acclimated photosynthetic efficiencies, respectively. Using RNA-Seq, we show similar stress responses to heat with and without deoxygenated seawater, both activating putative key genes of the hypoxia-inducible factor response system indicative of cellular hypoxia. We also detect distinct deoxygenation responses, including a disruption of O 2 -dependent photo-reception/-protection, redox status, and activation of an immune response prior to the onset of bleaching. Thus, corals are even more vulnerable when faced with heat stress in deoxygenated waters. This highlights the need to integrate dissolved O 2 measurements into global monitoring programs of coral reefs.
Heat budget and thermal microenvironment of shallow-water corals: Do massive corals get warmer than branching corals?
Publisher: Wiley
Date: 07-2008
In situ metabolomic- and transcriptomic-profiling of the host-associated cyanobacteria Prochloron and Acaryochloris marina
Publisher: Springer Science and Business Media LLC
Date: 31-10-2017
Sediment resuspension and deposition on seagrass leaves impedes internal plant aeration and promotes phytotoxic H2 S intrusion
Publisher: Frontiers Media SA
Date: 09-05-2017
Widespread oxyregulation in tropical corals under hypoxia
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.MARPOLBUL.2022.113722
Abstract: Hypoxia (low oxygen stress) is increasingly reported on coral reefs, caused by ocean deoxygenation linked to coastal nutrient pollution and ocean warming. While the ability to regulate respiration is a key driver of hypoxia tolerance in many other aquatic taxa, corals' oxyregulatory capabilities remain virtually unexplored. Here, we examine O
The in situ light microenvironment of corals
Publisher: Wiley
Date: 05-2014
APPARENT LIGHT REQUIREMENT FOR ACTIVATION OF PHOTOSYNTHESIS UPON REHYDRATION OF DESICCATED BEACHROCK MICROBIAL MATS1
Publisher: Wiley
Date: 02-2002
Resolving Chemical Gradients Around Seagrass Roots—A Review of Available Methods
Publisher: Frontiers Media SA
Date: 29-10-2021
DOI: 10.3389/FMARS.2021.771382
Abstract: Steep geochemical gradients surround roots and rhizomes of seagrass and protect the plants against the harsh conditions in anoxic sediment, while enabling nutrient uptake. Imbalance of these gradients, due to e.g., low plant performance and/or changing sediment biogeochemical conditions, can lead to plant stress and large-scale seagrass meadow die-off. Therefore, measuring and mapping the dynamic gradients around seagrass roots and rhizomes is needed to better understand plant responses to human impact and environmental changes. Historically, electrochemical microsensors enabled the first measurements of important chemical species like O 2 , pH or H 2 S with high sensitivity and spatial resolution giving important insights to the seagrass rhizosphere microenvironment however, such measurements only provide information in one dimension at a time. In recent years, the use of reversible optical sensors (in the form of planar optodes or nanoparticles) and accumulative gel s ling methods like Diffusive Gradients in Thin films (DGT) have extended the array of analytes and allowed 2-D mapping of chemical gradients in the seagrass rhizosphere. Here, we review and discuss such microscale methods from a practical angle, discuss their application in seagrass research, and point toward novel experimental approaches to study the (bio)geochemistry around seagrass roots and rhizomes using a combination of available techniques, both in the lab and in situ .
Fluorescent pigments in corals are photoprotective
Publisher: Springer Science and Business Media LLC
Date: 12-2000
DOI: 10.1038/35048564
Abstract: All reef-forming corals depend on the photosynthesis performed by their algal symbiont, and such corals are therefore restricted to the photic zone. The intensity of light in this zone declines over several orders of magnitude--from high and damaging levels at the surface to extreme shade conditions at the lower limit. The ability of corals to tolerate this range implies effective mechanisms for light acclimation and adaptation. Here we show that the fluorescent pigments (FPs) of corals provide a photobiological system for regulating the light environment of coral host tissue. Previous studies have suggested that under low light, FPs may enhance light availability. We now report that in excessive sunlight FPs are photoprotective they achieve this by dissipating excess energy at wavelengths of low photosynthetic activity, as well as by reflecting of visible and infrared light by FP-containing chromatophores. We also show that FPs enhance the resistance to mass bleaching of corals during periods of heat stress, which has implications for the effect of environmental stress on the ersity of reef-building corals, such as enhanced survival of a broad range of corals allowing maintenance of habitat ersity.
Temperature Effects on Leaf and Epiphyte Photosynthesis, Bicarbonate Use and Diel O2 Budgets of the Seagrass Zostera marina L.
Publisher: Frontiers Media SA
Date: 16-03-2022
DOI: 10.3389/FMARS.2022.822485
Abstract: Ocean warming along with nutrient enrichment are major stressors causing global seagrass decline. While the effects of global warming on metabolic parameters in seagrasses are well described, the effect of increasing temperature on the epiphytic overgrowth of seagrass leaves and the consequences for the seagrass plant are poorly understood. Here, we investigated the effects of elevating temperature on the photosynthetic efficiency of the seagrass species Zostera marina L. and its associated epiphytes, to explore how ocean warming might affect epiphytism in seagrasses. Gas exchange and final pH measurements on bare seagrass leaves, leaves with epiphytes, and epiphytes separated from seagrass leaves were used to quantify photosynthesis and respiration rates, and the inorganic carbon extraction capacity of leaves and epiphytes as a function of photon scalar irradiance and temperature (12, 17, 22, and 27°C). Seagrass without epiphytic biofilm had a high ability to exploit the incoming irradiance regardless of the light intensity and temperature, shown as continuously high light use efficiency and maximum net photosynthesis rates. The presence of epiphytic biofilm on the seagrass leaves impaired plant photosynthesis by increasing light requirements and reducing the photosynthetic efficiency (especially at 27°C). Epiphytes showed the lowest respiration rates in darkness and had the highest oxygen surplus over diel cycles up to 22°C, whereas bare leaves had the highest diel oxygen surplus at 27°C. Both bare leaves and epiphytes lost the ability to utilize bicarbonate at 27°C, and epiphytes also did not show use of bicarbonate at 12°C. Our results indicate a competitive advantage for epiphytes in cold CO 2 -rich environments, whereas seagrass with bare leaves could be less affected under elevated seawater temperatures.
Chlorophyll d: the puzzle resolved
Publisher: Elsevier BV
Date: 08-2005
DOI: 10.1016/J.TPLANTS.2005.06.005
Abstract: Chlorophyll a (Chl a) has always been regarded as the sole chlorophyll with a role in photochemical conversion in oxygen-evolving phototrophs, whereas chlorophyll d (Chl d), discovered in small quantities in red algae in 1943, was often regarded as an artefact of isolation. Now, as a result of discoveries over the past year, it has become clear that Chl d is the major chlorophyll of a free-living and widely distributed cyanobacterium that lives in light environments depleted in visible light and enhanced in infrared radiation. Moreover, Chl d not only has a light-harvesting role but might also replace Chl a in the special pair of chlorophylls in both reactions centers of photosynthesis.
Fine‐scale mapping of physicochemical and microbial landscapes of the coral skeleton
Publisher: Wiley
Date: 28-03-2023
Abstract: The coral skeleton harbours a erse community of bacteria and microeukaryotes exposed to light, O 2 and pH gradients, but how such physicochemical gradients affect the coral skeleton microbiome remains unclear. In this study, we employed chemical imaging of O 2 and pH, hyperspectral reflectance imaging and spatially resolved taxonomic and inferred functional microbiome characterization to explore links between the skeleton microenvironment and microbiome in the reef‐building corals Porites lutea and Paragoniastrea benhami . The physicochemical environment was more stable in the deep skeleton, and the ersity and evenness of the bacterial community increased with skeletal depth, suggesting that the microbiome was stratified along the physicochemical gradients. The bulk of the coral skeleton was in a low O 2 habitat, whereas pH varied from pH 6–9 with depth. Physicochemical gradients of O 2 and pH of the coral skeleton explained the β‐ ersity of the bacterial communities, and skeletal layers that showed O 2 peaks had a higher relative abundance of endolithic algae, reflecting a link between the abiotic environment and the microbiome composition. Our study links the physicochemical, microbial and functional landscapes of the coral skeleton and provides new insights into the involvement of skeletal microbes in the coral holobiont metabolism.
Every refuge has its price: Ostreobium as a model for understanding how algae can live in rock and stay in business
Publisher: Elsevier BV
Date: 2022
Variation in photosynthesis and respiration in geographically distinct populations of two reef‑building coral species
Publisher: Inter-Research Science Center
Date: 19-05-2011
DOI: 10.3354/AB00338
A niche for cyanobacteria containing chlorophyll d
Publisher: Springer Science and Business Media LLC
Date: 02-2005
DOI: 10.1038/433820A
Abstract: The cyanobacterium known as Acaryochloris marina is a unique phototroph that uses chlorophyll d as its principal light-harvesting pigment instead of chlorophyll a, the form commonly found in plants, algae and other cyanobacteria this means that it depends on far-red light for photosynthesis. Here we demonstrate photosynthetic activity in Acaryochloris-like phototrophs that live underneath minute coral-reef invertebrates (didemnid ascidians) in a shaded niche enriched in near-infrared light. This discovery clarifies how these cyanobacteria are able to thrive as free-living organisms in their natural habitat.
Elevated CO2 Leads to Enhanced Photosynthesis but Decreased Growth in Early Life Stages of Reef Building Coralline Algae
Publisher: Frontiers Media SA
Date: 07-01-2019
A split flow chamber with artificial sediment to examine the below-ground microenvironment of aquatic macrophytes
Publisher: Springer Science and Business Media LLC
Date: 16-09-2014
Photosynthetic capacity in seagrass seeds and early-stage seedlings ofZostera marinaL
Publisher: Cold Spring Harbor Laboratory
Date: 12-12-2022
DOI: 10.1101/2022.12.12.520078
Abstract: In many terrestrial seeds, photosynthetic activity supplies O 2 to the developing plant embryo to sustain aerobic metabolism and enhance biosynthetic activity. However, whether seagrass seeds possess similar photosynthetic capacity to alleviate intra-seed hypoxic stress conditions is unknown. We used a novel combination of microscale variable chlorophyll fluorescence imaging, a custom-made O 2 optode microrespirometry system, and planar optode O 2 imaging, to determine the O 2 microenvironment and photosynthetic activity in developing seeds and seedlings of seagrass ( Z. marina L.). Developing, sheath-covered seeds exhibited high O 2 concentrations in the photosynthetic active seed sheath and low O 2 concentrations in the center of the seed at the position of the embryo. In light, photosynthesis in the seed sheath increased O 2 availability in central parts of the seed enabling enhanced respiratory energy generation for biosynthetic activity. Early-stage seedlings also displayed photosynthetic capacity in hypocotyl and cotyledonary tissues, which may be beneficial for seedling establishment. Sheath O 2 production is important for alleviating intra-seed hypoxic stress and can increase endosperm storage activity improving the conditions for successful seed maturation and germination.
Importance of macro- versus microstructure in modulating light levels inside coral colonies
Publisher: Wiley
Date: 05-07-2011
DOI: 10.1111/J.1529-8817.2011.01021.X
Abstract: Adjusting the light exposure and capture of their symbiotic photosynthetic dinoflagellates (genus Symbiodinium Freud.) is central to the success of reef-building corals (order Scleractinia) across high spatio-temporal variation in the light environment of coral reefs. We tested the hypothesis that optical properties of tissues in some coral species can provide light management at the tissue scale comparable to light modulation by colony architecture in other species. We compared within-tissue scalar irradiance in two coral species from the same light habitat but with contrasting colony growth forms: branching Stylophora pistillata and massive Lobophyllia corymbosa. Scalar irradiance at the level of the symbionts (2 mm into the coral tissues) were <10% of ambient irradiance and nearly identical for the two species, despite substantially different light environments at the tissue surface. In S. pistillata, light attenuation (90% relative to ambient) was observed predominantly at the colony level as a result of branch-to-branch self-shading, while in L. corymbosa, near-complete light attenuation (97% relative to ambient) was occurring due to tissue optical properties. The latter could be explained partly by differences in photosynthetic pigment content in the symbiont cells and pigmentation in the coral host tissue. Our results demonstrate that different strategies of light modulation at colony, polyp, and cellular levels by contrasting morphologies are equally effective in achieving favorable irradiances at the level of coral photosymbionts.
Microenvironmental changes support evidence of photosynthesis and calcification inhibition in Halimeda under ocean acidification and warming
Publisher: Springer Science and Business Media LLC
Date: 08-09-2012
Intra-colonial variability in light acclimation of zooxanthellae in coral tissues of Pocillopora damicornis
Publisher: Springer Science and Business Media LLC
Date: 03-05-2006
Nanoparticle- and microparticle-based luminescence imaging of chemical species and temperature in aquatic systems: a review
Publisher: Springer Science and Business Media LLC
Date: 24-01-2019
DOI: 10.1007/S00604-018-3202-Y
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 in idual 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, ex les 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.
Disparate Inventories of Hypoxia Gene Sets Across Corals Align With Inferred Environmental Resilience
Publisher: Frontiers Media SA
Date: 19-05-2022
DOI: 10.3389/FMARS.2022.834332
Abstract: Aquatic deoxygenation has been flagged as an overlooked but key factor contributing to mass bleaching-induced coral mortality. During deoxygenation events triggered by coastal nutrient pollution and ocean warming, oxygen supplies lower to concentrations that can elicit an aerobic metabolic crisis i.e., hypoxia. Surprisingly little is known of the fundamental hypoxia gene set inventory that corals possess to respond to lowered oxygen (i.e., deoxygenation). For instance, it is unclear whether gene copy number differences exist across species that may affect the efficacy of a measured transcriptomic stress response. Therefore, we conducted an ortholog-based meta-analysis to investigate how hypoxia gene inventories differ amongst coral species to assess putative copy number variations (CNVs). We specifically elucidated CNVs for a compiled list of 32 hypoxia genes across 24 protein sets from species with a sequenced genome spanning corals from the robust and complex clade. We found approximately a third of the investigated genes exhibited copy number differences, and these differences were species-specific rather than attributable to the robust-complex split. Interestingly, we consistently found the highest gene expansion present in Porites lutea , which is considered to exhibit inherently greater stress tolerance than other species. Consequently, our analysis suggests that hypoxia stress gene expansion may coincide with increased stress tolerance. As such, the unevenly expanded (or reduced) hypoxia genes presented here provide key genes of interest to target in examining (or diagnosing) coral stress responses. Important next steps will involve determining to what extent such gene copy differences align with certain coral traits.
Coral reef survival under accelerating ocean deoxygenation
Publisher: Springer Science and Business Media LLC
Date: 31-03-2020
Desiccation stress in two intertidal beachrock biofilms
Publisher: Springer Science and Business Media LLC
Date: 17-05-2014
Effective light absorption and absolute electron transport rates in the coral Pocillopora damicornis
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.PLAPHY.2014.07.015
Abstract: Pulse Amplitude Modulation (PAM) fluorometry has been widely used to estimate the relative photosynthetic efficiency of corals. However, both the optical properties of intact corals as well as past technical constrains to PAM fluorometers have prevented calculations of the electron turnover rate of PSII. We used a new Multi-colour PAM (MC-PAM) in parallel with light microsensors to determine for the first time the wavelength-specific effective absorption cross-section of PSII photochemistry, σII(λ), and thus PAM-based absolute electron transport rates of the coral photosymbiont Symbiodinium both in culture and in hospite in the coral Pocillopora damicornis. In both cases, σII of Symbiodinium was highest in the blue spectral region and showed a progressive decrease towards red wavelengths. Absolute values for σII at 440 nm were up to 1.5-times higher in culture than in hospite. Scalar irradiance within the living coral tissue was reduced by 20% in the blue when compared to the incident downwelling irradiance. Absolute electron transport rates of P. damicornis at 440 nm revealed a maximum PSII turnover rate of ca. 250 electrons PSII(-1) s(-1), consistent with one PSII turnover for every 4 photons absorbed by PSII this likely reflects the limiting steps in electron transfer between PSII and PSI. Our results show that optical properties of the coral host strongly affect light use efficiency of Symbiodinium. Therefore, relative electron transport rates do not reflect the productivity rates (or indeed how the photosynthesis-light response is parameterised). Here we provide a non-invasive approach to estimate absolute electron transport rates in corals.
Light microenvironment and single-cell gradients of carbon fixation in tissues of symbiont-bearing corals
Publisher: Springer Science and Business Media LLC
Date: 04-08-2015
Effects of Epiphytic Biofilm Activity on the Photosynthetic Activity, pH and Inorganic Carbon Microenvironment of Seagrass Leaves (Zostera marina L.)
Publisher: Frontiers Media SA
Date: 10-05-2022
DOI: 10.3389/FMARS.2022.835381
Abstract: Epiphytic biofilms on seagrass leaves can lead to extreme microenvironmental conditions for the encapsulated leaf limiting both its photosynthesis and respiration. Yet, little is known about how the biological activity of the biofilm itself changes the seagrass phyllosphere microenvironment and dynamics. We used microsensors to measure O 2 concentrations and pH gradients and calculate fluxes of O 2 , CO 2 and bicarbonate ( HC O 3 − ) around seagrass leaves ( Z. marina L.) covered with artificial, inactive biofilms and natural epiphytic biofilms. A sterilized seawater-agar matrix was used to make an artificial “inactive” biofilm on seagrass leaves with the same thickness as the natural leaf epiphytic biofilm, which impeded turbulent exchange of gases but did not have microbial activity. We compared the concentration profiles and fluxes of O 2 and inorganic carbon of the “active” and “inactive” biofilm to investigate the effect of microbial activity and molecular diffusion in seagrass leaf biofilms. In light, the O 2 flux of leaves with inactive biofilm was only 31% of the leaves with active biofilm, indicating that the photosynthesis of the microbial community in the biofilm makes up the majority of O 2 production in the leaf microenvironment. During darkness, the O 2 concentration profiles and O 2 fluxes were almost identical in the “active” and “inactive” biofilms. The pH profiles showed the same trend with an increase in pH of ~1.0 in the “active” biofilms and ~0.3 pH units in the “inactive” biofilms in the light, and both showing a decrease of ~0.3 pH units in darkness compared to the bulk seawater. Our measurements thus demonstrate strong photosynthesis in the epiphyte layer driving phyllosphere basification and inorganic carbon limitation. The calculated CO 2 concentration on the leaf surface decreased to 0.09 μmol L -1 in the epiphytic biofilm in the light compared to leaf surface CO 2 concentrations of 13.8 μmol L -1 on bare seagrass leaves, and the CO 2 influxes were only 3.0% and 5.4% of O 2 effluxes for leaves with “active” and “inactive” biofilm, respectively. Calculations also showed that HC O 3 − influxes in light accounted for 91-97% of the total inorganic carbon influx to the seagrass leaf, although the HC O 3 − utilization via CO 2 concentration mechanisms is energy-consuming. Besides increasing mass transfer impedance, leaf epiphytic biofilm activity thus strongly affects the seagrass leaf microenvironment in the light by inducing higher O 2 concentration and pH, increasing CO 2 limitation and reducing the leaf photosynthetic efficiency.
In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?
Publisher: Frontiers Media SA
Date: 24-01-2017
Light gradients and optical microniches in coral tissues
Publisher: Frontiers Media SA
Date: 2012
Substantial near-infrared radiation-driven photosynthesis of chlorophyll f-containing cyanobacteria in a natural habitat
Publisher: eLife Sciences Publications, Ltd
Date: 21-01-2020
DOI: 10.7554/ELIFE.50871
Abstract: Far-red absorbing chlorophylls are constitutively present as chlorophyll (Chl) d in the cyanobacterium Acaryochloris marina, or dynamically expressed by synthesis of Chl f, red-shifted phycobiliproteins and minor amounts of Chl d via far-red light photoacclimation in a range of cyanobacteria, which enables them to use near-infrared-radiation (NIR) for oxygenic photosynthesis. While the biochemistry and molecular physiology of Chl f-containing cyanobacteria has been unraveled in culture studies, their ecological significance remains unexplored and no data on their in situ activity exist. With a novel combination of hyperspectral imaging, confocal laser scanning microscopy, and nanoparticle-based O2 imaging, we demonstrate substantial NIR-driven oxygenic photosynthesis by endolithic, Chl f-containing cyanobacteria within natural beachrock biofilms that are widespread on (sub)tropical coastlines. This indicates an important role of NIR-driven oxygenic photosynthesis in primary production of endolithic and other shaded habitats.
Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light
Publisher: Frontiers Media SA
Date: 28-03-2017
Newly Isolated Chl d-Containing Cyanobacteria
Publisher: Springer Berlin Heidelberg
Date: 2013
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