Seagrass meadows form highly productive and diverse ecosystems in coastal areas worldwide, where they are increasingly exposed to ocean acidification (OA). Efficient nitrogen (N) cycling and uptake are essential to maintain plant productivity, but the effects of OA on N transformations in these systems are poorly understood. Here we show that complete N cycling occurs on leaves of the Mediterranean seagrass Posidonia oceanica at a volcanic CO2 vent near Ischia Island (Italy), with OA affecting both N gain and loss while the epiphytic microbial community structure remains largely unaffected. Daily leaf-associated N2 fixation contributes to 35% of the plant’s N demand under ambient pH, while it contributes to 45% under OA. Nitrification potential is only detected under OA, and N-loss via N2 production increases, although the balance remains decisively in favor of enhanced N gain. Our work highlights the role of the N-cycling microbiome in seagrass adaptation to OA, with key N transformations accelerating towards increased N gain.
Continue reading ‘Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents’Posts Tagged 'phanerogams'
Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents
Published 22 March 2024 Science ClosedTags: adaptation, biogeochemistry, biological response, laboratory, Mediterranean, molecular biology, nitrogen fixation, otherprocess, phanerogams, physiology, prokaryotes, protists, vents
Cool-edge populations of the kelp Ecklonia radiata under global ocean change scenarios: strong sensitivity to ocean warming but little effect of ocean acidification
Published 9 February 2024 Science ClosedTags: biological response, individualmodeling, laboratory, modeling, morphology, multiple factors, phanerogams, photosynthesis, physiology, South Pacific, temperature
Kelp forests are threatened by ocean warming, yet effects of co-occurring drivers such as CO2 are rarely considered when predicting their performance in the future. In Australia, the kelp Ecklonia radiata forms extensive forests across seawater temperatures of approximately 7–26°C. Cool-edge populations are typically considered more thermally tolerant than their warm-edge counterparts but this ignores the possibility of local adaptation. Moreover, it is unknown whether elevated CO2 can mitigate negative effects of warming. To identify whether elevated CO2 could improve thermal performance of a cool-edge population of E. radiata, we constructed thermal performance curves for growth and photosynthesis, under both current and elevated CO2 (approx. 400 and 1000 µatm). We then modelled annual performance under warming scenarios to highlight thermal susceptibility. Elevated CO2 had minimal effect on growth but increased photosynthesis around the thermal optimum. Thermal optima were approximately 16°C for growth and approximately 18°C for photosynthesis, and modelled performance indicated cool-edge populations may be vulnerable in the future. Our findings demonstrate that elevated CO2 is unlikely to offset negative effects of ocean warming on the kelp E. radiata and highlight the potential susceptibility of cool-edge populations to ocean warming.
Continue reading ‘Cool-edge populations of the kelp Ecklonia radiata under global ocean change scenarios: strong sensitivity to ocean warming but little effect of ocean acidification’The vulnerability of World Heritage seagrass habitats to climate change
Published 23 January 2024 Science ClosedTags: adaptation, biological response, otherprocess, performance, phanerogams
Seagrass is an important natural attribute of 28 World Heritage (WH) properties. These WH seagrass habitats provide a wide range of services to adjacent ecosystems and human communities, and are one of the largest natural carbon sinks on the planet. Climate change is considered the greatest and fastest-growing threat to natural WH properties and evidence of climate-related impacts on seagrass habitats has been growing. The main objective of this study was to assess the vulnerability of WH seagrass habitats to location-specific key climate stressors. Quantitative surveys of seagrass experts and site managers were used to assess exposure, sensitivity and adaptive capacity of WH seagrass habitats to climate stressors, following the Climate Vulnerability Index approach. Over half of WH seagrass habitats have high vulnerability to climate change, mainly from the long-term increase in sea-surface temperature and short-term marine heatwaves. Potential impacts from climate change and certainty scores associated with them were higher than reported by a similar survey-based study from 10 years prior, indicating a shift in stakeholder perspectives during the past decade. Additionally, seagrass experts’ opinions on the cumulative impacts of climate and direct-anthropogenic stressors revealed that high temperature in combination with high suspended sediments, eutrophication and hypoxia is likely to provoke a synergistic cumulative (negative) impact (p < .05). A key component contributing to the high vulnerability assessments was the low adaptive capacity; however, discrepancies between adaptive capacity scores and qualitative responses suggest that managers of WH seagrass habitats might not be adequately equipped to respond to climate change impacts. This thematic assessment provides valuable information to help prioritize conservation actions, monitoring activities and research in WH seagrass habitats. It also demonstrates the utility of a systematic framework to evaluate the vulnerability of thematic groups of protected areas that share a specific attribute.
Continue reading ‘The vulnerability of World Heritage seagrass habitats to climate change’Adaptive responses of eelgrass (Zostera marina L.) to ocean warming and acidification
Published 21 December 2023 Science ClosedTags: biological response, laboratory, molecular biology, morphology, multiple factors, North Pacific, phanerogams, physiology, primary production, temperature
Highlights
- Ocean warming (OW) and acidification (OA) affect seagrass stability.
- Zostera marina L.’s response to OW and OA was studied using multi-omics analysis.
- Plant performance varied under different OW and OA combinations.
- OA’s effects on genes and metabolism depended on temperature.
- OA and OW interactions triggered diverse metabolic shifts in Z. marina.
Abstract
Ocean warming (OW) and ocean acidification (OA), driven by rapid global warming accelerating at unprecedented rates, are profoundly impacting the stability of seagrass ecosystems. Yet, our current understanding of the effects of OW and OA on seagrass remains constrained. Herein, we investigated the response of eelgrass (Zostera marina L.), a representative seagrass species, to OW and OA through comprehensive transcriptomic and metabolomic analyses. The results showed notable variations in plant performance under varying conditions: OW, OA, and OWA (a combination of both conditions). Specifically, under average oceanic temperature conditions for eelgrass growth over the past 20 years —from May to November—OA promoted the production of differentially expressed genes and metabolites associated with alanine, aspartate, and glutamate metabolism, as well as starch and sucrose metabolism. Under warming condition, eelgrass was resistant to OA by accelerating galactose metabolism, along with glycine, serine, and threonine metabolism, as well as the tricarboxylic acid (TCA) cycle. Under the combined OW and OA condition, eelgrass stimulated fructose and mannose metabolism, glycolysis, and carbon fixation, in addition to galactose metabolism and the TCA cycle to face the interplay. Our findings suggest that eelgrass exhibits adaptive capacity by inducing different metabolites and associated genes, primarily connected with carbon and nitrogen metabolism, in response to varying degrees of OW and OA. The data generated here support the exploration of mechanisms underlying seagrass responses to environmental fluctuations, which hold critical significance for the future conservation and management of these ecosystems.
Continue reading ‘Adaptive responses of eelgrass (Zostera marina L.) to ocean warming and acidification’Ocean acidification impairs seagrass performance under thermal stress in shallow and deep water
Published 24 November 2023 Science ClosedTags: biological response, field, growth, laboratory, Mediterranean, mesocosms, molecular biology, phanerogams, photosynthesis, physiology
Highlights
- Shallow and deep plants were exposed to ocean acidification and thermal stress;
- Plants were unaffected by ocean acidification when not exposed to thermal stress;
- Ocean acidification reduced plant performance under thermal stress;
- Deep plants showed higher levels of heat stress at genetic and physiological levels;
- Warming may play a key role in structuring future seagrass meadows.
Abstract
Despite the effects of ocean acidification (OA) on seagrasses have been widely investigated, predictions of seagrass performance under future climates need to consider multiple environmental factors. Here, we performed a mesocosm study to assess the effects of OA on shallow and deep Posidonia oceanica plants. The experiment was run in 2021 and repeated in 2022, a year characterized by a prolonged warm water event, to test how the effects of OA on plants are modulated by thermal stress. The response of P. oceanica to experimental conditions was investigated at different levels of biological organization. Under average seawater temperature, there were no effects of OA in both shallow and deep plants, indicating that P. oceanica is not limited by current inorganic carbon concentration, regardless of light availability. In contrast, under thermal stress, exposure of plants to OA increased lipid peroxidation and decreased photosynthetic performance, with deep plants displaying higher levels of heat stress, as indicated by the over-expression of stress-related genes and the activation of antioxidant systems. In addition, warming reduced plant growth, regardless of seawater CO2 and light levels, suggesting that thermal stress may play a fundamental role in the future development of seagrass meadows. Our results suggest that OA may exacerbate the negative effects of future warming on seagrasses.
Continue reading ‘Ocean acidification impairs seagrass performance under thermal stress in shallow and deep water’Seasonal temperature variation in Zostera marina seedlings under ocean acidification
Published 24 November 2023 Science ClosedTags: biological response, laboratory, molecular biology, morphology, multiple factors, North Pacific, phanerogams, physiology, temperature
Objective: To investigate the responses of Zostera marina seedlings to the individual and combined stresses of seasonal temperature increase and ocean acidification (OA) caused by global climate change and anthropogenic factors. This data will help in efforts to protect and restore seagrass beds in temperate coastal zones of China.
Methods: A mesoscale experimental system was utilized to analyze stress response mechanisms at multiple levels – phenotype, transcriptome, and metabolome – during the seedling stage of Z. marina, a dominant temperate seagrass species in China. The study monitored the seedlings under varying conditions: increased seasonal temperature, OA, and a combination of both.
Results: Findings revealed that under high-temperature conditions, carotenoid biosynthesis was stimulated through the upregulation of specific metabolites and enzymes. Similarly, the biosynthesis of certain alkaloids was promoted alongside modifications in starch, sucrose, and nitrogen metabolism, which improved the plant’s adaptation to OA. Unique metabolic pathways were activated under OA, including the degradation of certain amino acids and modifications in the citric acid cycle and pyruvate metabolism. When subjected to both temperature and OA stresses, seedlings actively mobilized various biosynthetic pathways to enhance adaptability and resilience, with distinct metabolic pathways enhancing the plant’s response under diversified stress conditions. In terms of growth, all treatment groups exhibited significant leaf length increase (p < 0.05), but the weakest growth index was observed under combined stress, followed by the thermal treatment group. Conversely, growth under OA treatment was better, showing a significant increase in wet weight, leaf length, and leaf width (p < 0.05).
Conclusion: Seasonal temperature increase was found to inhibit the growth of Z. marina seedlings to some extent, while OA facilitated their growth. However, the positive effects of OA did not mitigate the damage caused by increased seasonal temperature under combined stress due to seedlings’ sensitivity at this stage. Our findings elucidate differing plant coping strategies under varied stress conditions, contingent on the initial environment. This research anticipates providing significant data support for the adaptation of Z. marina seedlings to seasonal temperature fluctuations and global oceanic events like OA, propelling the effective conservation of seagrass beds.
Continue reading ‘Seasonal temperature variation in Zostera marina seedlings under ocean acidification’Microbial associates of an endemic Mediterranean seagrass enhance the access of the host and the surrounding seawater to inorganic nitrogen under ocean acidification
Published 21 November 2023 Science ClosedTags: biogeochemistry, biological response, BRcommunity, field, Mediterranean, molecular biology, nitrogen fixation, otherprocess, phanerogams, physiology, primary production, prokaryotes, vents
Seagrasses are important primary producers in oceans worldwide. They live in shallow coastal waters that are experiencing carbon dioxide enrichment and ocean acidification. Posidonia oceanica, an endemic seagrass species that dominates the Mediterranean Sea, achieves high abundances in seawater with relatively low concentrations of dissolved inorganic nitrogen. Here we tested whether microbial metabolisms associated with P. oceanica and surrounding seawater enhance seagrass access to nitrogen. Using stable isotope enrichments of intact seagrass with amino acids, we showed that ammonification by free-living and seagrass-associated microbes produce ammonium that is likely used by seagrass and surrounding particulate organic matter. Metagenomic analysis of the epiphytic biofilm on the blades and rhizomes support the ubiquity of microbial ammonification genes in this system. Further, we leveraged the presence of natural carbon dioxide vents and show that the presence of P. oceanica enhanced the uptake of nitrogen by water column particulate organic matter, increasing carbon fixation by a factor of 8.6–17.4 with the greatest effect at CO2 vent sites. However, microbial ammonification was reduced at lower pH, suggesting that future ocean climate change will compromise this microbial process. Thus, the seagrass holobiont enhances water column productivity, even in the context of ocean acidification.
Continue reading ‘Microbial associates of an endemic Mediterranean seagrass enhance the access of the host and the surrounding seawater to inorganic nitrogen under ocean acidification’Direct and indirect impacts of ocean acidification and warming on algae-herbivore interactions in intertidal habitats
Published 29 September 2023 Science ClosedTags: biological response, BRcommunity, communityMF, laboratory, mollusks, multiple factors, performance, phanerogams, physiology, temperature
Highlights
- Ocean acidification (OA) and warming (OW) alter algae-herbivore interactions
- OA and OW modify biochemical composition of the kelp Lessonia spicata.
- Changes in kelp biochemical composition affect snail’s feeding behaviour.
- OW and OA conditions increased snail’s metabolic stress.
- Nutritional quality of food plays a key role on grazers’ physiological energetics.
Abstract
Anthropogenically induced global climate change has caused profound impacts in the world ocean. Climate change related stressors, like ocean acidification (OA) and warming (OW) can affect physiological performance of marine species. However, studies evaluating the impacts of these stressors on algae-herbivore interactions have been much more scarce. We approached this issue by assessing the combined impacts of OA and OW on the physiological energetics of the herbivorous snail Tegula atra, and whether this snail is affected indirectly by changes in biochemical composition of the kelp Lessonia spicata, in response to OA and OW. Our results show that OA and OW induce changes in kelp biochemical composition and palatability (organic matter, phenolic content), which in turn affect snails’ feeding behaviour and energy balance. Nutritional quality of food plays a key role on grazers’ physiological energetics and can define the stability of trophic interactions in rapidly changing environments such as intertidal communities.
Continue reading ‘Direct and indirect impacts of ocean acidification and warming on algae-herbivore interactions in intertidal habitats’How does ocean acidification affect Zostera marina during a marine heatwave?
Published 22 August 2023 Science ClosedTags: biological response, laboratory, molecular biology, morphology, multiple factors, phanerogams, physiology, temperature
Highlights
- Under extreme conditions Z. marina grows in both leaf length and wet mass.
- Increasing CO2 levels for Z. marina at high temperatures may stimulate growth.
- Extremely high temperatures inhibit sucrose and starch synthesis in Z. marina.
- Out of 223 identified differentially expressed genes 70 were upregulated.
- Glycolysis and the TCA cycle controlling genes and metabolites were upregulated.
Abstract
Extreme ocean events caused by global warming, such as marine heatwaves (MHWs) and ocean acidification (OA), are projected to intensify. A combination of extreme events may have severe consequences for marine ecosystems. Zostera marina was selected to understand how seagrass adapts to OA in extremely hot conditions. By combining morphology, transcriptomics, and metabolomics under mesoscale experimental conditions, we systematically investigated the response characteristics of Z. marina. Extremely high temperatures had a pronounced effect on growth, and the combined effect of OA mitigated the inhibitory effect of MHW. Both transcriptomic and metabolomic results showed that Z. marina resisted OA and MHW by upregulating the TCA cycle, glycolysis, amino acid metabolism, and relevant genes, as well as by activating the antioxidant system. The results of this study serve to improve our understanding of dual effects of factors of climate change on seagrass and may be used to direct future management and conservation efforts.
Continue reading ‘How does ocean acidification affect Zostera marina during a marine heatwave?’Examining the reproductive success of bull kelp (Nereocystis luetkeana, Phaeophyceae, Laminariales) in climate change conditions
Published 10 August 2023 Science ClosedTags: biological response, growth, laboratory, mortality, multiple factors, North Pacific, phanerogams, reproduction, temperature
Climate change is affecting marine ecosystems in many ways, including raising temperatures and leading to ocean acidification. From 2014 to 2016, an extensive marine heat wave extended along the west coast of North America and had devastating effects on numerous species, including bull kelp (Nereocystis luetkeana). Bull kelp is an important foundation species in coastal ecosystems and can be affected by marine heat waves and ocean acidification; however, the impacts have not been investigated on sensitive early life stages. To determine the effects of changing temperatures and carbonate levels on Northern California’s bull kelp populations, we collected sporophylls from mature bull kelp individuals in Point Arena, CA. At the Bodega Marine Laboratory, we released spores from field-collected bull kelp, and cultured microscopic gametophytes in a common garden experiment with a fully factorial design crossing modern conditions (11.63 ± 0.54°C and pH 7.93 ± 0.26) with observed extreme climate conditions (15.56 ± 0.83°C and 7.64 ± 0.32 pH). Our results indicated that both increased temperature and decreased pH influenced growth and egg production of bull kelp microscopic stages. Increased temperature resulted in decreased gametophyte survival and offspring production. In contrast, decreased pH had less of an effect but resulted in increased gametophyte survival and offspring production. Additionally, increased temperature significantly impacted reproductive timing by causing female gametophytes to produce offspring earlier than under ambient temperature conditions. Our findings can inform better predictions of the impacts of climate change on coastal ecosystems and provide key insights into environmental dynamics regulating the bull kelp lifecycle.
Continue reading ‘Examining the reproductive success of bull kelp (Nereocystis luetkeana, Phaeophyceae, Laminariales) in climate change conditions’Seasonal production dynamics of high latitude seaweeds in a changing ocean: implications for bottom-up effects on temperate coastal food webs
Published 10 August 2023 Science ClosedTags: algae, biological response, BRcommunity, calcification, chemistry, dissolution, field, growth, laboratory, light, morphology, multiple factors, North Pacific, otherprocess, phanerogams, photosynthesis, physiology, primary production, temperature
As the oceans absorb excess heat and CO2 from the atmosphere, marine primary producers face significant changes to their abiotic environments and their biotic interactions with other species. Understanding the bottom-up consequences of these effects on marine food webs is essential to informing adaptive management plans that can sustain ecosystem and cultural services. In response to this need, this dissertation provides an in-depth consideration of the effects of global change on foundational macroalgal (seaweed) species in a poorly studied, yet highly productive region of our world’s oceans. To explore how seaweeds within seasonally dynamic giant kelp forest ecosystems will respond to ocean warming and acidification, I employ a variety of methods: year-round environmental monitoring using an in situ sensor array, monthly subtidal community surveys, and a series of manipulative experiments. I find that a complementary phenology of macroalgal production currently characterizes these communities, providing complex habitat and a nutritionally diverse energy supply to support higher trophic levels throughout the year. I also find that future ocean warming and acidification will lead to substantial shifts in the phenology, quantity and quality of macroalgal production in these systems. My results suggest that the giant kelp Macrocystis pyrifera may be relatively resilient to the effects of global change in future winter and summer seasons at high latitudes. In contrast, the calcifying coralline algae Bossiella orbigniana and Crusticorallina spp. and the understory kelps Hedophyllum nigripes and Neoagarum fimbriatum will experience a suite of negative impacts, especially in future winter conditions. The resulting indirect effects on macroalgal-supported coastal food webs will be profound, with projected reductions in habitat and seasonal food supply on rocky reefs. Coming at a time of heightened interest in seaweed production potential at high latitudes, this dissertation provides a comprehensive evaluation of the future of these foundational organisms in a changing environment.
Continue reading ‘Seasonal production dynamics of high latitude seaweeds in a changing ocean: implications for bottom-up effects on temperate coastal food webs’Seagrass Thalassia hemprichii and associated bacteria co-response to the synergistic stress of ocean warming and ocean acidification
Published 21 July 2023 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, phanerogams, photosynthesis, physiology, prokaryotes, temperature
Seagrass meadows play vital ecological roles in the marine ecosystem. Global climate change poses considerable threats to seagrass survival. However, it is unclear how seagrass and its associated bacteria will respond under future complex climate change scenarios. This study explored the effects of ocean warming (+2 °C) and ocean acidification (−0.4 units) on seagrass physiological indexes and bacterial communities (sediment and rhizosphere bacteria) of the seagrass Thalassia hemprichii during an experimental exposure of 30 days. Results demonstrated that the synergistic effect of ocean warming and ocean acidification differed from that of one single factor on seagrass and the associated bacterial community. The seagrass showed a weak resistance to ocean warming and ocean acidification, which manifested through the increase in the activity of typical oxidoreductase enzymes. Moreover, the synergistic effect of ocean warming and ocean acidification caused a significant decrease in seagrass’s chlorophyll content. Although the bacterial community diversity exhibited higher resistance to ocean warming and ocean acidification, further bacterial functional analysis revealed the synergistic effect of ocean warming and ocean acidification led to significant increases in SOX-related genes abundance which potentially supported the seagrass in resisting climate stress by producing sulfates and oxidizing hydrogen sulfide. More stable bacterial communities were detected in the seagrass rhizosphere under combined ocean warming and ocean acidification. While for one single environmental stress, simpler networks were detected in the rhizosphere. In addition, the observed significant correlations between several modules of the bacterial community and the physiological indexes of the seagrass indicate the possible intimate interaction between seagrass and bacteria under ocean warming and ocean acidification. This study extends our understanding regarding the role of seagrass associated bacterial communities and sheds light on both the prediction and preservation of the seagrass meadow ecosystems in response to global climate change.
Continue reading ‘Seagrass Thalassia hemprichii and associated bacteria co-response to the synergistic stress of ocean warming and ocean acidification’The effect of differences pH of waters on the growth rate of seagrass of Cymodocea rotundata (in Indonesian)
Published 20 July 2023 Science ClosedTags: biological response, growth, laboratory, phanerogams, physiology, South Pacific
The continued use of fossil fuels will increase the concentration of carbon dioxide (CO2) in the atmosphere. Ocean acidification occurs due to CO2 in the atmosphere diffusing into the oceans. The oceans are able to absorb CO2 in the atmosphere as much as 35 % more which causes a decrease in ocean pH. Seagrass Cymodocea rotundata is a type of seagrass that can be found growing in tropical waters. This situation raises concerns about the possible impact on the growth of seagrass C. rotundata. This study aims to analyze the content of nitrate, phosphate and potassium and the growth of seagrass C. rotundata which includes the growth of leaves, rhizomes and roots of C. rotundata against differences in pH. The study used an experimental method with a completely randomized design using a random table. A total of 15 jars with a diameter of 20 cm and a height of 25 cm were used with 3 treatments, each treatment was repeated 5 times. The results of the linear regression test showed that pH had an effect on nitrate concentrations, and had a strong effect on phosphate and potassium concentrations. The highest growth rate of C. rotundata seagrass leaves in the control ranged from 0.50–1.29 mm/day while the lowest at low pH ranged from 0.07–0.73 mm/day. The growth rate of seagrass rhizomes horizontally and vertically was highest at low pH while the lowest was at control pH. The highest growth rate of seagrass roots at low pH ranged from 0.20–0.90 mm/day. while the lowest was in the control ranged from 0.13–0.43 mm/day. pH also affects the growth rate of leaves, rhizomes and seagrass roots of C. rotundata. The lower the pH, the lower the leaf growth rate, in contrast to rhizomes and roots, the lower the pH, the higher the growth rate.
Continue reading ‘The effect of differences pH of waters on the growth rate of seagrass of Cymodocea rotundata (in Indonesian)’The potential role of Posidonia oceanica for mitigating acidification on coastal waters of Europe
Published 12 July 2023 Science ClosedTags: biogeochemistry, biological response, chemistry, field, Mediterranean, mitigation, phanerogams, review
Ocean acidification is a major environmental concern that has significant ecological., economic, and social implications. The plantation and restoration of seagrass meadows in coastal waters, specifically Posidonia oceanica, is one possible method to combat ocean acidification and has the potential to have a significant positive impact on the marine environment and the overall state of the biosphere. As there has been a decline of Posidonia oceanica of about 30% in the Mediterranean Sea over the past three decades to about 1.2 mio ha in the Mediterranean Sea, the positive effects of the sea grass have diminished due to anthropogenic influence. Still, its importance as a carbon sink should not be underestimated. By using recent literature and different studies that have been analysed of the capacity of sea grass to mitigate the impacts of ocean acidification and the effects on the marine ecosystems, supported by several experiments that have been conducted, this thesis demonstrated the importance of Posidonia oceanica. The experiments showed that seagrass ecosystems have higher pH than ecosystems without seagrass, with a mean difference of 0.43. As the pH is interlocked with the CO2-levels and the oxygen levels, also experiments on these factors have been conducted. In general, the concentration of oxygen with P. oceanica present is 2mg/L higher than without. Equally, the CO2 concentration was lower with P. oceanica present. The Posidonia oceanica meadows present in the Mediterranean Sea are able to fixate about 13,3 mio tons of CO2, which is equal to 0,3% of Europeans CO2 emissions. About 2,8 mio tons of CO2 are sequestered by the sea grass, which is about 0,07% of European CO2 emissions. Furthermore, recent plantation efforts show the successful restoration of seagrass meadows and their overall benefits for the regional environment. Overall, this paper provides valuable insights into the potential role of seagrass meadows in mitigating ocean acidification and improving marine biosystems while providing specific numbers to support its findings.
Continue reading ‘The potential role of Posidonia oceanica for mitigating acidification on coastal waters of Europe’Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves
Published 5 June 2023 Science ClosedTags: abundance, annelids, biological response, BRcommunity, chemistry, cnidaria, community composition, crustaceans, echinoderms, Indian, mollusks, otherprocess, phanerogams, phytoplankton, primary production, review, socio-economy
Highlights
- Overfishing and climate change show potential effects on MMI ES.
- MMI regulating ES can be quantified using species richness and functional traits.
- Digital platforms are valuable tools to retrieve data but have limitations.
- Baseline data and information on environmental changes and MMI ES is provided.
Abstract
This study aimed to investigate the impact of changing environmental conditions on MMI ES in seagrasses and mangroves. We used data from satellite and biodiversity platforms combined with field data to explore the links between ecosystem pressures (habitat conversion, overexploitation, climate change), conditions (environmental quality, ecosystem attributes), and MMI ES (provisioning, regulation, cultural). Both seagrass and mangrove extents increased significantly since 2016. While sea surface temperature showed no significant annual variation, sea surface partial pressure CO2, height above sea level and pH presented significant changes. Among the environmental quality variables only silicate, PO4 and phytoplankton showed significant annual varying trends. The MMI food provisioning increased significantly, indicating overexploitation that needs urgent attention. MMI regulation and cultural ES did not show significant trends overtime. Our results show that MMI ES are affected by multiple factors and their interactions can be complex and non-linear. We identified key research gaps and suggested future directions for research. We also provided relevant data that can support future ES assessments.
Continue reading ‘Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves’Acidification alters sediment nitrogen source-sink dynamics in eelgrass (Zostera marina (L.)) beds
Published 9 May 2023 Science ClosedTags: biogeochemistry, biological response, BRcommunity, laboratory, morphology, nitrogen fixation, North Atlantic, phanerogams, physiology, prokaryotes, sediment
Dissolved carbon dioxide (CO2) in seawater lowers water pH and can disrupt microbial nutrient cycles. It is unclear how acidification impacts hot spots of nutrient cycling in marine ecosystems such as eelgrass (Zostera marina) beds. We measured nutrient and gas fluxes in sediment cores from Z. marina beds and unvegetated-sediment habitats in Shinnecock Bay, New York, USA in a continuous-flow system with acidified and ambient pH treatments. Under ambient conditions, uptake of N2 by nitrogen (N) fixation was greater than production of N2 by denitrification. Denitrification, however, was dominant under acidified conditions. We then enriched flowing seawater with 15NO3− to test the impact of a nutrient pulse with ambient pH or acidified conditions in the eelgrass and unvegetated cores. Sediment N2 efflux was higher in eelgrass than unvegetated sediments under acidified pH with N-enriched treatments. Results suggest that eelgrass beds may serve as sinks rather than sources of N under the combined stressors of acidification and N-loading. Documenting changes to N pathways under acidification can inform efforts to manage marine ecosystems and conserve benthic habitats.
Continue reading ‘Acidification alters sediment nitrogen source-sink dynamics in eelgrass (Zostera marina (L.)) beds’Field development of Posidonia oceanica seedlings changes under predicted acidification conditions
Published 27 March 2023 Science ClosedTags: biological response, laboratory, Mediterranean, morphology, phanerogams, physiology, reproduction, vents
Ocean acidification has been consistently evidenced to have profound and lasting impacts on marine species. Observations have shown seagrasses to be highly susceptible to future increased pCO2 conditions, but the responses of early life stages as seedlings are poorly understood. This study aimed at evaluating how projected Mediterranean Sea acidification affects the survival, morphological and biochemical development of Posidonia oceanica seedlings through a long-term field experiment along a natural low pH gradient. Future ocean conditions seem to constrain the morphological development of seedlings. However, high pCO2 exposures caused an initial increase in the degree of saturation of fatty acids in leaves and then improved the fatty acid adjustment increasing unsaturation levels in leaves (but not in seeds), suggesting a nutritional compound translocation. Results also suggested a P. oceanica structural components remodelling which may counteract the effects of ocean acidification but would not enhance seagrass seedling productivity.
Continue reading ‘Field development of Posidonia oceanica seedlings changes under predicted acidification conditions’Climate change amelioration by marine producers: does dominance predict impact?
Published 13 January 2023 Science ClosedTags: biological response, BRcommunity, chemistry, community composition, mitigation, multiple factors, North Pacific, otherprocess, phanerogams, photosynthesis, temperature
Climate change threatens biodiversity worldwide, and assessing how those changes will impact communities will be critical for conservation. Dominant primary producers can alter local-scale environmental conditions, reducing temperature via shading and mitigating ocean acidification via photosynthesis, which could buffer communities from the impacts of climate change. We conducted two experiments on the coast of southeastern Alaska to assess the effects of a common seaweed species, Neorhodomela oregona, on temperature and pH in field tide pools and tide pool mesocosms. We found that N. oregona was numerically dominant in this system, covering >60% of habitable space in the pools and accounting for >40% of live cover. However, while N. oregona had a density-dependent effect on pH in isolated mesocosms, we did not find a consistent effect of N. oregona on either pH or water temperature in tide pools in the field. These results suggest that the amelioration of climate change impacts in immersed marine ecosystems by primary producers is not universal and likely depends on species’ functional attributes, including photosynthetic rate and physical structure, in addition to abundance or dominance.
Continue reading ‘Climate change amelioration by marine producers: does dominance predict impact?’Posidonia bonsai: dwarf Posidonia oceanica shoots associated to hydrothemal vent systems (Panarea Island, Italy)
Published 11 January 2023 Science ClosedTags: biological response, field, Mediterranean, morphology, phanerogams, vents
Highlights
- Dwarf Posidonia oceanica (bonsai) observed in hydrothermal vents off Panarea.
- Bonsai shoots are from 61–75% smaller in leaf biomass than regular-sized shoots
- Bonsai shoots lacks the regular seasonal pattern in sheath thickness (lepidochronology) of normal-sized shoots
Abstract
Very small-sized shoots of the Mediterranean seagrass Posidonia oceanica, defined as “bonsai” shoots, were found in areas with most intense CO2 emissions and low pH associated with four vents systems off Panarea island (Aeolian Archipelago, Sicily, Southern Tyrrhenian Sea). Bonsai shoots were sampled in September 2021 and October 2022: Bottaro crater (8 m depth), Camp 7 (16 m and 21 m), Black Point (20 m) and Hot/Cold Points (10 m). They had 2–6 leaves, and adult-intermediate leaves were 5–21 cm long and 3.5–7 mm wide, with leaf shoot surface ranging 4.8 and 44.5 cm2, and shoot leaf biomass between 16 and 89 mg (d.w.). These values were all significantly lower (t-test p < 0.006–0.0001) than those measured in normal-sized shoots collected within the vents and in control sites not affected by gas emissions. Bonsai shoots had 86–89% lower leaf surface, and 61–75% lower leaf biomass than all normal-sized shoots measured. The sheath thickness of the bonsai shoots was very low (0.1–0.8 mm), and the temporal trend of sheath thickness along the rhizome (lepidochronology) showed an irregular pattern, without the clear cyclical seasonal variation typical of normal-sized shoots. The reasons of size reduction and lack of temporal cycle in lepidochronology are discussed in the light of plant acclimatization and the constraints imposed by the continuous exposure to the stressful conditions of seawater acidification and presence of phytotoxic gases (e.g. hydrogen sulfide) in the vents.
Continue reading ‘Posidonia bonsai: dwarf Posidonia oceanica shoots associated to hydrothemal vent systems (Panarea Island, Italy)’Photorespiration in eelgrass (Zostera marina L.): a photoprotection mechanism for survival in a CO2-limited world
Published 17 November 2022 Science ClosedTags: biological response, laboratory, phanerogams, photosynthesis, physiology
Photorespiration, commonly viewed as a loss in photosynthetic productivity of C3 plants, is expected to decline with increasing atmospheric CO2, even though photorespiration plays an important role in the oxidative stress responses. This study aimed to quantify the role of photorespiration and alternative photoprotection mechanisms in Zostera marina L. (eelgrass), a carbon-limited marine C3 plant, in response to ocean acidification. Plants were grown in controlled outdoor aquaria at different [CO2]aq ranging from ~55 (ambient) to ~2121 μM for 13 months and compared for differences in leaf photochemistry by simultaneous measurements of O2 flux and variable fluorescence. At ambient [CO2], photosynthesis was carbon limited and the excess photon absorption was diverted both to photorespiration and non-photochemical quenching (NPQ). The dynamic range of NPQ regulation in ambient grown plants, in response to instantaneous changes in [CO2]aq, suggested considerable tolerance for fluctuating environmental conditions. However, 60 to 80% of maximum photosynthetic capacity of ambient plants was diverted to photorespiration resulting in limited carbon fixation. The photosynthesis to respiration ratio (PE: RD) of ambient grown plants increased 6-fold when measured under high CO2 because photorespiration was virtually suppressed. Plants acclimated to high CO2 maintained 4-fold higher PE: RD than ambient grown plants as a result of a 60% reduction in photorespiration. The O2 production efficiency per unit chlorophyll was not affected by the CO2 environment in which the plants were grown. Yet, CO2 enrichment decreased the light level to initiate NPQ activity and downregulated the biomass specific pigment content by 50% and area specific pigment content by 30%. Thus, phenotypic acclimation to ocean carbonation in eelgrass, indicating the coupling between the regulation of photosynthetic structure and metabolic carbon demands, involved the downregulation of light harvesting by the photosynthetic apparatus, a reduction in the role of photorespiration and an increase in the role of NPQ in photoprotection. The quasi-mechanistic model developed in this study permits integration of photosynthetic and morphological acclimation to ocean carbonation into seagrass productivity models, by adjusting the limits of the photosynthetic parameters based on substrate availability and physiological capacity.
Continue reading ‘Photorespiration in eelgrass (Zostera marina L.): a photoprotection mechanism for survival in a CO2-limited world’
