Posts Tagged 'phanerogams'

Posidonia bonsai: dwarf morphotypes of Posidonia oceanica in CO2 vents and non-vents areas suggest a novel growth strategy

Published 10 December 2025 Science Leave a Comment
Tags: , , , , ,

Highlights

  • Dwarf Posidonia oceanica shoots occur in vents and no-vents areas at Ischia, Palinuro and Ustica.
  • Dwarf shoots have a biomass reduced from 82 % to 97 % than normal-sized shoots.
  • Bonsai shoots also lack cyclic annual sheath-thickness pattern (lepidochronology).
  • Bonsai shoots occur in dead matte areas of the meadows, or behind regular terminal shoots.
  • Bonsai shoots suggest a novel growth strategy, likely to favour rapid substrate colonization.

Abstract

Dwarf shoots of the Mediterranean seagrass Posidonia oceanica, referred to as “Posidonia bonsai”, described in shallow hydrothermal vents, showed markedly reduced size and altered phenology, that were attributed to the extreme environmental conditions associated with ocean acidification and H2S emissions of these vent systems. Here we report new records of Posidonia “bonsai” from CO2 vent off the Ischia Island and non-vent areas with normal pH conditions at Ischia, and Ustica islands and at Palinuro. At Ustica and Palinuro, bonsai shoots we found exclusively on rocky bottoms, while at Ischia they occurred on the dead P. oceanica matte, both within vent systems and in control areas. Bonsai shoots exhibited a reduced number of leaves, significantly shorter leaf length and width, resulting in a drastic reduction of total leaf surface area (84–95 % lower) and biomass (82–97 % lower) compared to nearby regular-sized shoots. In addition, bonsai shoots lacked the typical annual cycle of leaf sheath thickness observed in normal shoots (lepidochronological cycle), as previously observed in bonsai from other sites. The high number of sheaths recorded per rhizome length, suggests high leaf production and turnover. The occurrence of bonsai shoots on dead matte at the meadow margins and in small clearings, or behind regular terminal shoots on creeping rhizomes in hard bottoms, leads to hypothesize that Posidonia bonsai represents a novel growth and colonization strategy, probably trigged by stressful conditions, not limited to ocean acidification, and point out the remarkable phenotypic plasticity of this seagrass.

Continue reading ‘Posidonia bonsai: dwarf morphotypes of Posidonia oceanica in CO2 vents and non-vents areas suggest a novel growth strategy’

Can ocean acidification alleviate carbon deficiency in eelgrass Zostera marina clonal ramets under conditions of nutrients, sulfate and ocean acidification?

Published 16 October 2025 Science Closed
Tags: , , , , , , ,

Highlights

  • The ratio of Chl a/b is reduced by the interaction between CO2 and NO3-N.
  • The interaction between CO2 and NO3-N reduces the soluble sugar contents in leaves.
  • CO2 promotes the content of soluble protein in leaves while reduces that in roots.
  • CO2 reduces both the SOD activities of the rhizomes and the eelgrass mortality rate.
  • Eelgrass has complex carbon supply and conversion mechanisms to ensure its survival.

Abstract

Carbon deficiency in the eelgrass caused by nutrient eutrophication and high concentrations of sulfate causes eelgrass mortality; however, ocean acidification provides sufficient carbon. Thus, it is inferred that ocean acidification might reduce the carbon deficiency. To verify this hypothesis, eelgrass clonal ramets were exposed to 72—h combined conditions of ocean acidification (CO2), nitrate (NO3-N), ammonia (NH4-N), phosphate (PO4-P) and sulfate (SO4-S). The pigment contents were affected by nutrients; however, the Chl a/b ratio was inhibited by the interaction between CO2 and NO3-N and was promoted by interaction between NO3-N and NH4-N. The soluble protein contents in leaves were increased by CO2; however, the soluble protein contents in roots were reduced by CO2. The soluble sugar contents in the leaves had negatively correlation with the interaction between NO3-N and CO2. Moreover, the SOD activities of the rhizomes were inhibited by CO2. All these findings suggest that ocean acidification does not seem to effectively alleviate the deficiency of soluble carbon in eelgrass under eutrophication and high concentrations of sulfate; however, the eelgrass mortality rate was inhibited by CO2 and the interaction between PO4-P and SO4-S. Thus, eelgrass has extremely complex carbon supply and conversion mechanisms to ensure its survival under composite conditions or eelgrass has another mechanism of death in eutrophication.

Continue reading ‘Can ocean acidification alleviate carbon deficiency in eelgrass Zostera marina clonal ramets under conditions of nutrients, sulfate and ocean acidification?’

In-situ measurements reveal alkalinity release from cold-temperate seagrass meadows

Published 25 September 2025 Science Closed
Tags: , , , , ,

Highlights

  • Cold-temperate seagrass meadows are net sources of alkalinity
  • Alkalinity generation exceeds soil organic carbon accumulation by fourfold
  • Seagrasses buffer ocean acidification locally during the day
  • Alkalinity generation in seagrasses is lower than in mangroves and saltmarshes

Abstract

Understanding the carbon sequestration potential of blue carbon ecosystems is important to inform climate policies and to guide restoration and protection efforts. Alkalinity generation is an often overlooked carbon sequestration mechanism, especially in seagrass meadows. Here, we quantified total alkalinity (TA) and dissolved inorganic carbon (DIC) fluxes in two cold-temperate Zostera marina seagrass meadows in Sweden using 24-hour in-situ chamber incubations at the end of the high-productivity season. The seagrass meadows were similar net sources of TA (16 ± 45 mmol m-2 d-1 in Smalsund, 17 ± 16 mmol m-2 d-1 in Bökevik), whereas DIC fluxes were highly variable (34 ± 59 mmol m-2 d-1 in Smalsund, -43 ± 35 mmol m-2 d-1 in Bökevik). Fluxes followed a diurnal cycle consistent with photosynthesis-respiration cycles. As a result, seagrass meadows ameliorated ocean acidification locally during the day, but not during the night. The large CO2 uptake provided higher buffering levels compared to mangroves and saltmarshes. The TA fluxes were comparable to those reported for Mediterranean and tropical seagrass meadows, but 16-times lower than in mangrove forests and 5-times lower than in saltmarshes. Alkalinity generation in these cold-temperate seagrasses exceeded soil organic carbon stocks accumulation by fourfold, potentially contributing to their carbon sequestration potential and warranting inclusion in seagrass meadow carbon budgets.

Continue reading ‘In-situ measurements reveal alkalinity release from cold-temperate seagrass meadows’

Short-term and long-term ocean acidification effects on seagrass performance: evidence from shallow CO2 vents

Published 8 August 2025 Science Closed
Tags: , , , , , ,

Highlights

  • Cymodocea nodosa performance under in-situ ocean acidification has been evaluated.
  • Morphology of long-term acidified plants does not differ from that of control plants.
  • Higher performance was found in short-term acidified plants.
  • The response of apical shoots was particularly enhanced.
Continue reading ‘Short-term and long-term ocean acidification effects on seagrass performance: evidence from shallow CO2 vents’

Mangrove-driven acidification and shell dissolution on intertidal oyster reefs in a subtropical estuary

Published 4 August 2025 Science Closed
Tags: , , , , , , , ,

Tropicalization, resulting from warmer minimum temperatures, has allowed mangroves to expand poleward and increase in abundance in historical ranges. Since 1984, mangrove abundance on intertidal oyster reefs in Mosquito Lagoon, Florida, USA, has increased by 198% due to tropicalization. Oysters provide abundant ecosystem services including engineering reef habitat and water filtration, but shells are prone to dissolution in acidic conditions. Mangroves are associated with soil acidification and therefore may alter the pH of oyster reef sediment. The goal of this research was to determine if mangroves acidify oyster reef porewater (i.e. water within the sediment) and determine if mangrove-correlated acidification caused oyster shell dissolution as indicated by shell mass loss. Porewater, up to 10 cm depth, was collected monthly for 2 yr, and the pH was compared between 4 habitats: mudflats, oyster-dominated reefs (oyster reefs), transitioning reefs (oyster reefs with mangroves), and mangrove-dominated sites (mangrove islands). Porewater was more acidic with mangroves present. Transitioning reefs had a mean pH of 7.13 compared to oyster-dominated reefs (mean pH: 7.52). To measure shell dissolution, bags containing 10 pre-weighed oyster shells were deployed and re-weighed after 6, 12, and 24 mo. After 24 mo, mangrove-dominated sites lost more shell mass (8% loss) compared to oyster-dominated sites (1% loss). Transitioning reefs had intermediate shell mass loss. Combined, these data suggest that mangrove expansion on intertidal oyster reefs can negatively impact oysters. With oyster reef habitats in global decline, understanding new sources of degradation, including mangrove-driven acidification, is crucial to supporting conservation and restoration efforts.

Continue reading ‘Mangrove-driven acidification and shell dissolution on intertidal oyster reefs in a subtropical estuary’

Impact of ocean acidification on fish health and marine ecosystem dynamics

Published 11 July 2025 Science Closed
Tags: , , , , , , , ,

Ocean acidification (OA) causes an increase in carbon dioxide (CO2) and a reduction in the pH of ocean waters. This chapter reviews the current literature to investigate the adverse effects of OA on fish health and marine ecosystem dynamics. OA poses serious threats to marine biodiversity and ecosystem dynamics. Fish experience severe physiological problems such as impaired growth, development, tissue damage, Impaired behavioral changes, sensory and brain functions, and disruption in predator-prey interactions due to acidification with a 74% decline in survival rates of egg and larval stages. Besides affecting fish, OA also affects marine ecosystem dynamics: reducing calcification rates in calcifying species, increasing seagrass production, causing effects on habitat-forming species, and disrupting the food web. Vulnerable species, such as coral reef fish, show high sensitivity, risking the stability of their habitats. The United Nations recognized the OA as a threat to marine biodiversity through the Convention on Biodiversity. The future research needs to focus on understanding fish and marine animals’ adaptive mechanisms to OA, its interaction with other stressors, and global collaboration to address the underlying causes of OA.

Continue reading ‘Impact of ocean acidification on fish health and marine ecosystem dynamics’

Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings 

Published 8 July 2025 Science Closed
Tags: , , , , , , , , , , ,

Ocean acidification (OA) and marine heatwaves (MHWs) are key drivers of marine ecosystem changes that can interact and influence marine organisms. Seagrasses, including the long-lived Posidonia oceanica endemic to the Mediterranean Sea, are widely distributed along coastal habitats, forming highly valuable underwater meadows. The germination and survival of the early life stages of P. oceanica are strongly affected by environmental changes. To assess the impact of warming and acidification on its future, we conducted a multifactorial experiment where P. oceanica seedlings were grown under OA conditions for six months and then exposed to a seawater warming event. Seedlings’ performance was investigated by analyzing photo-physiology, antioxidant capacity, energetic metabolism and transcriptomic profiles. The Weighted Gene Correlation Network Analysis (WGCNA) was used to integrate phenotypic plant traits with transcriptomic results to identify central genes involved in plant responses to OA and temperature exposure. Results demonstrated that prolonged OA exposure enhances P. oceanica seedling resilience to MHW. Specifically, seedlings regulated their antioxidant systems and transcriptomic machinery to better cope with thermal stress. Under current CO2 concentrations, elevated temperatures induced stress in P. oceanica seedlings, impacting photosynthesis and respiration. However, OA could mitigate the impact of warming in the future, enhancing P. oceanica‘s resilience to global stressors.

Continue reading ‘Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings ‘

Seaweed responses to ocean acidification: global impacts on growth, biochemical composition, and CO2 mitigation potential

Published 3 July 2025 Science Closed
Tags: , , , ,

Ocean acidification, driven by the absorption of elevated atmospheric CO2 levels, significantly affecting the growth and nutritional composition of marine biota, including seaweeds. The increasing expansion of the cultivation of seaweed is a promising method for removing carbon dioxide through both government and private sectors. There are notable comprehensive assessments that evaluated the effectiveness of seaweed farming to achieve significant climate change mitigation and it ended with positive outcome. Hence the present article reviews about the global impacts of ocean acidification on seaweed communities including growth dynamics, nutritional trends, and their potential for CO2 mitigation. The ecological consequences of ocean acidification and providing an overview of its status. Amplified CO2 levels affect seaweed physiology and ecosystem dynamics that have an influence on biodiversity, carbon cycling, and nutrient flows. The review highlights the trends in seaweed growth under elevated CO2 conditions, through identification of both opportunities and challenges for maintenance of productivity and nutritional quality. Seaweeds exhibit potential for CO2 sequestration, that whorls to offset carbon emissions through aquaculture practices. Furthermore, integrated seaweed farming practices can enhance environmental benefits, such as biodiversity conservation, nutrient remediation, and improved carbon storage. Finally, yet importantly this article emphasizes the necessity for targeted research that aimed at optimization of seaweed cultivation techniques, decipher species-specific responses to ocean acidification, and leveraging biotechnological advancements for maximation in mitigation of CO2. The findings underscore the role of seaweed aquaculture as a sustainable strategy to combat climate change and protect marine ecosystems.

Continue reading ‘Seaweed responses to ocean acidification: global impacts on growth, biochemical composition, and CO2 mitigation potential’

Biophysical model of eelgrass and water quality in Coos Bay, OR shows greater mitigation potential for ocean acidification than hypoxia

Published 30 June 2025 Science Closed
Tags: , , , , , ,

Seagrass beds provide important ecosystem services and are valued, in part, for their potential to mediate stressors such as ocean acidification and hypoxia (OAH) for sensitive species. However, the susceptibility of seagrasses to anthropogenic impacts and recent declines motivate the need to better understand the drivers of seagrass and the water quality consequences that occur with variation in seagrass abundance. To meet this need, we leveraged existing monitoring data (water quality and seagrass), hydrodynamic circulation model, and biogeochemical model framework with seagrass submodel, to produce a biophysical model of Coos Bay estuary, Oregon, U.S. The model includes biogeochemical processes involving water quality, plankton, seagrass, and sediment-water interactions. Ecosystem models like this are useful for evaluating complex estuarine systems because they allow us to extend our understanding of system dynamics beyond existing observations and perform experiments to identify the processes driving observed patterns. We used the biophysical model of Coos Bay to evaluate the dynamics of water quality and native eelgrass (Zostera marina) under three eelgrass abundance scenarios (zero eelgrass, current extent, and maximum observed extent) to elucidate the relationship between eelgrass and OAH. Including eelgrass in the Coos Bay model produced results that more closely resembled water quality observations – dissolved oxygen (DO) and pH were more dynamic in simulations with eelgrass, often having both higher highs and lower lows. While there were some areas of the estuary where DO improved with the addition of eelgrass to the model there was overall a small net increase in harmful DO conditions (based on a salmon physiological threshold). In contrast, ocean acidification conditions, pH and calcium carbonate saturation state for aragonite (Ω), were improved (based on oyster requirements) with the addition of eelgrass – although the magnitude of improvement differed seasonally and spatially. Our new model represents a useful tool – one which accounts for and controls the relevant physical and biogeochemical processes – to evaluate conditions that confer resilience or enhance vulnerability to OAH in an important Pacific Northwest coastal estuary and results can inform the OAH-related dynamics occurring in other eastern boundary current estuaries.

Continue reading ‘Biophysical model of eelgrass and water quality in Coos Bay, OR shows greater mitigation potential for ocean acidification than hypoxia’

Microbe-host associations as drivers of benthic carbon and nitrogen cycling in a changing Mediterranean Sea

Published 14 April 2025 Science Closed
Tags: , , , , , , , , ,

Seagrasses, such as the endemic Mediterranean species Posidonia oceanica, are critical components of coastal marine ecosystems, providing essential ecosystem services, including carbon sequestration, nutrient cycling, and habitat formation. P. oceanica forms extensive meadows that serve as biodiversity hotspots and play a crucial role in mitigating climate change through long-term carbon storage. Despite their ecological significance, the interactions between P. oceanica and associated organisms, as well as their combined contributions to biogeochemical cycling, remain poorly understood, particularly under changing environmental conditions. This thesis explores the carbon and nitrogen cycling processes within the P. oceanica holobiont, focusing on the epiphytic and microbial communities, microbial driven metabolic processes, and the interaction between P. oceanica and larger associated invertebrates, such as the sponge Chondrilla nucula. Through field and laboratory experiments, this work demonstrates the significant role of epiphytic algae in the primary production of the seagrass holobiont, contributing a substantial portion of net primary production. Nitrogen cycling processes such as N₂ fixation, nitrification, and denitrification in the seagrass phyllosphere were quantified, revealing their importance in meeting the N demands of the seagrass holobiont, especially under natural ocean acidification conditions. Experiments near marine CO₂ vents indicated that ocean acidification accelerates net primary production and nitrogen cycling, while the structure of the microbial community associated with P. oceanica leaves remains largely stable. The facultative mutualism between P. oceanica and the sponge C. nucula further highlights the complexity of the seagrass holobiont. P. oceanica releases dissolved organic carbon, which meets a portion of the sponge’s respiratory carbon demand. Conversely, C. nucula releases dissolved inorganic nitrogen, including ammonium and nitrate generated by microbial nitrification, which supports seagrass growth. Stable isotope analysis suggests that the association facilitates nutrient exchange, with P. oceanica preferentially absorbing sponge-derived ammonium, while epiphytes may benefit from sponge-produced nitrate. This dynamic reduces seasonal fluctuations in productivity, stabilizing the seagrass ecosystem during periods of senescence. Sponge-associated nitrification contributes to the nitrogen budget of the seagrass holobiont, potentially reducing nutrient limitations in oligotrophic Mediterranean waters. The microbiome of C. nucula plays a key role in these processes, harboring nitrifiers that mediate the production of nitrate. High-throughput sequencing revealed taxonomic diversity among microbes associated with both the sponge and seagrass, including microorganisms involved in carbon and nitrogen cycling processes. These microbial communities not only mediate nutrient exchange within the seagrass-sponge association but also contribute to the overall resilience and productivity of the ecosystem. This thesis highlights the intricate interactions within the P. oceanica holobiont and its nested ecosystem with C. nucula. These findings underscore the importance of microbial and epiphytic communities in maintaining the resilience and productivity of seagrass meadows, particularly in nutrient-poor environments like the Mediterranean Sea. This research enhances our understanding of the biogeochemical processes that support seagrass ecosystem stability and provides valuable insights to guide conservation efforts in the face of climate change and anthropogenic pressures.

Continue reading ‘Microbe-host associations as drivers of benthic carbon and nitrogen cycling in a changing Mediterranean Sea’

Thalassia hemprichii may benefit from ocean acidification and slightly increased salinity in the future

Published 13 February 2025 Science Closed
Tags: , , , , , , ,

Highlights

  • Thalassia hemprichii highly adapted to acidified environments.
  • The effect of elevated salinity on the physiology and growth of Thalassia hemprichii is not linearly.
  • Ocean acidification could further enhance the resilience of Thalassia hemprichii to high salinity.
  • Both acidification and slight salinity increased the photosynthetic activity of Thalassia hemprichii.

Abstract

Since the industrial revolution, the direct impacts of elevated CO2 concentrations, such as ocean acidification, and indirect impacts, such as extreme drought events, have synergistically influenced coastal ecosystems, including seagrass meadow. Consequently, investigating the individual and combined effects of ocean acidification and extreme drought-induced increased salinity on seagrasses is crucial for enhancing the management and monitoring of these ecosystems. This study used a two-factor crossover indoor simulation experiment to thoroughly examine the effects of seawater acidification at pH 7.7 and elevated salinity levels at 43‰ and 51‰ on the physiological responses and growth status of the dominant tropical seagrass species Thalassia hemprichii. The results indicated that seawater acidification at pH 7.7 significantly enhanced the growth rate and photosynthetic activity of T. hemprichii across all salinity levels. A salinity of 43‰ activated certain antioxidant enzymes without inducing severe osmotic stress in T. hemprichii and positively influenced leaf photosynthetic activity, with a 15.6% increase in growth rate compared to the CK group. The extreme salinity of 51‰ imposed osmotic stress, leading to increase in reactive oxygen species and decreased photosynthetic activity and a 52% decrease in growth rate compared to seagrasses in the CK group. Under future scenarios of ocean acidification and frequent extreme droughts, T. hemprichii inhabiting enclosed marine environments may exhibit greater adaptability and secure an ecologically competitive edge. Our findings underscore the importance of conserving declining meadows, forecasting the ecological trajectory of these ecosystems, and managing salinity in lagoons for the well-being of seagrass ecosystems.

Continue reading ‘Thalassia hemprichii may benefit from ocean acidification and slightly increased salinity in the future’

Global environmental change mediated response of wetland plants: evidence from past decades

Published 11 February 2025 Science Closed
Tags: , , ,

Highlights

  • Wetland plant research on climate change responses showed an upward trend.
  • Plant growth affected negatively by increase in CO2, temperature and sea level.
  • Extreme weather events harmed wetland plant landscapes.
  • Collaborative research is needed for sustainability of wetland plants

Abstract

Wetland ecosystems are critically affected by global environmental changes, yet understanding the impact of these changes on wetland plants remains a challenge. This review article employs a comprehensive approach, including bibliographic analysis, utilization of various climate models for historical data retrieval, and extensive literature survey, to investigate the response of wetland plants to environmental shifts over the past decades. The analysis conducted in this study uncovers a multitude of climatic parameters that exhibit an influence on the dynamics of wetland vegetation. Results indicated a significant positive trend in atmospheric CO2 concentration, leading to increased water use efficiency in some plant species, particularly C3 plants. However, C4 plants did not show the same positive response. Nitrous oxide growth rate showed a weaker, less consistent trend than CO2, highlighting the need for further investigation into the complex factors influencing Nitrous oxide emissions from wetlands. Methane growth rate and global mean sea level demonstrated a strong positive linear trend. Ocean pH exhibited a statistically significant downward trend (acidification), while sea surface temperature showed a moderate but statistically significant upward trend. Glacier mass balance revealed a significant negative trend. Although some plants may benefit from increased CO2 initially, but the combined effects of rising sea levels, ocean acidification, and temperature changes pose substantial threats to the overall health and diversity of wetland plant life.

Continue reading ‘Global environmental change mediated response of wetland plants: evidence from past decades’

Seagrass influence on mitigating ocean acidification and warming impacts on tropical calcifying macroalgae

Published 28 January 2025 Science Closed
Tags: , , , , , , , ,

Highlights

  • OA and warming reduce calcium carbonate for marine calcifiers.
  • Seagrass can capture excess carbon, possibly mitigating OA effects.
  • 12-week study tested algae with/without seagrass under increasing stress.
  • M. rosea was affected by OA and warming; H. opuntia by temperature alone.
  • Mesophyllum sp. was resilient, and seagrass did not reduce OA impacts.
  • Light, flow, combining OA and warming, likely to impact coralline algae

Abstract

Ocean acidification (OA) and warming pose significant threats to marine ecosystems, particularly by reducing calcium carbonate availability for marine calcifiers. Given that seagrasses can capture and store excess carbon, this study aimed to investigate whether seagrasses can mitigate the impacts of OA and elevated temperatures on three calcifying macroalgae: Mastophora rosea, Halimeda opuntia, and Mesophyllum sp. A 12-week mesocosm experiment was conducted, where the algae were cultured with and without seagrass under gradually increasing stress conditions: ambient conditions, OA alone for four weeks, OA combined with elevated (but non-stressful) temperatures (28°C) for four weeks, and OA plus a stress-inducing temperature (31°C) for two weeks. Results indicated that OA and warming negatively affected M. rosea, while H. opuntia was more strongly impacted by temperature alone. Mesophyllum sp. exhibited resilience to both OA and elevated temperatures. Contrary to expectations, the presence of seagrass did not mitigate the negative effects of OA and warming on these calcifying macroalgae species.

Continue reading ‘Seagrass influence on mitigating ocean acidification and warming impacts on tropical calcifying macroalgae’

Ocean acidification and global warming may favor blue carbon service in a Cymodocea nodosa community by modifying carbon metabolism and dissolved organic carbon fluxes

Published 9 January 2025 Science Closed
Tags: , , , , , , , , , , ,

Highlights

  • 45-days mesocosm experiment with whole-benthic community to mimic nature conditions
  • Global warming (GW) and ocean acidification (OA) modify C dynamics on seagrasses.
  • OA enhances GPP and NCP and synergistic effects when combined with GW.
  • DOC production decreased with OA and GW separately, but increased when combined.
  • Climate change potentially increases the blue carbon service of C. nodosa populations.

Abstract

Ocean acidification (OA) and global warming (GW) drive a variety of responses in seagrasses that may modify their carbon metabolism, including the dissolved organic carbon (DOC) fluxes and the organic carbon stocks in upper sediments. In a 45-day full-factorial mesocosm experiment simulating forecasted CO2 and temperature increase in a Cymodocea nodosa community, we found that net community production (NCP) was higher under OA conditions, particularly when combined with warming (i.e., synergistic effect). Moreover, under OA conditions, an increase in aboveground biomass and photosynthetic shoot area was recorded. Interestingly, DOC fluxes were reduced when exposed to OA; however, an increase occurred when both factors acted together (i.e., antagonistic effect), which was attributable to increased DOC release by plants. Our results suggest that C. nodosa populations in temperate latitude may favor blue carbon service in future scenarios of OA and GW by increasing the NCP, the DOC export with lower labile:recalcitrant ratio, and accumulating more organic carbon in upper sediments. These findings offer additional arguments for the urgent need to protect and conserve this valuable ecosystem.

Continue reading ‘Ocean acidification and global warming may favor blue carbon service in a Cymodocea nodosa community by modifying carbon metabolism and dissolved organic carbon fluxes’

Extreme abiotics drive sediment biocomplexity along pH gradients in a shallow submarine volcanic vent

Published 3 January 2025 Science Closed
Tags: , , , , , , , , , ,

Highlights

  • Shallow CO2 vents generate pH gradients that influence sediment biogeochemistry
  • Sedimentary organic matter (SOM) and prokaryotic community were analysed along a pH gradient
  • Environmental gradients drive distribution and abundance of benthic prokaryotic communities and origin of SOM
  • Vent-derived sources contributed largely to SOM up to 350 m from the vent
  • CO2-driven benthic community shifts affect spatial dynamics of SOM origin and composition with expected rebounds on biota

Abstract

Volcanic emissions in shallow vents influence the biogeochemistry of the sedimentary compartment, creating marked abiotic gradients. We assessed the spatial dynamics of the sediment compartment, as for the composition and origin of organic matter and associated prokaryotic community, in a volcanic shallow CO2 vent (Vulcano Island, Italy). Based on elemental (carbon, nitrogen content and their ratio) and isotopic composition (δ13C, δ15N and δ34S), the contribution of vent-derived organic matter (microbial mats) to sedimentary organic matter was high close to the vent, while the marine-derived end-members (seagrasses) contributed highly at increasing distance. Chemoautotrophic Campylobacterota and hyperthermophilic Achaea prevailed close to the vent, whilst phototrophic and chemoheterotrophic members dominated at increasing distance. Abiotic gradients generated by the volcanic CO2 vent drive relevant changes in the composition, origin and nutritional quality of sedimentary organic matter, and influence the structure and complexity of associated prokaryotic communities, with expected relevant impact on the entire food-web.

Continue reading ‘Extreme abiotics drive sediment biocomplexity along pH gradients in a shallow submarine volcanic vent’

Gene expression changes in the seagrass Cymodocea nodosa individuals in response to aquatic acidification

Published 2 January 2025 Science Closed
Tags: , , , , ,

Human activities have caused a rise in atmospheric carbon dioxide (CO2) levels, leading to greater absorption of CO2 by oceans and causing ocean acidification (OA). This phenomenon, marked by a reduction in pH, represents substantial risks to marine ecosystems, including seagrass meadows. Seagrasses are vital elements of coastal ecosystems, performing important functions in carbon storage, stabilizing shorelines, and preserving biodiversity; however, reactions to OA are not well understood, especially in molecular terms. This research study examined alterations in gene expression within seagrass meadows, namely Cymodocea nodosa, in reaction to simulated OA conditions. A climate chamber system was used to adjust CO2 levels to simulate future projections of OA, specifically following the RCP 8.5 scenario. Gene expression dynamics were assessed by collecting samples at different time intervals across a 36-h period. Research has demonstrated that genes related to photosynthesis are suppressed quickly after being exposed to increased amounts of CO2. Gene expression levels were found to change often over time, which is crucial for adaptation and acclimatization. However, antioxidant genes have varied responses to OA, with CAT and SOD being downregulated in distinct ways. Our findings offer valuable insights into the molecular mechanisms of seagrass responses to OA. They highlight the significance of examining short-term responses when evaluating the susceptibility of coastal ecosystems to climate change.

Continue reading ‘Gene expression changes in the seagrass Cymodocea nodosa individuals in response to aquatic acidification’

Local effects of Sargassum beds on the seawater carbonate system and plankton community

Published 30 December 2024 Science Closed
Tags: , , , , , , , , ,

Highlights

  • The ecological effect of the sargassum beds depends on seaweed biomass.
  • The biomass of the sargassum beds in Weizhou Island reached its peak in spring.
  • Sargassum beds significantly influenced the carbonate system and DOC pool in spring.
  • Sargassum beds is more likely to alter phytoplankton communities than zooplankton.

Abstract

Sargassum beds are recognized as important habitats for fostering species diversity and capturing blue carbon, exerting significant influence on seawater chemistry and planktonic communities. However, there is still much to uncover about the interactions between these biogenic habitats and seawater chemistry, as well as their impact on plankton communities in the water column. To address this gap, we conducted a study on the functions of natural Sargassum beds in various seasons around the northern part of Weizhou Island in the South China Sea. Our research involved quantifying carbonate chemistry, carbon stock potential, and seawater plankton communities in two distinct areas: the core area in the interior regions of the seaweed beds and the non-core areas at its periphery or external. Our findings revealed an estimated 3.7 km2 of benthic Sargassum, with an overall biomass of 21.2 Gg km−2, reaching its peak productivity in spring, equivalent to 1.14 Pg C km−2. Notably, during spring, the seaweed beds significantly influenced the exchange of CO2 at the air-sea interface, leading to reduced pCO2 (41 μatm) in the core area compared to the non-core area (p < 0.05), thus enhancing the local carbon sequestration capacity. Additionally, we observed significant regional differences in the concentration of dissolved organic carbon (DOC) only during the spring season, indicating the capacity of Sargassum to alter the DOC pool around its habitat. We anticipate that seaweed deposition will become a more frequent occurrence towards the end of the growth period, with increasing fragments facilitating a transition towards phytoplankton-dominated marine ecosystems. Furthermore, the fixation of extra CO2 by seaweed may lead to a pH increase, providing a refuge for copepods from ocean acidification. In summary, our observations suggest that the Sargassum beds plays a substantial role in nearshore carbon cycling and ecological impact, surpassing previous documentation.

Continue reading ‘Local effects of Sargassum beds on the seawater carbonate system and plankton community’

Coexisting mangrove-coral habitats: trends in seawater chemistry and coral diversity

Published 20 December 2024 Science Closed
Tags: , , , , , , ,

Coral reefs face unprecedented threats from climate change, with rising temperatures, ocean acidification, and other stressors endangering their survival. Coexisting mangrove-coral (CMC) habitats provide a natural laboratory to study coral resilience under extreme conditions. However, these habitats are rare and understudied, leaving gaps in understanding their biogeochemical and ecological dynamics. This thesis examines how mangrove proximity influences seawater chemistry, coral diversity, and morphology. A global review identified differences in seawater chemistry between habitat types and regions, driven by biogeochemical processes and freshwater inputs. Edge habitats, particularly in the Great Barrier Reef (GBR), were identified as understudied. An empirical study at Pioneer Bay, GBR, revealed significant spatial and temporal variations in seawater chemistry along a gradient from mangroves to open reefs. Corals near mangroves experienced greater fluctuations in pH, temperature, and oxygen, stabilizing with distance. Tidal flushing mitigated extremes, fostering coral resilience. Mangrove proximity significantly influenced benthic communities, coral morphology, and biodiversity. Extreme conditions near mangroves favored resilient corals like *Porites*, while intermediate sites supported the highest diversity due to nutrient influx and moderate disturbances. Farther sites were dominated by complex coral communities. Edge CMC habitats play a vital role in supporting coral adaptation to climate change. However, intensifying stressors threaten even resilient systems, underscoring the need for long-term monitoring and adaptive management to protect these critical biodiversity hotspots.

Continue reading ‘Coexisting mangrove-coral habitats: trends in seawater chemistry and coral diversity’

The influence of macrophytes on diurnal pH variability in subtropical estuaries: a mesocosm study

Published 4 December 2024 Science Closed
Tags: , , , , , , ,

Highlights

  • Macrophytes influence estuary water column pH levels.
  • Floating macrophytes decrease pH and submerged macrophytes increase pH.
  • Diurnal pH variability is more pronounced in submerged macroalgae.
  • Floating macrophytes exhibit lower diurnal variability.

Abstract

Coastal ecosystems are increasingly threatened by anthropogenic impacts, particularly from land-based activities that drive eutrophication. This research investigated eutrophication and the unique challenges facing southern hemisphere coastal ecosystems. We used a mesocosm study to measure the influence of a macroalga (Rhizoclonium riparium) and a floating macrophyte (Pistia stratiotes), on diurnal pH variability. Diurnal pH variability was more pronounced in the presence of macroalgae due to the direct release of metabolic byproducts into the water column during photosynthesis and respiration. In contrast, floating macrophyte treatments had lower diurnal pH variability, as metabolic byproducts are released into the atmosphere through floating foliage. Floating macrophytes influenced overall water column pH levels, resulting in an acidification effect, becoming more pronounced as macrophyte biomass increased. The study highlighted the importance of nutrient management and its association with macrophytes, to preserve the delicate balance of estuaries, and ensure the sustainable functioning of these critical ecosystems. Further in situ research is recommended to validate and expand on the mesocosm findings.

Continue reading ‘The influence of macrophytes on diurnal pH variability in subtropical estuaries: a mesocosm study’

The role of benthic TA and DIC fluxes on carbon sequestration in seagrass meadows of Dongsha Island

Published 27 November 2024 Science Closed
Tags: , , , ,

Coastal blue carbon ecosystems sequester carbon, storing it as plant biomass and particulate organic matter in sediments. Recent studies emphasize the importance of incorporating dissolved inorganic and organic forms into carbon assessments. As sediment-stored organic matter decomposes, it releases dissolved inorganic carbon (DIC) and total alkalinity (TA), both of which are critical for regulating the partial pressure of CO2 (pCO2) and thus carbon sequestration. This study investigated the role of benthic DIC and TA fluxes in carbon sequestration within seagrass meadows in Dongsha Island’s inner lagoon (IL) during the winter and summer seasons. Chamber incubation experiments revealed elevated benthic DIC and TA fluxes compared to global averages (107 ± 75.9 to 119 ± 144 vs. 1.3 ± 1.06 mmol m−2 d−1 for DIC, and 69.7 ± 40.7 to 75.8 ± 81.5 vs. 0.52 ± 0.43 mmol m−2 d−1 for TA). Despite DIC fluxes being approximately 1.5 times higher than TA fluxes, water pCO2 levels remained low (149 ± 26 to 156 ± 18 µatm). Mass balance calculations further indicated that benthic DIC was predominantly reabsorbed into plant biomass through photosynthesis (−135 to −128 mmol m−2 d−1). Conversely, TA accumulated in the water and was largely exported (−60.3 to −53.7 mmol m−2 d−1), demonstrating natural ocean alkalinity enhancement (OAE). This study highlights the crucial role of IL seagrass meadows in coastal carbon sequestration through net autotrophy and carbonate dissolution. Future research should explore the global implications of these processes and assess the potential of natural OAE in other coastal blue carbon ecosystems.

Continue reading ‘The role of benthic TA and DIC fluxes on carbon sequestration in seagrass meadows of Dongsha Island’

Subscribe

Search

  • Reset

OA-ICC Highlights

Resources