Archive Page 91

SOARCE Webinar Series: Ocean Acidification in the National Marine Sanctuary of American Samoa

Published 10 January 2024 Courses and training , Presentations Closed

American Samoa is home to some of the most resilient coral reefs in the world. From the 500-year-old giant Porites corals in Ta’u, to the heat resistant “super corals” in Ofu, and the thriving coral communities in Fagatele Bay. The reefs protect the shorelines, provide food for families, and play an integral role in Samoan culture and heritage. The National Marine Sanctuary of American Samoa is working with partners to better understand how ocean acidification may affect these resources and the communities that rely on them. Efforts include monitoring ocean acidification indicators, integration of ocean acidification into climate vulnerability and adaptation efforts, and education and outreach.

Sharing Ocean Acidification Resources for Communicators and Educators (SOARCE) webinar series aims to promote a better supported society. It is an initiative of the Ocean Acidification Programme (OAP) developed and implemented by NOAA.

Continue reading ‘SOARCE Webinar Series: Ocean Acidification in the National Marine Sanctuary of American Samoa’

Exploring our changing ocean

Published 10 January 2024 Web sites and blogs Closed

The project includes the development of six interactive StoryMaps showcasing relevant ocean acidification trends, science activities, stakeholder engagements and policy responses taking place across regions where NOAA supports U.S. Coastal Acidification Networks (“CANs”). The six regional NOAA CANs include activities in Alaska, California Current, North Atlantic, Mid-Atlantic, South Atlantic and the Gulf.  

Each regional storymap includes:

  • An overview of climate-ocean change, including the causes of ocean acidification (OA). 
  • Synopsis of OA trends and potential impacts to marine species, ecosystems, and human communities most at risk.
  • Highlight reel  of activities and policies occurring within the region to better understand and respond to OA and climate-ocean change. This includes leadership and examples from state government, seafood growers, Tribal government, Port/ municipalities, and community members.
  • Proposed “calls to action” that can be taken by an individual.
  • An Interactive map of the United States, indicating where relevant  ACP member Aquariums are located.

Each specific region’s storymap can be accessed with the following links:

  1. Alaska’s changing ocean
  2. Changes in the Mid-Atlantic
  3. The changing Pacific
  4. The changing Gulf
  5. Changes in the South Atlantic
Continue reading ‘Exploring our changing ocean’

Inferring the health of coral reefs on the Egyptian coast of the Gulf of Aqaba for three branching-coral species

Published 9 January 2024 Science Closed
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Abstract

This investigation examined the vulnerability of three branching coral species (Acropora humilis, Pocillopora damicornis, and Stylophora pistillata) to environmental changes within the marine reserves of Taba, Nuweiba, and Dahab in the Gulf of Aqaba. Coral growth rates were assessed as a key indicator of coral reef vitality, reacting to shifting physicochemical parameters. A. humilis manifested the highest growth rate, followed by S. pistillata and P. damicornis. Site-specific data analysis found Dahab displayed the greatest coral proliferation, with Taba exhibiting the least. Accounting for seasonal changes, spring showed maximal coral growth. Statistical analysis revealed a positive correlation between salinity and coral growth rate, contrasted by a negative correlation with variables such as pH, PO4-P, and silicate (SiO4-Si). This work underscores the significant influence of environmental factors on coral growth rates, and by extension, the health of coral reef ecosystems. These findings are integral to coral reef management, suggesting mitigation of adverse environmental factors could enhance these ecosystems’ resilience against climatic shifts and human-induced stressors. By combining species, site, seasonal, and physicochemical variations, this research underlines the importance of localized conservation strategies.

Highlights

  • Robust Reef Health: The paper’s findings reveal a remarkable resilience and overall good health of coral reefs in Egypt’s protected marine environments, even when compared to reefs in more polluted and anthropogenically impacted areas.
  • Effective Protection Measures: The study underscores the importance of the protective measures implemented in these marine preserves, indicating that they have played a crucial role in maintaining the health and status of the intricate and invaluable reef ecosystems.
  • Catalyst for Further Research: The research outcomes provide a strong foundation for future studies aimed at identifying and implementing effective protective measures and adaptive management strategies for coral reefs in diverse ecosystems, with the goal of ensuring their long-term health and preservation.
  • Highlighting Environmental Challenges: The paper emphasizes the relative health of the studied coral reefs despite broader environmental challenges, shedding light on the potential success of conservation efforts within these specific marine regions.
Continue reading ‘Inferring the health of coral reefs on the Egyptian coast of the Gulf of Aqaba for three branching-coral species’

Combined effect of anthropogenic and “natural” carbon on acidification of the subsurface ocean water at the tip of the Antarctic Peninsula

Published 8 January 2024 Science Closed
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Abstract

Dissolved inorganic carbon, total alkalinity, and dissolved N2O samples of upper 500 m were collected at the tip of the Antarctic Peninsula during the 32nd Chinese Antarctic National Research Expedition. The pH and anthropogenic carbon were calculated and the results show that the patterns of anthropogenic carbon uptake and acidification progresses are different in two adjacent regions of this study area. In the region of Weddell-Scotia confluence, hydrographic processes such as convection prompt the transport of anthropogenic carbon into the subsurface layer, whereas in the region east of Powell Basin, where stratification existed, the downward transport of anthropogenic carbon to this depth is inhibited. However, the pH values indicate that the acidification status of the subsurface waters that are influenced by the above two hydrographic features are similar or even identical at a certain depth range. The progress of ocean acidification in the well-ventilated region are dominated by anthropogenic carbon uptake, while in the adjacent well-stratified region, anthropogenic carbon uptake and in situ remineralization of organic matter or horizontal advection of carbon rich water masses or both. In the later region, anthropogenic carbon uptake and in situ remineralization (or horizontal advection) contribute 40% and 60% to pH decline, respectively, suggesting that pH value in water mass of this region may significantly influenced by natural processes.

Key points

  • Vertical convection enhancing the intrusion of anthropogenic carbon into the subsurface layer at the tip of Antarctic Peninsula
  • Both anthropogenic carbon and remineralization will contribute to ocean acidification at the tip of Antarctic Peninsula
Continue reading ‘Combined effect of anthropogenic and “natural” carbon on acidification of the subsurface ocean water at the tip of the Antarctic Peninsula’

The Ocean of Tomorrow: Episode 2 with Linn Hoffmann – Ocean Acidification and the Marine World

Published 8 January 2024 Educational Materials , Presentations , Resources Closed

Welcome to our new Ocean Acidification series!

This expert talk is based on chapter 2 in The Ocean of Tomorrow teachers booklet, created by the New Zealand Marine Studies Centre and can be downloaded in the link below.

This short talk is perfect for teacher and student PD! Use the video as a stand-alone or together with the classroom activity demonstrated in The Ocean of Tomorrow: Activity 2B. Enjoy!

Continue reading ‘The Ocean of Tomorrow: Episode 2 with Linn Hoffmann – Ocean Acidification and the Marine World’

OA-ICC bibliographic database updated

Published 5 January 2024 Science Closed

An updated version of the OA-ICC bibliographic database is available online.

The database currently contains 10,643 references and includes citations, abstracts and assigned keywords. Updates are made every month.

The database is available as a group on Zotero. Subscribe online or, for a better user experience, download the Zotero desktop application and sync with the group OA-ICC in Zotero. Please see the “User instructions” for further details.

Continue reading ‘OA-ICC bibliographic database updated’

Transport of anthropogenic carbon from the Antarctic shelf to deep Southern Ocean triggers acidification

Published 5 January 2024 Science Closed
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Abstract

Flow of dense shelf water provide an efficient mechanism for pumping CO2 to the deep ocean along the continental shelf slope, particularly around the Antarctic bottom water (AABW) formation areas where much of the global bottom water is formed. However, the contribution of the formation of AABW to sequestering anthropogenic carbon (Cant) and its consequences remain unclear. Here, we show prominent transport of Cant (25.0 ± 4.7 Tg C yr−1) into the deep ocean (>2,000 m) in four AABW formation regions around Antarctica based on an integrated observational data set (1974–2018). This maintains a lower Cant in the upper waters than that of other open oceans to sustain a stronger CO2 uptake capacity (16.9 ± 3.8 Tg C yr−1). Nevertheless, the accumulation of Cant can further trigger acidification of AABW at a rate of −0.0006 ± 0.0001 pH unit yr−1. Our findings elucidate the prominent role of AABW in controlling the Southern Ocean carbon uptake and storage to mitigate climate change, whereas its side effects (e.g., acidification) could also spread to other ocean basins via the global ocean conveyor belt.

Key points

  • We show evidence for the accumulation of Cant along the Antarctic shelf-slope into the deep ocean
  • The process of AABW formation drives Cant downward transport at 25.0 ± 4.7 Tg C yr−1, sustaining the CO2 uptake in the surface ocean
  • This further triggers acidification of AABW at a rate of −0.0006 ± 0.0001 pH unit yr−1, which is faster than in other deep oceans
Continue reading ‘Transport of anthropogenic carbon from the Antarctic shelf to deep Southern Ocean triggers acidification’

The impacts of climate change on the reproduction of native and invasive kelps

Published 5 January 2024 Science Closed
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Climate change represents a threat to coastal marine ecosystems through variable effects on community structure and function due to increasing mean sea-surface temperatures (SST), marine heatwaves, variation in salinity, and ocean acidification. Among the most at risk species are California kelps, which have already experienced significant die-offs over the past several years as a result of elevated SST and urchin grazing. However, the effects of these stresses on the very sensitive microscopic kelp life stage (gametophyte) are much less understood. Gametophytes are generally less resilient to changes in abiotic conditions, so global environmental change could result in drastic changes in kelp forest community structure and composition via impacts on this life stage. My dissertation research used manipulative laboratory experiments to investigate the interacting role of abiotic stressors on kelp reproduction and community compositions, specifically, the growth and survival of early kelp life stages. My first chapter focused on the effects of climate-driven temperature increases and ocean acidification on bull kelp (Nereocystis luetkeana) gametophytes from Point Arena, CA (Korabik et al. 2023). From 2014 to 2016, the largest marine heatwave in history appeared off the coast of California resulting in large kelp die off events. In this chapter, I asked how increased temperature and lowered pH impact the survival of bull kelp gametophytes and the production of juvenile bull kelp sporophytes. My results showed that increased temperature resulted in a significant decrease in the survival of gametophytes and a lower number of juveniles produced, whereas lowered pH only had a significant effect on the production of juveniles, slowing their rate of development. These results indicate that the predicted increase of marine heatwaves could have devastating effects on the persistence of bull kelp forest ecosystems. My second chapter considered the interacting effects of climate driven changes in temperature and salinity and interactions with the invasive seaweed (Sargassum muticum) on the growth and survival of giant kelp (Macrocystis pyrifera) gametophytes from Tomales Bay, CA. In my experiments, I tested: 1) how different salinities and temperatures impact giant kelp early life stages from different sources within Tomales Bay, 2) how the presence of invasive Sargassum propagules affect giant kelp gametophyte development, and 3) how the combined effects of salinity, temperature, and Sargassum presence affect giant kelp early life stages. My results indicate that 1) the presence of Sargassum had little effect on the survival of giant kelp gametophytes, 2) Sargassum accelerated development of giant kelp juvenile sporophytes, and 3) high temperatures resulted in the greatest reduction of giant kelp gametophyte survival. These results imply that giant kelp reproduction and presence within estuaries is more influenced by temperature than salinity and microscopic-stage competition with invasive species. My third chapter examined the effects of increased temperature and lowered salinities on invasive Wakame (Undaria pinnatifida) gametophytes in the San Francisco Bay. Previous studies have shown that low salinity can limit the distribution of Undaria, but there is no information about these effects on gametophyte stages. Using a full factorial design, I exposed Undaria gametophytes to five salinity conditions ranging from low to ambient salinity and two temperatures representing pre-2013 temperature maxima in San Francisco and maximum increased temperatures experienced under the 2014-2016 marine heatwave. I found that Undaria microstages were unable to survive below 20 psu and generally survived better under warmer temperatures of 18°C. Climate change in California is predicted to result in higher temperatures and reduced annual rainfall in drought years, which may facilitate future northward expansion of Wakame populations. With this research, I can better predict the impacts of climate change on kelp ecosystems to help coastal managers prioritize future protection efforts. Early life stages are often the most vulnerable to stress, and in this era of rapid climate change, understanding early life stage responses to stress will allow scientists and managers to better work towards the protection of our planet.

Continue reading ‘The impacts of climate change on the reproduction of native and invasive kelps’

Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes

Published 2 January 2024 Science Closed
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Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g., wetland inputs. Here, we investigate how mangroves and saltmarshes influence coastal carbonate chemistry and quantify the contribution of alkalinity and dissolved inorganic carbon (DIC) outwelling to blue carbon budgets. Observations from 45 mangroves and 16 saltmarshes worldwide revealed that >70% of intertidal wetlands export more DIC than alkalinity, potentially decreasing the pH of coastal waters. Porewater-derived DIC outwelling (81 ± 47 mmol m−2 d−1 in mangroves and 57 ± 104 mmol m−2 d−1 in saltmarshes) was the major term in blue carbon budgets. However, substantial amounts of fixed carbon remain unaccounted for. Concurrently, alkalinity outwelling was similar or higher than sediment carbon burial and is therefore a significant but often overlooked carbon sequestration mechanism.

Continue reading ‘Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes’

The Ocean of Tomorrow: Episode 1 with Kim Currie – Ocean Acidification and the Marine World

Published 2 January 2024 Educational Materials , Resources Closed

Welcome to our new Ocean Acidification series for teachers and students!

This expert talk is based on chapter 1 in The Ocean of Tomorrow teachers booklet, created by the New Zealand Marine Studies Centre and can be downloaded in the link below.

This short talk is perfect for teacher and student PD! Use it as a stand-alone or together with the classroom activity demonstrated in The Ocean of Tomorrow: Activity 1B. Enjoy!

Continue reading ‘The Ocean of Tomorrow: Episode 1 with Kim Currie – Ocean Acidification and the Marine World’

Season’s Greetings!

Published 29 December 2023 Uncategorized Closed

Dynamics of pH at Santa Catalina Island

Published 28 December 2023 Science Closed
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The local expression of ocean acidification may depend on local oceanographic features in addition to global forcings. Our objective is to provide a baseline of pH behavior at Santa Catalina Island, situated within the unique oceanographic characteristics of the Southern California Bight, and to gain insight into ocean acidification at the island. Measurements of the upper water column (to 30-m depth) of pH, temperature, conductivity, chlorophyll and dissolved oxygen at Santa Catalina were made from a fixed mooring and by profiling the water column from a boat and on Self-Contained Underwater Breathing Apparatus (SCUBA). The average pH (8.095 at 18-m depth) was found to be higher than that reported off the nearby mainland and the Northern Channel Islands. The higher value is thought to result from both downwelling produced by internal waves as well as less upwelling at the island compared to other locations. Large modulations in pH at depth corresponded to advection of gradients by internal waves. Within the accuracy of the sensors there was no seasonal dependence detected at near-surface, nor a pH signal associated with the sub-surface chlorophyll and oxygen maxima. We conclude that marine life living at depths affected by internal waves experience significant variation in pH.

Continue reading ‘Dynamics of pH at Santa Catalina Island’

Climate change threatens a quarter of Australia’s low-lying coral reef islands

Published 28 December 2023 Press releases Closed

Coral islands support and extend legal maritime jurisdictions.

University of Sydney researchers have found 25 percent of Australia’s coral islands, land masses formed by reefs, currently face high to very high risk of being wiped out by climate change.

The findings, published in the latest edition of the journal Science of the Total Environment, identified that all of the 56 investigated Australian coral islands are exposed to some degree of climate risk but that three small, unvegetated coral islands in Western Australia, on Scott, Clerke and Imperieuse reefs, are the most vulnerable.

Lead researcher Dr Tommy Fellowes from the School of Geosciences said: “The fate of low-lying coral reef islands and their associated reef ecosystems hangs in the balance, threatened by the compounding effects of climate change – rising sea levels, warming oceans, intensifying storms and acidification.”

“We quantified the risks to Australia’s coral islands for the first time and our findings make clear the urgent need to address these threats and the vulnerable state of these islands.

Continue reading ‘Climate change threatens a quarter of Australia’s low-lying coral reef islands’

Shallow-water carbonate facies herald the onset of the Palaeocene eocene thermal maximum (Hazara basin, Northern Pakistan)

Published 27 December 2023 Science Closed
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Highlights

  • Pre-PETM-onset neritic carbonates show early signs of what will occur during PETM.
  • Corals declined over the study period, whereas foraminifera and red algae increased.
  • Similar patterns can be observed in most of the Neotethys.
  • Quantitative data are crucial to better understanding palaeo-environmental changes.

Abstract

We investigate the Palaeocene succession of the Hazara Basin (Northern Pakistan) to better understand the impact of climate change on marine carbonate-producing organisms. These shallow-water carbonates, deposited during the Late Palaeocene, before the onset of the Palaeocene-Eocene Thermal Maximum, were studied using a quantitative approach to highlight changes in the skeletal assemblage. We recognise a decrease in the abundance of colonial corals and green calcareous algae and an increase in larger benthic foraminifera and red calcareous algae from the early Thanetian to the late Thanetian. Increasing temperatures may represent a plausible cause for the decline of the more sensitive colonial corals in favor of the more tolerant larger benthic foraminifera. A similar pattern is observed in most successions deposited along the margins of the Neotethys Ocean, suggesting a connection with the Late Palaeocene environmental changes that heralded the PETM hyperthermal event. Our stratigraphic analysis of the Hazara Basin strata suggests that the biotic turnovers occurred during the Palaeocene – Eocene transition started already before the onset of the Palaeocene Eocene Thermal Maximum as recorded by the geochemical proxies.

Continue reading ‘Shallow-water carbonate facies herald the onset of the Palaeocene eocene thermal maximum (Hazara basin, Northern Pakistan)’

Spatiotemporal reconstruction of global ocean surface pCO2 based on optimized random forest

Published 27 December 2023 Science Closed
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Highlights

  • Conduct comprehensive research on the global ocean surface pCO2 from a holistic perspective
  • Analyze ocean surface pCO2 and twelve factors of the ocean using a geographical detector
  • Compare multiple machine learning models of pCO2, including MLR, CNN, XGBoost, SVM, RF, and ORF
  • Reconstruct the resolution of ocean surface pCO2 to 0.25° × 0.25°
  • The ORF model improves the reconstruction accuracy of ocean surface pCO2.

Abstract

The partial pressure of ocean surface CO2 (pCO2) plays an important role in quantifying the carbon budget and assessing ocean acidification. For such a vast and complex ocean system as the global ocean, most current research practices tend to study the ocean into regions. In order to reveal the overall characteristics of the global ocean and avoid mutual influence between zones, a holistic research method was used to detect the correlation of twelve predictive factors, including chlorophyll concentration (Chlor_a), diffuse attenuation coefficient at 490 nm (Kd_490), density ocean mixed layer thickness (Mlotst), eastward velocity (East), northward velocity (North), salinity (Sal), temperature (Temp), dissolved iron (Fe), dissolved silicate (Si), nitrate (NO3), potential of hydrogen (pH), phosphate (PO4), at the global ocean scale. Based on measured data from the Global Surface pCO2 (LDEO) database, combined with National Aeronautics and Space Administration (NASA) Ocean Color satellite data and Copernicus Ocean reanalysis data, an improved optimized random forest (ORF) method is proposed for the overall reconstruction of global ocean surface pCO2, and compared with various machine learning methods. The results indicate that the ORF method is the most accurate in overall modeling at the global ocean scale (mean absolute error of 6.27μatm, root mean square error of 15.34μatm, R2 of 0.92). Based on independent observations from the LDEO dataset and time series observation stations, the ORF model was further validated, and the global ocean surface pCO2 distribution map of 0.25° × 0.25° for 2010 to 2019 was reconstructed, which is of significance for the global ocean carbon cycle and carbon assessment.

Continue reading ‘Spatiotemporal reconstruction of global ocean surface pCO2 based on optimized random forest’

Resilience against the impacts of climate change in an ecologically and economically significant native oyster

Published 22 December 2023 Science Closed
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Highlights

  • Climate change is acidifying and warming oceans.
  • Building resilience of marine species will be essential to ensure their persistence.
  • Resilience to climate change in oysters was identified in a large-scale experiment as the capacity to defend acid-base balance and have a positive Scope for Growth.
  • Only 8 of 24 genetically distinct family lines of this economically and ecologically important oyster species had resilience.

Abstract

Climate change is acidifying and warming our oceans, at an unprecedented rate posing a challenge for marine invertebrates vital across the globe for ecological services and food security. Here we show it is possible for resilience to climate change in an ecologically and economically significant oyster without detrimental effects to the energy budget. We exposed 24 pair-mated genetically distinct families of the Sydney rock oyster, Saccostrea glomerata to ocean acidification and warming for 4w and measured their resilience. Resilience was identified as the capacity to defend their acid-base balance without a loss of energy available for Scope for Growth (SFG). Of the 24 families, 13 were better able to defend their acid-base balance while eight had no loss of energy availability with a positive SFG. This study has found oyster families with reslience against climate change without a loss of SFG, is an essential mitigation strategy, in a critical mollusc.

Continue reading ‘Resilience against the impacts of climate change in an ecologically and economically significant native oyster’

Late Cenomanian Plenus event in the Western Interior seaway

Published 22 December 2023 Science Closed
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The Late Cenomanian Plenus Cold Event is one of the most enigmatic paleoclimate episodes in Earth history with potential to inform understanding of global climate system variability under greenhouse warming conditions, as well as internal feedback pathways that modulate such variability. Following an interpreted massive addition of volcanic CO2 to the atmosphere and warming that led to a major ocean anoxic event (OAE2), there was a brief interval of cooling recorded in oxygen isotopes and biogeographic data. Here we present evidence that cooling was absent or muted within the Western Interior Seaway (WIS). Clumped isotope data from the basin suggest persistent extreme warmth during the Late Cenomanian, macroinvertebrate fossil assemblages do not record a decrease in temperature, and changes in other paleoceanographic proxies do not correlate temporally with Plenus interval signals from other locales. Using select proxy data to guide construction of GCM model simulations, we explore possible hypotheses to explain these observations. Our results suggest that the paleogeographic configuration of the basin and its gateways to adjoining oceans, which evolved in association with changing pCO2 and sea level, influenced winter sea ice formation at the northern aperture of the seaway, water mass circulation, salinity, temperature, and water column stratification. We propose that northward advection of warm Tethyan water muted expression of Plenus cooling in the seaway. Understanding the unique character of the Western Interior paleoceanographic record provides critical input for the development of robust models of ancient Earth System dynamics and should aid predictions of future climate system dynamics.

Continue reading ‘Late Cenomanian Plenus event in the Western Interior seaway’

Risk classification of low-lying coral reef islands and their exposure to climate threats

Published 21 December 2023 Science Closed
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Highlights

  • Coral islands classified based on their risk from and resilience to climate change
  • Approach uses a risk matrix assigns coral islands into 5 classes (Very Low to Very High).
  • Methods use open-access and published ocean climate data and have global application.
  • 14 out of the 56 islands investigated (25 %) have High or Very High risk classification.
  • Our results will support informed coastal management and policy.

Abstract

The bio-physical responses of low-lying coral islands to climate change are of concern. These islands exist across a broad range of bio-physical conditions, and vulnerabilities to rising and warming seas, ocean acidification and increased storminess. We propose a risk-based classification that scores 6 island eco-morphometric attributes and 6 bio-physical ocean/climate conditions from recent open-access data, to assign islands with respect to 5 risk classes (Very Low, Low, Moderate, High and Very High). The potential responses of 56 coral islands in Australia’s jurisdiction (Coral Sea, NW Shelf and NE Indian Ocean) to climate change is considered with respect to their bio-physical attributes and eco-morphometrics. None of the islands were classed as Very Low risk, while 8 were classed as Low (14.3 %), 34 were Moderate (60.7 %), 11 were High (19.6 %), and 3 were Very High (5.4 %). Islands in the Very High risk class (located on the NW Shelf) are most vulnerable due to their small size (mean 10 Ha), low elevation (mean 2.6 m MSL), angular/elongated shape, unvegetated state, below average pH (mean 8.05), above average rates of sea-level rise (SLR; mean 4.6 mm/yr), isolation from other islands, and frequent tropical storms and marine heatwaves. In contrast, islands in the Low (and Very Low) risk class are less vulnerable due to their large size (mean 127 Ha), high elevation (mean 8.5 m MSL), sub-angular/round shape, vegetated state, near average pH (mean 8.06), near average SLR rates (mean 3.9 mm/yr), proximity to adjacent islands, and infrequent cyclones and marine heatwaves. Our method provides a risk matrix to assess coral island vulnerability to current climate change related risks and supports future research on the impacts of projected climate change scenarios. Findings have implications for communities living on coral islands, associated ecosystem services and coastal States that base their legal maritime zones on these islands.

Continue reading ‘Risk classification of low-lying coral reef islands and their exposure to climate threats’

Adaptive responses of eelgrass (Zostera marina L.) to ocean warming and acidification

Published 21 December 2023 Science Closed
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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’

Future warming stimulates growth and photosynthesis in an Arctic microalga more strongly than changes in light intensity or pCO2

Published 20 December 2023 Science Closed
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We assessed the responses of solitary cells of Arctic Phaeocystis pouchetii grown under a matrix of temperature (2°C vs. 6°C), light intensity (55 vs. 160 μmol photons m−2 s−1) and pCO2 (400 vs. 1000 μatm CO2, i.e., 40.5 vs. 101.3 Pa). Next to acclimation parameters (growth rates, particulate and dissolved organic C and N, Chlorophyll a content), we measured physiological processes in vivo (electron transport rates and net photosynthesis) using fast-repetition rate fluorometry and membrane-inlet mass spectrometry. Within the applied driver ranges, elevated temperature had the most pronounced impacts, significantly increasing growth, elemental quotas and photosynthetic performance. Light stimulations manifested more prominently under 6°C, underlining temperature’s role as a “master-variable”. pCO2 was the least effective driver, exerting mostly insignificant effects. The obtained data were used for a simplistic upscaling simulation to investigate potential changes in P. pouchetii‘s bloom dynamics in the Fram Strait with increasing temperatures over the 21st century. Although solitary cells might not be fully representative of colonial cells commonly observed in the field, our results suggest that global warming accelerates bloom dynamics, with earlier onsets of blooms and higher peak biomasses. Such a temperature-induced acceleration in the phenology of Phaeocystis and likely other Arctic phytoplankton might cause temporal mismatches, e.g., with the development of grazers, and therefore substantially affect the biogeochemistry and ecology of the Arctic.

Continue reading ‘Future warming stimulates growth and photosynthesis in an Arctic microalga more strongly than changes in light intensity or pCO2’

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