Archive Page 90

South Florida’s nearshore reefs less vulnerable to ocean acidification, study finds

Published 19 January 2024 Press releases Closed

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Scientists recover the CTD, an instrument used to measure conductivity, temperature, and depth of the ocean on the back of the R/V F.G. Walton Smith in choppy weather during water sampling. 
Photo: Tyler Christian, Cooperative Institute for Marine and Atmospheric Studies. 

Researchers studying South Florida’s coral reefs found that the region’s nearshore reefs and more sheltered inshore areas are less vulnerable to ocean acidification than previously thought – a major climate-related threat to coral reefs as ocean waters absorb more atmospheric CO2 from the burning of fossil fuels. 

This new study, led by scientists at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science offers a glimmer of hope for Florida’s iconic coral reefs as ocean acidification, along with marine heat waves and other climate-related threats are impacting coral reefs worldwide.

Continue reading ‘South Florida’s nearshore reefs less vulnerable to ocean acidification, study finds’

Ocean acidification linking science with society

Published 19 January 2024 Events Closed

The GOA-ON SAROA hub will be hosting an international meeting on Feburary 1-2 2024 in Kolkata, India focusing on ocean acidification and linking science with society. Several international experts are invited to give their perspectives on this critical topic, including Dr. Vengatesen Thiyagarajan, Prof. Steve Widdicombe, and Prof. Jan Newton. 

The link to the event: https://forms.gle/Cn1bMS2Q85A3XsUw6

For more information, please contact itmerg.ngs@gmail.com. Register for the event here:  Ocean Acidification- Linking Science with Society (google.com)

You can access more information about the SAROA hub and GOA-ON via this link SAROA : About (goa-on.org)

A comprehensive review of the effects of salinity, dissolved organic carbon, pH, and temperature on copper biotoxicity: implications for setting the copper marine water quality criteria

Published 18 January 2024 Science Closed
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Highlights

  • Salinity, DOC, pH and temperature will significantly influence copper toxicity.
  • DOC is the most studied factor in the establishment of Cu WQCs in seawater.
  • Cu WQC values were primarily determined using BLM, WER, QSAR and regression models.
  • Salinity, DOC and temperature should be considered in determining the Cu marine WQCs.

Abstract

In recent years, there has been a growing concern about the ecological hazards associated with copper, which has sparked increased interest in copper water quality criteria (WQC). The crucial factors affecting the bioavailability of copper in seawater are now acknowledged to be salinity, dissolved organic carbon (DOC), pH, and temperature. Research on the influence of these four water quality parameters on copper toxicity is rapidly expanding. However, a comprehensive and clear understanding of the relevant mechanisms is currently lacking, hindering the development of a consistent international method to establish the seawater WQC value for copper. As a response to this knowledge gap, this study presents a comprehensive summary with two key focuses: (1) It meticulously analyzes the effects of salinity, DOC, pH, and temperature on copper toxicity to marine organisms. It takes into account the adaptability of different species to salinity, pH and temperature. (2) Additionally, the study delves into the impact of these four water parameters on the acute toxicity values of copper on marine organisms while also reviewing the methods used in establishing the marine WQC value of copper. The study proposed a two-step process: initially zoning based on the difference of salinity and DOC, followed by the establishment of Cu WQC values for different zones during various seasons, considering the impacts of water quality parameters on copper toxicity. By providing fundamental scientific insights, this research not only enhances our understanding and predictive capabilities concerning water quality parameter-dependent Cu toxicity in marine organisms but also contributes to the development of copper seawater WQC values. Ultimately, this valuable information facilitates more informed decision-making in marine water quality management efforts.

Continue reading ‘A comprehensive review of the effects of salinity, dissolved organic carbon, pH, and temperature on copper biotoxicity: implications for setting the copper marine water quality criteria’

Coral reef carbonate chemistry reveals interannual, seasonal, and spatial impacts on ocean acidification off Florida

Published 18 January 2024 Science Closed
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Abstract

Ocean acidification (OA) threatens coral reef persistence by decreasing calcification and accelerating the dissolution of reef frameworks. The carbonate chemistry of coastal areas where many reefs exist is strongly influenced by the metabolic activity of the underlying benthic community, contributing to high spatiotemporal variability. While characterizing this variability is difficult, it has important implications for the progression of OA and the persistence of the ecosystems. Here, we characterized the carbonate chemistry at 38 permanent stations located along 10 inshore-offshore transects spanning 250 km of the Florida Coral Reef (FCR), which encompass four major biogeographic regions (Biscayne Bay, Upper Keys, Middle Keys, and Lower Keys) and four shelf zones (inshore, mid-channel, offshore, and oceanic). Data have been collected since 2010, with approximately bi-monthly periodicity starting in 2015. Increasing OA, driven by increasing DIC, was detected in the mid-channel, offshore, and oceanic zones in every biogeographic region. In the inshore zone, however, increasing TA counteracted any measurable OA trend. Strong seasonal variability occurred at inshore sites and included periods of both exacerbated and mitigated OA. Seasonality was region-dependent, with greater variability in the Lower and Middle Keys. Elevated pH and aragonite saturation states (ΩAr) were observed in the Upper and Middle Keys, which could favor reef habitat persistence in these regions. Offshore reefs in the FCR could be more susceptible to global OA by experiencing open-ocean-like water chemistry conditions. By contrast, higher seasonal variability at inshore reefs could offer a temporary OA refuge during periods of enhanced primary production.

Key points

  • Interannual acidification trends were detected in the mid-channel, offshore, and oceanic zones of Florida’s Coral Reef
  • At the inshore reefs, strong seasonal variability in carbonate chemistry and increasing TA mitigated or obscured acidification trends
  • Higher pH and aragonite saturation states occur in the Upper and Middle Keys, which could favor reef habitat persistence in these regions

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Continue reading ‘Coral reef carbonate chemistry reveals interannual, seasonal, and spatial impacts on ocean acidification off Florida’

Sometimes (often?) responses to multiple stressors can be predicted from single-stressor effects: a case study using an agent-based population model of croaker in the Gulf of Mexico

Published 18 January 2024 Science Closed
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Abstract

Objective

Rapid changes in the world’s oceans make assessment of fish population responses to multiple stressors, especially on scales relevant to management, increasingly important. I used an existing agent-based, spatially explicit model of Atlantic Croaker Micropogonias undulatus in the northern Gulf of Mexico to examine how temperature, hypoxia, and ocean acidification, singly and in combinations, affect long-term population dynamics.

Methods

I performed a factorial simulation experiment with each stressor at three levels and analyzed various treatment combinations to assess the additivity and multiplicity of interactions. The response variables were long-term equilibrium (final year) values of spawning stock biomass (SSB), recruitment, weight at age, and two measures of stock productivity (recruits per SSB and maximum recruitment) derived from the spawner–recruit relationship fitted to model output. I used the single-stressor effects from the experiment to predict how the response variables would change when all three stressors were changed. Single-stressor effects were combined as the sum of the fractional changes (additive scale) and the product of ratios of changes (multiplicative scale) and compared to the responses in simulations with all stressors imposed.

Result

Analyzing the factorial design for two-way and three-way interactions showed that there were many interactions on the additive scale but very few on the multiplicative scale. Thus, the responses to multiple stressors were well predicted from single stressor effects when combined as multiplicative effects.

Conclusion

I discuss how the lack of strong interactions could be due to model assumptions, the structure of the model, or oversimplified representation of stressor effects. Alternatively, the model and analysis may be sufficiently realistic and weak interactions on the multiplicative scale may be common. This would reduce a complicated multi-factor situation to a series of more tractable single-factor effects. A critical next step is to determine how we can a priori identify situations of low interactions (i.e., predictable from single-stressor effects) without having to already know the multi-stressor response.

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Continue reading ‘Sometimes (often?) responses to multiple stressors can be predicted from single-stressor effects: a case study using an agent-based population model of croaker in the Gulf of Mexico’

Ocean acidification linking science with society

Published 18 January 2024 Events Closed

The GOA-ON SAROA hub will be hosting an international meeting on Feburary 1-2 2024 in Kolkata, India focusing on ocean acidification and linking science with society. Several international experts are invited to give their perspectives on this critical topic, including Dr. Vengatesen Thiyagarajan, Prof. Steve Widdicombe, and Prof. Jan Newton. 

The link to the event: https://forms.gle/Cn1bMS2Q85A3XsUw6

For more information, please contact itmerg.ngs@gmail.com. Register for the event here:  Ocean Acidification- Linking Science with Society (google.com)

You can access more information about the SAROA hub and GOA-ON via this link SAROA : About (goa-on.org)

Paleoceanographic importance of tri- and di-unsaturated alkenones through the early phase of Cretaceous Oceanic Anoxic Event 2 from southern high latitudes of the proto-Indian Ocean

Published 17 January 2024 Science Closed
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Alkenones are biomarkers derived exclusively from species of haptophyte algae. The relative abundance of di- to tri-unsaturated C37 alkenones expressed as UK’37 is widely applied as a sea surface paleotemperature proxy for Cenozoic marine sediments. However, the absence of alkatrienones prior to the Eocene has precluded application of the UK’37 proxy for assessment of Cretaceous paleoclimates. Herein, we report a C40 alkatrienone (tetraconta-9E, 16E, 23E-trien-3-one; C40:3 Et) in deep-sea sediments from southern high latitudes (International Ocean Discovery Program: IODP site U1516). This discovery extends the geologic record of alkatrienones to the late Cenomanian, ∼70 million years earlier than previous reports. The parallel occurrence of higher abundances of a C40 alkadienone (tetraconta-16E, 23E-dien-3-one; C40:2 Et) allowed calculation of the UK’40 unsaturation index, comparable to UK’37. Stratigraphic variations in the δ13C of C40:2 Et revealed an elevated (∼1.5 ‰) positive carbon isotope excursion (CIE) relative to those observed in carbonate from other OAE2 sequences likely reflecting a decrease in global pCO2. The UK’40 profile suggests a concurrent drop in sea surface temperature associated with the decline in pCO2 during the early phase of OAE2. The timing of these environmental perturbations in the southern high latitude of the proto-Indian Ocean suggests they were triggered by volcanism associated with large igneous province (LIP) formation.

Continue reading ‘Paleoceanographic importance of tri- and di-unsaturated alkenones through the early phase of Cretaceous Oceanic Anoxic Event 2 from southern high latitudes of the proto-Indian Ocean’

Skeletal Mg content in common echinoderm species from Deception and Livingston Islands (South Shetland Islands, Antarctica) in the context of global change

Published 17 January 2024 Science Closed
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Highlights

  • This is the first assessment of the Mg content in echinoderms from Deception and Livingston Islands.
  • Echinoderms showed interclass as well as inter- and intraspecific differences in their Mg content.
  • The sea stars displayed the highest Mg content levels, followed by the brittle stars and sea urchins.
  • The Mg content of echinoderms inhabiting Deception Island may be influenced by local environmental conditions.

Abstract

Echinoderms with high levels of magnesium (Mg) in their skeletons may be especially sensitive to ocean acidification, as the solubility of calcite increases with its Mg content. However, other structural characteristics and environmental/biological factors may affect skeletal solubility. To better understand which factors can influence skeletal mineralogy, we analyzed the Mg content of Antarctic echinoderms from Deception Island, an active volcano with reduced pH and relatively warm water temperatures, and Livingston Island. We found significant interclass and inter- and intraspecific differences in the Mg content, with asteroids exhibiting the highest levels, followed by ophiuroids and echinoids. Specimens exposed to hydrothermal fluids showed lower Mg levels, which may indicate local environmental effects. These patterns suggest that environmental factors such as seawater Mg2+/Ca2+ ratio and temperature may influence the Mg content of some echinoderms and affect their susceptibility to future environmental changes.

Continue reading ‘Skeletal Mg content in common echinoderm species from Deception and Livingston Islands (South Shetland Islands, Antarctica) in the context of global change’

Incidence of the early Toarcian global change on Dasycladales (Chlorophyta) and the subsequent recovery: comparison with end-Triassic Mass Extinction

Published 17 January 2024 Science Closed
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The early Toarcian biotic crisis (∼ 183 Ma), characterized in marine environments by abrupt temperature fluctuations, included a hyperthermal event (Jenkyns Event) with sea-level fluctuations, a carbon cycle perturbation, a crisis of carbonate productivity, and oxygen depleted conditions in some basins, resulting in a second order mass extinction. We suggest that the early Toarcian biotic crisis was key in the evolution of primary producers, including chlorophycean Dasycladales. The effect of the Jenkyns Event on Dasycladales has not been studied previously despite the fact that the impact on many groups of organisms have been the subject of many articles. In this work the stratigraphic distribution of Dasycladalean species from Upper Triassic to end of Jurassic is presented, discussed and compared with climatic fluctuations and sea-level changes.

The end-Triassic Mass Extinction constitutes a main biotic crisis for Dasycladales. All Triassic species became extinct at the Rhaetian-Hettangian boundary, and Dasycladales are not recorded in the lower Hettangian. The diversity of Dasycladales increased after the end-Triassic Mass Extinction and reached a maximum in the Sinemurian. Abrupt climatic changes related to the Pliensbachian/Toarcian boundary and the Jenkyns Event strongly affected the diversity of Dasycladales, very sensitive to sea-level and temperature fluctuations, as sessile benthic organisms inhabiting very shallow marine environments. Dasycladales are not recorded during the Toarcian. Sea-water acidification, enhanced weathering and increased terrigenous input from emerged lands —as well as potentially increased turbidity related to eutrophic conditions in some basins— were additional unfavorable conditions for Dasycladales, augmenting their ecological stress during the early Toarcian. The fragmentation of carbonate platforms in many Tethys paleomargins limited the shallower-water carbonate areas available for Dasycladales.

Warm conditions persisted during the middle and late Toarcian, less severe than during the Jenkyns Event according to oxygen isotopic data, and Dasycladales did not recover until the Bajocian and Bathonian. This biotic crisis for Dasycladales was longer than that of the end-Triassic Mass Extinction. The Callovian-Oxfordian transition was characterized by a cooling episode and a sea-level fall that produced a new biotic crisis affecting Dasycladales. From the middle Oxfordian, the increased temperature and sea-level rise, along with the development of large epeiric platforms, favored the carbonate productivity and diversity of primary producers, including Dasycladales, calcareous nannoplankton, dinoflagellate, calcareous Udoteaceae, and charophyte Clavatoraceae.

Continue reading ‘Incidence of the early Toarcian global change on Dasycladales (Chlorophyta) and the subsequent recovery: comparison with end-Triassic Mass Extinction’

Ocean acidification linking science with society

Published 17 January 2024 Events Closed

The GOA-ON SAROA hub will be hosting an international meeting on Feburary 1-2 2024 in Kolkata, India focusing on ocean acidification and linking science with society. Several international experts are invited to give their perspectives on this critical topic, including Dr. Vengatesen Thiyagarajan, Prof. Steve Widdicombe, and Prof. Jan Newton. 

The link to the event: https://forms.gle/Cn1bMS2Q85A3XsUw6

For more information, please contact itmerg.ngs@gmail.com. Register for the event here:  Ocean Acidification- Linking Science with Society (google.com)

You can access more information about the SAROA hub and GOA-ON via this link SAROA : About (goa-on.org)

Synergistic and antagonistic interactions of oxybenzone and ocean acidification: new insight into vulnerable cellular processes in non-calcifying anthozoans

Published 16 January 2024 Science Closed
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Cnidarians face significant threats from ocean acidification (OA) and anthropogenic pollutants such as oxybenzone (BP-3). The convergence of threats from multiple stressors is an important area to investigate because of potential significant synergistic or antagonistic interactions. Real-time quantitative PCR was performed to characterize the expression profiles of twenty-two genes of interest (GOI) in sea anemones (Exaiptasia diaphana) exposed to one of four treatments: 1) 96 h of OA conditions followed by a 4 h exposure to 20 ppb BP-3; 2) Exposure to 4 h 20 ppb BP-3 without 96 h of OA; 3) Exposure to 96 h of OA alone; or 4) laboratory conditions with no exposure to BP-3 and/or OA. These 22 GOIs represent cellular processes associated with proton-dependent transport, sodium-dependent transport, metal cation binding/transport, extracellular matrix, amino acid metabolism/transport, immunity, and/or steroidogenesis. These 22 GOIs provide new insight into vulnerable cellular processes in non-calcifying anthozoans exposed to OA and BP-3. Expression profiles were categorized as synergistic, antagonistic, or additive of BP-3 in the presence of OA. Two GOIs were synergistic. Fifteen GOIs were antagonistic and the remaining five GOIs were additive in response to BP-3 in acidified seawater. A subset of these GOIs appear to be candidate biomarkers for future in situ investigations. In human health, proton-dependent monocarboxylate transporters (MCTs) are promising pharmacological targets and recognized as potential biomarkers. By comparison, these same MCTs appear to be targets of xenobiotic chemical pollutants in cnidarian physiology. In the presence of BP-3, a network of collagen synthesis genes are upregulated and antagonistic in their expression profiles. Cytochrome b561 is a critical protein required for collagen synthesis and in silico modeling demonstrates BP-3 binds in the pocket of cytochrome b561. Understanding the underlying molecular mechanisms of “drug-like” compounds such as BP-3 may lead to a more comprehensive interpretation of transcriptional expression profiles. The collective antagonistic responses of GOIs associated with collagen synthesis strongly suggests these GOIs should be considered candidate biomarkers of effect. GOIs with synergistic and additive responses represent candidate biomarkers of exposure. Results show the effects of OA and BP-3 are interactive with respect to their impact on cnidarians. This investigation offers mechanistic data that supports the expression profiles and underpins higher order physiological responses.

Continue reading ‘Synergistic and antagonistic interactions of oxybenzone and ocean acidification: new insight into vulnerable cellular processes in non-calcifying anthozoans’

The molecular response of Mytilus coruscus mantle to shell damage under acute acidified sea water revealed by iTRAQ based quantitative proteomic analysis

Published 16 January 2024 Science Closed
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Mytilus coruscus is an economically important marine bivalve that lives in estuarine sea areas with seasonal coastal acidification and frequently suffers shell injury in the natural environment. However, the molecular responses and biochemical properties of Mytilus under these conditions are not fully understood. In the present study, we employed tandem mass spectrometry combined with isobaric tagging to identify differentially expressed proteins in the mantle tissue of M. coruscus under different short-term treatments, including shell-complete mussels raised in normal seawater (pH 8.1), shell-damaged mussels raised in normal seawater (pH 8.1), and acidified seawater (pH 7.4). A total of 2694 proteins were identified in the mantle, and analysis of their relative abundance from the three different treatments revealed alterations in the proteins involved in immune regulation, oxidation-reduction processes, protein folding and processing, energy provision, and cytoskeleton. The results obtained by quantitative proteomic analysis of the mantle allowed us to delineate the molecular strategies adopted by M. coruscus in the shell repair process in acidified environments, including an increase in proteins involved in oxidation-reduction processes, protein processing, and cell growth at the expense of proteins involved in immune capacity and energy metabolism.

Continue reading ‘The molecular response of Mytilus coruscus mantle to shell damage under acute acidified sea water revealed by iTRAQ based quantitative proteomic analysis’

A global biogeography analysis reveals vulnerability of surface marine zooplankton to anthropogenic stressors

Published 16 January 2024 Science Closed
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Highlights

  • Multiple stress factors for zooplankton overlap in the surface ocean
  • Stress brought by surface warming and acidification strongly increased in ∼50 years
  • More research on anthropogenic impacts on zooplankton is urgently needed

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Summary

Anthropogenic impacts on zooplankton at the surface ocean pose an urgent challenge because these keystone species are crucial for oceanic processes. Some anthropogenic stressors for zooplankton have been identified, such as acidification due to climate change, but a multitude of other stressors exist, and the combination of these may lead to unknown impacts. We utilized global biogeochemical models to assess the temporal and spatial distribution of zooplankton stress factors, including changes in sea surface temperature, acidification, prey quantity, food quality, and contaminants. We highlighted regional hotspots where multiple stress factors overlap and revealed that most stress factors are increasing. By linking stress factors to zooplankton distribution, we introduced a zooplankton vulnerability index. We found that the zooplankton vulnerability index has doubled in 50 years, and this suggests that zooplankton populations are increasingly at risk from anthropogenic stressors. Further research is needed to develop strategies for mitigating the impacts of anthropogenic stressors on zooplankton.

Continue reading ‘A global biogeography analysis reveals vulnerability of surface marine zooplankton to anthropogenic stressors’

Ocean acidification linking science with society

Published 16 January 2024 Events Closed

The GOA-ON SAROA hub will be hosting an international meeting on Feburary 1-2 2024 in Kolkata, India focusing on ocean acidification and linking science with society. Several international experts are invited to give their perspectives on this critical topic, including Dr. Vengatesen Thiyagarajan, Prof. Steve Widdicombe, and Prof. Jan Newton. 

The link to the event: https://forms.gle/Cn1bMS2Q85A3XsUw6

For more information, please contact itmerg.ngs@gmail.com. Register for the event here:  Ocean Acidification- Linking Science with Society (google.com)

You can access more information about the SAROA hub and GOA-ON via this link SAROA : About (goa-on.org)

Functional changes across marine habitats due to ocean acidification

Published 15 January 2024 Science Closed
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Global environmental change drives diversity loss and shifts in community structure. A key challenge is to better understand the impacts on ecosystem function and to connect species and trait diversity of assemblages with ecosystem properties that are in turn linked to ecosystem functioning. Here we quantify shifts in species composition and trait diversity associated with ocean acidification (OA) by using field measurements at marine CO2 vent systems spanning four reef habitats across different depths in a temperate coastal ecosystem. We find that both species and trait diversity decreased, and that ecosystem properties (understood as the interplay between species, traits, and ecosystem function) shifted with acidification. Furthermore, shifts in trait categories such as autotrophs, filter feeders, herbivores, and habitat-forming species were habitat-specific, indicating that OA may produce divergent responses across habitats and depths. Combined, these findings reveal the importance of connecting species and trait diversity of marine benthic habitats with key ecosystem properties to anticipate the impacts of global environmental change. Our results also generate new insights on the predicted general and habitat-specific ecological consequences of OA.

Continue reading ‘Functional changes across marine habitats due to ocean acidification’

Thermal fluctuations and CO2 enrichment synergistically accelerate biomass yield of Neopyropia yezoensis

Published 15 January 2024 Science Closed
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Due to the rising atmospheric pCO2, the greenhouse effect in the natural environment has intensified, leading to ocean acidification and frequently extreme temperature events. Limited research has been conducted on the effects of near-shore temperature fluctuations and ocean acidification on macroalgae. In this study, Neopyropia yezoensis (Bangiales, Rhodophyta) was cultured under two CO2 concentrations (LC: 400 μatm and HC: 1000 μatm) and three temperature conditions (10 ℃, 14 ℃, and fluctuation: increased from 10 ℃ to 14 ℃ and then decreased back to 10 ℃ with a fluctuation of 1 ℃ per day). The growth, chlorophyll fluorescence, photosynthetic pigments, and soluble carbohydrate of N. yezoensis were measured. The results showed that the relative growth rate, rETRmax, contents of chlorophyll a, phycoerythrin, and carotenoid in the thalli increased at 14 ℃ and thermal fluctuation, while the content of soluble carbohydrate were inhibited. Moreover, the effect of pCO2 on growth was significant only under temperature fluctuation. Even when the temperature dropped to 10 ℃, the physiological responses of N. yezoensis were still promoted by the thermal fluctuation condition. These findings indicate that the yield and quality of N. yezoensis could potentially improve in the future warming scenarios, and changes observed in N. yezoensis could serve as an early indicator for global climate change.

Continue reading ‘Thermal fluctuations and CO2 enrichment synergistically accelerate biomass yield of Neopyropia yezoensis’

Extinction risk of the world’s chondrichthyan fishes: a global assessment of the interplay between anthropogenic factors and marine protected areas

Published 15 January 2024 Science Closed
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Patterns of Chondrichthyes species richness (CSR) are widely recognized as being influenced by environmental conditions. However, untangling the intricate interplay between anthropogenic impacts and spatial patterns of CSR remains a challenging endeavor. In this study, we evaluate the influence of thirteen human-related variables, encompassing human-induced effects and marine protected areas, on global CSR. Additionally, we explore their effects on threatened species, those declining, those utilized and traded, and those facing direct human-induced threats. Utilizing simple, multiple, and simultaneous regression models, we comprehensively investigated the relationship between human-altered variables and marine protected areas on CSR across oceanic regions. Our findings distinctly reveal a compelling convergence of human-related variables with CSR. Notably, factors such as global ocean acidification, demersal destructive practices (e.g., bottom trawling), pelagic low bycatch techniques (e.g., hook and line), and demersal non-destructive high bycatch methods (e.g., pots, traps) exhibit robust negative associations. Intriguingly, a positive association emerges with the presence of marine protected areas. Furthermore, our study underscores the profound impact of diverse human activities on CSR, significantly heightening their vulnerability to threats and imminent extinction risks. These results accentuate the critical significance of conservation strategies centered on marine protected areas, maximizing the optimized preservation of Chondrichthyes across marine ecosystems. In light of these insights, we stress the paramount role of planners and managers in mitigating direct human impacts on marine ecosystems, which is crucial for ensuring the enduring presence of Chondrichthyes across the oceans.

Continue reading ‘Extinction risk of the world’s chondrichthyan fishes: a global assessment of the interplay between anthropogenic factors and marine protected areas’

Incidence of the early Toarcian global change on Dasycladales (Chlorophyta) and the subsequent recovery: comparison with end-Triassic Mass Extinction

Published 15 January 2024 Science Closed
Tags: , , , , , ,

The early Toarcian biotic crisis (∼ 183 Ma), characterized in marine environments by abrupt temperature fluctuations, included a hyperthermal event (Jenkyns Event) with sea-level fluctuations, a carbon cycle perturbation, a crisis of carbonate productivity, and oxygen depleted conditions in some basins, resulting in a second order mass extinction. We suggest that the early Toarcian biotic crisis was key in the evolution of primary producers, including chlorophycean Dasycladales. The effect of the Jenkyns Event on Dasycladales has not been studied previously despite the fact that the impact on many groups of organisms have been the subject of many articles. In this work the stratigraphic distribution of Dasycladalean species from Upper Triassic to end of Jurassic is presented, discussed and compared with climatic fluctuations and sea-level changes.

The end-Triassic Mass Extinction constitutes a main biotic crisis for Dasycladales. All Triassic species became extinct at the Rhaetian-Hettangian boundary, and Dasycladales are not recorded in the lower Hettangian. The diversity of Dasycladales increased after the end-Triassic Mass Extinction and reached a maximum in the Sinemurian. Abrupt climatic changes related to the Pliensbachian/Toarcian boundary and the Jenkyns Event strongly affected the diversity of Dasycladales, very sensitive to sea-level and temperature fluctuations, as sessile benthic organisms inhabiting very shallow marine environments. Dasycladales are not recorded during the Toarcian. Sea-water acidification, enhanced weathering and increased terrigenous input from emerged lands —as well as potentially increased turbidity related to eutrophic conditions in some basins— were additional unfavorable conditions for Dasycladales, augmenting their ecological stress during the early Toarcian. The fragmentation of carbonate platforms in many Tethys paleomargins limited the shallower-water carbonate areas available for Dasycladales.

Warm conditions persisted during the middle and late Toarcian, less severe than during the Jenkyns Event according to oxygen isotopic data, and Dasycladales did not recover until the Bajocian and Bathonian. This biotic crisis for Dasycladales was longer than that of the end-Triassic Mass Extinction. The Callovian-Oxfordian transition was characterized by a cooling episode and a sea-level fall that produced a new biotic crisis affecting Dasycladales. From the middle Oxfordian, the increased temperature and sea-level rise, along with the development of large epeiric platforms, favored the carbonate productivity and diversity of primary producers, including Dasycladales, calcareous nannoplankton, dinoflagellate, calcareous Udoteaceae, and charophyte Clavatoraceae.

Continue reading ‘Incidence of the early Toarcian global change on Dasycladales (Chlorophyta) and the subsequent recovery: comparison with end-Triassic Mass Extinction’

Survival of nutrient-starved diatoms under ocean acidification: perspective from nutrient sensing, cadmium detection, and nitrogen assimilation

Published 15 January 2024 Science Closed
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Increased anthropogenic emissions of carbon dioxide (CO2) have resulted in ocean acidification (OA) that is intertwined with enhanced ocean stratification. Diatoms are assumed to suffer from a more nutrient-limited condition in the future ocean. This study aimed to explore how OA affects the diatom dynamics under nutrient-poor conditions and the ability of diatoms to perceive nutrients (nitrogen, phosphorus, silicon, and trace metals) and cadmium (Cd) stimuli and assimilate nitrogen when receiving nutrients or Cd supplementation. Our study observed that diatom population grown under OA condition declined faster than those grown under ambient condition. Ocean acidification greatly lower intracellular Ca2+ concentration in diatom cells. Intracellular Ca2+ burst was involved in phosphorus accumulation but not in nitrogen, silicon, essential metals, and cadmium uptake. Our data demonstrate slower NO3– assimilation rates of diatoms grown in acidified seawater. Our study also indicates that diatoms have a poor perception of phosphorus availability under OA condition.

Continue reading ‘Survival of nutrient-starved diatoms under ocean acidification: perspective from nutrient sensing, cadmium detection, and nitrogen assimilation’

Low molecular weight carbohydrate patterns of mangrove macroalgae from different climatic niches under ocean acidification, warming and salinity variation

Published 12 January 2024 Science Closed
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Ocean acidification has increased due to the enhanced solubility of CO2 in seawater. Mangrove macroalgae in tropical and subtropical coastal regions can benefit from the higher availability of CO2 for photosynthesis and primary production. However, they can be negatively affected by the simultaneously occurring warming and increased salinity in estuaries. Thus, we analyzed the isolated effects of ocean acidification and the interactive effects of increased temperature and salinity on the low molecular weight carbohydrate (LMWC) contents of the mangrove red macroalgae Bostrychia montagnei and Bostrychia calliptera from Brazilian tropical and subtropical populations. Specimens from both climatic niches were tolerant to pH decreased by CO2 enrichment and enhanced their LMWC contents under increased availability of CO2. Specimens from both climatic niches also accumulated their dulcitol and sorbitol contents to cope with warming and salt stress. Nevertheless, temperature of 34 °C was lethal for tropical macroalgae, while 29 °C and 31 °C were lethal for subtropical B. calliptera under salinity of 35. Tropical and subtropical B. montagnei synthesized dulcitol (5–110 mmol kg−1 dry weight) and sorbitol (5–100 mmol kg−1 dry weight) as osmoregulatory, energy and thermal protection compounds, whereas tropical and subtropical B. calliptera synthesized mainly dulcitol (10–210 mmol kg−1 dry weight). Although digeneaside has an energy function in Bostrychia spp., it is not an osmolyte or thermal protection compound. Our data demonstrated that both tropical and subtropical Bostrychia spp. benefit from ocean acidification by CO2 enrichment, increasing their LMWC contents. However, warming and increased salinity in estuaries will be detrimental to them, even they producing protective metabolites. Multifactorial approaches are recommended to investigate whether negative effects of increased temperature and salinity nullify positive effects of ocean acidification on these Bostrychia species/populations.

Continue reading ‘Low molecular weight carbohydrate patterns of mangrove macroalgae from different climatic niches under ocean acidification, warming and salinity variation’

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