The ocean is warming, losing oxygen and being acidified, primarily as a result of anthropogenic carbon emissions. With ocean warming, acidification and deoxygenation projected to increase for decades, extreme events, such as marine heatwaves, will intensify, occur more often, persist for longer periods of time and extend over larger regions. Nevertheless, our understanding of oceanic extreme events that are associated with warming, low oxygen concentrations or high acidity, as well as their impacts on marine ecosystems, remains limited. Compound events—that is, multiple extreme events that occur simultaneously or in close sequence—are of particular concern, as their individual effects may interact synergistically. Here we assess patterns and trends in open ocean extremes based on the existing literature as well as global and regional model simulations. Furthermore, we discuss the potential impacts of individual and compound extremes on marine organisms and ecosystems. We propose a pathway to improve the understanding of extreme events and the capacity of marine life to respond to them. The conditions exhibited by present extreme events may be a harbinger of what may become normal in the future. As a consequence, pursuing this research effort may also help us to better understand the responses of marine organisms and ecosystems to future climate change.
Continue reading ‘Biogeochemical extremes and compound events in the ocean’Archive Page 27
Biogeochemical extremes and compound events in the ocean
Published 24 January 2022 Science ClosedTags: globalmodeling, modeling, review
The responses of harmful dinoflagellate Karenia mikimotoi to simulated ocean acidification at the transcriptional level
Published 24 January 2022 Science ClosedTags: biological response, molecular biology, morphology, photosynthesis, physiology, phytoplankton
Highlights
- 1121 genes were up- and 1369 down-regulated in K. mikimotoi upon ocean acidification (OA).
- OA led to down-regulation of carbon concentration mechanism-related factors.
- OA up-regulated energy metabolism, boosting growth and enhancing pigment content.
- Increased CAT and GR activities helped acclimate to OA.
- Up-regulated HSP genes enhanced tolerance of cells to low pH caused by OA.
Abstract
The HAB-forming, toxic dinoflagellate Karenia mikimotoi, previously found to benefit from ocean acidification (OA), was cultivated to investigate its transcriptional response to simulated OA for 30 generations. Batch cultures were grown under two CO2 concentrations, 450 (control) and 1100 (simulated OA) μatm, and physiological parameters [growth, pigments, catalase (CAT), glutathione reductase (GR), and superoxide dismutase (SOD) activity], as well as transcriptomes (obtained via RNA-seq), were compared. Chlorophyll a (Chl a) and carotenoid (Caro) contents, as well as CAT and GR activities, were significantly increased under OA conditions. Transcriptomic analysis revealed 2,490 differentially expressed unigenes in response to OA, which comprised 1.54% of all unigenes. A total of 1,121 unigenes were upregulated, and 1,369 unigenes were downregulated in OA compared to control conditions. The downregulated expression of bicarbonate transporter and carbonic anhydrase genes was a landmark of OA acclimation. Key genes involved in energy metabolism, e.g., photosynthesis, tricarboxylic acid cycle, oxidative phosphorylation, and nitrogen metabolism, were highly upregulated under OA, contributing to increases in the Chl a (55.05%) and Caro (28.37%). The enhanced antioxidant enzyme activities (i.e. CAT, GR) and upregulated genes (i.e. glutathione peroxidase, ascorbate peroxidase, heat shock protein, 20S proteasome, aldehyde dehydrogenase, and apolipoprotein) benefit cells against the potential lower pH stress condition under OA. In addition, the downregulation of four genes associated with motility suggested that the preserved energy could further boost growth. In conclusion, the present study suggests that K. mikimotoi exhibits efficient gene expression regulation for the utilization of energy and resistance to OA-induced stress. Taken together, K. mikimotoi appeared as a tolerant species in response to OA. Thus, more extensive algal blooms that threaten marine organisms are likely in the future. These findings expand current knowledge on the gene expression of HAB-forming species in response to future OA.
Continue reading ‘The responses of harmful dinoflagellate Karenia mikimotoi to simulated ocean acidification at the transcriptional level’Internal controls for quantitative RT-PCR analysis of gene expression in response to ocean acidification in edible oysters
Published 24 January 2022 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, North Pacific, reproduction
The increase of CO2 by anthropogenic activities leads to a decrease of pH in the ocean surface due to ocean acidification (OA) process. Generally, OA not only reduces the rate of calcification in marine environments but also affects various physiological activities, especially in calcifiers, including edible oysters. Quantitative real-time PCR (qRT-PCR) is often used to detect gene expression in response to OA, which relies on the stability of internal control. However, the appropriate internal controls for OA experiments remain scarce especially in the marine calcifiers. Hence, this study developed internal controls for qRT-PCR assays using the Hong Kong oyster (Crassostrea hongkongensis) as a model to reveal gene expression profile during development under OA. In this study, 17 housekeeping genes were selected as the possible candidate of the internal controls. After a comprehensive interpretation from the multiple algorithms and software, GAPDH paired with RL23 is recommended for the normalization for planktonic larvae and benthic juveniles, but beyond that, TUBB and EF2 are recommended for post-metamorphic stage. Moreover, GAPDH and EF2 were suitable for various pH treatments, and TUBB, RL35 and RL23 could be the alternatives for OA experiments. These results are instrumental for the selection of internal control in Crassostrea hongkongensis during the development, and shed light on other molecular OA experiments in marine invertebrates for reference.
Continue reading ‘Internal controls for quantitative RT-PCR analysis of gene expression in response to ocean acidification in edible oysters’Seasonal variability and future projection of ocean acidification on the East China Sea shelf off the Changjiang Estuary
Published 24 January 2022 Science ClosedTags: chemistry, field, North Pacific
Ocean acidification (OA) occurs universally in the world’s oceans. Marginal seas are facing more serious OA than the open ocean due to strong anthropogenic and natural impacts. This study investigates carbonate dynamics on the East China Sea (ECS) shelf off the Changjiang Estuary using field observations made from 2015 to 2019 that cover all four seasons. In the low productivity cold seasons, the water was well-mixed vertically. The coastal area and the northern ECS were occupied by water characterized by high dissolved inorganic carbon (DIC), low pH25 (pH at 25°C), and low ΩAr (saturation state index of aragonite), and influenced by the coastal water from the Yellow Sea (YS). However, during highly productive warm seasons, pH25 and ΩAr increased in the surface water but decreased in the bottom water as a result of strong biological DIC uptake in the surface water and CO2 production by strong organic matter remineralization in the bottom water. Strong remineralization decreased pH25 and ΩAr by 0.18 ± 0.08 and 0.73 ± 0.35 in the hypoxic bottom water in summer, even though the bottom water remained oversaturated with respect to aragonite (ΩAr > 1.0) during the surveys. Under the context of global OA and the strong seasonal acidification, the projected bottom water on the ECS shelf will be corrosive for aragonite by mid-century.
Continue reading ‘Seasonal variability and future projection of ocean acidification on the East China Sea shelf off the Changjiang Estuary’In situ skeletal growth rates of the solitary cold-water coral Tethocyathus endesa from the Chilean Fjord region
Published 21 January 2022 Science ClosedTags: biological response, BRcommunity, chemistry, corals, field, growth, laboratory, South Pacific
Cold-water corals (CWC) can be found throughout a wide range of latitudes (79°N–78°S). Since they lack the photosymbiosis known for most of their tropical counterparts, they may thrive below the euphotic zone. Consequently, their growth predominantly depends on the prevalent environmental conditions, such as general food availability, seawater chemistry, currents, and temperature. Most CWC communities live in regions that will face CaCO3 undersaturation by the end of the century and are thus predicted to be threatened by ocean acidification (OA). This scenario is especially true for species inhabiting the Chilean fjord system, where present-day carbonate water chemistry already reaches values predicted for the end of the century. To understand the effect of the prevailing environmental conditions on the biomineralization of the CWC Tethocyathus endesa, a solitary scleractinian widely distributed in the Chilean Comau Fjord, a 12-month in situ experiment was conducted. The in situ skeletal growth of the test corals was assessed at two sites using the buoyant weight method. Sites were chosen to cover the naturally present carbonate chemistry gradient, with pH levels ranging between 7.90 ± 0.01 (mean ± SD) and 7.70 ± 0.02, and an aragonite saturation (Ωarag) between 1.47 ± 0.03 and 0.98 ± 0.05. The findings of this study provide one of the first in situ growth assessments of a solitary CWC species, with a skeletal mass increase of 46 ± 28 mg per year and individual, at a rate of 0.03 ± 0.02% day. They also indicate that, although the local seawater chemistry can be assumed to be unfavorable for calcification, growth rates of T. endesa are comparable to other cold-water scleractinians in less corrosive waters (e.g., Lophelia pertusa in the Mediterranean Sea).
Continue reading ‘In situ skeletal growth rates of the solitary cold-water coral Tethocyathus endesa from the Chilean Fjord region’Regulation of the coral-associated bacteria and symbiodiniaceae in Acropora valida under ocean acidification
Published 20 January 2022 Science ClosedTags: biological response, BRcommunity, community composition, corals, laboratory, molecular biology, North Pacific, otherprocess, photosynthesis, protists
Ocean acidification is one of many stressors that coral reef ecosystems are currently contending with. Thus, understanding the response of key symbiotic microbes to ocean acidification is of great significance for understanding the adaptation mechanism and development trend of coral holobionts. Here, high-throughput sequencing technology was employed to investigate the coral-associated bacteria and Symbiodiniaceae of the ecologically important coral Acropora valida exposed to different pH gradients. After 30 days of acclimatization, we set four acidification gradients (pH 8.2, 7.8, 7.4, and 7.2, respectively), and each pH condition was applied for 10 days, with the whole experiment lasting for 70 days. Although the Symbiodiniaceae density decreased significantly, the coral did not appear to be bleached, and the real-time photosynthetic rate did not change significantly, indicating that A. valida has strong tolerance to acidification. Moreover, the Symbiodiniaceae community composition was hardly affected by ocean acidification, with the C1 subclade (Cladocopium goreaui) being dominant among the Symbiodiniaceae dominant types. The relative abundance of the Symbiodiniaceae background types was significantly higher at pH 7.2, indicating that ocean acidification might increase the stability of the community composition by regulating the Symbiodiniaceae rare biosphere. Furthermore, the stable symbiosis between the C1 subclade and coral host may contribute to the stability of the real-time photosynthetic efficiency. Finally, concerning the coral-associated bacteria, the stable symbiosis between Endozoicomonas and coral host is likely to help them adapt to ocean acidification. The significant increase in the relative abundance of Cyanobacteria at pH 7.2 may also compensate for the photosynthesis efficiency of a coral holobiont. In summary, this study suggests that the combined response of key symbiotic microbes helps the whole coral host resist the threats of ocean acidification.
Continue reading ‘Regulation of the coral-associated bacteria and symbiodiniaceae in Acropora valida under ocean acidification’Seven-Year Commitment Funds University of Hawaiʻi at Mānoa SOEST Ocean Conservation Research
Today, the University of Hawaiʻi at Mānoa’s School of Ocean and Earth Science and Technology (SOEST) announced a seven-year $50 million commitment from Dr. Priscilla Chan and Mark Zuckerberg, which will support various research groups within Hawaiʻi Institute of Marine Biology (HIMB). HIMB will leverage this gift to make meaningful progress in restoring Hawaiʻi’s ocean health.
This gift will fund research and programs that document changing ocean conditions, explore solutions to support healthier ocean ecosystems, enhance coastal resilience from storms and sea-level rise, and tackle challenges to marine organisms ranging from the tiniest corals to the largest predators.
University of Hawai‘i (UH) President David Lassner said, “This transformative gift will enable our world-class experts to accelerate conservation research for the benefit of Hawaiʻi and the world.” Lassner continued, “The ocean ecosystems that evolved over eons now face unprecedented threats from our growing human population and our behaviors. It is critical that we learn from previous generations who carefully balanced resource use and conservation. The clock is ticking, and we must fast-track not only our understanding of marine ecosystems and the impacts of climate change, but the actions we must take to reverse the devastation underway. There is no place on Earth better than Hawai‘i to do this work, and no institution better able than UH. We could not be more grateful for the investment of Dr. Priscilla Chan and Mark Zuckerberg in a better future for all of us and our planet.”
Hawai‘i is home to a rich diversity of marine life, including many threatened and endangered species. The accelerated pace of climate change and ocean acidification has altered environmental conditions faster than expected. Many species have difficulty adapting to the rapid changes taking place in the oceans and scientists see growing impacts to marine ecosystems.
The gift funds research on the impact of climate change on Hawaiian coastal waters, including areas of particular concern or natural refuges from ocean acidification effects. It will also support research on methods for more accurate forecasting of future ocean conditions, as well as efforts to study marine organisms like coral reefs, sharks, and other species.
Continue reading ‘$50M gift aims to improve Hawaiʻi’s ocean health’The Leibniz Centre for Tropical Marine Research (ZMT) in Bremen is a member of the Leibniz Association, which is supported by the German Federal and State Governments. Through its research, ZMT contributes to developing strategies for sustainable use of tropical coastal systems.
Project rationale and summary:
Species are “on the move” throughout the planet escaping hostile climatic conditions. These movements have advanced four times faster in the ocean than on land, causing dramatic ecosystem changes and redistributing resources across borders. The ecological, food security, and governance implications are obvious. Yet, two persistent gaps hinder our capacity to effectively manage coastal social-ecological systems to safeguard both fisheries and human wellbeing in the face of such challenges: i) regional studies documenting recent species redistributions have not quantified the societal repercussions, and ii) future projections have mapped expected catches and metrics of socio-economic impact (e.g. fisheries revenue) globally and at coarse resolutions, unfitting to support local or regional decision-making. Fish redistributions are particularly concerning, as three billion people depend on them for 15% of their animal protein intake and essential nutrients to tackle malnutrition. Although fish range shifts should be urgently investigated in the Global South, studies have focused disproportionately on wealthy parts of the world. EASMO will investigate for the first time the impact of climate change on the distribution of reef fish throughout the Eastern Tropical Pacific Ocean (ETP) considering cascading effects on biodiversity, ecosystem function, reefs’ contributions to people, climate feedbacks, and socio-economic wellbeing. Ultimately, it will deliver several layers of new scientific knowledge that can be directly integrated into decision-making tools, support adaptive transboundary governance approaches, and propel actions for meeting the UN Sustainable Development Goals 2 Zero hunger, 13 Climate action, and 14 Life below water. Find more details on the project here.
Selection criteria:
- PhD degree on marine fish ecophysiology, species distribution modelling and climate change ecology
- Knowledge on behavioural and physiological responses of fish to climate stressors (ocean warming and acidification)
- Practical experience in fish husbandry and experimental ecology and conducting single and/or multi-stressor climate change experiments on fish
- Research experience integrating empirical datasets across biological levels and/or into statistical models
- Familiarity and experience in modelling future climate change effects on species distribution
- Interest and knowledge on the effects of ocean acidification on fish and the pathways through which fish may affect the ocean’s carbonate chemistry
- Attention to detail and demonstrated proficiency in managing large datasets
- Strong analytical skills including demonstrated proficiency in applying a broad range of basic to advanced modelling and statistical analysis tools
- Demonstrated excellence in English scientific writing and oral communication
- A positive collaborative work ethics that promotes diversity, equality, and inclusiveness
Climate change, marine resources and a small Chilean community: making the connections
Published 19 January 2022 Science ClosedTags: fisheries, modeling, regionalmodeling, South Pacific
Climate change is affecting large-scale oceanic processes. How and when these changes will impact those reliant on marine resources is not yet clear. Here we use end-to-end modeling to track the impacts of expected changes through the marine ecosystem on a specific, small community: Cochamó, in the Gulf of Ancud wider area, Chile. This area is important for Chilean fisheries and aquaculture, with Cochamó reliant on both lower and upper trophic level marine resources. We applied the GOTM-ERSEM-BFM coupled hydro-biogeochemical water-column model to gauge lower-trophic level marine ecological community response to bottom-up stressors (climate change, ocean acidification), coupled to an existing Ecopath with Ecosim model for the area, which included top-down stressors (fishing). Social scientists also used participatory modeling (Systems Thinking and Bayesian Belief Networking) to identify key resources for Cochamó residents and to assess the community’s vulnerability to possible changes in key resources. Modeling results suggest that flagellate phytoplankton abundance will increase at the cost of other species (particularly diatoms), resulting in a greater risk of harmful algae blooms. Both climate change and acidification slightly increased primary production in the model. Higher trophic level results indicate that some targeted pelagic resources will decline (while benthic ones may benefit), but that these effects might be mitigated by strong fisheries management efforts. Participatory modeling suggests that Cochamó inhabitants anticipate marine ecosystem changes but are divided about possible adaptation strategies. For climate change impact quantification, detailed experimental studies are recommended based on the dominant threats identified here, with specific local species.
Continue reading ‘Climate change, marine resources and a small Chilean community: making the connections’Ocean acidification crisis and global warming observations from tropical corals (text & video)
Published 19 January 2022 Presentations ClosedHuman induced increases in atmospheric CO2 levels are warming the Earth’s ocean and also increasing the acidity of our shallow marine environments. This process, known as ocean acidification (OA), is caused by the absorption of atmospheric CO2 by the oceans and is threatening the ability of calcifying organisms to build their calcium carbonate skeletons. Our current understanding of the changes caused by OA in the tropical oceans is severely limited due to the lack of reliable long-term seawater pH monitoring and the difficulty in reconstructing past changes in pH and ocean chemistry in these remote environments. This project uses techniques to reconstruct past seawater conditions from long-living corals to observe the evolution of pH and carbonate chemistry in our tropical oceans. Improved multi-proxy techniques are also applied to observe sea surface temperature and hydroclimate changes over the past few hundred years to provide a historical context to our current climate crisis.
Continue reading ‘Ocean acidification crisis and global warming observations from tropical corals (text & video)’VIU science and technology community lecture series: ocean acidification in British Columbia’s coastal waters
Published 19 January 2022 Events ClosedDate: 2 March 2022
Time: 7:00 – 8:00 pm
Location: virtual
Description: Ocean acidification is a chemical change in seawater that is caused by the uptake of carbon dioxide from the atmosphere. As carbon dioxide increases in the atmosphere from human activity, this chemical change intensifies and impacts marine life. This talk will review what we know and what we need to know about the patterns and impacts of ocean acidification in British Columbia coastal waters.
Bio: Dr. Wiley Evans is a chemical oceanographer at the Hakai Institute in British Columbia, Canada. He completed his PhD at Oregon State University studying carbon dioxide exchange between the ocean and atmosphere from northern California to southeast Alaska. He then worked on monitoring ocean acidification as a postdoctoral researcher at the University of Alaska Fairbanks, and then as a research associate at the U.S. National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory before joining the Hakai Institute. Wiley manages Hakai Institute’s Ocean Acidification Program and is the co‐chair for the British Columbia Ocean Acidification and Hypoxia Action Plan led by the Ministry of Agriculture, Food and Fisheries.
Vancouver Island University’s (VIU’s) spring 2022 Science and Technology Lecture Series is shining the spotlight on climate change research.
“Climate change is one of the greatest challenges currently facing humanity, and everyone will be impacted by the rapid environmental changes that are currently occurring on Earth,” says Dr. Tim Stokes, a VIU Earth Sciences Professor and the series coordinator and organizer.
At each lecture, researchers will share their findings on climate change science and delve into topics such as investigating changing snowpacks in Coastal BC, water resource management on Vancouver Island, and tracking past shifts in sea levels and their effects on humans. The Science and Technology Lecture Series has been offered almost every spring term for the last 15 years and was created as an opportunity for researchers to share their findings on a range of different science issues and topics with the VIU community and the public.
The series runs on Wednesdays, from 7-8 pm, from January 19 to April 6. There is no lecture on February 23, during VIU’s Reading Week. Lectures are offered in-person at Building 355, Room 203 at VIU’s Nanaimo campus and most lectures will be live streamed via Zoom. In-person attendance is at a reduced capacity of 50% and attendees must provide proof of vaccination and wear masks at all times. For Zoom links or to register to attend in-person lectures please visit the Science and Technology Community Lecture Series website.
Continue reading ‘VIU science and technology community lecture series: ocean acidification in British Columbia’s coastal waters’Impact of ocean acidification on physiology and microbiota in hepatopancreas of Pacific oyster Crassostrea gigas
Published 18 January 2022 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, North Pacific, physiology
The hepatopancreas is an important tissue involved in various biological metabolism for mollusks, but its responses to ocean acidification (OA) have not been well evaluated. In this study, the oysters were cultured in simulated conditions by continuously bubbling with ambient air (pH=8.10) or air-CO2 (pH=7.50) for up to two months, and the variations on the antioxidant capacity, digestive ability, and microbiota composition in hepatopancreas of Crassostrea gigas were analyzed. The results show that although superoxide dismutase and glutathione responded quickly to OA stress, the antioxidant capacity of the hepatopancreas was inhibited, as revealed by the decrease of the total antioxidant capacity, which led to an upward trend of the malondialdehyde, demonstrating that the oxidative damages were accumulated under the OA process. The determination of the digestive ability manifested as the decrease of pepsin activity and the recovery of lipase and amylase activity after long-term acidification, which may be helpful to improve the adaptability of oysters. In addition, analysis on 16S rDNA amplicon revealed that the total species abundance and diversity of the hepatopancreas microbiota experienced a dynamic change, but finally it decreased greatly after long-term acidification. The structure of the hepatopancreas microbiota was changed drastically with the change of the dominant species from aerobic to the anaerobic and facultative anaerobic bacteria, and the abnormal proliferation of some species, such as genus of Mycoplasma and order Clostridiales, which may aggravate the adverse effects of OA on the physiological functions of the hepatopancreas. As a result, our findings enrich our understanding of the accumulated oxidative damage and adaptive digestive ability in oyster hepatopancreas caused by OA. For the first time, the changes of the hepatopancreas microbiota under long-term acidification conditions are described, proving a good reference for the study of the response and adaptation mechanisms of bivalve mollusks in a wide range of oceans OA.
Continue reading ‘Impact of ocean acidification on physiology and microbiota in hepatopancreas of Pacific oyster Crassostrea gigas’
Effects of water acidification on immune responses of the gercacinid,
Cardiosoma armatum (Herklots, 1851)
Published 18 January 2022
Science
Closed
Tags: biological response, crustaceans, laboratory, North Atlantic, physiology, toxicants
The biological response to chemical pollutants reflects the acid–base status of an aquatic ecosystem. The gercacinid, Cardiosoma armatum (75±0.1 g) was exposed to acidified waters to evaluate the effects on its immune parameters. The crabs were exposed to pH 4.0, 5.0, 6.0 and 7.8 (control) for 28 days. The hematological parameters of control crabs and crabs exposed to varied doses of acidified water indicated a marked reduction. Significant (p<0.05) higher alkaline phosphatase and albumen were obtained in pH 4.0, 5.0 and 6.0 compared to control; other values were mostly similar to control. The highest superoxide dismutase (SOD) (252.61±0.06 min/mg pro) was recorded in control group, while highest CAT activity (2.08±0.16 min/mg protein) was recorded in crabs exposed to pH 4 treatment. Furthermore, the control group’s SOD activity was significantly higher than the exposed groups. With a lower pH, the quantities of malondialdehyde increased substantially and were significantly different from the control group. While these findings demonstrate that changes in pH have limited impact on energy use, decreasing immune system conditions show that C. armatum is susceptible to pH variations and may be influenced in aquaculture, where a pH drop is more prominent.
Continue reading ‘Effects of water acidification on immune responses of the gercacinid,Cardiosoma armatum (Herklots, 1851)’
Ecosystem metabolism modulates the dynamics of hypoxia and acidification across temperate coastal habitat types
Published 17 January 2022 Science ClosedTags: chemistry, field, North Atlantic
Changes in photosynthetic and respiration rates in coastal marine habitats cause considerable variability in ecosystem metabolism on timescales ranging from diel to tidal to seasonal. Here, temporal and spatial dynamics of dissolved oxygen (DO), carbonate chemistry, and net ecosystem metabolism (NEM) were quantified from spring through fall in multiple, distinct, temperate estuarine habitats: seagrass meadows, salt marshes, an open water estuary, and a shallow water habitat dominated by benthic macroalgae. DO and pHT (total scale) measurements were made via high frequency sensor arrays coupled with discrete measurements of dissolved inorganic carbon (DIC) and high-resolution spatial mapping was used to document intra-habitat spatial variability. All habitats displayed clear diurnal patterns of pHT and DO that were stronger than tidal signals, with minimums and maximums observed during early morning and afternoon, respectively. Diel ranges in pHT and DO varied by site. In seagrass meadows and the open estuarine site, pHT ranged 7.8–8.4 and 7.5–8.2, respectively, while DO exceeded hypoxic thresholds and aragonite was typically saturated (ΩAr > 1). Conversely, pHT in a shallow macroalgal and salt marsh dominated habitats exhibited strong diel oscillations in pHT (6.9–8.4) with diel acidic (pHT < 7) and hypoxic (DO < 3 mg L–1) conditions often observed during summer along with extended periods of aragonite undersaturation (ΩAr < 1). The partial pressure of carbon dioxide (pCO2) exceeded 3000 and 2000 μatm in the salt marsh and macroalgal bed, respectively, while pCO2 never exceeded 1000 μatm in the seagrass and open estuarine site. Mesoscale (50–100 m) spatial variability was observed across sites with the lowest pHT and DO found within regions of more restricted flow. NEM across habitats ranged from net autotrophic (macroalgae and seagrass) to metabolically balanced (open water) and net heterotrophic (salt marsh). Each habitat exhibited distinct buffering capacities, varying seasonally, and modulated by adjacent biological activity and variations in total alkalinity (TA) and DIC. As future predicted declines in pH and DO are likely to shrink the spatial extent of estuarine refuges from acidification and hypoxia, efforts are required to expand seagrass meadows and the aquaculture of macroalgae to maximize their ecosystem benefits and maintain these estuarine refuges.
Continue reading ‘Ecosystem metabolism modulates the dynamics of hypoxia and acidification across temperate coastal habitat types’Responses of benthic calcifying algae to ocean acidification differ between laboratory and field settings
Published 17 January 2022 Science ClosedTags: algae, biological response, calcification, chemistry, field, laboratory, methods
Accurately predicting the effects of ocean and coastal acidification on marine ecosystems requires understanding how responses scale from laboratory experiments to the natural world. Using benthic calcifying macroalgae as a model system, we performed a semi-quantitative synthesis to compare directional responses between laboratory experiments and field studies. Variability in ecological, spatial, and temporal scales across studies, and the disparity in the number of responses documented in laboratory and field settings, make direct comparisons difficult. Despite these differences, some responses, including community-level measurements, were consistent across laboratory and field studies. However, there were also mismatches in the directionality of many responses with more negative acidification impacts reported in laboratory experiments. Recommendations to improve our ability to scale responses include: (i) developing novel approaches to allow measurements of the same responses in laboratory and field settings, and (ii) researching understudied calcifying benthic macroalgal species and responses. Incorporating these guidelines into research programs will yield data more suitable for robust meta-analyses and will facilitate the development of ecosystem models that incorporate proper scaling of organismal responses to in situ acidification. This, in turn, will allow for more accurate predictions of future changes in ecosystem health and function in a rapidly changing natural climate.
Continue reading ‘Responses of benthic calcifying algae to ocean acidification differ between laboratory and field settings’Direct and latent effects of ocean acidification on the transition of a sea urchin from planktonic larva to benthic juvenile
Published 17 January 2022 Science ClosedTags: biological response, echinoderms, laboratory, morphology, mortality, North Atlantic, reproduction
Ongoing ocean acidification (OA) is expected to affect marine organisms and ecosystems. While sea urchins can survive a wide range of pH, this comes at a high energetic cost, and early life stages are particularly vulnerable. Information on how OA affects transitions between life-history stages is scarce. We evaluated the direct and indirect effects of pH (pHT 8.0, 7.6 and 7.2) on the development and transition between life-history stages of the sea urchin Strongylocentrotus droebachiensis, from fertilization to early juvenile. Continuous exposure to low pH negatively affected larval mortality and growth. At pH 7.2, formation of the rudiment (the primordial juvenile) was delayed by two days. Larvae raised at pH 8.0 and transferred to 7.2 after competency had mortality rates five to six times lower than those kept at 8.0, indicating that pH also has a direct effect on older, competent larvae. Latent effects were visible on the larvae raised at pH 7.6: they were more successful in settling (45%) and metamorphosing (30%) than larvae raised at 8.0 (17 and 1% respectively). These direct and indirect effects of OA on settlement and metamorphosis have important implications for population survival.
Continue reading ‘Direct and latent effects of ocean acidification on the transition of a sea urchin from planktonic larva to benthic juvenile’Ocean acidification triggers cell signaling, suppress immune and calcification in the Pacific oyster larvae
Published 14 January 2022 Science ClosedTags: biological response, calcification, laboratory, molecular biology, mollusks, physiology, reproduction
Elevated carbon dioxide levels in ocean waters, an anthropogenic stressor, can alter the chemical equilibrium of seawater through a process called ocean acidification (OA). The resultant reduction of pH can be detrimental during the early developmental stages of the commercially important edible Pacific oyster Crassostrea gigas; the ability of larvae to join a population is likely to be compromised by declining ocean pH. Given this threat, it is important to study the molecular mechanisms that these organisms use to overcome OA stress at the gene expression level. Here, we performed transcriptome profiling in oyster larvae following exposure to ambient (8.1) and reduced (7.4) pH during the pre-settlement growth period (i.e., 18 d post fertilization) using RNA-seq with Illumina sequencing technology. In total, 1,808 differentially expressed genes (DEGs) were identified, 1,410 of which were matched by BLAST against the Swiss-Prot database. Gene ontology classification showed that most of these DEGs were related to ribosomal, calcium ion binding, cell adhesion and apoptotic processes. Pathway enrichment analysis revealed that low pH (7.4) enhanced energy production and organelle biogenesis but prominently suppressed several immune response pathways. Moreover, activation of the MAPK signaling pathway was observed along with inhibition of the Wnt, VEGF, and ErbB pathways, highlighting the fact that the initiation of stress responses is given priority over larval development or shell growth when the larvae cope with low pH. In conclusion, our study demonstrated a unique gene expression profiling approach in studying oyster larval responses to OA, which not only provides comprehensive insights into the mechanisms underlying oyster tolerance to CO2-driven decreases in ocean pH but also supplies a valuable genomic resource for further studies in this species.
Continue reading ‘Ocean acidification triggers cell signaling, suppress immune and calcification in the Pacific oyster larvae’Assessment of the juvenile vulnerability of symbiont-bearing giant clams to ocean acidification
Published 14 January 2022 Science ClosedTags: biological response, calcification, laboratory, molecular biology, mollusks, morphology, mortality, physiology
Highlights
- Physiological and molecular responses were investigated in response to OA.
- OA did not caused reduction in survival and shell growth performance.
- OA significantly reduced NCR, symbiont photosynthetic yield and density.
- Giant clams can modulating expression of metabolic and ion transport genes to OA.
Abstract
Ocean acidification (OA) severely affects marine bivalves, especially their calcification processes. However, very little is known about the fate of symbiont-bearing giant clams in the acidified oceans, which hinders our ability to develop strategies to protect this ecologically and economically important group in coral reef ecosystems. Here, we explored the integrated juvenile responses of fluted giant clam Tridacna squamosa (Lamarck, 1819) to acidified seawater at different levels of biological organization. Our results revealed that OA did not cause a significant reduction in survival and shell growth performance, indicating that T. squamosa juveniles are tolerated to moderate acidification. Yet, significantly reduced net calcification rate demonstrated the calcifying physiology sensitivity to OA, in line with significant declines in symbiont photosynthetic yield and zooxanthellae density which in turn lowered the amount of energy supply for energetically expensive calcification processes. Subsequent transcriptome sequencing and comparative analysis of differentially expressed genes revealed that the regulation of calcification processes, such as transport of calcification substrates, acid-base regulation, synthesis of organic matrix in the calcifying fluid, as well as metabolic depression were the major response to OA. Taken together, the integration of physiological and molecular responses can provide a comprehensive understanding of how the early life history stages of giant clams respond to OA and make an important leap forward in assessing their fate under future ocean conditions.
Continue reading ‘Assessment of the juvenile vulnerability of symbiont-bearing giant clams to ocean acidification’
