This study examines the physiological response of the Atlantic surfclam (Spisula solidissima) to ocean acidification in warm summer temperatures. Working with ambient seawater, this experiment manipulated pH conditions while maintaining natural diel fluctuations and seasonal shifts in temperature. One-year-old surfclams were exposed to one of three pH conditions (ambient (control): 7.8 ± 0.07, medium: 7.51 ± 0.10, or low: 7.20 ± 0.10) in flow-through conditions for six weeks, and feeding and digestive physiology was measured after one day, two weeks, and six weeks. After six weeks of exposure to medium and low pH treatments, growth was not clearly affected, and, contrastingly, feeding and digestive physiology displayed variable responses to pH over time. Seemingly, low pH reduced feeding and absorption rates compared to both the medium treatment and ambient (control) condition; however, this response was clearer after two weeks compared to one day. At six weeks, suppressed physiological rates across both pH treatments and the ambient condition suggest thermal stress from high ambient water temperatures experienced the week prior (24–26 °C) dominated over any changes from low pH. Results from this study provide important information about reduced energy acquisition in surfclams in acidified environments and highlight the need for conducting multistressor experiments that consider the combined effects of temperature and pH stress.
Continue reading ‘Effects of ocean acidification and summer thermal stress on the physiology and growth of the atlantic surfclam (Spisula solidissima)’Posts Tagged 'morphology'
Effects of ocean acidification and summer thermal stress on the physiology and growth of the atlantic surfclam (Spisula solidissima)
Published 29 April 2024 Science Leave a CommentTags: biological response, chemistry, laboratory, mollusks, morphology, performance
Influencing intertidal food web: implications of ocean acidification on the physiological energetics of key species the ‘wedge’ clam Donax faba
Published 26 April 2024 Science Leave a CommentTags: biological response, chemistry, growth, Indian, laboratory, mollusks, morphology, physiology
Highlights
- Daily growth rate & calcium concentration have significantly decreased in acidified condition.
- Total antioxidants and antioxidant enzymes showed an upward tendency.
- Nutrient composition in clams has altered in acidified condition compared to control.
- Prolonged exposure to OA will cause deleterious effects on clams thereby upsetting the intertidal food chain.
Abstract
Ocean acidification has become increasingly severe in coastal areas. It poses emerging threats to coastal organisms and influences ecological functioning. Donax faba, a dominant clam in the intertidal zone of the Bay of Bengal, plays an important role in the coastal food web. This clam has been widely consumed by the local communities and also acts as a staple diet for shorebirds and crustaceans. In this paper, we investigated how acidified conditions will influence the physiology, biochemical constituents, and energetics of Donax faba. Upon incubation for 2 months in lowered pH 7.7 ± 0.05 and control 8.1 ± 0.05 conditions, we found a delayed growth in the acidified conditions followed by decrease in calcium ions in the clam shell. Although not significant, we found the digestive enzymes showed a downward trend. Total antioxidant was significantly increased in the acidified condition compared to the control. Though not significant, the expression level of MDA and antioxidant enzymes (SOD, CAT, GST, GPX, and APX) showed increasing trend in acidified samples. Among nutrients such as amino acids and fatty acids, there was no significant difference between treatments, however, showed a downward trend in the acidified conditions compared to control. Among the minerals, iron and zinc showed significant increase in the acidified conditions. The above results suggest that the clam growth, and physiological energetics may have deleterious effects if exposed for longer durations at lowered pH condition thereby affecting the organisms involved in the coastal food web.
Continue reading ‘Influencing intertidal food web: implications of ocean acidification on the physiological energetics of key species the ‘wedge’ clam Donax faba’Using museum collections to assess the impact of industrialization on mussel (Mytilus edulis) calcification
Published 23 April 2024 Science Leave a CommentTags: biological response, chemistry, laboratory, mollusks, morphology, North Atlantic, physiology
Mytilus edulis is a commercially and ecologically important species found along the east coast of the United States. Ecologically, M. edulis improves water quality through filtration feeding and provides habitat formation and coastal protection through reef formation. Like many marine calcifiers, ocean warming, and acidification are a growing threat to these organisms—impacting their morphology and function. Museum collections are useful in assessing long-term environmental impacts on organisms in a natural multi-stressor environment, where acclimation and adaptation can be considered. Using the American Museum of Natural History collections ranging from the early 1900s until now, we show that shell porosity changes through time. Shells collected today are significantly more porous than shells collected in the 1960s and, at some sites, than shells collected from the early 1900s. The disparity between porosity changes matches well with the warming that occurred over the last 130 years in the north Atlantic suggesting that warming is causing porosity changes. However, more work is required to discern local environmental impacts and to fully identify porosity drivers. Since, porosity is known to affect structural integrity, porosity increasing through time could have negative consequences for mussel reef structural integrity and hence habitat formation and storm defenses.
Continue reading ‘Using museum collections to assess the impact of industrialization on mussel (Mytilus edulis) calcification’Narrowed gene functions and enhanced transposon activity are associated with high tolerance to ocean acidification in a juvenile subarctic crustacean
Published 11 April 2024 Science ClosedTags: biological response, chemistry, crustaceans, growth, laboratory, molecular biology, morphology, mortality, North Pacific, physiology, reproduction
Ocean acidification (OA) threatens marine crustaceans, particularly those at high latitudes where conditions are rapidly changing. Red king crab (RKC) support important fisheries in Alaskan waters. RKC early life stages are sensitive to OA when exposure occurs as embryos and juveniles. However, in a supporting study, RKC were surprisingly tolerant of varying OA conditions (pH 7.5, 7.8, & 8.0) when reared long-term from larval hatching to the first crab stage (C1). Here, we examined gene expression in the C1 juveniles to characterize transcriptional activity of these OA-tolerant crabs. Expression of nearly half of all genes (44%) correlated with OA treatment, suggesting a strong molecular response to OA, contrary to the phenotypic results. Downregulated functions were numerous in response to OA, and included reduced energy production, biosynthesis, immune function, and notably lipid and carbohydrate metabolic processes, which suggest a shift in metabolic strategy to protein catabolism, possibly to reduce CO2 production and facilitate acid/base regulation. Only a handful of functions were enriched in OA-induced genes, which were related to transcription regulation, control of growth and cell death, and signaling activity. Transposon activity was high in OA-reared crab, many of which were upregulated at consistent levels, suggesting that transposon mobilization may be a component of the RKC OA-response system. Genetic composition did not differ among OA treatments indicating that transcriptional differences in OA-reared crab were more likely attributed to phenotypic plasticity than selective mortality. Our results suggest that OA-reared RKC have a narrowed, possibly optimized, set of gene functions that enables OA-tolerance through the early juvenile stage. OA-exposure from hatch may benefit RKC and related species by “hardening” them against OA through physiological reprogramming. Future studies should test OA-hardened crabs in additional challenges, as metabolic and immune limitations may ultimately make them more vulnerable to infection or secondary stressors.
Continue reading ‘Narrowed gene functions and enhanced transposon activity are associated with high tolerance to ocean acidification in a juvenile subarctic crustacean’A laboratory study of the increasing competitiveness of Karenia mikimotoi under rising CO2 scenario
Published 3 April 2024 Science ClosedTags: algae, biological response, community composition, laboratory, morphology, multiple factors, North Pacific, otherprocess, physiology, phytoplankton, temperature
Highlights
- Rising CO2 level promoted the growth of Karenia mikimotoi.
- Rising CO2 weakened allelopathic effects of Ulva pertusa on K. mikimotoi.
- High CO2 level disturbed the synthesis of free fatty acids in U. pertusa, decreasing its allelopathic effects.
- Rising CO2 increases the outbreak risk of K. mikimotoi.
Abstract
Ocean acidification (OA) driven by elevated carbon dioxide (CO2) levels is expected to disturb marine ecological processes, including the formation and control of harmful algal blooms (HABs). In this study, the effects of rising CO2 on the allelopathic effects of macroalgae Ulva pertusa to a toxic dinoflagellate Karenia mikimotoi were investigated. It was found that high level of CO2 (1000 ppmv) promoted the competitive growth of K. mikimotoi compared to the group of present ambient CO2 level (420ppmv), with the number of algal cell increased from 32.2 × 104 cells/mL to 36.75 × 104 cells/mL after 96 h mono-culture. Additionally, rising CO2 level weakened allelopathic effects of U. pertusa on K. mikimotoi, as demonstrated by the decreased inhibition rate (50.6 % under the original condition VS 34.3 % under the acidified condition after 96 h co-culture) and the decreased reactive oxygen species (ROS) level, malondialdehyde (MDA) content, antioxidant enzymes activity (superoxide dismutase (SOD), peroxidase (POD), glutathione peroxidase (GPX), glutathione reductase (GR) and catalase (CAT) and non-enzymatic antioxidants (glutathione (GSH) and ascorbic acid (ascorbate, vitamin C). Indicators for cell apoptosis of K. mikimotoi including decreased caspase-3 and -9 protease activity were observed when the co-cultured systems were under rising CO2 exposure. Furthermore, high CO2 level disturbed fatty acid synthesis in U. pertusa and significantly decreased the contents of fatty acids with allelopathy, resulting in the allelopathy weakening of U. pertusa. Collectively, rising CO2 level promoted the growth of K. mikimotoi and weakened allelopathic effects of U. pertusa on K. mikimotoi, indicating the increased difficulties in controlling K. mikimotoi using macroalgae in the future.
Continue reading ‘A laboratory study of the increasing competitiveness of Karenia mikimotoi under rising CO2 scenario’Adverse environmental perturbations may threaten kelp farming sustainability by exacerbating enterobacterales diseases
Published 25 March 2024 Science ClosedTags: algae, biological response, community composition, field, laboratory, light, molecular biology, morphology, mortality, multiple factors, North Pacific, otherprocess, physiology, prokaryotes, protists, reproduction
Globally kelp farming is gaining attention to mitigate land-use pressures and achieve carbon neutrality. However, the influence of environmental perturbations on kelp farming remains largely unknown. Recently, a severe disease outbreak caused extensive kelp mortality in Sanggou Bay, China, one of the world’s largest high-density kelp farming areas. Here, through in situ investigations and simulation experiments, we find indications that an anomalously dramatic increase in elevated coastal seawater light penetration may have contributed to dysbiosis in the kelp Saccharina japonica’s microbiome. This dysbiosis promoted the proliferation of opportunistic pathogenic Enterobacterales, mainly including the genera Colwellia and Pseudoalteromonas. Using transcriptomic analyses, we revealed that high-light conditions likely induced oxidative stress in kelp, potentially facilitating opportunistic bacterial Enterobacterales attack that activates a terrestrial plant-like pattern recognition receptor system in kelp. Furthermore, we uncover crucial genotypic determinants of Enterobacterales dominance and pathogenicity within kelp tissue, including pathogen-associated molecular patterns, potential membrane-damaging toxins, and alginate and mannitol lysis capability. Finally, through analysis of kelp-associated microbiome data sets under the influence of ocean warming and acidification, we conclude that such Enterobacterales favoring microbiome shifts are likely to become more prevalent in future environmental conditions. Our study highlights the need for understanding complex environmental influences on kelp health and associated microbiomes for the sustainable development of seaweed farming.
Continue reading ‘Adverse environmental perturbations may threaten kelp farming sustainability by exacerbating enterobacterales diseases’Short periods of decreased water flow may modulate long-term ocean acidification in reef-building corals
Published 14 March 2024 Science ClosedTags: biological response, chemistry, corals, flow, growth, laboratory, morphology, multiple factors, photosynthesis, physiology, respiration
Ocean acidification (OA) poses a major threat to reef-building corals. Although water flow variability is common in coral reefs and modulates coral physiology, the interactive effects of flow and OA on corals remain poorly understood. Therefore, we performed a three-month OA experiment investigating the effect of changes in flow on coral physiology. We exposed the reef-building corals Acropora cytherea, Pocillopora verrucosa, and Porites cylindrica to control (pH 8.0) and OA (pH 7.8) conditions at moderate flow (6 cm s-1) and monitored OA effects on growth. Throughout the experiment, we intermittently exposed all corals to low flow (2 cm s-1) for 1.5 h and measured their photosynthesis:photosynthesis (P:R) ratio under low and moderate flow. On average, corals under OA calcified 18 % less and grew 23 % less in surface area than those at ambient pH. We observed species-specific interactive effects of OA and flow on coral physiology. P:R ratios decreased after 12 weeks of OA in A. cytherea (22 %) and P. cylindrica (28 %) under moderate flow, but were unaffected by OA under low flow. P:R ratios were stable in P. verrucosa. These results suggest that short periods of decreased water flow may modulate OA effects on some coral species, indicating that flow variability is a factor to consider when assessing long-term effects of climate change.
Continue reading ‘Short periods of decreased water flow may modulate long-term ocean acidification in reef-building corals’Ocean acidification impact on the uptake of trace elements by mussels and their biochemical effects
Published 13 March 2024 Science ClosedTags: biological response, chemistry, laboratory, metals, mollusks, morphology, multiple factors, North Atlantic, performance, physiology
Highlights
- Copper and cerium bioavailability may increase under ocean acidification.
- Ocean acidification impacts metal accumulation in mussel gills.
- Biochemical responses in M. galloprovincialis altered by trace metals and OA.
- Complex interplay of oxidative stress markers affected by OA and metals.
Abstract
This study delves into the intricate interplay between ocean acidification (OA), metal bioaccumulation, and cellular responses using mussels (Mytilus galloprovincialis) as bioindicators. For this purpose, environmentally realistic concentrations of isotopically labelled metals (Cd, Cu, Ag, Ce) were added to investigate whether the OA increase would modify metal bioaccumulation and induce adverse effects at the cellular level. The study reveals that while certain elements like Cd and Ag might remain unaffected by OA, the bioavailability of Cu and Ce could potentially escalate, leading to amplified accumulation in marine organisms. The present findings highlight a significant rise in Ce concentrations within different mussel organs under elevated pCO2 conditions, accompanied by an increased isotopic fractionation of Ce (140/142Ce), suggesting a heightened potential for metal accumulation under OA. The results suggested that OA influenced metal accumulation in the gills of mussels. Conversely, metal accumulation in the digestive gland was unaffected by OA. The exposure to both trace metals and OA affects the biochemical responses of M. galloprovincialis, leading to increased metabolic capacity, changes in energy reserves, and alterations in oxidative stress markers, but the specific effects on other biomarkers (e.g., lipid peroxidation, some enzymatic responses or acetylcholinesterase activity) were not uniform, suggesting complex interactions between the stressors and the biochemical pathways in the mussels.
Continue reading ‘Ocean acidification impact on the uptake of trace elements by mussels and their biochemical effects’Quantifying the impacts of multiple stressors on the production of marine benthic resources
Published 11 March 2024 Science ClosedTags: abundance, algae, biogeochemistry, biological response, BRcommunity, chemistry, communityMF, laboratory, mesocosms, methods, modeling, mollusks, morphology, mortality, multiple factors, North Atlantic, nutrients, otherprocess, performance, physiology, regionalmodeling, temperature
Coastal ecosystems are among the most heavily affected by climate change and anthropogenic activities, which impacts their diversity, productivity and functioning and puts many of the key ecosystem services that they provide at risk. Although empirical studies have moved beyond single-stressor-single-species experiments with limited extrapolation potential and have increasingly investigated the cumulative effects of simultaneously occurring multiple stressors, consistent generalities have not yet been identified. Upscaling from controlled experiments to natural ecosystems, therefore, remains an unsolved challenge. Disentangling the independent and cumulative effects of multiple stressors across different levels of biological complexity, revealing the underlying mechanisms and understanding how coastal ecosystems may respond to predicted scenarios of global change is critical to manage and protect our natural capital.
In this thesis, I advance multiple stressor research by applying complementary approaches to quantify the impact of multiple stressors on marine benthic resources and thereby help predict the consequences of expected climate change for coastal habitats. First, I present the newly developed experimental platform QIMS (Quantifying the Impacts of Multiple Stressors) that overcomes some of the shortfalls of previous multiple stressor research (Chapter 2). Second, in a novel empirical study, I investigate the independent and combined effects of moderate ocean warming and acidification on the functioning and production of mussels and algae, considering the effects of interspecific interactions in the presence or absence of the respective other species (Chapter 3). Third, I synthesise monitoring data from Dublin Bay (representative of a typical metropolitan estuary) using conditional interference and a Bayesian Network model and provide alternative system trajectories according to different climate change scenarios. From this new model, I deepen the understanding of the complex linkages between environmental conditions and the diversity and functioning of Dublin Bay to support local decision making and management (Chapter 4).
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Continue reading ‘Quantifying the impacts of multiple stressors on the production of marine benthic resources’Physiological impacts of climate change on juvenile American lobster Homarus americanus (Decapoda: Astacidea: Nephropidae), a commercially important species
Published 6 March 2024 Science ClosedTags: abundance, biological response, BRcommunity, calcification, crustaceans, laboratory, morphology, multiple factors, North Atlantic, otherprocess, temperature
The American lobster, Homarus americanus, H. Milne Edwards, 1837 is an ecologically, economically, and culturally valuable marine resource for the coastal communities in the Gulf of Maine. Lobsters in the Gulf of Maine are experiencing the effects of rapid warming and acidification due to climate change. Lobster shells are comprised of chitin with precisely precipitated minerals (calcite, amorphous calcium carbonate, and carbonate apatite) that provide structural integrity to the shell and protection against predators and microbial intrusion. We examined the combined effects of ocean warming and acidification on shell mineralogy, epibiont abundance, and growth in early benthic juveniles. Lobsters were grown under six different temperature/pCO2 treatment conditions over 52 days (three replicates per treatment) aligned with environmentally relevant as well as predicted future extremes. Elevated pCO2 and temperature led to a decrease in shell calcium and magnesium content, suggesting that these environmental stressors inhibit shell biomineralization. There was an interactive effect of the stressors on epibiont abundance with the probability of epibiont coverage increasing with increasing pCO2 and temperature. Elevated pCO2 alone was significantly correlated (P = 0.002) to decreased growth, but only for female lobsters. Ocean acidification and warming significantly affect shell integrity in juvenile lobster, increasing risk to injury and disease with potential downstream consequences for the lobster fishery.
Continue reading ‘Physiological impacts of climate change on juvenile American lobster Homarus americanus (Decapoda: Astacidea: Nephropidae), a commercially important species ‘Morphometric changes in Watznaueria barnesiae across the mid Cretaceous: Paleoecological implications
Published 5 March 2024 Science ClosedTags: biological response, field, Mediterranean, morphology, paleo, phytoplankton, sediment
Highligthts
- W. barnesiae evidenced moderate size variations in the mid Cretaceous (western Tethys).
- Size variations in W. barnesiae differed from those of B. constans.
- During OAE1a and OAE1b both species showed size reduction and ellipticity increase.
- The effects of fertility were opposite on the two species size variations.
Abstract
This study reveals moderate yet important variations in Watznaueria barnesiae coccolith and central unit size throughout the Aptian–late Cenomanian (27 my) time interval in western Tethys. A new statistical approach was applied to determine whether non-random size trends apply to these metrics and to identify possible links between their variation and fertility or temperature. During OAE 1a, W. barnesiae coccoliths were the smallest and the most elliptical, with reduced central unit size. A further minor size decrease occurs during OAE 1b but not during OAE 1d. From the middle Albian to the middle Cenomanian, larger and less elliptical coccoliths are observed, with unchanged central unit dimensions. These results, together with concomitantly larger size changes in Biscutum constans confirm that W. barnesiae is a tolerant taxon. High-frequency, high-amplitude paleoenvironmental changes during the Aptian–early Albian indicate that temperature and fertility – either individually or in combination – had no direct impact on the mean coccolith size and potentially other factors affected coccolith size. Instead, lower nutrients with lower temperatures probably played a role in promoting larger W. barnesiae but smaller B. constans coccoliths during the middle Albian–Cenomanian. The size and ellipticity changes during OAE 1a and 1b were the strongest, likely resulting from ocean acidification and trace metal inputs, in addition to (or independently of) fertility and temperature variations.
Continue reading ‘Morphometric changes in Watznaueria barnesiae across the mid Cretaceous: Paleoecological implications’Marine benthic communities of the future: use of acidified natural systems
Published 5 March 2024 Science ClosedTags: adaptation, biological response, BRcommunity, chemistry, community composition, echinoderms, field, molecular biology, morphology, North Atlantic, otherprocess, vents
Ocean acidification (OA) is one of the most significant threats to marine organisms and is linked to climate change. It occurs when anthropogenic CO2 is absorbed by the oceans, resulting in a decrease in seawater pH and the dissolution of calcium carbonate. Projections indicate that OA will exacerbate in the future, highlighting the need to understand its impact on marine ecosystems. Much of our knowledge about the effects of OA comes from laboratory experiments, as predicting responses in natural conditions is challenging. Therefore, studies focusing on species living in naturally acidified systems, such as shallow CO2 seeps or vents, are becoming increasingly popular to obtain more realistic predictions.
This doctoral thesis, consisting of 5 chapters, explores the effects of ocean acidification on benthic communities in the subtropical Atlantic Ocean, using the naturally acidified CO2 vent system off the southern coast of La Palma Island in the Canary Islands, Spain, as a natural laboratory. Chapter 1 serves as an introduction to this thesis, explaining what naturally acidified systems are and discussing the research conducted in various locations worldwide where they have been discovered. Specifically, it focuses on studies that have utilized CO2 vents, which originate from volcanic activity. This chapter provides an overview of the importance, advantages, and disadvantages of using these acidified systems as natural laboratories to study OA in situ. It highlights that although there is no perfect analogue for future oceans, these systems help us to better understand the direct and indirect impacts of OA on different marine communities.
Among all the CO2 vents in the world, one of the few naturally acidified shallow systems in the Atlantic Ocean, and the only one with subtropical communities is located off the southern coast of Fuencaliente municipality in La Palma Island, Canary Islands. Chapter 2 of the thesis characterizes the chemical properties of this natural CO2 system in La Palma. It provides information about its volcanic and hydrological origins, as well as the different emission points along the Punta de Fuencaliente. Furthermore, it describes the carbon dynamics of the system, including variations in total inorganic carbon (CT) from 2120.10 to 10784.84 μmol kg-1, alkalinity (AT) from 2415.20 to 10817.12 μmol kg-1, pH from 7.12 to 8.07, aragonite saturation state (Ω) from 0.71 to 4.15, and calcite Ω from 1.09 to 6.49 units. A high CO2 emission flux ranging from 2.8 to 28 kg of CO2 d-1 has also been detected, making this zone an important natural carbon source. Due to its origins, this acidified system presents disadvantages as a natural laboratory for studying OA, such as natural fluctuations caused by tides or additional input of alkaline substances. Nevertheless, it creates a natural gradient of CO2 or pH along the coast with chemical characteristics very similar to those predicted for future scenarios, making it an exceptional location for studying the long-term and multi-level effects of acidification on marine ecosystems.
Chapter 3 explores rocky benthic communities along the natural pH gradient generated by the CO2 vent system in front of Punta de Fuencaliente. The objective of this chapter was to understand the direct and indirect effects of OA on the diversity and species composition of these subtropical marine communities. The study utilized a high-resolution molecular technique called DNA metabarcoding, which sequences fragments of the mitochondrial gene Cytochrome C Oxidase subunit I (COI) to detect the actual species diversity in each area. In this chapter, metabarcoding analysis reveals, for the first time, high levels of taxonomic diversity in a naturally acidified area. These high levels of diversity are attributed to the detection of small and cryptic species that are undetectable by traditional techniques and are tolerant to natural acidification. The results of this chapter unveil that future subtropical communities could maintain high taxonomic diversity values under an acidification scenario, although they will tend toward miniaturization due to the dominance of small algae and invertebrate species. This will have significant consequences for benthic subtropical communities, leading to important changes in ecosystem functions.
It is not the first time that an increase in species diversity related to environmental variations has been detected. In 1978, Connell first proposed the “Intermediate Disturbance Hypothesis” (IDH), which suggests that ecosystems are more diverse when disturbances occur at intermediate scales.
Chapter 4 investigates whether the IDH can be applied to a naturally acidified system at different biological organization levels (from organisms to communities) using molecular data. In La Palma’s acidified system, a fluctuating pH gradient caused by tides can act as a physical disturbance to marine ecosystems. This chapter utilizes sequenced fragments of the mitochondrial COI gene from two species of sea urchins (Arbacia lixula and Paracentrotus lividus) and metabarcoding analyses of benthic communities from the previous chapter. High levels of genetic and taxonomic diversity were detected at both biological organization levels under intermediate pH fluctuation, respectively. Therefore, the results of this chapter support the validity of the IDH in marine ecosystems affected by natural pH fluctuations and at different biological organization levels. Among the species living under natural acidification in the CO2 vents of La Palma, the sea urchin Arbacia lixula stands out. This is because sea urchins, like other calcareous organisms, should be susceptible to acidification due to their calcareous skeletons, however, this species has been found to live apparently unaffected in both Mediterranean and Atlantic CO2 vents.
The final chapter 5 explores the adaptation potential of A. lixula populations along the natural pH gradient of La Palma Island. Using the 2bRADseq molecular technique, a total of 14,883 SNPs (Single Nucleotide Polymorphisms) were detected in 74 individuals, of which 432 loci were correlated with the pH gradient of La Palma and are considered potential SNPs under selection. Analysis of these SNPs demonstrates that despite the short distance between the studied A. lixula populations, significant differences exist in the genomic structure of the populations correlated with the pH gradient. Additionally, these sequences are aligned and compared with available A. lixula transcriptomes, revealing 17 annotated genes involved in biological functions related to growth, development, membrane functions, and calcification. This chapter suggests that A. lixula can adapt to acidification and, therefore, able to withstand future changes anticipated for the oceans.
This thesis is the first to be developed at the Marine Observatory of Climate Change in Punta de Fuencaliente (OMaCC), where the naturally acidified system of La Palma is located. It emphasizes the importance of these natural laboratories in overcoming the experimental limitations of laboratory studies and contributes to understand how subtropical benthic ecosystems may change in the future. Moreover, it has uncovered evidence of local adaptation to ocean acidification in populations living in these natural laboratories. This thesis highlights the importance of these special environments and observatories for future research on the effects of OA.
Continue reading ‘Marine benthic communities of the future: use of acidified natural systems’Ocean acidification alters shellfish-algae nutritional value and delivery
Published 1 March 2024 Science ClosedTags: biological response, BRcommunity, growth, laboratory, mollusks, morphology, multiple factors, North Pacific, nutrients, photosynthesis, physiology, phytoplankton
Highlights
- Ocean acidification promotes microalgae growth.
- The nutrient value of microalgae is positively altered under acidifying conditions.
- Nutrient changes in primary producers can have indirect effects through trophic transfer.
- Fatty acid content of food sources affects shellfish macromolecular ratios.
Abstract
The ecological effects of climate change and ocean acidification (OA) have been extensively studied. Various microalgae are ecologically important in the overall pelagic food web as key contributors to oceanic primary productivity. Additionally, no organism exists in isolation in a complex environment, and shifts in food quality may lead to indirect OA effects on consumers. This study aims to investigate the potential effects of OA on algal trophic composition and subsequent bivalve growth. Here, the growth and nutrient fractions of Chlorella sp., Phaeodactylum tricornutum and Chaetocetos muelleri were used to synthesize and assess the impact of OA on primary productivity. Total protein content, total phenolic compounds, and amino acid (AA) and fatty acid (FA) content were evaluated as nutritional indicators. The results demonstrated that the three microalgae responded positively to OA in the future environment, significantly enhancing growth performance and nutritional value as a food source. Additionally, certain macromolecular fractions found in consumers are closely linked to their dietary sources, such as phenylalanine, C14:0, C16:0, C16:1, C20:1n9, C18:0, and C18:3n. Our findings illustrate that OA affects a wide range of crucial primary producers in the oceans, which can disrupt nutrient delivery and have profound impacts on the entire marine ecosystem and human food health.
Continue reading ‘Ocean acidification alters shellfish-algae nutritional value and delivery’Nannofossil imprints across the Paleocene-Eocene thermal maximum
Published 29 February 2024 Science ClosedTags: BRcommunity, chemistry, field, morphology, North Atlantic, paleo, phytoplankton, protists, sediment
The Paleocene–Eocene thermal maximum (PETM; ca. 56 Ma) geological interval records a marked decline in calcium carbonate (CaCO3) in seafloor sediments, potentially reflecting an episode of deep- and possibly shallow-water ocean acidification. However, because CaCO3 is susceptible to postburial dissolution, the extent to which this process has influenced the PETM geological record remains uncertain. Here, we tested for evidence of postburial dissolution by searching for imprint fossils of nannoplankton preserved on organic matter. We studied a PETM succession from the South Dover Bridge (SDB) core, Maryland, eastern United States, and compared our imprint record with previously published data from traditionally sampled CaCO3-preserved nannoplankton body fossils. Abundant imprints through intervals devoid of CaCO3 would signify that postburial dissolution removed much of the CaCO3 from the rock record. Imprints were recorded from most samples but were rare and of low diversity. Body fossils were substantially more numerous and diverse, capturing a more complete record of the living nannoplankton communities through the PETM. The SDB succession records a dissolution zone/low-carbonate interval at the onset of the PETM, through which nannoplankton body fossils are rare. No nannoplankton imprints were found from this interval, suggesting that the rarity of body fossils is unlikely to have been the result of postburial dissolution. Instead, our findings suggest that declines in CaCO3 through the PETM at the SDB location were the result of: (1) biotic responses to changes that were happening during this event, and/or (2) CaCO3 dissolution that occurred before lithification (i.e., in the water column or at the seafloor).
Continue reading ‘Nannofossil imprints across the Paleocene-Eocene thermal maximum’Archival records of the Antarctic clam shells from Marian Cove, King George Island suggest a protective mechanism against ocean acidification
Published 21 February 2024 Science ClosedTags: Antarctic, biological response, dissolution, field, mollusks, morphology, paleo, physiology, sediment
Abstract
Continuous emissions of anthropogenic CO2 are changing the atmospheric and oceanic environment. Although some species may have compensatory mechanisms to acclimatize or adapt to the changing environment, most marine organisms are negatively influenced by climate change. In this study, we aimed to understand the compensatory mechanisms of the Antarctic clam, Laternula elliptica, to climate-related stressors by using archived shells from 1995 to 2018. Principal component analysis revealed that seawater pCO2 and salinity in the Antarctic Ocean, which have increased since the 2000’s, are the most influential factors on the characteristics of the shell. The periostracum thickness ratio and nitrogen on the outermost surface have increased, and the dissolution area (%) has decreased. Furthermore, the calcium content and mechanical properties of the shells have not changed. The results suggest that L. elliptica retains the mechanism of protecting the shell from high pCO2 by thickening the periostracum as a phenotype plasticity.
Highlights
- We analyzed archival shells of the Antarctic clams in response to climate change.
- Seawater pCO2 and salinity in the Antarctic Ocean have increased since the 2000’s.
- Shell dissolution decreased over time while total shell thickness remained constant.
- The calcium content and mechanical properties of the shell remained unchanged.
- Shell integrity was retained by thickening the organic layer enriched with nitrogen.
Turf algae drives coral bioerosion under high CO2
Published 20 February 2024 Science ClosedTags: abundance, algae, biogeochemistry, biological response, BRcommunity, calcification, chemistry, communityMF, corals, dissolution, field, laboratory, morphology, multiple factors, North Pacific, otherprocess, photosynthesis, respiration, temperature, vents
Turf algal prevalence will increase in coral ecosystems under ocean acidification yet their contribution towards the ongoing and projected degradation of reefs is often overlooked. Turf algal settlement was induced on exposed coral skeleton adjacent to live coral tissue to investigate coral-turf algal interactions through a combination of laboratory and field transplantation (shallow volcanic CO2 seep) experiments across two temperature regimes. Here, we show that turf algae are competitively favored over corals under high pCO2 conditions. Turf algae-associated biological activity locally acidified the microenvironment overlying the exposed coral skeleton, leading to its bioerosion. Increases in coral-turf algal interactions could shift coral ecosystems towards net dissolution and should be integrated into global accretion models when considering future carbonate budgets under climate change.
Continue reading ‘Turf algae drives coral bioerosion under high CO2’Divergent morphological and microbiome strategies of two neighbor sponges to cope with low pH in Mediterranean CO2 vents
Published 14 February 2024 Science ClosedTags: abundance, biological response, BRcommunity, community composition, field, Mediterranean, molecular biology, morphology, otherprocess, porifera, prokaryotes, vents
Highlights
- Sponges are seen as winner taxa of future OA, yet not all species respond equally.
- Neighbor sponges had different morphology and microbiome patterns in CO2 vents.
- Vent S. cunctatrix displayed morphology changes and incipient microbial dysbiosis.
- C. reniformis microbiomes were normobiotic, diverse and functionally flexible.
- Symbioses supplying C–N–S cycles, vitamins and probiotics uphold resilience to OA.
Abstract
Ocean Acidification (OA) profoundly impacts marine biochemistry, resulting in a net loss of biodiversity. Porifera are often forecasted as winner taxa, yet the strategies to cope with OA can vary and may generate diverse fitness status. In this study, microbial shifts based on the V3–V4 16S rRNA gene marker were compared across neighboring Chondrosia reniformis sponges with high microbial abundance (HMA), and Spirastrella cunctatrix with low microbial abundance (LMA) microbiomes. Sponge holobionts co-occurred in a CO2 vent system with low pH (pHT ~ 7.65), and a control site with Ambient pH (pHT ~ 8.05) off Ischia Island, representing natural analogues to study future OA, and species’ responses in the face of global environmental change. Microbial diversity and composition varied in both species across sites, yet at different levels. Increased numbers of core taxa were detected in S. cunctatrix, and a more diverse and flexible core microbiome was reported in C. reniformis under OA. Vent S. cunctatrix showed morphological impairment, along with signs of putative stress-induced dysbiosis, manifested by: 1) increases in alpha diversity, 2) shifts from sponge related microbes towards seawater microbes, and 3) high dysbiosis scores. Chondrosia reniformis in lieu, showed no morphological variation, low dysbiosis scores, and experienced a reduction in alpha diversity and less number of core taxa in vent specimens. Therefore, C. reniformis is hypothesized to maintain an state of normobiosis and acclimatize to OA, thanks to a more diverse, and likely metabolically versatile microbiome. A consortium of differentially abundant microbes was identified associated to either vent or control sponges, and chiefly related to carbon, nitrogen and sulfur-metabolisms for nutrient cycling and vitamin production, as well as probiotic symbionts in C. reniformis. Diversified symbiont associates supporting functional convergence could be the key behind resilience towards OA, yet specific acclimatization traits should be further investigated.
Continue reading ‘Divergent morphological and microbiome strategies of two neighbor sponges to cope with low pH in Mediterranean CO2 vents’Effects of seawater acidification and warming on morphometrics and biomineralization-related gene expression during embryo-larval development of a lightly-calcified echinoderm
Published 12 February 2024 Science ClosedTags: biological response, echinoderms, laboratory, molecular biology, morphology, multiple factors, North Pacific, temperature
CO2-induced ocean acidification and warming pose ecological threats to marine life, especially calcifying species such as echinoderms, who rely on biomineralization for skeleton formation. However, previous studies on echinoderm calcification amid climate change had a strong bias towards heavily calcified echinoderms, with little research on lightly calcified ones, such as sea cucumbers. Here, we analyzed the embryo-larval development and their biomineralization–related gene expression of a lightly calcified echinoderm, the sea cucumber (Apostichopus japonicus), under experimental seawater acidification (OA) and/or warming (OW). Results showed that OA (– 0.37 units) delayed development and decreased body size (8.58–56.25 % and 0.36–19.66 % decreases in stage duration and body length, respectively), whereas OW (+3.1 °C) accelerated development and increased body size (33.99–55.28 % increase in stage duration and 2.44–14.41 % enlargement in body length). OW buffered the negative effects of OA on the development timing and body size of A. japonicus. Additionally, no target genes were expressed in the blastula stage, and only two biomineralization genes (colp3α, cyp2) and five TFs (erg, tgif, foxN2/3, gata1/2/3, and tbr) were expressed throughout the embryo-larval development. Our findings suggest that the low calcification in A. japonicus larvae may be caused by biomineralization genes contraction, and low expression of those genes. Furthermore, this study indicated that seawater acidification and warming affect expression of biomineralization-related genes, and had an effect on body size and development rate during the embryo-larval stage in sea cucumbers. Our study is a first step toward a better understanding of the complexity of high pCO2 on calcification and helpful for revealing the adaptive strategy of less-calcified echinoderms amid climate change.
Continue reading ‘Effects of seawater acidification and warming on morphometrics and biomineralization-related gene expression during embryo-larval development of a lightly-calcified echinoderm’Cool-edge populations of the kelp Ecklonia radiata under global ocean change scenarios: strong sensitivity to ocean warming but little effect of ocean acidification
Published 9 February 2024 Science ClosedTags: biological response, individualmodeling, laboratory, modeling, morphology, multiple factors, phanerogams, photosynthesis, physiology, South Pacific, temperature
Kelp forests are threatened by ocean warming, yet effects of co-occurring drivers such as CO2 are rarely considered when predicting their performance in the future. In Australia, the kelp Ecklonia radiata forms extensive forests across seawater temperatures of approximately 7–26°C. Cool-edge populations are typically considered more thermally tolerant than their warm-edge counterparts but this ignores the possibility of local adaptation. Moreover, it is unknown whether elevated CO2 can mitigate negative effects of warming. To identify whether elevated CO2 could improve thermal performance of a cool-edge population of E. radiata, we constructed thermal performance curves for growth and photosynthesis, under both current and elevated CO2 (approx. 400 and 1000 µatm). We then modelled annual performance under warming scenarios to highlight thermal susceptibility. Elevated CO2 had minimal effect on growth but increased photosynthesis around the thermal optimum. Thermal optima were approximately 16°C for growth and approximately 18°C for photosynthesis, and modelled performance indicated cool-edge populations may be vulnerable in the future. Our findings demonstrate that elevated CO2 is unlikely to offset negative effects of ocean warming on the kelp E. radiata and highlight the potential susceptibility of cool-edge populations to ocean warming.
Continue reading ‘Cool-edge populations of the kelp Ecklonia radiata under global ocean change scenarios: strong sensitivity to ocean warming but little effect of ocean acidification’
