This study aimed to explore the impact of acute acidification on the antioxidant, metabolic performance, and liver histology of juvenile yellowfin tuna. The experiment subjected juvenile yellowfin tuna to a pH gradient environment of 8.1, 7.6, 7.1, and 6.6 for 48 h. The findings indicate that a seawater pH of 7.1 significantly impacts the antioxidant and metabolic systems of the juvenile yellowfin tuna in comparison to the control group. At pH 7.1, there were observed increases in glutathione reductase (GR), total antioxidant capacity (T-AOC), lactate dehydrogenase (LDH), hexokinase (HK), pyruvate kinase (PK), sodium-potassium ATPase (Na+K+-ATP), and calcium-magnesium ATPase (Ca2+Mg2+-ATP). Conversely, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TGs) were not significantly different across the treatment groups. However, an increase in transaminases at pH 7.1 suggested potential liver damage, which was further supported by observed structural liver tissue degeneration and hepatocyte vacuolation. In conclusion, under conditions of acute acidification stress, there is a decrease in antioxidant capacity and a suppression of metabolic levels in juvenile yellowfin tuna, leading to oxidative damage. This study lays the foundation for an in-depth understanding of the response mechanisms of juvenile yellowfin tuna in response to seawater acidification as well as healthy tuna farming in the broader context of seawater acidification.
Continue reading ‘Antioxidant and metabolic response to acute acidification stress of juvenile yellowfin tuna (Thunnus albacares)’Posts Tagged 'morphology'
Antioxidant and metabolic response to acute acidification stress of juvenile yellowfin tuna (Thunnus albacares)
Published 12 July 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, morphology, North Pacific, physiology
Long-term effects of ocean acidification and its interaction with warming on calcifying organisms and their associated microbiome: bryozoans as emerging sentinels of global change?
Published 4 July 2024 Science ClosedTags: biological response, BRcommunity, bryozoa, chemistry, laboratory, Mediterranean, molecular biology, morphology, physiology
Global ocean warming and acidification are two of the major threats to many marine calcifying habitat-forming species, potentially affecting entire ecosystems. Consequently, the need for a better understanding and predicting the response of marine calcifiers has never been more pressing. Paradoxically, the individual and combined long-term effects of these stressors on bryozoans have remained largely unexplored, despite their great abundance and diversity globally. Here, we first evaluate the changes in skeletal structure and mineralogy, and the associated microbiome composition on the populations of Pentapora ottomuelleriana (encrusting) and Myriapora truncata (erect) bryozoan species living inside and outside a volcanic CO2 vent in Ischia Island. We then examine the effects of a long-term exposure to elevated pCO2 and its combined effects of ocean warming on the proportion of cover of populations of the encrusting species through time after summer. Both bryozoan species show indicators of acclimatization by adjusting skeletal properties and having stable microbial communities under acidification conditions. However, we document novel patterns about microbiome shifts in response to future ocean acidification in bryozoans for the first time. Microbial genera known to have essential functions to the host such as biosynthesis of defense compounds or thermal protection were depleted at the acidified site, which suggest early warnings of potential deterioration of bryozoan health under near future ocean conditions. The proportion of cover of the encrusting species also decreased from 2016 to 2020 in both studied sites, with faster declines at the acidified ones. Our model suggests that the increasing seawater temperature drove a decline in the bryozoan cover although the combined effects with acidification accelerated its mortality rates in the CO2 vent. More multidisciplinary research combining both environmental stressors on a wider range of calcifying species is needed to better understand the adaptive capacity of the holobiont to a changing environment.
Continue reading ‘Long-term effects of ocean acidification and its interaction with warming on calcifying organisms and their associated microbiome: bryozoans as emerging sentinels of global change?’Intraspecific variation in response to elevated pCO2 and temperature in the branching reef coral Acropora digitifera from different habitats
Published 27 June 2024 Science ClosedTags: biological response, BRcommunity, calcification, chemistry, corals, laboratory, morphology, mortality, multiple factors, North Pacific, photosynthesis, protists, temperature
Ocean acidification (OA) and ocean warming (OW) affect the calcification of corals, and intraspecific variations in response to these stressors in the population level need to be clarified for better future predictions. Using Acropora digitifera as our subject, we examined the intraspecific variability in calcification and maximum quantum yield (Fv/Fm) of photosystem II of symbiotic zooxanthella in responses to OA, OW, and OA + OW. Samples were taken from two different sites: Sesoko Station (warmer) and Sesoko South (cooler) in Okinawa, Japan. Calcification rates varied between the two sites, and noticeable differences were observed only among coral colonies from the Sesoko South site, specifically under control and OA treatments. Furthermore, Fv/Fm showed no variation between the sites due to those stresses. Hence, the calcification rates among A. digitifera colonies varied by habitat, and we found within-site variation only in the lower temperature location, Sesoko South. We observed diminished variation in response among colonies in the warmer site. The adapting to diverse environmental conditions and responding to changes such as seawater pCO2 and temperature, may lead to differences in sensitivity between the two populations to OA, OW, and OA + OW. These intraspecific variation could arise from factors like acclimatizations, the influence of specific genotypes, or phenotypic plasticity of the colonies.
Continue reading ‘Intraspecific variation in response to elevated pCO2 and temperature in the branching reef coral Acropora digitifera from different habitats’Taphonomy and aleoecology of lycoptera: a case study from the lower jehol group in Western Liaoning, Northeastern China
Published 27 June 2024 Science ClosedTags: biogeochemistry, biological response, fish, laboratory, morphology, North Pacific, paleo
Taphonomy and paleoecology (biological behavior) of the Early Cretaceous fish fossils are poorly described. This study reports for the first time a detailed taphonomical and paleoecological study on Lycoptera in the Mesozoic strata of western Liaoning Province, NE China. The XRD analysis shows that gismondine is the dominant clay minerals that could have contributed to the preservation of Lycoptera fossils and microbial mat fragments in the fossil-bearing horizon. Gismondine may have formed under volcanism-related hydrothermal regime that was transformed from crystal and lithic fragments. The μ-XRF imaging analysis shows a dominant chemical composition of Al, Si, P, S, Rh, K, Ca, Ti, C, Cr, Mn, Fe, Ni, among which P, Ca, C and S are enriched in the fish skeleton in comparison to the matrix. This suggests a dominant apatite composition for the fish skeleton. Hydrothermal influence did not smear off these organic signals probably because of protection of gismondine. The coexistance of C and S with Ni is assumed to represent recovered primary productivity following volcanic explosions and toxic gas emissions. The head of juvenile fish stays close to the body of adult fish. Pending further discoveries, such phenomenon is interpreted to suggest that adult fish actively protected juvenile fish in the presence of environmental pressures such as anoxia and deterioration of water quality induced by volcanism. Ocean acidification and hypoxia in association with volcanism created a harmful environment causing mass extinction of fish. The adult Lycoptera protected their juveniles by its body at the moment before death. Such biological behavior will be increasingly reported given the wide occurrence of Lycoptera in Mesozoic strata.
Continue reading ‘Taphonomy and aleoecology of lycoptera: a case study from the lower jehol group in Western Liaoning, Northeastern China’Rubble persistence under ocean acidification threatened by accelerated bioerosion and lower-density coral skeletons
Published 20 June 2024 Science ClosedTags: abundance, biological response, BRcommunity, calcification, chemistry, community composition, corals, dissolution, laboratory, morphology, North Atlantic, otherprocess, primary production, protists, respiration
As the balance between erosional and constructive processes on coral reefs tilts in favor of framework loss under human-induced local and global change, many reef habitats worldwide degrade and flatten. The resultant generation of coral rubble and the beds they form can have lasting effects on reef communities and structural complexity, threatening the continuity of reef ecological functions and the services they provide. To comprehensively capture changing framework processes and predict their evolution in the context of climate change, heavily colonized rubble fragments were exposed to ocean acidification (OA) conditions for 55 days. Controlled diurnal pH oscillations were incorporated in the treatments to account for the known impact of diel carbonate chemistry fluctuations on calcification and dissolution response to OA. Scenarios included contemporary pH (8.05 ± 0.025 diel fluctuation), elevated OA (7.90 ± 0.025), and high OA (7.70 ± 0.025). We used a multifaceted approach, combining chemical flux analyses, mass alteration measurements, and computed tomography scanning images to measure total and chemical bioerosion, as well as chemically driven secondary calcification. Rates of net carbonate loss measured in the contemporary conditions (1.36 kg m−2 year−1) were high compared to literature and increased in OA scenarios (elevated: 1.84 kg m−2 year−1 and high: 1.59 kg m−2 year−1). The acceleration of these rates was driven by enhanced chemical dissolution and reduced secondary calcification. Further analysis revealed that the extent of these changes was contingent on the density of the coral skeleton, in which the micro- and macroborer communities reside. Findings indicated that increased mechanical bioerosion rates occurred in rubble with lower skeletal density, which is of note considering that corals form lower-density skeletons under OA. These direct and indirect effects of OA on chemical and mechanical framework-altering processes will influence the permanence of this crucial habitat, carrying implications for biodiversity and reef ecosystem function.
Continue reading ‘Rubble persistence under ocean acidification threatened by accelerated bioerosion and lower-density coral skeletons’Predictable patterns within the kelp forest can indirectly create temporary refugia from ocean acidification
Published 20 June 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, dissolution, growth, mesocosms, mollusks, morphology, North Pacific
Highlights
- Potential of kelp as ocean acidification refugia has been addressed through an integration of observations, modelling and mesocosm work.
- Kelp did not have a direct mitigating effect against OA in the low retentive habitats.
- Improved biological responses were observed in investigated calcifiers.
- Positive responses were related to increased predictability in pH autocorrelation signal and improved habitat provisioning through resource utilization.
- Kelp can improve ecosystem services
Abstract
Kelps are recognized for providing many ecosystem services in coastal areas and considered in ocean acidification (OA) mitigation. However, assessing OA modification requires an understanding of the multiple parameters involved in carbonate chemistry, especially in highly dynamic systems. We studied the effects of sugar kelp (Saccharina latissima) on an experimental farm at the north end of Hood Canal, Washington—a low retentive coastal system. In this field mesocosm study, two oyster species (Magallana gigas, Ostrea lurida) were exposed at locations in the mid, edge, and outside the kelp array. The Hood Head Sugar Kelp Farm Model outputs were used to identify dominating factors in spatial and temporal kelp dynamics, while wavelet spectrum analyses helped in understanding predictability patterns. This was linked to the measured biological responses (dissolution, growth, isotopes) of the exposed organisms. Positioned in an area of high (sub)-diel tidal fluxes with low retention potential, there were no measurable alterations of the seawater pH at the study site, demonstrating that the kelp array could not induce a direct mitigating effect against OA. However, beneficial responses in calcifiers were still observed, which are linked to two causes: increased pH predictability and improved provisioning through kelp-derived particulate organic resource utilization and as such, kelp improved habitat suitability and indirectly created refugia against OA. This study can serve as an analogue for many coastal bay habitats where prevailing physical forcing drives chemical changes. Future macrophyte studies that investigate OA mitigating effects should focus also on the importance of predictability patterns, which can additionally improve the conditions for marine calcifiers and ecosystem services vulnerable to or compromised by OA, including aquaculture sustainability.
Continue reading ‘Predictable patterns within the kelp forest can indirectly create temporary refugia from ocean acidification’Red king crab larval survival and development are resilient to ocean acidification
Published 14 June 2024 Science ClosedTags: biological response, chemistry, crustaceans, laboratory, morphology, mortality, North Pacific, reproduction
Ocean acidification, a decrease in oceanic pH resulting from the uptake of anthropogenic CO2, can be a significant stressor for marine organisms. In this study, we reared red king crab larvae from hatching to the first crab stage in four different pH treatments: current surface ambient, diel fluctuation to mimic larval migration between the surface and mixed layer under current ambient conditions, pH 7.8, and pH 7.5. Larvae were monitored throughout development and the average length of each stage was determined. At each of the zoeal stages, the glaucothoe stage, and the first crab stage, we measured survival, morphometry, dry mass, and carbon, nitrogen, calcium, and magnesium content. Red king crab larvae were highly resilient to ocean acidification. There were no differences among treatments in survival or in average stage length. Although there were clear ontogenetic trends in size, weight, and elemental composition, most of these did not vary with pH treatment. Zoeal morphology did not vary among treatments, although glaucothoe and C1 crabs were slightly smaller in pH 7.8 than in the ambient treatment. Ambient larvae also had a slightly higher mass than pH 7.8 larvae but not pH 7.5. Ambient larvae had higher magnesium contents than pH 7.8 and pH 7.5, but calcium levels were the same. Ambient larvae also had slightly lower carbon and nitrogen content than pH 7.8 and pH 7.5 larvae but only in the 4th zoeal stage. Overall this study suggests that red king crab larvae are well adapted to a wide range of pH conditions and appear resilient to ocean acidification levels projected for the next two centuries.
Continue reading ‘Red king crab larval survival and development are resilient to ocean acidification’Macroalgal presence decreases coral calcification rates more than ocean acidification
Published 12 June 2024 Science ClosedTags: algae, biological response, BRcommunity, calcification, chemistry, corals, growth, laboratory, mesocosms, morphology, Red Sea
Global coral reef degradation has precipitated phase shifts toward macroalgal-dominated communities. Despite the negative repercussions for reefscapes, higher abundances of primary producers have the potential to positively impact the physicochemical environment and mitigate negative impacts of ocean acidification (OA). In this study, we investigated the influence of macroalgal (cf. Sargassum vulgare) density on coral (Acropora millepora and A. hemprichii) calcification rates under current and future OA conditions. Corals were resistant to OA up to ~ 1100 µatm, with no changes in calcification rates. However, the presence of (low and high density) algae reduced calcification rates by ~ 41.8%, suggesting either a chemical defense response due to algal metabolites or potential physical impacts from shading or abrasion. Documented beneficial buffering effects of macroalgae in OA may also elicit negative impacts on coral calcification, suggesting further work is needed to elucidate how species interactions influence responses to projected climate change.
Continue reading ‘Macroalgal presence decreases coral calcification rates more than ocean acidification’Effects of water flow and ocean acidification on oxygen and pH gradients in coral boundary layer
Published 10 June 2024 Science ClosedTags: biological response, chemistry, corals, morphology
Reef-building corals live in highly hydrodynamic environments, where water flow largely controls the complex chemical microenvironments surrounding them—the concentration boundary layer (CBL). The CBL may be key to alleviate ocean acidification (OA) effects on coral colonies by partially isolating them. However, OA effects on coral CBL remain poorly understood, particularly under different flow velocities. Here, we investigated these effects on the reef-building corals Acropora cytherea, Pocillopora verrucosa, and Porites cylindrica. We preconditioned corals to a control (pH 8.0) and OA (pH 7.8) treatment for four months and tested how low flow (2 cm s−1) and moderate flow (6 cm s−1) affected O2 and H+ CBL traits (thickness, surface concentrations, and flux) inside a unidirectional-flow chamber. We found that CBL traits differed between species and flow velocities. Under OA, traits remained generally stable across flows, except surface pH. In all species, the H+ CBL was thin and led to lower surface pH. Still, low flow thickened H+ CBLs and increased light elevation of surface pH. In general, our findings reveal a weak to null OA modulation of the CBL. Moreover, the OA-buffering capacity by the H+ CBL may be limited in coral species, though low flow could enhance CBL sheltering.
Continue reading ‘Effects of water flow and ocean acidification on oxygen and pH gradients in coral boundary layer’Physiological responses of Atlantic cod to climate change indicate that coastal ecotypes may be better adapted to tolerate ocean stressors
Published 7 June 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, morphology, multiple factors, North Atlantic, performance, physiology, respiration, salinity, temperature
Healthy ecosystems and species have some degree of resilience to changing conditions, however as the frequency and severity of environmental changes increase, resilience may be diminished or lost. In Sweden, one example of a species with reduced resilience is the Atlantic cod (Gadus morhua). This species has been subjected to overfishing, and with additional pressures such as habitat degradation and changing environmental conditions there has been little to no recovery, despite more than a decade of management actions. Given the historical ecological, economical, and cultural significance of cod, it is important to understand how Atlantic cod respond to global climate change to recover and sustainably manage this species in the future. A multi-stressor experiment was conducted to evaluate physiological responses of juvenile cod exposed to warming, ocean acidification, and freshening, changes expected to occur in their nursery habitat. The response to single drivers showed variable effects related to fish biometrics and increased levels of oxidative stress dependent parameters. Importantly, two separate responses were seen within a single treatment for the multi-stressor and freshening groups. These within-treatment differences were correlated to genotype, with the offshore ecotype having a heightened stress response compared to the coastal ecotype, which may be better adapted to tolerate future changes. These results demonstrate that, while Atlantic cod have some tolerance for future changes, ecotypes respond differently, and cumulative effects of multiple stressors may lead to deleterious effects for this important species.
Continue reading ‘Physiological responses of Atlantic cod to climate change indicate that coastal ecotypes may be better adapted to tolerate ocean stressors’Stochastic modeling of eastern oyster (Crassostrea virginica) production in a Mexican tropical coastal lagoon using alternative stocking density management schemes
Published 5 June 2024 Science ClosedTags: biological response, chemistry, growth, laboratory, methods, mollusks, morphology, North Atlantic
A stochastic model was developed to analyze Crassostrea virginica production when cultivated at three stocking densities, defined as the area occupation (50, 75, and 100%) in Nestier-type trays, using juvenile oysters with an initial size (height) of 29.40 ± 0.18 mm. A 25-week grow-out was first conducted in the Rio Lagartos lagoon, showing that final oyster size was inversely related to density (P < 0.05), ranging from 61.87 mm (100% density) to 68.00 mm (50% density). At the same time, mortality was negligible (lower than 1.0%). The environmental conditions in the lagoon were stable, and the oyster growth rate positively correlated with water temperature and pH. Low pH was associated with slow oyster growth, possibly as an adverse effect of acidic conditions on the oyster shell formation. The model indicated that, for an initial 100,000 oyster population, the maximum production (oyster dozens) is obtained after 20 weeks (8310 at 50% density) and 25 weeks (8250 at 75%, and 6670 at 100% density). There was a 100% probability of oysters reaching a minimum commercial size (MCS) of 60.00 mm when using the 50 and 75% densities and 80.6% when using 100%. The model estimated that, for the maximum density, extending the grow-out up to 32 weeks would allow reaching MCS with 100% probability, although this should be experimentally confirmed. The random variability of oyster production in 50 and 75% densities was minimal, while at 100% density, it was extremely high. A sensitivity analysis indicated that for 50 and 75% densities, the main stochastic elements influencing production, are related to oyster mortality, while at 100% density, they are related to oyster growth.
Continue reading ‘Stochastic modeling of eastern oyster (Crassostrea virginica) production in a Mexican tropical coastal lagoon using alternative stocking density management schemes’Elucidating responses of the intertidal clam Ruditapes philippinarum to compound extreme oceanic events
Published 3 June 2024 Science ClosedTags: biological response, chemistry, laboratory, mollusks, morphology, multiple factors, North Pacific
Highlights
- Heatwaves and acidification increasingly co-occur as climate drivers.
- Declining enzymes showed heat and acidification suppress metabolism.
- Transient antioxidant spikes revealed initial heat damage defenses.
- Gene changes showed bioenergetic, protein, and ion transport issues.
Abstract
Ocean acidification and heatwaves caused by rising CO2 affect bivalves and other coastal organisms. Intertidal bivalves are vital to benthic ecosystems, but their physiological and metabolic responses to compound catastrophic climate events are unknown. Here, we examined Manila clam (Ruditapes philippinarum) responses to low pH and heatwaves. Biochemical and gene expression demonstrated that pH and heatwaves greatly affect physiological energy enzymes and genes expression. In the presence of heatwaves, Manila clams expressed more enzymes and genes involved in physiological energetics regardless of acidity, even more so than in the presence of both. In this study, calcifying organisms’ biochemical and molecular reactions are more susceptible to temperature rises than acidity. Acclimation under harsh weather conditions was consistent with thermal stress increase at lower biological organization levels. These substantial temporal biochemical and molecular patterns illuminate clam tipping points. This study helps us understand how compound extreme weather and climate events affect coastal bivalves for future conservation efforts.
Continue reading ‘Elucidating responses of the intertidal clam Ruditapes philippinarum to compound extreme oceanic events’Differences in larval acidification tolerance among populations of the eastern oyster, Crassostrea virginica
Published 31 May 2024 Science ClosedTags: biological response, chemistry, laboratory, mollusks, morphology, North Atlantic, physiology, reproduction
Highlights
- Larval oysters are threatened by ongoing ocean acidification.
- Shell growth was the most sensitive metric to conditions of mild acidification.
- Protein and triglyceride content were more insightful responses at lower pH.
- Oyster populations differed in responses to conditions of acidification.
- Physiology varied between oyster populations, even under control conditions.
Abstract
The eastern oyster, Crassostrea virginica, is an ecologically and economically important species that is threatened by ongoing coastal ocean acidification. Oyster larvae are known to be more susceptible to acidification than either juvenile or adult life stages, but less is known about what levels of acidification induce a stress response and how this stress response changes with increasing acidification. Furthermore, little is known about population-level variability in acidification tolerance in C. virginica, making predictions of how this species will respond to future environmental scenarios difficult. To address these knowledge gaps, both whole animal and cellular metrics were used to quantify the acidification response of larvae produced by adults collected from Page Rock reef and Parrot’s Rock reef, two spatially distinct reefs in adjacent tributaries of Chesapeake Bay. A comparison of Page Rock reef larvae among four acidification scenarios (pH 7.8, 7.5, 7.2, 7.0) revealed differences in shell length, total protein content, and triglyceride content, with growth increasingly impacted as acidification intensity increased. However, the sensitivity of these traits to acidification varied, where shell length was similarly impacted between pH 7.5 and 7.2, while protein and triglyceride content continued to decrease between these acidification scenarios. Triglyceride accumulation was most severely impacted under the lowest pH tested (pH 7.0), signaling that acidification could ultimately reduce the number of individuals successfully recruiting into the adult population if adequate energy stores cannot be accumulated for metamorphosis. A comparison of larvae between the two reefs at pH 7.8 and 7.2 revealed differences in survival, growth, and energy accumulation that suggest clear underlying physiological variations in larvae between reefs and unique sensitivities to acidification stress. These findings demonstrate that acidification tolerance within C. virginica can vary by population, which will have important implications for industry and conservation efforts as more resilient populations would make better candidates for future selective breeding efforts as well as restoration initiatives.
Continue reading ‘Differences in larval acidification tolerance among populations of the eastern oyster, Crassostrea virginica’Shell size variation of pteropod Heliconoides inflatus: inferences on Indian Ocean carbonate chemistry during late Quaternary
Published 30 May 2024 Science ClosedTags: biological response, chemistry, Indian, laboratory, mollusks, morphology, sediment
The current study is an effort to understand the relationship between the average shell size and Limacina Dissolution Index (LDX) of pteropod species, Heliconoides inflatus as a metric for shell calcification using several cores, ranging in age from recent to 1.2 Myr. The current study is based on the variability of H. inflatus average shell size, LDX, and fragmentation ratio (FR) and their correlation among different spatial and temporal sediment core records from the Northern Indian Ocean. Results suggest that in the cores collected above the Aragonite lysocline (Aly) and the Aragonite Compensation Depth (ACD) (SPC 05, 06, 09, 11, 12, 13, 14, and NGHP-17), the average shell size values exhibited larger shells during the stadials/glacial periods (Little Ice Age (LIA), Marine Isotope Stages (MIS) 3, 6, 10 − 9 transition etc.) which corresponds to lower LDX values. However, the cores beyond the ACD (SK168, AAS11, and RVS2) show larger shell size values during the warm interstadials (e.g., Bølling–Allerød) with higher FR. The variability in shell size and LDX shows an indication of the carbonate ion saturation in the water column over glacial/interglacial time scales and the impact of changing atmospheric CO2 in the atmosphere. However, the factors adding to the carbonate ion saturation within the water column could be varied physiographically. The calcification proxy complements the dissolution proxies and reveals that the most intense aragonite dissolution occurred during the Holocene and interstadials/interglacials.
Continue reading ‘Shell size variation of pteropod Heliconoides inflatus: inferences on Indian Ocean carbonate chemistry during late Quaternary’Utilizing biogeochemical and genetic tools to understand and support clam populations in a changing ocean
Published 29 May 2024 Science ClosedTags: biological response, chemistry, fisheries, laboratory, molecular biology, mollusks, morphology, North Pacific, physiology
Marine bivalves are at risk due to anthropogenic climate change. This poses a threat to commercial aquaculture, and the communities that depend on bivalves for food security. Ocean acidification, the lowering of seawater pH, is of particular concern for marine calcifiers, including bivalves. Ocean acidification occurs as carbon dioxide enters the atmosphere at a rate faster than natural geologic processes can buffer. It is energetically costly for marine calcifiers like clams, mussels, and oysters, to mineralize under acidic conditions, and low pH leads to the dissolution of calcium carbonate shells and skeletons. This problem warrants research on acidification adaptation strategies that will keep coastal populations healthy. Adding calcium carbonate shell hash to coastal sediments may mitigate negative effects of acidification on infaunal shellfish by altering the chemistry of pore fluids, thus providing a potential mitigation strategy for local populations, including species like the Pacific littleneck clam (Leukoma staminea).
Here, I present the first in-depth description of the shell mineralogy, microstructure, body size variability, and geochemical properties of modern L. staminea, a common eastern Pacific, shallow, infaunal bivalve. Additionally, I document the impact of ocean acidification on the shell growth and gene expression of L. staminea, and test whether adding shell hash to its infaunal environement can promote growth under acidified conditions. Juvenile clams were raised in four experimental conditions for 90 days: control seawater, acidified seawater, control seawater with shell hash, and acidified seawater with shell hash. Clam shell weight, soft tissue weight, and new shell growth were measured. The presence of shell hash increased the pH, alkalinity and aragonite saturation state of pore fluids across all treatments, and increased shell growth on average, although growth metrics were variable across and within treatments. Lastly, RNA-sequencing revealed the impacts of experimental acidification on juvenile clam gene expression. Clams grown in the presence of shell hash had gene expression profiles more similar to those grown in control (non-acidified) conditions. In all, this research suggests that adding shell hash to coastal sediments alters the chemistry of pore fluids and buffers against acidic conditions that deleteriously affects clam mineralization.
Continue reading ‘Utilizing biogeochemical and genetic tools to understand and support clam populations in a changing ocean’Cross-generational plasticity in Atlantic silversides (Menidia menidia) under the combined effects of hypoxia and acidification
Published 28 May 2024 Science ClosedTags: biological response, chemistry, fish, growth, laboratory, molecular biology, morphology, multiple factors, North Atlantic, oxygen, physiology, reproduction
We investigated the potential for cross-generational plasticity to influence how offspring respond to hypoxia and ocean acidification (hereafter HypOA) in the coastal forage fish Atlantic silverside (Menidia menidia). Mature wild silversides were treated with a control [dissolved oxygen (DO):100% air saturation (a.s.) / pCO2: 650 μatm] or HypOA conditions [DO: 40% a.s. / pCO2: 2300 μatm] for 10 days prior to spawning. Their offspring were reared under both treatments in factorial experimental design. Parental acclimation to HypOA altered several offspring traits, including increased embryo survival under HypOA and an overall reduction in post-hatch growth rate. Offspring from HypOA-treated parents that were reared under control conditions had larger eyes across the developmental period. When compared against the overall control group, larvae directly exposed to HypOA exhibited 2,416 differentially expressed transcripts (DETs). Although most of these DETs were specific to individual parental treatments, the most enriched Gene Ontology terms were conserved across parental treatments, including terms related to neurotransmitter secretion, nervous system development, axon pathfinding, calcium channel activity, proteolysis, and extracellular matrix organization. Larvae from HypOA-treated parents that were reared under control conditions exhibited a shift in constitutive gene expression similar to that seen in larvae directly exposed to HypOA. This highly consistent finding indicates that parental acclimation before fertilization promotes the transcriptional frontloading of genes in offspring that are responsive to direct HypOA exposure. This highly consistent finding indicates that parental acclimation before fertilization promotes the transcriptional frontloading of genes in offspring. This effect may have primed regulatory functions in offspring that sense and respond to low DO and elevated pCO2 conditions. Though, our results suggest that this altered developmental phenotype may have some negative fitness consequences for offspring.
Continue reading ‘Cross-generational plasticity in Atlantic silversides (Menidia menidia) under the combined effects of hypoxia and acidification’Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness
Published 23 May 2024 Science ClosedTags: abundance, biological response, chemistry, laboratory, light, morphology, multiple factors, otherprocess, oxygen, physiology, phytoplankton
Respiratory activity in the oceans is declining due to the expansion of hypoxic zones and progressive deoxygenation, posing threats to marine organisms along with impacts of concurrent ocean acidification. Therefore, understanding the combined impacts of reduced pO2 and elevated pCO2 on marine primary producers is of considerable significance. Here, to simulate diatoms’ sinking into the aphotic zone of turbid coastal water, we exposed the diatoms Thalassiosira pseudonana and Thalassiosira weissflogii in darkness at 20°C to different levels of pO2 and pCO2 conditions for ~3 weeks, and monitored their biomass density, photosynthetic activity and dark respiration, and examined their recovery upon subsequent exposure to light at 20°C, simulating surface water conditions. Along with decreased cell abundance and size, measured photosynthetic capacity and dark respiration rates in these two diatoms both gradually decreased during the prolonged darkness. Reduced pO2 alone did not negatively affect the photosynthetic machinery in both the dark-survived diatom, and enhanced their subsequent recovery upon light exposure. Nevertheless, the combination of the elevated pCO2 and reduced pO2 (equivalent to hypoxia) led to the biomass loss by about 90% in T. pseudonana, and delayed the recovery of both species upon subsequent exposure to light, though it did not reduce the cell concentration of T. weissflogii during the elongated darkness. Our results suggest that reduced O2 availability diminishes the abilities of the diatoms to cope with the acidic stress associated with ocean acidification, and the expansion of hypoxic waters could delay the photosynthetic recovery of coastal diatoms when they are transported upwards through mixing from dark layers to sunlit waters.
Continue reading ‘Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness’Multiple carbonate system parameters independently govern shell formation in a marine mussel
Published 23 May 2024 Science ClosedTags: biological response, calcification, chemistry, laboratory, mollusks, morphology, North Atlantic, physiology
Calcification is vital to marine organisms that produce calcium carbonate shells and skeletons. However, how calcification is impacted by ongoing environmental changes, including ocean acidification, remains incompletely understood due to complex relationships among the carbonate system variables hypothesized to drive calcification. Here, we experimentally decouple these drivers in an exploration of shell formation in adult marine mussels, Mytilus californianus. In contrast to models that focus on single parameters like calcium carbonate saturation state, our results implicate two independent factors, bicarbonate concentration and seawater pH, in governing calcification. While qualitatively similar to ideas embodied in the related substrate-inhibitor ratio (bicarbonate divided by hydrogen ion concentration), our data highlight that merging bicarbonate ion and hydrogen ion concentrations into a simple quotient obscures important features of calcification. Considering a dual-parameter framework improves mechanistic understanding of how calcifiers interact with complex and changing chemical conditions.
Continue reading ‘Multiple carbonate system parameters independently govern shell formation in a marine mussel’Drivers of biological response to fluctuating seawater ph conditions in sea urchin echinus esculentus larvae
Published 22 May 2024 Science ClosedTags: adaptation, biological response, chemistry, echinoderms, growth, laboratory, morphology, mortality, North Atlantic, otherprocess, physiology, reproduction
Highlights
- Low pH has a negative effect on sea urchin larval fitness.
- Under fluctuating pH conditions, the minimum pH is not driving the biological response.
- Larvae are pre-adapted to fluctuating conditions and inverting the pH diurnal cycle leads to negative effects on fitness.
- Adaptation to variability in a coastal species is associated with a cost of plasticity but not cost of canalization.
Abstract
A large body of evidence is documenting the impact of reduced pH on marine species and ecosystems. This information is used to infer the present and future impacts of ocean acidification. However, a vast majority of the studies were performed using constant pH and the high level of pH variability experienced by marine organisms on the coastal zone was often overlooked. Recent studies highlight the key role of this variability in driving biological response to pH as well as species sensitivity to ocean acidification. For example, it was hypothesized that because of local adaptation, the extreme of the present range of pH variability is a good predictor for local biological thresholds. Using a complex experimental design, we investigated what part of the pH variability is driving the biological response of the sea urchin Echinus esculentus larvae. Comparing stable (pH 8.13, 7.82, 7.53) and fluctuating treatments (12 h at pH 8.13 and 12 h at pH 7.53) following natural or inverted diurnal cycles, we were able to show that (i) under constant conditions, low pH deviating from the present range of natural variability had a negative effect on larval growth rate and calcification; (ii) under fluctuating conditions, a desynchronization of the pH variation with the photoperiod led to decreased larval growth rate and calcification; (iii) overall, larval fitness (survival, growth and calcification) was higher under fluctuating conditions as compared to constant. While these data do not support the hypothesis that the minimum pH is the main driver of the biological response, they provide evidence of adaptation to variability in a coastal species with associated a cost of plasticity but not a cost of canalization.
Continue reading ‘Drivers of biological response to fluctuating seawater ph conditions in sea urchin echinus esculentus larvae’Measures of Rhizostoma pulmo ephyrae statoliths synthesized under warming and ocean acidification conditions (IPCC SSP5-8.5 scenario)
Published 16 May 2024 Science ClosedTags: biological response, cnidaria, laboratory, morphology, physiology
Abstract
This data set includes data collected from ICMAN-CSIC (Spain), consisting of measurements of the size and number of the statoliths present in newly released Rhizostoma pulmo ephirae under conditions of oceanic warming and acidification (IPCC SSP5-8.5 scenario). From each ephyra, three of its eight statocysts were randomly selected and all the statoliths inside were counted and measured.
Description
The dataset provides Rhizostoma pulmo newly released ephyrae statoliths measurements.The data set is provided as an Excel file within a compressed folder that also includes a single README file (in text format) containing a detailed description of the data structure. [METHODOLOGY] Description of methods used for collection/generation of data: Six combinations of temperature and PCO2 (18, 24 and 30ºC with a PCO2 of 500 and 1000 ppm each) were applied during 32 days to different groups of polyps of Rhizostoma pulmo. From the released ephyrae during this period, three specimens from each treatment were randomly taken. From each ephyra, three of its eight statocysts were randomly selected and all the statoliths inside were counted and measured via inverted optical microscopy.– Methods for processing the data: Data were analyzed using RStudio software. To obtain the variable “volume”, its values were obtained using the formula for the volume of a regular hexagonal prism.
Continue reading ‘Measures of Rhizostoma pulmo ephyrae statoliths synthesized under warming and ocean acidification conditions (IPCC SSP5-8.5 scenario)’
