How organisms respond to environmental changes is crucial for their survival, especially in the face of rapid climate change. One of the mechanisms facilitating acclimation to novel environments is phenotypic plasticity, the ability of a single genotype to produce multiple phenotypes in different environments. Phenotypic plastic responses are influenced by various factors like environmental stability, parental experiences, and genetic factors and can be classified as acute, developmental, or intergenerational responses based on the timeframe involved. This dissertation investigates molecular basis of all these three types of plasticity in marine fishes in response to changes in their physical and social environment. Physical environmental changes mediated by ocean acidification negatively affects various fish species however, some thrive in naturally occurring CO2 seeps, potentially benefiting from habitat shifts induced by reduced pH levels. In the anemone goby, a species that has increased population density at CO2 seeps in Vulcano Island, Italy, differential regulation of key pathways resulting in acclimation to acidified waters, potentially mediated by developmental plasticity, were identified. While overall increase in CO2 levels elicits molecular responses in fish, the stability of CO2 concentration is crucial. Exposure of spiny damselfish to both stable and fluctuating CO2 conditions resulted in loss of natural rhythmic splicing events however, fish in fluctuating CO2 conditions alone showed increased capability of time-dependent regulation of splicing events in genes associated with synaptic plasticity and neuronal functioning. This might be mediated by the observed amplitude change in circadian rhythm genes in the fluctuating CO2 treatment enabling the fish to coordinate biological processes in anticipation of periodic changes in CO2 levels. Furthermore, the spiny damselfish showed molecular signatures of intergenerational plasticity to ocean acidification conditions, particularly in the brain and liver. Specifically, within-generation transcriptional responses indicating altered neural signaling in the brain and metabolic depression in the liver returned to control levels when parents were also exposed to elevated CO2 conditions. Interestingly, these signatures indicating intergenerational acclimation were predominant in offspring of parents behaviourally tolerant to elevated CO2 conditions. This shows that parental phenotype and parental environment play a role in mediating offspring transcriptional response to ocean acidification. An organisms’ environment encompasses not only its physical environment but also the social environment. The last chapter of this thesis explores molecular processes underlying plastic responses of organisms to changes in their social environment by using the anemone-anemonefish mutualistic system. Significant changes in the transcriptome of both species were identified during the acclimation period of mutualistic association. Anemonefish showed activation of sensory pathways in response to cues received from the anemone, while the anemone showed upregulation of genes associated with nematocyst discharge and venom production, potentially in response to sensing fish movements. This study reveals an interplay of molecular events underlying mutualistic association in both partners. Taken together, the findings reported in this thesis furthers our understanding of the molecular processes underlying various types of phenotypic plastic responses to environmental changes and provides key information regarding the acclimation potential of marine fishes to global change.
Continue reading ‘Transcriptional plasticity and environmental change in marine fishes’Posts Tagged 'fish'
Transcriptional plasticity and environmental change in marine fishes
Published 14 August 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, molecular biology, physiology
The water content, apoptosis, and proliferation of the brain in marine medaka affected by seawater acidification
Published 8 August 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, North Pacific, performance, physiology
A possible explanation for ocean acidification-induced changes in fish behavior is a systemic effect on the nervous system. Three biological barriers at the blood–brain interface effectively separate the brain from the body fluids. It is not known whether fish brain regions in contact with these barriers are affected by acidification. Here, we studied structural changes in medaka (Oryzias melastigma) brain regions contacting cerebrospinal fluid (CSF) after short-term (7 days) CO2 exposure. The brain water content decreased significantly and the superficial structure of the pia mater was changed, but there was no obvious damage to the internal structures of the brain after seawater acidification. Seawater acidification also led to an increase in apoptosis and a decrease in the number of proliferative cells in brain areas contacting CSF. These results indicate that the structure of CSF-contacting brain regions in medaka was affected by seawater acidification, and the brain responded to seawater acidification stress by increasing apoptosis and reducing proliferation.
Continue reading ‘The water content, apoptosis, and proliferation of the brain in marine medaka affected by seawater acidification’Changes in gill neuroepithelial cells and morphology of threespine stickleback (Gasterosteus aculeatus) to hypoxia and simulated ocean acidification
Published 7 August 2024 Science ClosedTags: abundance, biological response, chemistry, fish, laboratory, morphology, North Pacific, otherprocess, physiology, respiration
Coastal marine environments are characterized by daily, seasonal and long-term changes in both O2 and CO2, driven by local biotic and abiotic factors. The neuroepithelial cells (NECs) of fish are thought to be the putative chemoreceptors for sensing oxygen and CO2, and, thus, NECs play a key role in detecting these environmental changes. However, the role of NECs as chemosensors in marine fish remains largely understudied. In this study, the NECs of marine threespine sticklebacks (Gasterosteus aculeatus) were characterized using immunohistochemistry. We then determined if there were changes in NEC size and density, and in gill morphology in response to either mild (10 kPa) or moderate (6.8 kPa) hypoxia and two levels of elevated CO2 (1,500 and 3,000 µatm). We found that the NECs of stickleback contained synaptic vesicles and were innervated, and were 50–300% larger and 2 to 4 times more abundant than in other similar sized freshwater fishes. NEC size and density were largely unaffected by exposure to hypoxia, but there was a 50% decrease in interlamellar cell mass (ILCM) in response to mild and moderate hypoxia. NECs increased in size, but not abundance in response to elevated CO2. Moreover, fish exposed to moderate or elevated CO2 had 53–78% larger ILCMs compared to control fish. Our results demonstrated that adult marine sticklebacks have NECs that can respond to environmentally relevant pCO2 and likely hypoxia, which highlights the importance of NECs in marine fishes under the heterogeneity of environmental conditions in coastal areas.
Continue reading ‘Changes in gill neuroepithelial cells and morphology of threespine stickleback (Gasterosteus aculeatus) to hypoxia and simulated ocean acidification’Hepatic transcriptomic responsiveness of Polar Cod, Boreogadus saida, to ocean acidification and warming
Published 6 August 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, molecular biology, physiology
Background: This study was part of a larger comprehensive project (BIOACID) addressing the physiological resilience of Polar cod, Boreogadus saida, to ocean acidification and global warming and aimed to unravel underlying molecular mechanisms of the observed physiological responses. Methods: Fish were acclimated long-term to three CO2 concentrations comprising control conditions (390 ppm) and two projected climate scenarios (780 ppm and 1170 ppm). Each CO2 treatment was combined with four temperatures: 0, 3, 6, and 8 °C. Here, we focused on the hepatic transcriptomic profiles from these previously physiologically characterized fish. Results: Generally, we did not detect signs of a classical stress response. Consistent with functional observations, warming induced much stronger molecular responses compared to elevated PCO2, but an interaction between both factors existed to some extent. Gene ontology analysis revealed a strong response in lipid, amino acid, and protein metabolism. With increasing temperature, we observed a shift away from lipid metabolism, while carbohydrate metabolic pathways remained stable. Conclusions: Although we found Polar cod to be quite resilient to ocean acidification, temperature will remain a critical parameter for this valuable Arctic keystone species, and the question remains as to whether the observed acclimation strategies can be implemented in its natural habitat, especially when food supply is limited.
Continue reading ‘Hepatic transcriptomic responsiveness of Polar Cod, Boreogadus saida, to ocean acidification and warming’Species sensitivity distributions: understanding ocean acidification’s impact on marine biota
Published 30 July 2024 Science ClosedTags: biological response, cnidaria, crustaceans, echinoderms, fish, mollusks, phytoplankton, review, zooplankton
This research paper investigates the repercussions of ocean acidification on marine ecosystems, focusing on the sensitivity of diverse taxa to changing pH stages. Drawing from recent research, we discover the complicated interaction among climate change, contaminant accumulation, and atmosphere dynamics, with a particular emphasis on coastal regions reliant on fisheries. Through a complete assessment, we recognize substantial differences in sensitivity amongst calcifying taxa, highlighting the implications for each polar and temperate/tropical region. Furthermore, we propose tailored management techniques relying on distinct climate zones and taxonomic groups to mitigate the destructive effects of ocean acidification. Our sensitivity analyses monitoring of capability shifts in Species Sensitivity Distributions (SSDs) under preindustrial pH situations, underscoring the importance of historic baselines in predicting future influences. This paper contributes to our understanding of how ocean acidification threatens marine biodiversity and underscores the urgency of implementing efficient conservation measures.
Continue reading ‘Species sensitivity distributions: understanding ocean acidification’s impact on marine biota’From nutrients to fish: impacts of mesoscale processes in a global CESM-FEISTY eddying ocean model framework
Published 26 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, fish, globalmodeling, modeling, otherprocess, phytoplankton, review, zooplankton
The ocean sustains ecosystems that are essential for human livelihood and habitability of the planet. The ocean holds an enormous amount of carbon, and serves as a critical source of nutrition for human societies worldwide. Climate variability and change impacts marine biogeochemistry and ecosystems. Thus, having state-of-the-art simulations of the ocean, which include marine biogeochemistry and ecosystems, is critical for understanding the role of climate variability and change on the ocean biosphere. Here we present a novel global eddy-resolving (0.1° horizontal resolution) simulation of the ocean and sea ice, including ocean biogeochemistry, performed with the Community Earth System Model (CESM). The simulation is forced by the atmospheric dataset based on the Japanese Reanalysis (JRA-55) product over the 1958 – 2021 period. We present a novel configuration of the CESM marine ecosystem model in this simulation which includes two zooplankton classes: microzooplankton and mesozooplankton. This novel planktonic food web structure facilitates “offline” coupling with the Fisheries Size and Functional Type (FEISTY) model. FEISTY is a size- and trait-based model of fish functional types contributing to fisheries. We present an evaluation of the ocean biogeochemistry, marine ecosystem (including fish types), and sea ice in this high-resolution simulation compared to available observations and a corresponding low resolution (nominal 1°) simulation. Our analysis offers insights into environmental controls on trophodynamics within the ocean. We find that this high resolution simulation provides a realistic reconstruction of nutrients, oxygen, sea ice, plankton and fish distributions over the global ocean. On global and large regional scales the high-resolution simulation is comparable to the standard 1° simulation, but on smaller scales, explicitly resolving the mesoscale dynamics is shown to be important for accurately capturing trophodynamic structuring, especially in coastal ecosystems. We show that fine scale ocean features leave imprints on ocean ecosystems, from plankton to fish, from the tropics to polar regions. This simulation also offers insights on ocean acidification over the past 64 years, as well as how large scale climate variations may impact upper trophic levels. The data generated by the simulations are publicly available and will be a fruitful community resource for a large variety of oceanographic science questions.
Continue reading ‘From nutrients to fish: impacts of mesoscale processes in a global CESM-FEISTY eddying ocean model framework’Modelling the multiple action pathways of projected climate change on the Pacific cod (Gadus macrocephalus) early life stages
Published 23 July 2024 Science ClosedTags: biological response, chemistry, fish, growth, individualmodeling, modeling, mortality, North Pacific
Highlights
- We used projections of oceanographic conditions and an individual-based model (IBM) to study the impacts of climate on the early life stages of Pacific cod in the eastern Bering Sea from 2021 to 2100.
- Besides temperature and prey density, we also examined the impacts of ocean acidification on some biological aspects of cod larvae.
- We found that a high CO2 emission scenario (RCP8.5) may increase starvation events and decrease cod survival, while the moderate CO2 emission scenario (RCP4.5) may not produce significant impacts.
- We identified a retention area in the southeastern Bering Sea that may provide a refuge for larval cod under future environmental conditions.
- Our IBM can be used for other gadids in the same region to study the impacts of projected climate conditions on early life stages.
Abstract
Understanding how future ocean conditions will impact early life stages and population recruitment of fishes is critical for adapting fisheries communities to climate change. In this study, we incorporated projected changes in physical and biological ecosystem dynamics from an oceanographic model into a mechanistic individual-based model for larval and juvenile stages of the Pacific cod (Gadus macrocephalus) in the eastern Bering Sea. We particularly investigated the impacts of ocean currents, temperature, prey density, and pCO2 on the hatching success, growth, survival, and spatial distribution of this species during 2021–2100. We evaluated two CO2 emission scenarios: RCP8.5 (high CO2 emissions, low mitigation efforts) and RCP4.5 (medium CO2 emissions and mitigation efforts). We found that the increase in temperature and decrease in prey density were the main drivers of faster growth rates and lower survival through increased starvation by the end of the century. Conversely, pCO2 had negligible impacts, which suggests that this species might be resilient to ocean acidification. The largest effects were observed under the high CO2 emission scenario, while the RCP4.5 projections displayed minimal impacts. We also identified an area with favourable conditions in the southeastern Bering Sea that will likely persist in future decades. This study provides relevant information on the future impacts of climate change on Pacific cod, and our results can be used to implement and inform climate-ready management for this important stock in Alaska.
Continue reading ‘Modelling the multiple action pathways of projected climate change on the Pacific cod (Gadus macrocephalus) early life stages’Effects of elevated pCO2 on bioenergetics and disease susceptibility in Pacific herring Clupea pallasii
Published 17 July 2024 Science ClosedTags: biological response, chemistry, fish, growth, laboratory, mortality, North Pacific, performance, physiology, reproduction
Ocean acidification can affect the immune responses of fish, but effects on pathogen susceptibility remain uncertain. Pacific herring Clupea pallasii were reared from hatch under 3 CO2 partial pressure ( pCO2) treatments (ambient, ∼650 µatm; intermediate, ∼1500 µatm; high, ∼3000 µatm) through metamorphosis (98 d) to evaluate the effects of ocean acidification on bioenergetics and susceptibility to an endemic viral disease. Mortality from viral hemorrhagic septicemia (VHS) was comparable between herring reared under ambient and intermediate pCO2 (all vulnerability testing at ambient pCO2). By contrast, fish reared under high pCO2 experienced significantly higher rates of VHS mortality, and the condition factor of survivors was significantly lower than in the other pCO2 treatments. However, the prevalence of infection among survivors was not influenced by pCO2 treatment. Pre-flexion larval development was not affected by elevated pCO2, as growth rate, energy use, and feeding activity were comparable across treatments. Similarly, long-term growth (14 wk) was not affected by chronic exposure to elevated pCO2. Herring reared under both elevated pCO2 treatments showed an average reduction in swimming speed; however, wide intra-treatment variability rendered the effect nonsignificant. This study demonstrates that the VHS susceptibility and bioenergetics of larval and post-metamorphic Pacific herring are not affected by near-future ocean acidification predicted for coastal systems of the North Pacific. However, increased susceptibility to VHS in fish reared under 3000 µatm pCO2 indicates potential health and fitness consequences from extreme acidification.
Continue reading ‘Effects of elevated pCO2 on bioenergetics and disease susceptibility in Pacific herring Clupea pallasii’Bottom’s up – focusing on habitat shifts as mediators of anthropogenic impacts on marine ecosystems
Published 16 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, corals, fish, otherprocess, South Pacific
Marine ecosystems face unprecedented challenges in the Anthropocene, an age characterized by escalating environmental stressors such as ocean acidification, warming and the intrusion of human infrastructure into coastal seascapes. As we hasten to understand the ecological consequences of these mounting pressures, much attention has been devoted to characterizing the traits of individual taxa that are likely to dictate their response to future conditions. However, we are increasingly recognizing the pivotal role that habitat may play in shaping the response of communities to such broad-scale changes. In this thesis, I present empirical evidence of the capacity of habitat-level responses to stress to propagate upwards through the broader ecosystem, inducing substantial and meaningful changes in supported fish assemblages. In my first project, I trace the indirect effects of ocean acidification from the habitat level through to the structure of an assemblage of small-bodied reef fish. I use the natural laboratory provided by a volcanic seep in Papua New Guinea to approximate future acidification conditions under current climate change projections. Here, coral communities chronically exposed to elevated CO2 exhibit a shift in competitive interactions that favours fast-growing, morphologically simple taxa, with the implication that other coral reefs globally may undergo an equivalent structural simplification in coming decades in response to ocean acidification. I show that several common, ecologically important reef fishes display strong and relatively inflexible associations with branching corals, with some even preferencing structure over living tissue when selecting habitat. I then demonstrate that acidified and structurally simplified reefs show a drastically reduced capacity to support healthy populations of these fishes. This chapter contributes two important findings: first, that simplification of coral morphology in response to ocean acidification can induce substantial negative changes in supported reef fish assemblages, even if the total cover of live coral remains unchanged; and secondly, that reef fish may be more vulnerable to these indirect, habitat level changes than to the simple direct effects wrought by acidification. Shifting focus to temperate ecosystems, my second project examines how warming, coastal urbanisation and marine protection interact to influence the distributions and assemblage structures of rangeshifting tropical fishes as they venture poleward in response to ocean warming. Using breakwalls as a ubiquitous and readily accessible test case, I reveal that the structural complexity and shelter from wave action offered by coastal infrastructure can render these environments hotspots for tropical fish recruitment. Importantly, this chapter both identifies coastal infrastructure as potentially significant contributors to the process of tropicalisation, highlighting the need for further research attention and monitoring, but also recognises that marine protected areas can offer an effective means of mitigating the effects of coastal urbanisation. Together, the two projects presented in this thesis demonstrate the power of both the direct and indirect effects of habitat changes. In light of the ongoing and accelerating accumulation of anthropogenically induced stressors, my research underscores the necessity of accounting for habitat-level responses when projecting future fish assemblages, and frames habitat protection as a vital element of safeguarding healthy ecosystems.
Continue reading ‘Bottom’s up – focusing on habitat shifts as mediators of anthropogenic impacts on marine ecosystems’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
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)’Temperate coastal fish shows resilience to extreme low pH in early larval stages
Published 11 July 2024 Science ClosedTags: biological response, chemistry, fish, Indian, laboratory, performance, physiology, reproduction, respiration
Highlights
- Coastal species is tolerant short term, acute low pH conditions in dynamic coastal habitats.
- Tolerance exceeds projected ocean acidification for local coastal habitat.
- Physiological capacity sufficient to compensate for low pH conditions even in the early post-flexion stage of Diplodus capensis.
- Diplodus capensis shows potential for behavioural plasticity at low pH.
Abstract
Fishes have shown varying responses to the decline in seawater pH associated with ocean acidification. Coastal marine species inhabit characteristically dynamic environments which requires physiological adaptation to variability, including fluctuations in pH and associated carbonate chemistry parameters. Our study assessed the response of the early life stages (postflexion) of a common coastal fish species (Diplodus capensis) that is found in coastal nearshore and estuarine habitats along the South African coastline. We assessed their metabolic and behavioural response to a range of pH conditions which covered a high pH (8.02), the lowest pH that they are naturally exposed to (7.75) as well as extremely low pH levels (∼7.75–7.27) exceeding their current range of exposure, which may occur with future coastal acidification. Our findings suggest that this species is metabolically tolerant of acute low pH conditions (down to 7.27 pH) showing no changes in either routine or active metabolic rates. Although our study identified a slight increase in swimming activity in D. capensis larvae exposed to low pH, there was no change in feeding activity. These results suggest that this species may have the physiological capacity to withstand the present and future high pH variability associated with its environments, in the absence of other stressors and ecological interactions. However, the increased swimming activity at low pH may translate into downstream ecological impacts, for which the mechanisms need to be assessed with further research.
Continue reading ‘Temperate coastal fish shows resilience to extreme low pH in early larval stages’Out of shape: ocean acidification simplifies coral reef architecture and reshuffles fish assemblages
Published 3 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, corals, fish, otherprocess, performance, physiology, South Pacific
- Climate change stressors are progressively simplifying biogenic habitats in the terrestrial and marine realms, and consequently altering the structure of associated species communities.
- Here, we used a volcanic CO2 seep in Papua New Guinea to test in situ if altered reef architecture due to ocean acidification reshuffles associated fish assemblages.
- We observed replacement of branching corals by massive corals at the seep, with simplified coral architectural complexity driving abundance declines between 60% and 86% for an assemblage of damselfishes associated with branching corals. An experimental test of habitat preference for a focal species indicated that acidification does not directly affect habitat selection behaviour, with changes in habitat structural complexity consequently appearing to be the stronger driver of assemblage reshuffling. Habitat health affected anti-predator behaviour, with P. moluccensis becoming less bold on dead branching corals relative to live branching corals, irrespective of ocean acidification.
- We conclude that coral reef fish assemblages are likely to be more sensitive to changes in habitat structure induced by increasing pCO2 than any direct effects on behaviour, indicating that changes in coral architecture and live cover may act as important mediators of reef fish community structures in a future ocean.
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’Ocean acidification induces changes in circadian alternative splicing profiles in a coral reef fish
Published 26 June 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, molecular biology, physiology, South Pacific
Background
Alternative splicing is a fundamental mechanism of gene expression regulation that increases the mRNA diversity expressed from the genome and can be partially regulated by the circadian clock. The time-dependent production of transcript isoforms from the same gene facilitates coordination of biological processes with the time of day and is a crucial mechanism enabling organisms to cope with environmental changes. In this study, we aim to determine the impact of future ocean acidification conditions on circadian splicing patterns in the brain of fish, while also accounting for diel CO2 fluctuations that naturally occur on coral reefs.
Results
Fish in the control group exhibited a temporal splicing pattern across the 24-hour period, however, these splicing events were largely absent in fish exposed to either stable or fluctuating elevated CO2 conditions. Furthermore, the molecular responses were influenced not only by an overall increase in CO2 concentration but also by its stability, with 6am and 6pm being key timepoints when the majority of the aberrant splicing events were identified. We found that fish in fluctuating CO2 conditions exhibited increased plasticity in transcriptional regulation by varying the proportion of transcript isoforms depending on the time-of-day. This was especially notable for genes associated with neural functioning.
Conclusions
Our findings suggest that fish rely on different molecular mechanisms to respond to elevated CO2 exposure in stable and fluctuating conditions. Periodic variation in CO2 levels in the fluctuating CO2 treatment might enable fish to rely on feed-forward mechanisms to synchronize neural functions with external environmental conditions. Such interconnectedness between external pH changes and transcriptional regulation via alternative splicing may provide fish in fluctuating CO2 environments with greater flexibility in biological responses, which may alleviate sensory and behavioural impairments enabling them to better cope with future ocean acidification conditions.
Continue reading ‘Ocean acidification induces changes in circadian alternative splicing profiles in a coral reef fish’Resiliency of black sea bass, Centropristis striata, early life stages to future high CO2 conditions
Published 12 June 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, mortality, North Atlantic, reproduction
Ocean acidification is a symptom of marine climate change resulting from the uptake of anthropogenic carbon dioxide (CO2) into the world’s ocean, thereby potentially affecting survival, growth, and numerous other traits in fish early life stages. But some fish species are clearly more CO2-resilient than others, perhaps because they reside in more CO2-variable, inshore habitats as opposed to more CO2-stable offshore waters. Here we studied the early life CO2 sensitivity of an ecologically and economically important fish species (Black Sea Bass, Centropristis striata) that seasonally migrates between offshore overwintering and inshore feeding and nursery grounds. We produced embryos from wild spawners and reared them until 10 days post-hatch (dph) at three contrasting pCO2 levels (~400, ~2200, ~3000 µatm), finding no statistical effects of pCO2 on hatching success (~28%) or survival to 10 dph (~23%). At the extreme pCO2 level, surviving larvae were 1.2× larger and grew 55% faster compared to control pCO2 conditions. These results extend pioneering work by Meseck et al. (2022; https://doi.org/10.1002/mcf2.10200) to confirm a surprising CO2 tolerance of C. striata early life stages. This suggests existing adaptation to high CO2 conditions either because of seasonal exposures at productive inshore environments or at offshore depths during overwintering.
Continue reading ‘Resiliency of black sea bass, Centropristis striata, early life stages to future high CO2 conditions’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’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’Projecting marine fish distributions during early life stages under future climate scenarios
Published 24 May 2024 Science ClosedTags: biological response, fish, fisheries, reproduction, review
Changes to Earth’s climate affect organisms globally; in marine systems, these impacts are seen through warming water temperatures, ocean acidification, hypoxia and frequent marine heatwaves. These effects may lead to the movement of species to more favourable conditions. While climate-driven movement is well studied at the adult stage, how the early life stages of marine fish will respond to future variability is less clear. Many fish species are constrained by specific spawning locations or phenology. Spawning in certain locations allows for local retention of offspring, while precise timing can facilitate transport of offspring to nursery locations through seasonal circulation patterns. Our research investigates how changing oceans impact the location and timing of spawning of Bering Sea groundfishes over the next century. We used ROMS SST and SSS model output and NOAA survey data in species distribution models to hindcast and project distributions and centre of gravity for eggs and larvae of six groundfish species. Our analyses found that most of our study species exhibit flexible geography. However, the speed and direction of egg and larval movement did not track the speed and direction of their respective thermal niches. Hence, the projected distributional patterns of adult stages may be limited by their early life stages. This response is likely to be mirrored globally by other species with planktonic eggs and larvae. These results indicate that life history considerations are critical for the management of commercially important species, as effects on early life stages are strongly connected to the success or failure of adult populations.
Continue reading ‘Projecting marine fish distributions during early life stages under future climate scenarios’Shark critical life stage vulnerability to monthly temperature variations under climate change
Published 8 May 2024 Science ClosedTags: biological response, fish, growth, laboratory, morphology, multiple factors, North Atlantic, performance, physiology, reproduction, respiration, temperature
Highlights
- Summer temperatures revealed embryo vulnerability to seasonal fluctuations.
- Hatching success ranged from 82% in control and SSP2-4.5 to 11% in SSP5-8.5.
- The death of embryos was preceded by distinct individual growth trajectories.
Abstract
In a 10-month experimental study, we assessed the combined impact of warming and acidification on critical life stages of small-spotted catshark (Scyliorhinus canicula). Using recently developed frameworks, we disentangled individual and group responses to two climate scenarios projected for 2100 (SSP2-4.5: Middle of the road and SSP5-8.5: Fossil-fueled Development). Seasonal temperature fluctuations revealed the acute vulnerability of embryos to summer temperatures, with hatching success ranging from 82% for the control and SSP2-4.5 treatments to only 11% for the SSP5-8.5 treatment. The death of embryos was preceded by distinct individual growth trajectories between the treatments, and also revealed inter-individual variations within treatments. Embryos with the lowest hatching success had lower yolk consumption rates, and growth rates associated with a lower energy assimilation, and almost all of them failed to transition to internal gills. Within 6 months after hatching, no additional mortality was observed due to cooler temperatures.
Continue reading ‘Shark critical life stage vulnerability to monthly temperature variations under climate change’
