Posts Tagged 'reproduction'

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Effects of ocean acidification and warming on the specific dynamic action of California Grunion (Leuresthes tenuis) larvae

Published 27 March 2023 Science Closed
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Highlights

  • SDA was measured as the difference in metabolic rate of fed and non-fed fish.
  • SDA is ∼15% of the daily metabolic energy costs for California Grunion larvae.
  • OA conditions shifted the SDA response earlier.
  • Changes in SDA with climate can have downstream effects on larval growth.

Abstract

Ocean acidification (OA) and Ocean Warming (OW) are ongoing environmental changes that present a suite of physiological challenges to marine organisms. Larval stages may be especially sensitive to the effects of climate change because the larval phase is a time of critical growth and development. Of particular importance to growth is Specific Dynamic Action (SDA) – the energy used in digestion, absorption, and assimilation of food. Relatively little is known about the energetics of SDA for larval fishes and even less is known about how SDA may be affected by climate change. In this study we used feeding experiments and respirometry assays to characterize the functional form of SDA for California Grunion (Leuresthes tenuis). In a second set of experiments, we tested the independent and combined effects of ocean acidification and warming on SDA. Our first experiment revealed that an elevated metabolic rate was detectable within an hour of feeding, peaked at 3–6 h post feeding, and lasted about 24 h in total. Experiments testing the effects of acidification and warming revealed that temperature generally increased the maximum rate of postprandial respiration and the total amount of energy expended via SDA. In an experiment where feeding level was the same for fish held at different temperatures, elevated pCO2 increased the maximum rate of postprandial respiration and shortened the SDA response. However, in an experiment that allowed fish to consume more food at high temperatures, effects of pCO2 on SDA were minimal. The effects of OA on SDA may depend on a combination of temperature and food availability, and the disruption of SDA with OA may be part of a chain of events where digestion and assimilation efficiency are impaired with potential consequences for growth, survival, and population replenishment.

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Field development of Posidonia oceanica seedlings changes under predicted acidification conditions

Published 27 March 2023 Science Closed
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Ocean acidification has been consistently evidenced to have profound and lasting impacts on marine species. Observations have shown seagrasses to be highly susceptible to future increased pCO2 conditions, but the responses of early life stages as seedlings are poorly understood. This study aimed at evaluating how projected Mediterranean Sea acidification affects the survival, morphological and biochemical development of Posidonia oceanica seedlings through a long-term field experiment along a natural low pH gradient. Future ocean conditions seem to constrain the morphological development of seedlings. However, high pCO2 exposures caused an initial increase in the degree of saturation of fatty acids in leaves and then improved the fatty acid adjustment increasing unsaturation levels in leaves (but not in seeds), suggesting a nutritional compound translocation. Results also suggested a P. oceanica structural components remodelling which may counteract the effects of ocean acidification but would not enhance seagrass seedling productivity.

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Effects of ocean acidification on the early life history processes of the breadcrumb sponge Halichondria panicea

Published 20 March 2023 Science Closed
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Ocean acidification (OA) is predicted to result in reduced survival, growth, reproduction, and overall biodiversity of marine invertebrates, and yet we lack information about the response to OA of some major groups of marine organisms. In particular, we know relatively little about how OA will impact temperate sponges, which will experience more extreme low pH conditions than tropical species. In this study, we quantified OA-induced changes in early life history patterns (larval mortality and condition, settlement rate, recruit survival, and size) in the non-calcifying breadcrumb sponge Halichondria panicea collected from a temperate intertidal site in the California Current Large Marine Ecosystem. Sponge larvae were exposed to OA conditions for 15 days, and early life history patterns were observed. Compared with baseline (“present”) conditions, larval mortality and settlement rates increased in the acidified treatment (“future”). This effect was restricted to larval stages; treatment had no effect on the growth and survival of recruits. This study is significant in that it shows that H. panicea may be particularly vulnerable to changes in ocean pH during the larval stage, which could ultimately reduce total sponge abundance by diminishing the number of larvae that survive to settlement.

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Evaluating environmental controls on the exoskeleton density of larval Dungeness crab via micro computed tomography

Published 16 March 2023 Science Closed
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Dungeness crab (Metacarcinus magister) have significant socioeconomic value, but are threatened by ocean acidification (OA) and other environmental stressors that are driven by climate change. Despite evidence that adult harvests are sensitive to the abundance of larval populations, relatively little is known about how Dungeness megalopae will respond to these stressors. Here we evaluate the ability to use micro-computed tomography (μCT) to detect variations in megalope exoskeleton density and how these measurements reflect environmental variables and calcification mechanisms. We use a combination of field data, culture experiments, and model simulations to suggest resolvable differences in density are best explained by minimum pH at the time zoeae molt into megalopae. We suggest that this occurs because more energy must be expended on active ion pumping to reach a given degree of calcite supersaturation at lower pH. Energy availability may also be reduced due to its diversion to other coping mechanisms. Alternate models based on minimum temperature at the time of the zoea-megalope molt are nearly as strong and complicate the ability to conclusively disentangle pH and temperature influences. Despite this, our results suggest that carryover effects between life stages and short-lived extreme events may be particularly important controls on exoskeleton integrity. μCT-based estimates of exoskeleton density are a promising tool for evaluating the health of Dungeness crab populations that will likely provide more nuanced information than presence-absence observations, but future in situ field sampling and culture experiments are needed to refine and validate our results.

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Nanoplastics induce epigenetic signatures of transgenerational impairments associated with reproduction in copepods under ocean acidification

Published 15 March 2023 Science Closed
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Graphical abstract

Ocean acidification (OA) is one of many major global climate changes that pose a variety of risks to marine ecosystems in different ways. Meanwhile, there is growing concern about how nanoplastics (NPs) affect marine ecosystems. Combined exposure of marine organisms to OA and NPs is inevitable, but their interactive effects remain poorly understood. In this study, we investigated the multi- and transgenerational toxicity of NPs on copepods under OA conditions for ten generations. The findings revealed that OA and NPs have a synergistic negative effect on copepod reproduction across generations. In particular, the transgenerational groups showed reproductive impairments in the F1 and F2 generations (F1T and F2T), even though they were never exposed to NPs. Moreover, our epigenetic examinations demonstrated that the observed intergenerational reproductive impairments are associated with differential methylation patterns of specific genes, suggesting that the interaction of OA and NPs can pose a significant threat to the sustainability of copepod populations through epigenetic modifications. Overall, our findings provide valuable insight into the intergenerational toxicity and underlying molecular mechanisms of responses to NPs under OA conditions.

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Directional fabrication and dissolution of larval and juvenile oyster shells under ocean acidification

Published 15 March 2023 Science Closed
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Biomineralization is one of the key biochemical processes in calcifying bivalve species such as oysters that is affected by ocean acidification (OA). Larval life stages of oysters are made of aragonite crystals whereas the adults are made of calcite and/or aragonite. Though both calcite and aragonite are crystal polymorphs of calcium carbonate, they have different mechanical properties and hence it is important to study the micro and nano structure of different life stages of oyster shells under OA to understand the mechanisms by which OA affects biomineralization ontogeny. Here, we have studied the larval and juvenile life stages of an economically and ecologically important estuarine oyster species, Crassostrea hongkongensis, under OA with focus over shell fabrication under OA (pHNBS 7.4). We also look at the effect of parental exposure to OA on larvae and juvenile microstructure. The micro and nanostructure characterization reveals directional fabrication of oyster shells, with more organized structure as biomineralization progresses. Under OA, both the larval and juvenile stages show directional dissolution, i.e. the earlier formed shell layers undergo dissolution at first, owing to longer exposure time. Despite dissolution, the micro and nanostructure of the shell remains unaffected under OA, irrespective of parental exposure history.

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Elevated CO2 levels did not induce species- or tissue-specific damage in young-of-year salmonids

Published 14 March 2023 Science Closed
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There are few studies that assess CO2 effects on fish tissues. To study these effects, young-of-year Arctic Charr (Salvelinus alpinus), Rainbow Trout (Oncorhynchus mykiss), and Brook Charr (S. fontinalis) were exposed to either control levels of CO2 (1,400 μatm) or elevated levels of CO2 (5,236 μatm) for 15 days. Fish were then sampled for gill, liver, and heart tissues and histologically analyzed. A species effect was observed for the length of secondary lamellae, as Arctic Charr had significantly shorter secondary lamellae than the other species. No notable changes within the gills and livers of Arctic Charr, Brook Charr, or Rainbow Trout exposed to elevated CO2 were observed. Generally, our results indicated that elevated CO2 levels over 15 days do not induce catastrophic tissue damage and it is unlikely that fish health would be seriously impacted. Ongoing research dedicated to examining how elevated CO2 long-term may affect internal tissues of fish will allow for a more comprehensive understanding of how fish may fair with ongoing climate change and in aquaculture facilities.

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Seawater carbonate parameters function differently in affecting embryonic development and calcification in Pacific abalone (Haliotis discus hannai)

Published 14 March 2023 Science Closed
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pH or pCO2 are usually taken to study the impact of ocean acidification on molluscs. Here we studied the different impact of seawater carbonate parameters on embryonic development and calcification of the Pacific abalone (Haliotis discus hannai). Early embryonic development was susceptible to elevated pCO2 level. Larvae hatching duration was positively and hatching rate was negatively correlated with the pCO2 level, respectively. Calcium carbonate (CaCO3) deposition of larval shell was found to be susceptible to calcium carbonate saturation state (Ω) rather than pCO2 or pH. Most larvae incubated in seawater with Ωarag = 1.5 succeeded in shell formation, even when seawater pCO2 level was higher than 3700 μatm and pHT was close to 7.4. Nevertheless, larvae failed to generate CaCO3 in seawater with Ωarag ≤ 0.52 and control level of pCO2, while seawater DIC level was lowered (≤ 852 μmol/kg). Surprisingly, some larvae completed CaCO3 deposition in seawater with Ωarag = 0.6 and slightly elevated DIC (2266 μmol/kg), while seawater pCO2 level was higher than 2700 μatm and pHT was lower than 7.3. This indicates that abalone may be capable of regulating carbonate chemistry to support shell formation, however, the capability was limited as surging pCO2 level lowered growth rate and jeopardized the integrity of larval shells. Larvae generated thicker shell in seawater with Ωarag = 5.6, while adult abalone could not deposit CaCO3 in seawater with Ωarag = 0.29 and DIC = 321 μmol/kg. This indicates that abalone may lack the ability to directly remove or add inorganic carbon at the calcifying sites. In conclusion, different seawater carbonate parameters play different roles in affecting early embryonic development and shell formation of the Pacific abalone, which may exhibit limited capacity to regulate carbonate chemistry.

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The multi-generational effect of seawater acidification on larval development, reproduction, ingestion rate, and ATPase activity of Tigriopus japonicus Mori, 1938

Published 13 March 2023 Science Closed
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Ocean acidification threatens marine organisms continuously. To ascertain if adaptation of marine species to ocean acidification enhanced over multiple generations, we studied the transgenerational effects of ocean acidification on the development, reproduction, ingestion rate, and ATPase activity of a copepod Tigriopus japonicus Mori, 1938. In the first mode, individuals were exposed to either one of the pH levels (8.1 (control), 7.7, 7.3) for five successive generations. In the second mode, each successive generation was exposed to a lower pH level (pH levels: 8.1, 7.9, 7.7, 7.5, 7.3). After prolonged exposure to a constant seawater acidification level, the capacity to adapt to the stress increased. However, when exposed to seawater of descending pH, the detrimental effects gradually increased. Energy allocated to development and reproduction was reduced although the ingestion rate continued to improve in successive generations. Therefore, ongoing ocean acidification might lower the energy transfer of copepods to higher trophic levels.

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Effects of elevated CO2 on metabolic rate and nitrogenous waste handling in the early life stages of yellowfin tuna (Thunnus albacares)

Published 6 March 2023 Science Closed
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Graphical abstract

Highlights

  • Little is known about how tuna species will respond to ocean acidification (OA).
  • CO2 altered nitrogenous waste excretion and metabolic rate in yolk sac larvae.
  • CO2 did not change yolk sac depletion in embryos.
  • CO2 did not alter nitrogen accumulation in yellowfin tuna.
  • Yellowfin tuna were more robust to CO2 than predicted.

Abstract

Ocean acidification is predicted to have a wide range of impacts on fish, but there has been little focus on broad-ranging pelagic fish species. Early life stages of fish are thought to be particularly susceptible to CO2 exposure, since acid-base regulatory faculties may not be fully developed. We obtained yellowfin tuna (Thunnus albacares) from a captive spawning broodstock population and exposed them to control or 1900 μatm CO2 through the first three days of development as embryos transitioned into yolk sac larvae. Metabolic rate, yolk sac depletion, and oil globule depletion were measured to assess overall energy usage. To determine if CO2 altered protein catabolism, tissue nitrogen content and nitrogenous waste excretion were quantified. CO2 exposure did not significantly impact embryonic metabolic rate, yolk sac depletion, or oil globule depletion, however, there was a significant decrease in metabolic rate at the latest measured yolk sac larval stage (36 h post fertilization). CO2-exposure led to a significant increase in nitrogenous waste excretion in larvae, but there were no differences in nitrogen tissue accumulation. Nitrogenous waste accumulated in embryos as they developed but decreased after hatch, coinciding with a large increase in nitrogenous waste excretion and increased metabolic rate in newly hatched larvae. Our results provide insight into how yellowfin tuna are impacted by increases in CO2 in early development, but more research with higher levels of replication is needed to better understand long-term impacts and acid-base regulatory mechanisms in this important pelagic fish.

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Thanks mum. Maternal effects in response to ocean acidification of sea urchin larvae at different ecologically relevant temperatures

Published 3 March 2023 Science Closed
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Graphical abstract

Highlights

  • Ocean acidification and temperature differently influence larval development of Arbacia lixula and Paracentrotus lividus.
  • Larvae of the two A. lixula populations (ambient-pH vs vent sites) respond differently to ocean acidification and temperature.
  • Maternal buffer effect was observed in response to ocean acidification and temperature in both species.
  • A. lixula seems to be more tolerant to changes in temperature than P. lividus.

Abstract

Juvenile stages of marine species might be more vulnerable than adults to climate change, however larval vulnerability to predictable environmental changes can be mitigated by parental anticipatory buffer effects occurring during gametogenesis. In this study, ocean acidification effect were investigated on larval growth of two sea urchins, Arbacia lixula and Paracentrotus lividus, at different temperature levels. Results showed that altered pH and temperature affected larval development in both species, with significant length reductions of spicules and significant increases in abnormal larvae. Detrimental effects of reduced pH and high temperature were however dependent on the mother. Furthermore, the responses of A. lixula larvae from the ambient site (pH ∼ 8.0) were compared with those of larvae obtained from mothers collected from a natural CO2 vent (pH ∼ 7.7) in Ischia. Comparisons highlighted a transgenerational response, as the CO2 vent larvae proved to be more resilient to reduced pH, although more sensitive to increased temperature.

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The effect of pH on the larvae of two sea urchin species using different pH manipulation methods

Published 27 February 2023 Science Closed
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Climate change alters ocean pH, temperature, and salinity, which presents challenges for oceanic organisms, especially those with calcium carbonate skeletons. Our research examines how decreasing pH impacts larval survivorship and calcium carbonate skeletal development of two sea urchin species, Lytechinus variegatus and Arbacia punctulata. Based on previous work in various sea urchin species, it is expected that as pH decreases, survivorship decreases and skeletal malformations increase. Both L. variegatus and A. punctulata have been used in prior studies to explore pH change on survivorship and development, but these studies incorporated various outcomes and pH manipulation methods, limiting how comparable they are. Therefore, we wanted to measure the same outcomes between species and compare the effect of different pH manipulation within species. We altered pH by either HCL addition or CO2 bubbling through seawater. Larvae, at a concentration of 3 larvae/ml, were exposed to seawater of pH 8.4, 8.0, or 7.6. For each treatment, survivorship of 30-40 larvae was measured daily for 10-14 days depending on the trial. Larval malformations were quantified for about 10 larvae from daily fixed samples. Larval arm length, body length, and body width were measured using Image J. For both methods of pH manipulation and both species, there was a statistically significant (p<0.001) decrease in survivorship as pH decreases consistent with the prediction. Preliminary analysis of skeletal deformities suggests malformations increase as pH decreases, but data are still being collected. Similar abnormalities observed between species regardless of pH manipulations include uneven or missing arms and misshapen aboral sides. The effect of pH on larval survivorship and development in L. variegatus and A. punctulata are comparable to observations in other species suggesting effects are consistent across manipulation methods and species. With this research, we can continue to fine-tune methodology and build on our understanding of how climate change-driven ocean acidification can impact species.

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Parental exposure to ocean acidification impacts gamete production and physiology but not offspring performance in Nematostella vectensis

Published 21 February 2023 Science Closed
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Ocean acidification (OA) resulting from anthropogenic CO2 emissions is impairing the reproduction of marine organisms. While parental exposure to OA can protect offspring via carryover effects, this phenomenon is poorly understood in many marine invertebrate taxa. Here, we examined how parental exposure to acidified (pH 7.40) versus ambient (pH 7.72) seawater influenced reproduction and offspring performance across six gametogenic cycles (13 weeks) in the estuarine sea anemone Nematostella vectensis. Females exhibited reproductive plasticity under acidic conditions, releasing significantly fewer but larger eggs compared to ambient females after four weeks of exposure, and larger eggs in two of the four following spawning cycles despite recovering fecundity, indicating long-term acclimatization and greater investment in eggs. Males showed no changes in fecundity under acidic conditions, but produced a greater percentage of sperm with high mitochondrial membrane potential (MMP; a proxy for elevated motility), which corresponded with higher fertilization rates relative to ambient males. Finally, parental exposure to acidic conditions did not significantly influence offspring development rates, respiration rates, or heat tolerance. Overall, this study demonstrates that parental exposure to acidic conditions impacts gamete production and physiology but not offspring performance in N. vectensis, suggesting that increased investment in individual gametes may promote fitness.

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RNAi silencing of the biomineralization gene perlucin impairs oyster ability to cope with ocean acidification

Published 17 February 2023 Science Closed
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Calcifying marine organisms, including the eastern oyster (Crassostrea virginica), are vulnerable to ocean acidification (OA) because it is more difficult to precipitate calcium carbonate (CaCO3). Previous investigations of the molecular mechanisms associated with resilience to OA in C. virginica demonstrated significant differences in single nucleotide polymorphism and gene expression profiles among oysters reared under ambient and OA conditions. Converged evidence generated by both of these approaches highlighted the role of genes related to biomineralization, including perlucins. Here, gene silencing via RNA interference (RNAi) was used to evaluate the protective role of a perlucin gene under OA stress. Larvae were exposed to short dicer-substrate small interfering RNA (DsiRNA-perlucin) to silence the target gene or to one of two control treatments (control DsiRNA or seawater) before cultivation under OA (pH ~7.3) or ambient (pH ~8.2) conditions. Two transfection experiments were performed in parallel, one during fertilization and one during early larval development (6 h post-fertilization), before larval viability, size, development, and shell mineralization were monitored. Silenced oysters under acidification stress were the smallest, had shell abnormalities, and had significantly reduced shell mineralization, thereby suggesting that perlucin significantly helps larvae mitigate the effects of OA.

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Life-stage-dependent effects of multiple flood-associated stressors on a coastal foundational species

Published 15 February 2023 Science Closed
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Global changes in precipitation patterns have increased the frequency and duration of flooding events. Freshwater inflows into estuaries reduce salinity levels and increase nutrient inputs, which can lead to eutrophication and impaired water quality. Oysters are important ecosystem engineers in coastal environments that are vulnerable to co-occurring environmental stressors associated with freshwater flooding events. Successful recruitment is necessary to maintain adult oyster populations, but early life stage responses to multiple stressors are not well understood. Flood-associated stressor conditions were observed near oyster habitats at multiple locations across the northern Gulf of Mexico during peak recruitment months in the spring and summer of 2021. In the laboratory, we examined the interactive effects of acidification, hypoxia, and low salinity on larval and juvenile life stages of the eastern oyster (Crassostrea virginica) to better understand the impact of flooding events on oyster development and survival. Salinity stress in isolation reduced larval growth and settlement, and decreased survival and growth at the juvenile stage. Hypoxia was more stressful to oyster larvae than to juveniles, whereas low pH had negative effects on juvenile growth. There were no synergistic effects of multiple flood-associated stressors on early oyster life stages and effects were either additive or predicted by the salinity stress response. The negative impacts of flooding disturbances on recruitment processes in benthic populations need to be considered in restoration planning and flood control mitigation strategies as the frequency and intensity of extreme freshwater events continue to rise worldwide.

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Analysis of spawning behaviour and growth indices of zebrafish in response to CO2 acidification

Published 10 February 2023 Science Closed
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The growth parameters and spawning behaviour of zebrafish in response to CO2 acidification demonstrated differential results. The growth performance of zebrafish is determined by key indices, BWG, SGR, CF and CV. BWG shows subtle gain in 1500 µatm group (0.09 g) and a slight decrease in 2200 µatm group (0.056 g). SGR index showed similar pattern of results, whereas CF showed a gradual decrease. The other growth index CV again showed an increase in 1500 µatm group and slight decrease in 2200 µatm group in comparison to the control group. A significant decrease in the performance of spawning behaviour was observed. At 96 hpf, the survival rate of the embryos showed a significant hit and the number of dead embryos increased dose dependently. The embryos exposed to CO2 showed a decrease in hatching rate with the increase in dose of CO2. The CO2 acidification causes notable changes in the growth and significant effect on reproductive behaviour.

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Multi-stress interplay: time and duration of ocean acidification modulate the toxicity of mercury and other metals

Published 8 February 2023 Science Closed
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The current understanding of multi-stress interplay assumes stresses occur in perfect synchrony, but this assumption is rarely met in the natural marine ecosystem. To understand the interplay between non-perfectly overlapped stresses in the ocean, we manipulated different temporal scenarios of acidification and assessed their effect on mercury toxicity in a marine copepod. We found that the scenario of past acidification aggravated mercury toxicity, but personal and persistent acidification mitigated the toxicity. This is because personal and persistent acidification initiated the energy compensation to enhance growth and mercury efflux. To explore how general temporal scenarios of acidification affected multi-stress interplay, we conducted a meta-analysis on marine animals and found that scenarios significantly changed the toxicity of several other metals. Our study thus demonstrates that time and duration of stresses modulate multi-stress interplay in the marine ecosystem, and suggests that future studies should move beyond the scenario of perfect synchrony.

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Potential ecosystem regime shift resulting from elevated CO2 and inhibition of macroalgal recruitment by turf algae

Published 31 January 2023 Science Closed
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Rising carbon dioxide (CO2) concentrations are predicted to cause an undesirable transition from macroalgae-dominant to turf algae-dominant ecosystems due to its effect on community structuring processes. As turf algae are more likely to proliferate due to the CO2 fertilization effect than macroalgae and often inhibit macroalgal recruitment, increased CO2 beyond certain levels may produce novel positive feedback loops that promote turf algae growth and thus can stabilize turf algae-dominant ecosystems. In this study, we built a simple competition model between macroalgae and turf algae in a homogeneous space to investigate the steady-state response of the ecosystem to changes in the partial pressure of CO2 (pCO2). We found that discontinuous regime shifts in response to pCO2 change can occur once turf algae coverage reaches a critical level capable of inhibiting macroalgal recruitment. The effect of localized turf algae density on the success rate of macroalgae recruitment was also investigated using a patch model that simulated a two-dimensional heterogeneous space. This suggested that in addition to the inhibitory effect by turf algae, a self-enhancing effect by macroalgae could also be important in predicting the potential discontinuous regime shifts in response to future pCO2 changes.

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Response mechanism of harmful algae Phaeocystis globosa to ocean warming and acidification

Published 30 January 2023 Science Closed
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Graphical abstract

Simultaneous ocean warming and acidification will alter marine ecosystem structure and directly affect marine organisms. The alga Phaeocystis globosa commonly causes harmful algal blooms in coastal areas of eastern China. P. globosa often outcompetes other species due to its heterotypic life cycle, primarily including colonies and various types of solitary cells. However, little is known about the adaptive response of P. globosa to ocean warming and acidification. This study aimed to reveal the global molecular regulatory networks implicated in the response of P. globosa to simultaneous warming and acidification. After exposure to warming and acidification, the phosphatidylinositol (PI) and mitogen-activated protein kinase (MAPK) signaling pathways of P. globosa were activated to regulate other molecular pathways in the cell, while the light harvesting complex (LHC) genes were downregulated to decrease photosynthesis. Exposure to warming and acidification also altered the intracellular energy flow, with more energy allocated to the TCA cycle rather than to the biosynthesis of fatty acids and hemolytic substances. The upregulation of genes associated with glycosaminoglycan (GAG) degradation prevented the accumulation of polysaccharides, which led to a reduction in colony formation. Finally, the upregulation of the Mre11 and Rad50 genes in response to warming and acidification implied an increase in meiosis, which may be used by P. globosa to increase the number of solitary cells. The increase in genetic diversity through sexual reproduction may be a strategy of P. globosa that supports rapid response to complex environments. Thus, the life cycle of P. globosa underwent a transition from colonies to solitary cells in response to warming and acidification, suggesting that this species may be able to rapidly adapt to future climate changes through life cycle transitions.

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Effect of pH on the early development of the biofouling ascidian Ciona robusta

Published 26 January 2023 Science Closed
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Ocean acidification (OA) impacts the survival, fertilization, and community structure of marine organisms across the world. However, some populations or species are considered more resilient than others, such as those that are invasive, globally distributed, or biofouling. Here, we tested this assumption by investigating the effect of pH on the larval development of one such tunicate, Ciona robusta, which is currently exposed to a wide range of pH levels. Consistent with our hypothesis, C. robusta larvae developed and metamorphosed at a rate comparable to control (pH 8.0) at modest near-future conditions (pH 7.7) over a 58-hour period. However, development was stunted at the extreme low pH of 6.8 such that no embryo progressed beyond late cleavage after 58 hours. Interestingly, piecewise regression of the proportion of embryos at the most advanced stage at a given time point against pH identified a breakpoint with the highest pH (~pH 7.6) at around hatching. The variation in breakpoint pH throughout ontogeny highlighted that the sensitivity to decreasing pH differs significantly between developmental stages. More broadly, our results show that even a cosmopolitan, biofouling, invasive species could be negatively impacted by decreasing pH.

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