Posts Tagged 'adaptation'



Effects of ocean acidification on the levels of primary and secondary metabolites in the brown macroalga Sargassum vulgare at different time scales

Highlights

Sargassum vulgare growing at CO2 vents was compared with those growing at control site.
S. vulgare from control site was transplanted to CO2 vents for 2 weeks.
• In short-term responses, S. vulgare showed increased level of sugars, PUFAs, and EAAs.
• Natural population at vents showed decreased sugars, PUFAs, phenols, and increased EAAs.
• Nutritional values of algae will decrease under acidification in long time scale.

Abstract

Most of the studies regarding the impact of ocean acidification on macroalgae have been carried out for short-term periods, in controlled laboratory conditions, thus hampering the possibility to scale up the effects on long-term. In the present study, the volcanic CO2 vents off Ischia Island were used as a natural laboratory to investigate the metabolic response of the brown alga Sargassum vulgare to acidification at different time scales. For long-term effects, algal populations naturally growing at acidified and control sites were compared. For short-term responses, in situ reciprocal transplants from control to acidified site and vice-versa were performed. Changes in the levels of sugars, fatty acids (FAs), amino acids (AAs), antioxidants, and phenolic compounds were examined. Our main finding includes variable metabolic response of this alga at different time scales to natural acidification. The levels of sugars, FAs, and some secondary metabolites were lower in the natural population at the acidified site, whereas the majority of AAs were higher than those detected in thalli growing at control site. Moreover, in algae transplanted from control to acidified site, soluble sugars (glucose and mannose), majority of AAs, and FAs increased in comparison to control plants transplanted within the same site. The differences in the response of the macroalga suggest that the metabolic changes observed in transplants may be due to acclimation that supports algae to cope with acidification, thus leading to adaptation to lowered pH in long time scale.

Graphical abstract

Unlabelled Image

Continue reading ‘Effects of ocean acidification on the levels of primary and secondary metabolites in the brown macroalga Sargassum vulgare at different time scales’

Population-specific responses in physiological rates of Emiliania huxleyi to a broad CO2 range

Although coccolithophore physiological responses to CO2-induced changes in seawater carbonate chemistry have been widely studied in the past, there is limited knowledge on the variability of physiological responses between populations from different areas. In the present study, we investigated the specific responses of growth, particulate organic (POC) and inorganic carbon (PIC) production rates of three populations of the coccolithophore Emiliania huxleyi from three regions in the North Atlantic Ocean (Azores: six strains, Canary Islands: five strains, and Norwegian coast near Bergen: six strains) to a CO2 partial pressure (pCO2) range from 120 to 2630 µatm. Physiological rates of each population and individual strain increased with rising pCO2 levels, reached a maximum and declined thereafter. Optimal pCO2 for growth, POC production rates, and tolerance to low pH (i.e., high proton concentration) was significantly higher in an E. huxleyi population isolated from the Norwegian coast than in those isolated near the Azores and Canary Islands. This may be due to the large environmental variability including large pCO2 and pH fluctuations in coastal waters off Bergen compared to the rather stable oceanic conditions at the other two sites. Maximum growth and POC production rates of the Azores and Bergen populations were similar and significantly higher than that of the Canary Islands population. This pattern could be driven by temperature–CO2 interactions where the chosen incubation temperature (16 °C) was slightly below what strains isolated near the Canary Islands normally experience. Our results indicate adaptation of E. huxleyi to their local environmental conditions and the existence of distinct E. huxleyi populations. Within each population, different growth, POC, and PIC production rates at different pCO2 levels indicated strain-specific phenotypic plasticity. Accounting for this variability is important to understand how or whether E. huxleyi might adapt to rising CO2 levels.

Continue reading ‘Population-specific responses in physiological rates of Emiliania huxleyi to a broad CO2 range’

Ocean acidification conditions increase resilience of marine diatoms

The fate of diatoms in future acidified oceans could have dramatic implications on marine ecosystems, because they account for ~40% of marine primary production. Here, we quantify resilience of Thalassiosira pseudonana in mid-20th century (300 ppm CO2) and future (1000 ppm CO2) conditions that cause ocean acidification, using a stress test that probes its ability to recover from incrementally higher amount of low-dose ultraviolet A (UVA) and B (UVB) radiation and re-initiate growth in day–night cycles, limited by nitrogen. While all cultures eventually collapse, those growing at 300 ppm CO2 succumb sooner. The underlying mechanism for collapse appears to be a system failure resulting from “loss of relational resilience,” that is, inability to adopt physiological states matched to N-availability and phase of the diurnal cycle. Importantly, under elevated CO2 conditions diatoms sustain relational resilience over a longer timeframe, demonstrating increased resilience to future acidified ocean conditions. This stress test framework can be extended to evaluate and predict how various climate change associated stressors may impact microbial community resilience.

Continue reading ‘Ocean acidification conditions increase resilience of marine diatoms’

Epigenome-associated phenotypic acclimatization to ocean acidification in a reef-building coral

There are increasing concerns that the current rate of climate change might outpace the ability of reef-building corals to adapt to future conditions. Work on model systems has shown that environmentally induced alterations in DNA methylation can lead to phenotypic acclimatization. While DNA methylation has been reported in corals and is thought to associate with phenotypic plasticity, potential mechanisms linked to changes in whole-genome methylation have yet to be elucidated. We show that DNA methylation significantly reduces spurious transcription in the coral Stylophora pistillata. Furthermore, we find that DNA methylation also reduces transcriptional noise by fine-tuning the expression of highly expressed genes. Analysis of DNA methylation patterns of corals subjected to long-term pH stress showed widespread changes in pathways regulating cell cycle and body size. Correspondingly, we found significant increases in cell and polyp sizes that resulted in more porous skeletons, supporting the hypothesis that linear extension rates are maintained under conditions of reduced calcification. These findings suggest an epigenetic component in phenotypic acclimatization that provides corals with an additional mechanism to cope with environmental change.

Continue reading ‘Epigenome-associated phenotypic acclimatization to ocean acidification in a reef-building coral’

Effects of parental acclimation and energy limitation in response to high CO2 exposure in Atlantic cod

Ocean acidification (OA), the dissolution of excess anthropogenic carbon dioxide in ocean waters, is a potential stressor to many marine fish species. Whether species have the potential to acclimate and adapt to changes in the seawater carbonate chemistry is still largely unanswered. Simulation experiments across several generations are challenging for large commercially exploited species because of their long generation times. For Atlantic cod (Gadus morhua), we present first data on the effects of parental acclimation to elevated aquatic CO2 on larval survival, a fundamental parameter determining population recruitment. The parental generation in this study was exposed to either ambient or elevated aquatic CO2 levels simulating end-of-century OA levels (~1100 µatm CO2) for six weeks prior to spawning. Upon fully reciprocal exposure of the F1 generation, we quantified larval survival, combined with two larval feeding regimes in order to investigate the potential effect of energy limitation. We found a significant reduction in larval survival at elevated CO2 that was partly compensated by parental acclimation to the same CO2 exposure. Such compensation was only observed in the treatment with high food availability. This complex 3-way interaction indicates that surplus metabolic resources need to be available to allow a transgenerational alleviation response to ocean acidification.

Continue reading ‘Effects of parental acclimation and energy limitation in response to high CO2 exposure in Atlantic cod’

The capacity of oysters to regulate energy metabolism‐related processes may be key to their resilience against ocean acidification

Bivalve molluscs, such as oysters, are threatened by shifts in seawater chemistry resulting from climate change. However, a few species and populations within a species stand out for their capacity to cope with the impacts of climate change‐associated stressors. Understanding the intracellular basis of such differential responses can contribute to the development of strategies to minimise the pervasive effects of a changing ocean on marine organisms. In this study, we explored the intracellular responses to ocean acidification in two genetically distinct populations of Sydney rock oysters (Saccostrea glomerata). Selectively bred and wild type oysters exhibited markedly different mitochondrial integrities (mitochondrial membrane potential) and levels of reactive oxygen species (ROS) in their hemocytes under CO2 stress. Analysis of these cellular parameters after 4 and 15 days of exposure to elevated CO2 indicated that the onset of intracellular responses occurred earlier in the selectively bred oysters when compared to the wild type population. This may be due to an inherent capacity for increased intracellular energy production or adaptive energy reallocation in the selectively bred population. The differences observed in mitochondrial integrity and in ROS formation between oyster breeding lines reveal candidate biological processes that may underlie resilience or susceptibility to ocean acidification. Such processes can be targeted in breeding programs aiming to mitigate the impacts of climate change on threatened species.

Continue reading ‘The capacity of oysters to regulate energy metabolism‐related processes may be key to their resilience against ocean acidification’

Residing at low pH matters, resilience of the egg jelly coat of sea urchins living at a CO2 vent site

The sea urchin egg jelly coat is important in fertilisation as a source of sperm activating compounds, in species-specific gamete recognition and in increasing egg target size for sperm. The impact of ocean acidification (− 0.3 to 0.5 pHT units) on the egg jelly coat of Arbacia lixula was investigated comparing populations resident in a control (pHT 8.00) and a CO2 vent site (mean pHT 7.69) in Ischia. Measurements of egg and jelly coat size showed no significant differences between sea urchins from the different sites; however, sensitivity of the jelly coat to decreased pH differed depending on the origin of the population. Acidification to pHT 7.7 and 7.5 significantly decreased egg jelly coat size of control urchins by 27 and 23%, respectively. In contrast, the jelly coat of the vent urchins was not affected by acidification. For the vent urchins, there was a significant positive relationship between egg and jelly coat size, a relationship not seen for the eggs of females from the control site. As egg and jelly coat size was similar between both populations, vent A. lixula jelly coats are likely to be chemically fine-tuned for the low pH environment. That the egg jelly coat of sea urchins from the vent site was robust to low pH shows intraspecific variation in this trait, and that this difference may be a maternal adaptive strategy or plastic response. If this is a common response in sea urchins, this would facilitate the maintenance of gamete function, facilitating fertilisation success in a low pH ocean.

Continue reading ‘Residing at low pH matters, resilience of the egg jelly coat of sea urchins living at a CO2 vent site’

Trans‐life cycle acclimation to experimental ocean acidification affects gastric pH homeostasis and larval recruitment in the sea star Asterias rubens

Aim
Experimental simulation of near‐future ocean acidification (OA) has been demonstrated to affect growth and development of echinoderm larval stages through energy allocation towards ion and pH compensatory processes. To date, it remains largely unknown how major pH regulatory systems and their energetics are affected by trans‐generational exposure to near‐future acidification levels.

Methods
Here we used the common sea star Asterias rubens in a reciprocal transplant experiment comprising different combinations of OA scenarios, in order to study trans‐generational plasticity using morphological and physiological endpoints.

Results
Acclimation of adults to pHT 7.2 (pCO2 3500μatm) led to reductions in feeding rates, gonad weight, and fecundity. No effects were evident at moderate acidification levels (pHT 7.4; pCO2 2000μatm). Parental pre‐acclimation to pHT 7.2 for 85 days reduced developmental rates even when larvae were raised under moderate and high pH conditions, whereas pre‐acclimation to pHT 7.4 did not alter offspring performance. Microelectrode measurements and pharmacological inhibitor studies carried out on larval stages demonstrated that maintenance of alkaline gastric pH represents a substantial energy sink under acidified conditions that may contribute up to 30% to the total energy budget.

Conclusion
Parental pre‐acclimation to acidification levels that are beyond the pH that is encountered by this population in its natural habitat (e.g. pHT 7.2) negatively affected larval size and development, potentially through reduced energy transfer. Maintenance of alkaline gastric pH and reductions in maternal energy reserves probably constitute the main factors for a reduced juvenile recruitment of this marine keystone species under simulated OA.

Continue reading ‘Trans‐life cycle acclimation to experimental ocean acidification affects gastric pH homeostasis and larval recruitment in the sea star Asterias rubens’

Transgenerational deleterious effects of ocean acidification on the reproductive success of a keystone crustacean (Gammarus locusta)

Highlights

• High CO2 reduced survival and mate-guarding duration.
• Initial stimulation of egg production in F0 was followed by a decline in F1.
• Drop in fecundity revealed in the second generation under high CO2.
• Overall negative carry-over effects of transgenerational exposure to high CO2.

Abstract

Ocean acidification (OA) poses a global threat to marine biodiversity. Notwithstanding, marine organisms may maintain their performance under future OA conditions, either through acclimation or evolutionary adaptation. Surprisingly, the transgenerational effects of high CO2 exposure in crustaceans are still poorly understood. For the first time, the present study investigated the transgenerational effect of OA, from hatching to maturity, of a key amphipod species (Gammarus locusta). Negative transgenerational effects were observed on survival of the acidified lineage, resulting in significant declines (10–15%) compared to the control groups in each generation. Mate-guarding duration was also significantly reduced under high CO2 and this effect was not alleviated by transgenerational acclimation, indicating that precopulatory behaviours can be disturbed under a future high CO2 scenario. Although OA may initially stimulate female investment, transgenerational exposure led to a general decline in egg number and fecundity. Overall, the present findings suggest a potential fitness reduction of natural populations of G. locusta in a future high CO2 ocean, emphasizing the need of management tools towards species’ sustainability.

Continue reading ‘Transgenerational deleterious effects of ocean acidification on the reproductive success of a keystone crustacean (Gammarus locusta)’

Impacts of ocean acidification on sea urchin growth across the juvenile to mature adult life-stage transition is mitigated by warming

Understanding how growth trajectories of calcifying invertebrates are affected by changing climate requires acclimation experiments that follow development across life-history transitions. In a long-term acclimation study, the effects of increased acidification and temperature on survival and growth of the tropical sea urchin Tripneustes gratilla from the early juvenile (5 mm test diameter—TD) through the developmental transition to the mature adult (60 mm TD) were investigated. Juveniles were reared in a combination of three temperature and three pH/pCO2 treatments, including treatments commensurate with global change projections. Elevated temperature and pCO2/pH both affected growth, but there was no interaction between these factors. The urchins grew more slowly at pH 7.6, but not at pH 7.8. Slow growth may be influenced by the inability to compensate coelomic fluid acid–base balance at pH 7.6. Growth was faster at +3 and +6°C compared to that in ambient temperature. Acidification and warming had strong and interactive effects on reproductive potential. Warming increased the gonad index, but acidification decreased it. At pH 7.6 there were virtually no gonads in any urchins regardless of temperature. The T. gratilla were larger at maturity under combined near-future warming and acidification scenarios (+3°C/pH 7.8). Although the juveniles grew and survived in near-future warming and acidification conditions, chronic exposure to these stressors from an early stage altered allocation to somatic and gonad growth. In the absence of phenotypic adjustment, the interactive effects of warming and acidification on the benthic life phases of sea urchins may compromise reproductive fitness and population maintenance as global climatic change unfolds.

Continue reading ‘Impacts of ocean acidification on sea urchin growth across the juvenile to mature adult life-stage transition is mitigated by warming’


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Ocean acidification in the IPCC AR5 WG II

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