Posts Tagged 'adaptation'

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

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.

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.

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.

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)


• 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.


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’

Larval ecology in the face of changing climate – impacts of ocean warming and ocean acidification

Ocean warming and acidification are major climate change stressors for marine invertebrate larvae, and their impacts differ between habitats and regions. In many regions species with pelagic propagules are on the move, exhibiting poleward trends as temperatures rise and ocean currents change. Larval sensitivity to warming varies among species, influencing their invasive potential. Broadly distributed species with wide developmental thermotolerances appear best able to avail of the new opportunities provided by warming. Ocean acidification is a multi-stressor in itself and the impacts of its covarying stressors differ among taxa. Increased pCO2 is the key stressor impairing calcification in echinoid larvae while decreased mineral saturation is more important for calcification in bivalve larvae. Non-feeding, non-calcifying larvae appear more resilient to warming and acidification. Some species may be able to persist through acclimatization/adaptation to produce resilient offspring. Understanding the capacity for adaptation/acclimatization across generations is important to predicting the future species composition of marine communities.

Continue reading ‘Larval ecology in the face of changing climate – impacts of ocean warming and ocean acidification’

Adaptation strategies to climate change in marine systems

The world’s oceans are highly impacted by climate change and other human pressures, with significant implications for marine ecosystems and the livelihoods that they support. Adaptation for both natural and human systems is increasingly important as a coping strategy due to the rate and scale of ongoing and potential future change. Here, we conduct a review of literature concerning specific case studies of adaptation in marine systems, and discuss associated characteristics and influencing factors, including drivers, strategy, timeline, costs, and limitations. We found ample evidence in the literature that shows that marine species are adapting to climate change through shifting distributions and timing of biological events, while evidence for adaptation through evolutionary processes is limited. For human systems, existing studies focus on frameworks and principles of adaptation planning, but examples of implemented adaptation actions and evaluation of outcomes are scarce. These findings highlight potentially useful strategies given specific social–ecological contexts, as well as key barriers and specific information gaps requiring further research and actions.

Continue reading ‘Adaptation strategies to climate change in marine systems’

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Ocean acidification in the IPCC AR5 WG II

OUP book