Posts Tagged 'biological response'



The role of epiphytes in seagrass productivity under ocean acidification

Ocean Acidification (OA), due to rising atmospheric CO2, can affect the seagrass holobiont by changing the plant’s ecophysiology and the composition and functioning of its epiphytic community. However, our knowledge of the role of epiphytes in the productivity of the seagrass holobiont in response to environmental changes is still very limited. CO2 vents off Ischia Island (Italy) naturally reduce seawater pH, allowing to investigate the adaptation of the seagrass Posidonia oceanica L. (Delile) to OA. Here, we analyzed the percent cover of different epiphytic groups and the epiphytic biomass of P. oceanica leaves, collected inside (pH 6.9–7.9) and outside (pH 8.1–8.2) the CO2 vents. We estimated the contribution of epiphytes to net primary production (NPP) and respiration (R) of leaf sections collected from the vent and ambient pH sites in laboratory incubations. Additionally, we quantified net community production (NCP) and community respiration (CR) of seagrass communities in situ at vent and ambient pH sites using benthic chambers. Leaves at ambient pH sites had a 25% higher total epiphytic cover with encrusting red algae (32%) dominating the community, while leaves at vent pH sites were dominated by hydrozoans (21%). Leaf sections with and without epiphytes from the vent pH site produced and respired significantly more oxygen than leaf sections from the ambient pH site, showing an average increase of 47 ± 21% (mean ± SE) in NPP and 50 ± 4% in R, respectively. Epiphytes contributed little to the increase in R; however, their contribution to NPP was important (56 ± 6% of the total flux). The increase in productivity of seagrass leaves adapted to OA was only marginally reflected by the results from the in situ benthic chambers, underlining the complexity of the seagrass community response to naturally occurring OA conditions.

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Effects of ocean acidification over successive generations decrease larval resilience to ocean acidification & warming but juvenile European sea bass could benefit from higher temperatures in the NE Atlantic

European sea bass (Dicentrarchus labrax) is a large, economically important fish species with a long generation time whose long-term resilience to ocean acidification (OA) and warming (OW) is not clear. We incubated sea bass from Brittany (France) for two generations (>5 years in total) under ambient and predicted OA conditions (PCO2: 650 and 1700 µatm) crossed with ambient and predicted ocean OW conditions in F1 (temperature: 15-18°C and 20-23°C) to investigate the effects of climate change on larval and juvenile growth and metabolic rate.

We found that in F1, OA as single stressor at ambient temperature did not affect larval or juvenile growth and OW increased developmental time and growth rates, but OAW decreased larval size at metamorphosis. Larval routine and juvenile standard metabolic rates were significantly lower in cold compared to warm conditioned fish and also lower in F0 compared to F1 fish. We did not find any effect of OA as a single stressor on metabolic rates. Juvenile PO2crit was not affected by OA or OAW in both generations.

We discuss the potential underlying mechanisms resulting in the resilience of F0 and F1 larvae and juveniles to OA and in the beneficial effects of OW on F1 larval growth and metabolic rate, but on the other hand in the vulnerability of F1, but not F0 larvae to OAW. With regard to the ecological perspective, we conclude that recruitment of larvae and early juveniles to nursery areas might decrease under OAW conditions but individuals reaching juvenile phase might benefit from increased performance at higher temperatures.

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The olfactory tract: basis for future evolution in response to rapidly changing ecological niches

Within the forebrain the olfactory sensory system is unique from other sensory systems both in the projections of the olfactory tract and the ongoing neurogenic potential, characteristics conserved across vertebrates. Olfaction plays a crucial role in behaviors such as mate choice, food selection, homing, escape from predators, among others. The olfactory forebrain is intimately associated with the limbic system, the region of the brain involved in learning, memory, and emotions through interactions with the endocrine system and the autonomic nervous system. Previously thought to lack a limbic system, we now know that teleost fishes process emotions, have exceptional memories, and readily learn, behaviors that are often associated with olfactory cues. The association of neuromodulatory hormones, and more recently, the immune system, with odor cues underlies behaviors essential for maintenance and adaptation within natural ecological niches. Increasingly anthropogenic perturbations affecting ecosystems are impacting teleost fishes worldwide. Here we examine the role of the olfactory tract as the neural basis for the integration of environmental cues and resulting behaviors necessary for the regulation of biotic interactions that allow for future adaptation as the climate spins out of control.

“I should think we might fairly gauge the future of biological science, centuries ahead, by estimating the time it will take to reach a complete, comprehensive understanding of odor. It may not seem a profound enough problem to dominate all the life sciences, but it contains, piece by piece all the mysteries.”

—Lewis Thomas (1985).

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Characterization factors for ocean acidification impacts on marine biodiversity

Rising greenhouse gas emissions do not only accelerate climate change but also make the ocean more acidic. This applies above all to carbon dioxide (CO2). Lower ocean pH levels threaten marine ecosystems and especially strongly calcifying species. Impacts on marine ecosystem quality are currently underrepresented in life cycle assessments (LCAs). Here, we developed characterization factors for the life cycle impact assessment of ocean acidification. Our main contribution was developing new species sensitivity distributions (SSDs), from which we derived effect factors for different impact perspectives: Marginal, linear, and average changes for both the past and four future emission scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5). Based on a dataset that covered five taxa (corals, crustaceans, echinoderms, fishes, molluscs) and three climate zones, we showed significantly higher sensitivities for strongly calcifying than slightly calcifying taxa and in polar regions compared to tropical and temperate regions. Experimental duration, leading to acute, subchronic, or chronic toxicological endpoints, did not significantly affect the species sensitivities. With ocean acidification impacts still accelerating, the future-oriented average effects are higher than the marginal or past-oriented average effects. While our characterization factors are ready for use in LCA, we also point to opportunities for improvement in future developments.

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Acidification impacts and acclimation potential of foraminifera

Ocean acidification is expected to negatively affect many ecologically important organisms. Here we explored the response of Caribbean benthic foraminiferal communities to naturally discharging low-pH waters similar to expected future projections for the end of the 21st century. At low-pH (~ 7.7 pH units), low calcite saturation, agglutinated and symbiont-bearing species were relatively more abundant, indicating higher resistance to potential carbonate chemistry changes. Diversity and other taxonomical metrics declined steeply with decreasing pH despite exposure of this ecosystem for millennia to low pH conditions, suggesting that tropical foraminifera communities will be negatively impacted under acidification scenarios SSP3-7.0 and SSP5-8.5. The species Archaias angulatus, a major contributor to sediment production in the Caribbean was able to calcify at conditions more extreme than those projected for the late 21st century (7.1 pH units), but the calcified tests were of lower density than those exposed to high-pH ambient conditions (7.96 pH units), indicating that reef foraminiferal carbonate budget might decrease. Smaller foraminifera were highly sensitive to decreasing pH and our results demonstrate their potential as indicators to monitor increasing OA conditions.

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How do fungi survive in the sea and respond to climate change?

With the over 2000 marine fungi and fungal-like organisms documented so far, some have adapted fully to life in the sea, while some have the ability to tolerate environmental conditions in the marine milieu. These organisms have evolved various mechanisms for growth in the marine environment, especially against salinity gradients. This review highlights the response of marine fungi, fungal-like organisms and terrestrial fungi (for comparison) towards salinity variations in terms of their growth, spore germination, sporulation, physiology, and genetic adaptability. Marine, freshwater and terrestrial fungi and fungal-like organisms vary greatly in their response to salinity. Generally, terrestrial and freshwater fungi grow, germinate and sporulate better at lower salinities, while marine fungi do so over a wide range of salinities. Zoosporic fungal-like organisms are more sensitive to salinity than true fungi, especially Ascomycota and Basidiomycota. Labyrinthulomycota and marine Oomycota are more salinity tolerant than saprolegniaceous organisms in terms of growth and reproduction. Wide adaptability to saline conditions in marine or marine-related habitats requires mechanisms for maintaining accumulation of ions in the vacuoles, the exclusion of high levels of sodium chloride, the maintenance of turgor in the mycelium, optimal growth at alkaline pH, a broad temperature growth range from polar to tropical waters, and growth at depths and often under anoxic conditions, and these properties may allow marine fungi to positively respond to the challenges that climate change will bring. Other related topics will also be discussed in this article, such as the effect of salinity on secondary metabolite production by marine fungi, their evolution in the sea, and marine endophytes.

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Reanalysis shows the extreme decline effect does not exist in fish ocean acidification studies

Contradictory Results

A meta-analysis published in PLoS Biology by Clements et al. (2022) claims there is an extreme decline effect in studies published between 2009-2019 on the impacts of ocean acidification (OA) on fish behaviour. Here I show that the extreme decline effect reported by Clements et al. is a statistical artifact caused by the way they corrected for zero values in percentage data, which was more common in the earliest experiments compared with later studies. Furthermore, selective choices for excluding or including data, along with serious errors in the compilation of data and missing studies with strong effects, weakened the effect sizes reported for papers after 2010, further exacerbating the decline effect reported by Clements et al. When the data is reanalyzed using appropriate corrections for zero values in percentage and proportional data, and using a complete, corrected and properly screened data set, the extreme decline effect reported by Clements et al. no longer exists.

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Assessment of paracetamol toxic effects under varying seawater pH conditions on the marine polychaete Hediste diversicolor using biochemical endpoints

Simple Summary

Context of climate change is being widely studied, nevertheless its effects in the toxicity of other contaminants have been poorly study. Particularly, the effects of ocean acidification on the modulation of pharmaceutical absorption and consequent effects, have not been extensively addressed before. In this study, we aimed to assess the effects of ocean acidification (specifically pH values of 8.2, 7.9, and 7.6) combined with paracetamol exposure (0, 30, 60, and 120 µg/L) on the polychaeta Hediste diversicolor. To do so, specific biomarkers were measured namely (CAT), glutathione S-transferases (GSTs), acetylcholinesterase (AChE), and cyclooxygenase (COX) activities, as well as thiobarbituric acid reactive substance (TBARS), were quantified to serve as ecotoxicological endpoints. Alterations of CAT, and GSTs activities, and TBARS levels indicate an alteration in redox balances. Differences in exposed pH levels indicate the possible modulation of the absorption of this pharmaceutical in ocean acidifications scenarios. Alterations in AChE were only observed following paracetamol exposure, not being altered by media pH. Hereby obtained results suggest that seawater acidification is detrimental to marine wildlife, since it may enhance toxic effects caused by environmental realistic concentrations of pharmaceuticals. This work is crucial to understand the potential effects of pharmaceuticals in a climate change scenario.

Abstract

Increasing atmospheric carbon dioxide (CO2) levels are likely to lower ocean pH values, after its dissolution in seawater. Additionally, pharmaceuticals drugs are environmental stressors due to their intrinsic properties and worldwide occurrence. It is thus of the utmost importance to assess the combined effects of pH decreases and pharmaceutical contamination, considering that their absorption (and effects) are likely to be strongly affected by changes in oceanic pH. To attain this goal, individuals of the marine polychaete Hediste diversicolor were exposed to distinct pH levels (8.2, 7.9, and 7.6) and environmentally relevant concentrations of the acidic drug paracetamol (PAR: 0, 30, 60, and 120 µg/L). Biomarkers such as catalase (CAT), glutathione S-transferases (GSTs), acetylcholinesterase (AChE), and cyclooxygenase (COX) activities, as well as peroxidative damage (through thiobarbituric acid reactive substance (TBARS) quantification), were quantified to serve as ecotoxicological endpoints. Data showed a general increase in CAT and a decrease in GST activities (with significant fluctuations according to the tested conditions of PAR and pH). These changes are likely to be associated with alterations of the redox cycle driven by PAR exposure. In addition, pH levels seemed to condition the toxicity caused by PAR, suggesting that the toxic effects of this drug were in some cases enhanced by more acidic conditions. An inhibition of AChE was observed in animals exposed to the highest concentration of PAR, regardless of the pH value. Moreover, no lipid peroxidation was observed in most individuals, although a significant increase in TBARS levels was observed for polychaetes exposed to the lowest pH. Finally, no alterations of COX activities were recorded on polychaetes exposed to PAR, regardless of the pH level. The obtained results suggest that seawater acidification is detrimental to marine wildlife, since it may enhance toxic effects caused by environmental realistic concentrations of acidic drugs, such as PAR. This work was crucial to evidence that ocean acidification, in the context of a global change scenario of increased levels of both atmospheric and oceanic CO2, is a key factor in understanding the putative enhanced toxicity of most pharmaceutical drugs that are of an acidic nature.

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The symbiotic relationship between the Antarctic limpet, Nacella concinna, and epibiont coralline algae

The Antarctic limpet, Nacella concinna, is one of the most abundant benthic marine invertebrates found in the intertidal zone of King George Island, Antarctica. The shell of N. concinna is often encrusted with the coralline algae Clathromorphum obtectulum. In this study, to reveal the relationship between the limpet and coralline algae, we examined how the coralline algae affect the physical condition (survival and health) and morphology of the limpet. We cultured the limpets for 22 days and compared mortality, weight, condition factor (CF), fatty acid content, and the structure of the shell surface between limpets both with and without coralline algae in the laboratory. We also measured the environmental factors (i.e., temperature, pH, and salinity) of the seawater at each sampling site and the CF of the limpets and correlated them with coverage of coralline algae. The presence of coralline algae significantly increased the mortality of the limpets by 40% and the shell weight by 1.4-fold but did not affect the CF. Additionally, coralline algae altered the fatty acid profiles related to the limpet’s lipid metabolism (saturated fatty acids (SFA) and some polyunsaturated fatty acids (PUFA)). Specifically, C16:0, C17:0, C18:0, and total SFA increased, whereas C18:2 and C18:3 decreased. However, observations with a scanning electron microscope showed that shell damage in limpets with coralline algae was much less than in limpets without coralline algae, suggesting that coralline algae may provide protection against endolithic algae. The area of coralline algae on the limpet shell was positively correlated with the pH and temperature of the seawater. The results suggest that although coralline algae are generally assumed to be parasitical, the relationship between N. concinna and coralline algae may change to mutualism under certain conditions.

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The biological uptake of dissolved iron in the changing Daya Bay, South China Sea: effect of pH and DO

Highlights

  • Fe bioavailability affected by pH and DO regulates phytoplanktonic Fe uptake.
  • Nano-phytoplankton is more sensitive to the variation of seawater pH and DO.
  • Phytoplankton community tend to be miniaturized in the changing DYB.
  • Fe requirement in DYB goes higher accompanied with the phytoplankton miniaturization.
  • DYB is not an Fe-rich environment derived from the relative low Fe:C ratio.

Abstract

The oceanic acidification and coastal hypoxia have potential to enhance biological uptake of dissolved iron (Fe) by phytoplankton. In this study, the Fe uptake rate (FeUR) in Daya Bay was significantly negatively correlated with pH and dissolved oxygen (DO) (r = −0.81 and −0.73, respectively, p < 0.001). In addition, binary regression (FeUR = −1.45 × pH − 0.10 × DO + 13.64) also indicated that both pH and DO played key roles in FeUR variations. As pH and DO decreased, Fe uptake by phytoplankton was promoted, and the contribution of nano-phytoplankton to Fe uptake increased significantly, while that of pico-FeUR decreased. These will result in the phytoplankton community to be miniaturized and Fe requirement of phytoplankton goes higher, thereby leading changes of phytoplankton composition and coastal ecosystem. This study helps to understand how Fe could affect the coastal ecosystem under the increasing anthropogenic influences.

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No evidence of altered relationship between diet and consumer fatty acid composition in a natural plankton community under combined climate drivers

Fatty acids (FA), especially polyunsaturated fatty acids (PUFA), are key biomolecules involved in immune responses, reproduction, and membrane fluidity. PUFA in marine environments are synthesized exclusively by primary producers. Therefore the FA composition of these organisms at the base of the food web (i.e., phytoplankton) and their primary consumers (i.e., zooplankton) are important determinants of the health and productivity of entire ecosystems as they are transferred to higher trophic levels. However, environmental conditions such as seawater pH and temperature, which are already changing in response to climate change and predicted to continue to change in the future, can affect the FA composition of phytoplankton and zooplankton at both the organismal and community level. During a 20 day mesocosm experiment, we tested the effect of ocean acidification alone and in combination with ocean warming on 1) the fatty acid composition of a natural prey community for zooplankton (i.e. phytoplankton and microzooplankton), 2) the fatty acid composition of zooplankton, and 3) the relationship between prey and consumer fatty acid compositions in coastal waters. Significant effects of the climate stressors were not detected in the fatty acid composition of the prey or the relationship between diet and consumer fatty acids. A significant decrease in C18:4n-3 (stearidonic acid) was observed in the zooplankton but not their diet, but understanding the mechanism behind this decrease and its potential biological implications requires further investigation. These results highlight the importance of multi-stressor investigations on dynamics and variability contained within natural coastal plankton communities.

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Species specific responses to grazer cues and acidification in phytoplankton- winners and losers in a changing world

Phytoplankton induce defensive traits in response to chemical alarm signals from grazing zooplankton. However, these signals are potentially vulnerable to changes in pH and it is not yet known how predator recognition may be affected by ocean acidification. We exposed four species of diatoms and one toxic dinoflagellate to future pCO2 levels, projected by the turn of the century, in factorial combinations with predatory cues from copepods (copepodamides). We measured the change in growth, chain length, silica content, and toxin content. Effects of increased pCO2 were highly species specific. The induction of defensive traits was accompanied by a significant reduction in growth rate in three out of five species. The reduction averaged 39% and we interpret this as an allocation cost associated with defensive traits. Copepodamides induced significant chain length reduction in three of the four diatom species. Under elevated pCO2 Skeletonema marinoi reduced silica content by 30% and in Alexandrium minutum the toxin content was reduced by 30%. Using copepodamides to induce defensive traits in the absence of direct grazing provides a straightforward methodology to assess costs of defense in microplankton. We conclude that copepodamide signalling system is likely robust to ocean acidification. Moreover, the variable responses of different taxa to ocean acidification suggest that there will be winners and losers in a high pCO2 world, and that ocean acidification may have structuring effects on phytoplankton communities.

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A calcification-related calmodulin-like protein in the oyster Crassostrea gigas mediates the enhanced calcium deposition induced by CO2 exposure

Highlights

  • A novel and calcification-related gene CgCaLP was identified.
  • The protein level of CgCaLP in hemocytes increased, but decreased in gill and mantle after CO2 exposure.
  • CgCaLP translocated to the outer mantle epithelium cells under CO2 exposure.
  • Calcium-rich deposites were observed in the outer mantle epithelium cells.

Abstract

Calcium transportation and homeostasis are essential for marine bivalves to maintain basic metabolism and build their shells. Calmodulin-like proteins (CaLPs) are important calcium sensors and buffers and can respond to ocean acidification (OA) in marine calcifiers. However, no further study of their physiological function in calcium metabolism under elevated CO2 has been performed. Here, we identified a novel CaLP (designated CgCaLP) in the Pacific oyster Crassostrea gigas and demonstrated its participation in the calcification process: the mRNA expression level of CgCaLP peaked at the trochophore larval stage and remained high at stages when shells were shaped; the mRNA and protein of CgCaLP were more highly expressed in mantle tissue than in other tissues. Under elevated CO2 levels, the protein expression level of CgCaLP in hemocytes increased, while in contrast, significantly decreased protein levels were detected in gill and mantle tissues. Shell dissolution caused the imbalance of calcium in hemocytes and decreased calcium absorption and transportation demand in gill and mantle tissues, inducing the molecular function allocation of CgCaLP under CO2 exposure. Despite the decreased protein level in mantle tissue, CgCaLP was found to translocate to outer mantle epithelium (OME) cells where condensed calcium-rich deposits (CRDs) were detected. We further demonstrated that CgCaLP mRNA and protein expression levels could respond to seawater Ca2+ availability, suggesting that the calcium deposition capacity of oysters might be enhanced to fight against shell dissolution problems and that CgCaLP might serve as an essential participator of the process. In summary, CgCaLP might enhance calcium deposition under CO2 exposure and thus play a significant and flexible molecular function involved in a compensation strategy of oysters to fight against the acidified ocean.

Continue reading ‘A calcification-related calmodulin-like protein in the oyster Crassostrea gigas mediates the enhanced calcium deposition induced by CO2 exposure’

Schizosphaerella size and abundance variations across the Toarcian Oceanic Anoxic Event in the Sogno Core (Lombardy Basin, Southern Alps)

Highlights

  • Schizospharella spp. size and abundance variations during the Jenkyns event.
  • Abundance drop caused by the failure of S. punctulata > 7 μm.
  • Size decrease due to the relative increase in abundance of small specimens.
  • Drop in abundance and size consequence of ocean acidification and global warming.
  • Presence of diagenetic crust diagnostic to distinguish S. punctulata from S. astraea

Abstract

Abundance and size variations of nannofossil Schizosphaerella punctulata were quantified in the uppermost Pliensbachian–Lower Toarcian succession recovered with the Sogno Core (Lombardy Basin, Northern Italy). High-resolution nannofossil biostratigraphy and C-isotopic chemostratigraphy identified the Jenkyns Event within the Toarcian oceanic anoxic event (T-OAE) interval. Absolute abundances and morphometric changes of “small S. punctulata” (< 7 μm), S. punctulata (7–10 μm; 10–14 μm; > 14 μm) and “encrusted S. punctulata” (specimens with a fringing crust) show large fluctuations across the negative δ13C Jenkyns Event. The Schizosphaerella crisis is further characterized by a decrease in average valve size in the early–middle Jenkyns Event. The abundance fall was caused by the failure of S. punctulata specimens >7 μm and “encrusted S. punctulata” that along with the increased relative abundance of small specimens, produced the reduction of average dimensions also documented in the Lusitanian and Paris Basins, although with a diachronous inception. The average valve size from the Lombardy Basin is ~2 μm smaller than in these other basins. Hyperthermal conditions associated with excess CO2 and ocean acidification possibly forced the drastic reduction of S. punctulata abundance/size. In the pelagic succession of the Sogno Core there is a strong positive correlation between the S. punctulata (> 7 μm) absolute abundance/size and the CaCO3 content, with a negligible contribution by small specimens (< 7 μm). Encrusted specimens testify selective neomorphic processes: the diagenetic crust seems diagnostic to separate S. punctulata from S. astraea.

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Impaired hatching exacerbates the high CO2 sensitivity of embryonic sand lance Ammodytes dubius

Rising oceanic pCO2 levels could affect many traits in fish early life stages, but only few species to date have shown direct CO2-induced survival reductions. This might partly be because species from less CO2-variable, offshore environments in higher latitudes are currently underrepresented in the literature. We conducted new experimental work on northern sand lance Ammodytes dubius, a keystone forage fish on offshore Northwest Atlantic sand banks, which was recently suggested to be highly CO2-sensitive. In two complementary trials, we produced embryos from wild, Gulf of Maine (GoM) spawners and reared them at several pCO2 levels (~400–2000 µatm) in combination with static (6, 7, 10°C) and dynamic (10 → 5°C) temperature treatments. Again, we consistently observed large, CO2-induced reductions in hatching success (–23% at 1000 µatm, -61% at ~2000 µatm), and the effects were temperature-independent. To distinguish pCO2 effects during development from potential impacts on hatching itself, some embryos were switched between high and control pCO2 treatments just prior to hatch. This indeed altered hatching patterns consistent with the CO2-impaired hatching hypothesis. High CO2 also delayed the day of first hatch in one trial and peak hatch in the other, where later-hatched larvae were of similar size but with progressively less endogenous energy reserves. For context, we extracted seasonal pCO2 projections for Stellwagen Bank (GoM) from regional ensemble simulations, which indicated a CO2-induced reduction in sand lance hatching success to 71% of contemporary levels by 2100. The species’ unusual CO2 sensitivity has large ecological and scientific ramifications that warrant future in-depth research.

Continue reading ‘Impaired hatching exacerbates the high CO2 sensitivity of embryonic sand lance Ammodytes dubius’

Ocean acidification alters sperm responses to egg-derived chemicals in a broadcast spawning mussel

The continued emissions of anthropogenic carbon dioxide are causing progressive ocean acidification (OA). While deleterious effects of OA on biological systems are well documented in the growth of calcifying organisms, lesser studied impacts of OA include potential effects on gamete interactions that determine fertilization, which are likely to influence the many marine species that spawn gametes externally. Here, we explore the effects of OA on the signalling mechanisms that enable sperm to track egg-derived chemicals (sperm chemotaxis). We focus on the mussel Mytilus galloprovincialis, where sperm chemotaxis enables eggs to bias fertilization in favour of genetically compatible males. Using an experimental design based on the North Carolina II factorial breeding design, we test whether the experimental manipulation of seawater pH (comparing ambient conditions to predicted end-of-century scenarios) alters patterns of differential sperm chemotaxis. While we find no evidence that male–female gametic compatibility is impacted by OA, we do find that individual males exhibit consistent variation in how their sperm perform in lowered pH levels. This finding of individual variability in the capacity of ejaculates to respond to chemoattractants under acidified conditions suggests that climate change will exert considerable pressure on male genotypes that can withstand an increasingly hostile fertilization environment.

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Pelagic calcifiers face increased mortality and habitat loss with warming and ocean acidification

Global change is impacting the oceans in an unprecedented way with resulting changes in species distributions or species loss. There is increasing evidence that multiple environmental stressors act together to constrain species habitat more than expected from single stressor. Here, we conducted a comprehensive study of the combined impact of ocean warming and acidification (OWA) on a global distribution of pteropods, ecologically important pelagic calcifiers and an indicator species for ocean change. We co-validated three different approaches to evaluate the impact of OWA on pteropod survival and distribution. First, we used co-located physical, chemical, and biological data from oceanographic cruises and regional time-series; second, we conducted multifactorial experimental incubations using OWA to evaluate survival; and third, we validated pteropod distributions using global carbonate chemistry and observation datasets. Habitat suitability indices and global distributions suggest that a multi-stressor framework is essential for understanding distributions of this pelagic calcifier.

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Eelgrass beds can mitigate local acidification and reduce oyster malformation risk in a subarctic lagoon, Japan: a three-dimensional ecosystem model study

Highlights

  • An ecosystem model representing carbonate systems in a lagoon was developed.
  • The effect of ocean acidification on oyster malformation was evaluated.
  • Simulation under the absence of eelgrass bed was also performed.
  • The model could reproduce the spatiotemporal variations of the observed values.
  • Eelgrass beds mitigate the adverse effects of acidification on oyster growth.

Abstract

It is well known that ocean acidification (OA) inhibits growth of marine calcifying organisms. Therefore, the adverse effects of acidification on marine ecosystems and aquaculture, such as oyster farming, are of concern. Since eelgrass beds in neritic areas have a high potential for carbon assimilation, this study focuses on local scale mitigation of OA effects. Using a three-dimensional lower-trophic system ecosystem model, we modeled nitrogen and carbon cycles, and the dynamics of carbonate parameters in a subarctic shallow lagoon and bay, where nitrogen availability limits the photosynthesis of primary producers. Simulation of the present conditions allowed reproduction of spatiotemporal variations in water quality and, by assuming future environmental changes quantitatively, revealed that the progress of OA significantly elevated the probability of shell malformation in juvenile oysters. The results represent the spatiotemporal variations in carbonate parameters inside and outside eelgrass beds and enable the evaluation of the alleviation effect on local acidification by the presence of a dense eelgrass bed. Our study shows that in the absence of the eelgrass bed scenario, the effect of OA on oysters became more remarkable. The simulations revealed that maintaining eelgrass beds is essential to mitigate the effects of acidification on oysters.

Continue reading ‘Eelgrass beds can mitigate local acidification and reduce oyster malformation risk in a subarctic lagoon, Japan: a three-dimensional ecosystem model study’

Dynamic energy budget modeling of Atlantic surfclam, Spisula solidissima, under future ocean acidification and warming

Highlights

  • Surfclams were exposed to OA levels inducing effects on physiological rates
  • A DEB model was calibrated integrating effects on ingestion and maintenance costs
  • The model was validated on Georges Bank and Mid-Atlantic Bight population data
  • Effects of future OA and warming conditions projected by RCP scenarios were simulated
  • Under high pCO2 emissions, DEB projects effects on growth and reproduction by 2100

Abstract

A dynamic energy budget (DEB) model integrating pCO2 was used to describe ocean acidification (OA) effects on Atlantic surfclam, Spisula solidissima, bioenergetics. Effects of elevated pCO2 on ingestion and somatic maintenance costs were simulated, validated, and adapted in the DEB model based upon growth and biological rates acquired during a 12-week laboratory experiment. Temperature and pCO2 were projected for the next 100 years following the intergovernmental panel on climate change representative concentration pathways scenarios (2.6, 6.0, and 8.5) and used as forcing variables to project surfclam growth and reproduction. End-of-century water warming and acidification conditions resulted in simulated faster growth for young surfclams and more energy allocated to reproduction until the beginning of the 22nd century when a reduction in maximum shell length and energy allocated to reproduction was observed for the RCP 8.5 scenario.

Continue reading ‘Dynamic energy budget modeling of Atlantic surfclam, Spisula solidissima, under future ocean acidification and warming’

Nocturnal acidification: a coordinating cue in the Euprymna scolopes–Vibrio fischeri Symbiosis

The Vibrio fischeriEuprymna scolopes symbiosis has become a powerful model for the study of specificity, initiation, and maintenance between beneficial bacteria and their eukaryotic partner. In this invertebrate model system, the bacterial symbionts are acquired every generation from the surrounding seawater by newly hatched squid. These symbionts colonize a specialized internal structure called the light organ, which they inhabit for the remainder of the host’s lifetime. The V. fischeri population grows and ebbs following a diel cycle, with high cell densities at night producing bioluminescence that helps the host avoid predation during its nocturnal activities. Rhythmic timing of the growth of the symbionts and their production of bioluminescence only at night is critical for maintaining the symbiosis. V. fischeri symbionts detect their population densities through a behavior termed quorum-sensing, where they secrete and detect concentrations of autoinducer molecules at high cell density when nocturnal production of bioluminescence begins. In this review, we discuss events that lead up to the nocturnal acidification of the light organ and the cues used for pre-adaptive behaviors that both host and symbiont have evolved. This host–bacterium cross talk is used to coordinate networks of regulatory signals (such as quorum-sensing and bioluminescence) that eventually provide a unique yet stable environment for V. fischeri to thrive and be maintained throughout its life history as a successful partner in this dynamic symbiosis.

Continue reading ‘Nocturnal acidification: a coordinating cue in the Euprymna scolopes–Vibrio fischeri Symbiosis’

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