Posts Tagged 'mollusks'

DNA damage and oxidative stress responses of mussels Mytilus galloprovincialis to paralytic shellfish toxins under warming and acidification conditions – elucidation on the organ-specificity

Commonly affected by changes in climate and environmental conditions, coastal areas are very dynamic environments where shellfish play an important ecological role. In this study, the oxidative stress and genotoxic responses of mussels (Mytilus galloprovincialis) exposed to paralytic shellfish toxin (PST) – producing dinoflagellates Gymnodinium catenatum were evaluated under i) current conditions (CC: 19 °C; pH 8.0), ii) warming (W: 24 °C; pH 8.0), iii) acidification (A:19 °C; pH 7.6) and iv) combined effect of warming and acidification (WA: 24 °C; pH 7.6). Mussels were fed with G. catenatum for 5 days, and to a non-toxic diet during the following 10 days. A battery of oxidative stress biomarkers and comet assay was performed at the peak of toxin accumulation and at the end of the post-exposure phase. Under CC, gills and hepatopancreas displayed different responses/vulnerabilities and mechanisms to cope with PST. While gills presented a tendency for lipid peroxidation (LPO) and genetic damage (expressed by the Genetic Damage Indicator – GDI), hepatopancreas seems to better cope with the toxins, as no LPO was observed. However, the mechanisms involved in hepatopancreas protection were not enough to maintain DNA integrity. The absence of LPO, and the antioxidant system low responsiveness, suggests DNA damage was not oxidative. When exposed to toxic algae under W, toxin-modulated antioxidant responses were observed in both gills and hepatopancreas. Simultaneous exposure to the stressors highlighted gills susceptibility with a synergistic interaction increasing DNA damage. Exposure to toxic algae under A led to genotoxicity potentiation in both organs. The combined effect of WA did not cause relevant interactions in gills antioxidant responses, but stressors interactions impacted LPO and GDI. Antioxidant responses and LPO pointed out to be modulated by the environmental conditions in hepatopancreas, while GDI results support the dominance of toxin-triggered process. Overall, these results reveal that simultaneous exposure to warming, acidification and PSTs impairs mussel DNA integrity, compromising the genetic information due to the synergetic effects. Finally, this study highlights the increasing ecological risk of harmful algal blooms to Mytilus galloprovinciallis populations.

Continue reading ‘DNA damage and oxidative stress responses of mussels Mytilus galloprovincialis to paralytic shellfish toxins under warming and acidification conditions – elucidation on the organ-specificity’

Estuarine conditions more than pH modulate the physiological flexibility of mussel Perumytilus purpuratus populations

Highlights

  • Living under estuarine conditions causes physiological stress.
  • Estuarine conditions more than pH modulated the mussel performance and phenotypic plasticity.
  • Environmental variability of the habitat determines the phenotypic plasticity.
  • Environmental conditions of native habitats define the sensibility to climate change stressors.

Abstract

Coasts and their marine biota are exposed to major environmental heterogeneity as a consequence of natural drivers and anthropogenic stressors. Here, individuals of the mussel Perumytilus purpuratus from two different geographical populations exposed to contrasting environmental conditions (i.e. estuarine versus open coastal conditions) were used in a reciprocal transplant and a laboratory experiment in order to differential levels of local adaptation to their native sites, and sensibility to ocean acidification. After characterizing environmentally the two study sites, a set of life-history traits, as well as an estimated of the level of phenotypic plasticity were determined for both mussel populations. From the reciprocal transplant experiment, we observed that mussels originally coming from the estuarine habitat exhibited a distinctive performance pattern usually associated to physiological stress (i.e. higher metabolic rates, lower calcification and growth rates) leading also to important physiological trade-offs, and higher levels of phenotypic plasticity. Alternatively, mussels originating from the open coastal site showed lower physiological phenotypic plasticity suggesting a high grade of local adaptation. Contrary to expected, both populations responded very similar to lower pH conditions (i.e. increased metabolic rates with no important effects on growth and calcification, and lower physiological phenotypic plasticity). The study results indicated that overall estuarine conditions more than isolated pH would be modulating the performance and the level of phenotypic plasticity of the different P. purpuratus geographical populations studied. Our study also emphasizes the necessity of characterizing phenotypic plasticity under multiple-driver environments in order to cast more accurate predictions about the susceptibility of marine biota to future climate stressors such as the ocean acidification.

Continue reading ‘Estuarine conditions more than pH modulate the physiological flexibility of mussel Perumytilus purpuratus populations’

Impact of temperature increase and acidification on growth and the reproductive potential of the clam Ruditapes philippinarum using DEB

Highlights

  • A simulation model based on DEB theory was parameterized for the Manila clam.
  • The pH forecast in 2100 will limit the growth of Manila clam.
  • The temperature forecast in 2100 enhances the reproductive potential of Manila clam.

Abstract

We built a simulation model based on Dynamic Energy Budget theory (DEB) to assess the growth and reproductive potential of the Manila clam Ruditapes philippinarum under different temperature and pH conditions, based on environmental values forecasted for the end of the 21st c. under climate change scenarios. The parameters of the DEB model were calibrated with the results of seasonal growth experiments under two levels of temperature (ambient and plus 2–3 °C) and three levels of pH (8.1 used as control and 7.7 and 7.3 representing acidification). The results showed that R. philippinarum is expected to have moderate growth in length or individual body mass (ultimate length and body weight would be larger than current values by 2–3%) when taking into account only the effect of temperature increase. However, acidification is likely to have a deleterious effect on growth, with a decrease of 2–5% length or body weight under the pH value of 7.7 forecasted for the end of the 21st c, or 10–15% under a more extreme scenario (pH = 7.3). However, the aggregated reproductive potential, integrated along a lifetime of 10 years, is likely to increase by 30% with temperature increase. Decreasing pH would impact negatively on reproductive potential, but in all simulations under warmer conditions, reproductive potential values were higher than current, suggesting that temperature increase would compensate losses due to acidification. The results are discussed in relation to their possible impact on aquaculture and fisheries of this important commercial bivalve.

Continue reading ‘Impact of temperature increase and acidification on growth and the reproductive potential of the clam Ruditapes philippinarum using DEB’

Predicting potential impacts of ocean acidification on marine calcifiers from the Southern Ocean

Understanding the vulnerability of marine calcifiers to ocean acidification is a critical issue, especially in the Southern Ocean (SO), which is likely to be the one of the first, and most severely affected regions. Since the industrial revolution, ~30% of anthropogenic CO2 has been absorbed by the oceans. Seawater pH levels have already decreased by 0.1 and are predicted to decline by ~ 0.3 by the year 2100. This process, known as ocean acidification (OA), is shallowing the saturation horizon, which is the depth below which calcium carbonate (CaCO3) dissolves, likely increasing the vulnerability of many marine calcifiers to dissolution. The negative impact of OA may be seen first in species depositing more soluble CaCO3 mineral phases such as aragonite and high-Mg calcite (HMC). These negative effects may become even exacerbated by increasing sea temperatures. Here we combine a review and a quantitative meta-analysis to provide an overview of the current state of knowledge about skeletal mineralogy of major taxonomic groups of SO marine calcifiers and to make predictions about how OA might affect different taxa. We consider their geographic range, skeletal mineralogy, biological traits and potential strategies to overcome OA. The meta-analysis of studies investigating the effects of the OA on a range of biological responses such as shell state, development and growth rate shows response variation depending on mineralogical composition. Species-specific responses due to mineralogical composition suggest taxa with calcitic, aragonitic and HMC skeletons may be more vulnerable to the expected carbonate chemistry alterations, and low magnesium calcite (LMC) species may be mostly resilient. Environmental and biological control on the calcification process and/or Mg content in calcite, biological traits and physiological processes are also expected to influence species specific responses.

Continue reading ‘Predicting potential impacts of ocean acidification on marine calcifiers from the Southern Ocean’

Efeitos neurotóxicos do crack-cocaína combinado a cenários de acidificação oceânica no mexilhão marinho Perna perna (in Portuguese)

The oceans are undergoing physical and biogeochemical changes in response to the increasing atmospheric CO2 load and increased ocean uptake, such as surface warming, reduced oxygen and a reduction in calcium carbonate and pH saturation levels. Changes in the pH and chemical composition of seawater can modify the speciation of contaminants, interfering with their bioavailability and toxicity. The present study aimed to evaluate the sublethal effect of the illicit drug crack-cocaine at different concentrations (0.5; 5; 50 µg / L) combined with ocean acidification by CO2 at pH values of 8.1; 7.5; 7.0; 6.5 and 6.0. For this purpose, an analysis of the biomarker of neurotoxic effect acetylcholinesterase (AChe) was performed on mussels Perna perna. The inhibition of AChe after exposure to crack at pH 7.5, 7.0 and 6.5 was preliminarily observed, demonstrating a combined effect of crack-cocaine and pH reduction, which can be observed in future scenarios of acidification in coastal zones contaminated by illicit drugs.

Continue reading ‘Efeitos neurotóxicos do crack-cocaína combinado a cenários de acidificação oceânica no mexilhão marinho Perna perna (in Portuguese)’

Decoupling salinity and carbonate chemistry: low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels

The Baltic Sea has a salinity gradient decreasing from fully marine (> 25) in the West to below 7 in the Central Baltic Proper. Reef forming mytilid mussels exhibit decreasing growth when salinity < 11, however the mechanisms underlying reduced calcification rates in dilute seawater are not fully understood. In fact, both [HCO3] and [Ca2+] also decrease with salinity, challenging calcifying organisms through CaCO3 undersaturation (Ω ≤ 1) and unfavourable ratios of calcification substrate (Ca2+ and HCO3) to inhibitor (H+). In this study we assessed the impact of isolated individual factors (salinity, [Ca2+], [HCO3] and pH) on calcification and growth of mytilid mussel populations along the Baltic salinity gradient. Laboratory experiments rearing juvenile Baltic Mytilus at a range of salinities (6, 11 and 16), HCO3 concentrations (300–2100 µmol kg−1) and Ca2+ concentrations (0.5–4 mmol kg−1) were coupled with field monitoring in three Baltic mussel reefs. Results reveal that as individual factors, low [HCO3], pH and salinity cannot explain low calcification rates in the Baltic Sea. Calcification rates are impeded when Ωaragonite ≤ 1 or the substrate inhibitor ratio ≤ 0.7, primarily due to [Ca2+] limitation which corresponds to a salinity of ca. 11. Increased food availability may be able to mask these negative impacts, but not when seawater conditions are permanently adverse, as observed in two Baltic reefs at salinities < 11. Future climatic models predict rapid desalination of the southwest and Central Baltic and potentially a reduction in [Ca2+] which may lead to a westward distribution shift of marine calcifiers. It is therefore vital to understand the mechanisms by which the ionic composition of seawater impacts bivalve calcification for better predicting the future of benthic Baltic ecosystems.

Continue reading ‘Decoupling salinity and carbonate chemistry: low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels’

Eat, breathe, repeat: physiological responses of the mussel Mytilus galloprovincialis to Diclofenac and ocean acidification

Combined effects of the nonsteroidal anti-inflammatory drug diclofenac and lowered seawater pH were assessed on the physiological responses of the mussel Mytilus galloprovincialis. Bivalves were exposed for 1 week to natural pH (8.1) and two reduced pH values (pH −0.4 units and pH −0.7 units), as predicted under a climate change scenario. After the first week, exposure continued for additional 2 weeks, both in the absence and in the presence of environmentally relevant concentrations of diclofenac (0.05 and 0.5 µg/L). Clearance rate, respiration rate, and excretion rate were measured after 7 days of exposure to pH only and after 14 (T1) and 21 (T2) days of exposure to the various pH*diclofenac combinations. At all sampling times, pH significantly affected all the biological parameters considered, whereas diclofenac generally exhibited a significant influence only at T2. Overall, results demonstrated that the physiological performance of M. galloprovincialis was strongly influenced by the experimental conditions tested, in particular by the interaction between the two stressors after 21 days of exposure. Further studies are needed to assess the combined effects of climate changes and emerging contaminants on bivalve physiology during different life stages, especially reproduction.

Continue reading ‘Eat, breathe, repeat: physiological responses of the mussel Mytilus galloprovincialis to Diclofenac and ocean acidification’

DNA methylation changes in response to ocean acidification at the time of larval metamorphosis in the edible oyster, Crassostrea hongkongensis

Highlights

  • Low pH stress resulted in hyper- and hypo-methylated genes in the pediveliger larvae of the Hong Kong oyster
  • Differentially methylated loci were concentrated in the exon region within the gene bodies
  • High capability of oyster larvae to acclimate and adapt to low pH condition within single generation despite poor habitat selection for attachment
  • Differential methylation is associated to higher metamorphosis success rate and poor larval substratum selection under low pH stress.

Abstract

Unprecedented rate of increased CO2 level in the ocean and the subsequent changes in carbonate system including decreased pH, known as ocean acidification (OA), is predicted to disrupt not only the calcification process but also several other physiological and developmental processes in a variety of marine organisms, including edible oysters. Nonetheless, not all species are vulnerable to those OA threats, e.g. some species may be able to cope with OA stress using environmentally induced modifications on gene and protein expressions. For example, external environmental stressors including OA can influence the addition and removal of methyl groups through epigenetic modification (e.g. DNA methylation) process to turn gene expression “on or off” as part of a rapid adaptive mechanism to cope with OA. In this study, we tested the above hypothesis through testing the effect of OA, using decreased pH 7.4 as proxy, on DNA methylation pattern of an endemic and a commercially important estuary oyster species, Crassostrea hongkongensis at the time of larval habitat selection and metamorphosis. Larval growth rate did not differ between control pH 8.1 and treatment pH 7.4. The metamorphosis rate of the pediveliger larvae was higher at pH 7.4 than those in control pH 8.1, however over one-third of the larvae raised at pH 7.4 failed to attach on optimal substrate as defined by biofilm presence. During larval development, a total of 130 genes were differentially methylated across the two treatments. The differential methylation in the larval genes may have partially accounted for the higher metamorphosis success rate under decreased pH 7.4 but with poor substratum selection ability. Differentially methylated loci were concentrated in the exon regions and appear to be associated with cytoskeletal and signal transduction, oxidative stress, metabolic processes, and larval metamorphosis, which implies the high potential of C. hongkongensis larvae to acclimate and adapt through non-genetic ways to OA threats within a single generation.

Continue reading ‘DNA methylation changes in response to ocean acidification at the time of larval metamorphosis in the edible oyster, Crassostrea hongkongensis’

Effects of ocean acidification and microplastics on microflora community composition in the digestive tract of the thick shell mussel Mytilus coruscus through 16s RNA gene sequencing

Ocean acidification and microplastic pollution is a global environmental threat, this research evaluated the effects of ocean acidification and microplastics on mussel digestive tract microbial community. The 16S rRNA gene was sequenced to characterize the flora. Species diversity in the samples was assessed by clustering valid tags on 97% similarity. Bacteroidetes, Firmicutes and Proteobacteria were the three most abundant genera in the four groups, with Bacteroidetes showing the highest diversity. However, no differences in flora structure were evident under various treatments. Phylogenetic relationship analysis revealed Bacteroidetes and Firmicutes had the highest OTU diversity. The weighted UniFrac distance, principal coordinate analysis (PCoA), unweighted pair group method with arithmetic mean (UPGMA) cluster tree and analysis of molecular variance (AMOVA) evaluation results for all samples also showed that changes in pH and microplastics concentration did not significantly affect the microbial community structure in the mussel digestive tract. The results presented the no significant effects of ocean acidification and microplastics intake on mussel intestinal diversity.

Continue reading ‘Effects of ocean acidification and microplastics on microflora community composition in the digestive tract of the thick shell mussel Mytilus coruscus through 16s RNA gene sequencing’

The combined effects of ocean acidification and warming on a habitat-forming shell-crushing predatory crab

Highlights

  • We measured and compared traits at the cellular and organismal levels
  • Ocean warming and acidification affected crabs’ traits
  • Ocean warming increased the HSP70 levels
  • Crabs’ pinching strength was reduced by ocean acidification
  • Crabs’ self-righting speed was reduced by ocean warming and acidification

Abstract

In mid rocky intertidal habitats the mussel Perumytilus purpurarus monopolizes the substratum to the detriment of many other species. However, the consumption of mussels by the shell-crushing crab Acanthocyclus hassleri creates within the mussel beds space and habitat for several other species. This crab uses its disproportionately large claw to crush its shelled prey and plays an important role in maintaining species biodiversity. This study evaluated the consequences of projected near-future ocean acidification (OA) and warming (OW) on traits of A. hassleri linked with their predatory performance. Individual A. hassleri were maintained for 10-16 weeks under contrasting pCO2 (~500 and 1400 μatm) and temperature (~15 and 20 °C) levels. We compared traits at the organismal (oxygen consumption rate, survival, calcification rate, feeding rates, crusher claw pinching strength, self-righting speed, sarcomere length of the crusher claw muscles) and cellular (nutritional status ATP provisioning capacity through citrate synthase activity, expression of HSP70) level. Survival, calcification rate and sarcomere length were not affected by OA and OW. However, OW increased significantly feeding and oxygen consumption. Pinching strength was reduced by OA; meanwhile self-righting was increased by OA and OW. At 20 °C, carbohydrate content was reduced significantly by OA. Regardless of temperature, a significant reduction in energy reserves in terms of protein content by OA was found. The ATP provisioning capacity was significantly affected by the interaction between temperature and pCO2 and was highest at 15 °C and present day pCO2 levels. The HSP70 levels of crabs exposed to OW were higher than in the control crabs. We conclude that OA and OW might affect the amount and size of prey consumed by this crab. Therefore, by reducing the crab feeding performance these stressors might pose limits on their role in generating microhabitat for other rocky intertidal species inhabiting within mussel beds.

Continue reading ‘The combined effects of ocean acidification and warming on a habitat-forming shell-crushing predatory crab’

Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,400,306 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book

Archives