Posts Tagged 'toxicants'

Physiological and biochemical impacts induced by mercury pollution and seawater acidification in Hediste diversicolor

The present study evaluated the impacts of predicted seawater acidification and Hg pollution, when stressors were acting alone and in combination, on the polychaete Hediste diversicolor. Polychaetes were exposed during 28 days to low pH (7.5), Hg (5 μg/L) and pH 7.5 + Hg, and physiological alterations (respiration rate), biochemical markers related to metabolic potential (glycogen and protein content, electron transport system activity) and oxidative status (activity of antioxidant and biotransformation enzymes, lipid peroxidation) were evaluated. The results obtained clearly showed that polychaetes were sensitive to low pH and Hg contamination, both acting alone or in combination. Organisms used their energy reserves under stressful conditions, which decreased by up to half of the control content, probably to fuel defence mechanisms. Our findings further demonstrated that polychaetes exposed to these stressors presented increased antioxidant defence mechanisms (3 fold compared to control). However, organisms were not able to prevent cellular damage, especially noticed at Hg exposure and pH 7.5. Overall, although all the tested conditions induced oxidative stress in Hediste diversicolor, the combined effect of seawater acidification and Hg contamination did not induce higher impacts in polychaetes than single stressor exposures. These findings may indicate that predicted climate change scenarios may not increase Hediste diversicolor sensitivity towards Hg and may not significantly change the toxicity of this contaminant to this polychaete species.

Continue reading ‘Physiological and biochemical impacts induced by mercury pollution and seawater acidification in Hediste diversicolor’

Alleviation of mercury toxicity to a marine copepod under multigenerational exposure by ocean acidification

Ocean acidification (OA) may potentially modify the responses of aquatic organisms to other environmental stressors including metals. In this study, we investigated the effects of near-future OA (pCO2 1000 μatm) and mercury (Hg) on the development and reproduction of marine copepod Tigriopus japonicus under multigenerational life-cycle exposure. Metal accumulation as well as seven life history traits (survival rate, sex ratio, developmental time from nauplius to copepodite, developmental time from nauplius to adult, number of clutches, number of nauplii/clutch and fecundity) was quantified for each generation. Hg exposure alone evidently suppressed the number of nauplii/clutch, whereas single OA exposure negligibly affected the seven traits of copepods. However, OA exposure significantly alleviated the Hg inhibitory effects on number of nauplii/clutch and fecundity, which could be explained by the reduced Hg accumulation under OA. Such combined exposure also significantly shortened the development time. Thus, in contrast to earlier findings for other toxic metals, this study demonstrated that OA potentially mitigated the Hg toxicity to some important life traits in marine copepods during multigenerational exposure.

Continue reading ‘Alleviation of mercury toxicity to a marine copepod under multigenerational exposure by ocean acidification’

Benzo[a]pyrene exposure under future ocean acidification scenarios weakens the immune responses of blood clam, Tegillarca granosa

Persistent organic pollutants (POPs) are known to converge into the ocean and accumulate in the sediment, posing great threats to marine organisms such as the sessile bottom burrowing bivalves. However, the immune toxicity of POPs, such as B[a]P, under future ocean acidification scenarios remains poorly understood to date. Therefore, in the present study, the impacts of B[a]P exposure on the immune responses of a bivalve species, Tegillarca granosa, under present and future ocean acidification scenarios were investigated. Results obtained revealed an increased immune toxicity of B[a]P under future ocean acidification scenarios in terms of reduced THC, altered haemocyte composition, and hampered phagocytosis, which may attribute to the synergetic effects of B[a]P and ocean acidification. In addition, the gene expressions of pathogen pattern recognition receptors (TLR1, TLR2, TLR4, TLR6), pathway mediators (TRAF6, TAK1, TAB2, IKKα and Myd88), and effectors (NF-ĸB) of the important immune related pathways were significantly down-regulated upon exposure to B[a]P under future ocean acidification scenarios. Results of the present study suggested an increased immune toxicity of B[a]P under future ocean acidification scenarios, which will significantly hamper the immune responses of T. granosa and subsequently render individuals more susceptible to pathogens challenges.

Continue reading ‘Benzo[a]pyrene exposure under future ocean acidification scenarios weakens the immune responses of blood clam, Tegillarca granosa’

CO2-induced pH reduction increases physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus

The increasing usage of nanoparticles has caused their considerable release into the aquatic environment. Meanwhile, anthropogenic CO2 emissions have caused a reduction of seawater pH. However, their combined effects on marine species have not been experimentally evaluated. This study estimated the physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus under high pCO2 (2500–2600 μatm). We found that respiration rate (RR), food absorption efficiency (AE), clearance rate (CR), scope for growth (SFG) and O:N ratio were significantly reduced by nano-TiO2, whereas faecal organic weight rate and ammonia excretion rate (ER) were increased under nano-TiO2 conditions. High pCO2 exerted lower effects on CR, RR, ER and O:N ratio than nano-TiO2. Despite this, significant interactions of CO2-induced pH change and nano-TiO2 were found in RR, ER and O:N ratio. PCA showed close relationships among most test parameters, i.e., RR, CR, AE, SFG and O:N ratio. The normal physiological responses were strongly correlated to a positive SFG with normal pH and no/low nano-TiO2 conditions. Our results indicate that physiological functions of M. coruscus are more severely impaired by the combination of nano-TiO2 and high pCO2.

Continue reading ‘CO2-induced pH reduction increases physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus’

Habitat selection disruption and lateralization impairment of cryptic flatfish in a warm, acid, and contaminated ocean

Anthropogenic release of greenhouse gases is leading to significant changes in ocean physicochemical properties. Although marine organisms will have to deal with combined effects of ocean warming and acidification, little is known about the impact of interactions between these climate change variables and contaminants. Nowadays, mercury emissions are mostly of anthropogenic origin, and part of these emissions is deposited in the ocean sediment. Within this context, our goal was to determine the acclimation potential of a benthic flatfish, Solea senegalensis, to future climate change scenarios and methylmercury (MeHg) neurotoxicity. After 28 days of exposure under three-factor crossed treatments of MeHg contamination (non-contaminated and contaminated feed, 0.08 ± 0.02 and 8.51 ± 0.15 mg kg−1 dry weight, respectively), high CO2 (ΔCO2 ≈ 500 ppm), and temperature (ΔT = 4 °C), we investigated brain mercury accumulation, habitat preference, and relative/absolute lateralization, as well as acetylcholinesterase (AChE) activity in five brain regions. Our results indicate a differential effect of hypercapnia (decrease) on brain mercury accumulation. MeHg-contaminated flatfish displayed decreased AChE activity, impaired lateralization, and bottom choosing judgment. Contaminated fish spent significantly higher amounts of time in the complex habitat, where they could neither bury nor match the background. While warming led to higher enzymatic activity, acidification decreased Hg accumulation, but also affected AChE activity and disrupted habitat selection. Present-day MeHg environmental concentrations may lead to severe disruption of behavioral and neurological functions, which, combined with ocean warming and acidification, might further jeopardize the ecological fitness of flatfish.

Continue reading ‘Habitat selection disruption and lateralization impairment of cryptic flatfish in a warm, acid, and contaminated ocean’

Hemocyte responses of the thick shell mussel Mytilus coruscus exposed to nano-TiO2 and seawater acidification

With increasing production from nanotechnology industries, nanomaterials are inevitably released into the aquatic environment, thereby posing a potential risk to aquatic organisms. Thus, concerns have been raised on the potential ecotoxicological effect of nanoparticle. Furthermore, the ecotoxicological consequences caused by the interaction of nanoparticles with other environmental stresses, such as seawater acidification on marine animals, have not been evaluated. In particular, whether acidification enhances the susceptibility to nanoparticles in bivalves needs to be evaluated. In the present study, we investigated the combined effects of low pH and nanoscale titanium dioxide (nano-TiO2) on some immune parameters of hemocytes in the mussel Mytilus coruscus by flow cytometry under six combinations of two pH values (7.3 and 8.1) and three nano-TiO2 concentrations (0, 2.5, and 10 mg L−1) for 14 d. Afterward, the mussels were shifted to normal conditions without nano-TiO2 at pH 8.1 for 7 d further to test their recovery from the multiple stresses. Total hemocyte count (THC), phagocytosis (Pha), esterase (Est), and lysosomal content (Lyso) decreased under low pH and high nano-TiO2 concentration conditions, whereas hemocyte mortality (HM) and reactive oxygen species (ROS) increased with nano-TiO2 concentrations under low pH conditions. The interactive effects between pH and nano-TiO2 were observed at the latter part of the exposure experiment (7 and 14 d) in most hemocyte parameters. Nano-TiO2 influenced the immune functions of mussel more severely than low pH. Slight recovery from the combined stresses was observed for HM, THC, Pha, and Lyso, but significant carry-over effects of nano-TiO2 and low pH were still observed. This study demonstrated that both low pH and high concentration of nano-TiO2 had negative effects on mussels, and these effects still acted for some time even though the mussels were already out of such stressors.

Continue reading ‘Hemocyte responses of the thick shell mussel Mytilus coruscus exposed to nano-TiO2 and seawater acidification’

The impacts of As accumulation under different pH levels: Comparing Ruditapes decussatus and Ruditapes philippinarum biochemical performance

Marine bivalves have been used to assess environmental As contamination and the effects of seawater acidification when both factors are acting alone, but limited information is available regarding the impacts of both factors acting in combination. The aim of this study was to compare physiological (glycogen) and biochemical (lipid peroxidation, superoxide dismutase, catalase, glutathione-S-transferase and alkaline phosphatase) responses in both native (Ruditapes decussatus) and introduced (R. philippinarum) clams, when exposed to the combined effects of pH (7.8, control; 7.3) and As concentrations (0 and 4 mg/L). The combined effect of As and pH on the health risks associated with clam consumption was also analyzed. Results revealed that both species were able to accumulate As under both pH levels, although higher As concentrations where observed under low pH. Thus, predicted pH decrease will potentiate health risks associated with the consumption of such species, since less amount of clams exposed to As is needed for an adult to exceed the provisional tolerable weekly intake (PTWI). Low pH, As exposure and the combination of both factors did not negatively affect the native species, since clams were able to maintain their physiological and biochemical performance among all conditions. On the other hand, R. philippinarum was negatively affected by As exposure at control pH (7.8), inducing biotransformation and antioxidant defense mechanisms against As toxicity. R. philippinarum exposed and non-exposed to As presented similar responses under low pH although at this condition the introduced species accumulated twice the amount of As than R. decussatus.

Continue reading ‘The impacts of As accumulation under different pH levels: Comparing Ruditapes decussatus and Ruditapes philippinarum biochemical performance’


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