Posts Tagged 'mollusks'

Impacts of ocean acidification on carboxylated carbon nanotube effects induced in the clam species Ruditapes philippinarum

Although the increased production of nanoparticles (NPs) has raised extensive concerns about the potential toxic effects on aquatic organisms, as well as the increasing evidences which documented the impact of ocean acidification (OA) on the physiology and fitness of marine invertebrates, limited number of studies reported their combined toxic effects. For these reasons, in the present study, we investigated the physiological and biochemical responses of one of the most economically important bivalve species in the World, the Manila clam Ruditapes philippinarum, after the exposure to an environmnetally relevant concentration of carboxylated carbon nanotubes and predicted OA conditions. The results showed that the organisms were not only susceptible to NPs but also to seawater acidification. Different responses between low pH and NPs for most tested biomarkers were observed, both in terms of physiological (respiration rate) and biochemical responses (metabolic capacity, oxitative status and neurotoxicity). Acidified pH significantly decreased the respiration rate and metabolism and increased the energy reserves consumption. Moreover, increase of the oxidative damage was also detected under this condition confirming that the mechanism of enhanced toxicity in the organisms should be attributed to lower aggregation state with more suspended NPs in acidified seawater, indicating that seawater acidification significantly influenced the impact of the used NPs in the exposed organisms.

Continue reading ‘Impacts of ocean acidification on carboxylated carbon nanotube effects induced in the clam species Ruditapes philippinarum’

Physiological responses of juvenile Chilean scallops (Argopecten purpuratus) to isolated and combined environmental drivers of coastal upwelling

Coastal biota is exposed to continuous environmental variability as a consequence of natural and anthropogenic processes. Responding to heterogeneous conditions requires the presence of physiological strategies to cope with the environment. Ecosystems influenced by upwelling endure naturally cold, acidic and hypoxic conditions, nevertheless they sustain major fisheries worldwide. This suggests that species inhabiting upwelling habitats possess physiological adaptations to handle high environmental variability. Here, we assessed the impact of the main upwelling drivers (temperature, pH and oxygen) in isolation and combined on eco-physiological responses of Chilean scallop Argopecten purpuratus. A. purpuratus responded to hypoxia by increasing their metabolic performance to maintain growth and calcification. Calcification was only affected by pH and increased under acidic conditions. Further, A. purpuratus juveniles prioritized calcification at the expense of growth under upwelling conditions. Increasing temperature had a significant impact by enhancing the physiological performance of A. purpuratus juveniles independently of oxygen and pH conditions, but this was associated with earlier and higher mortalities. Our results suggest that A. purpuratus is acclimated to short-term colder, acidic and hypoxic conditions, and provide important information of how this species responds to the heterogeneous environment of upwelling, which is significantly relevant in the climatic context of upwelling intensification.

Continue reading ‘Physiological responses of juvenile Chilean scallops (Argopecten purpuratus) to isolated and combined environmental drivers of coastal upwelling’

Seawater acidification and emerging contaminants: a dangerous marriage for haemocytes of marine bivalves

Highlights

• Reduced pH and diclofenac affect haemocyte parameters in exposed mussels and clams.

• During exposure effects of pH persisted, those of diclofenac appeared later.

• Different patterns in haemocyte responses were observed in the two species.

• Interaction between pH and diclofenac was more evident in mussels.

Abstract

The combined effects of seawater acidification and the non-steroidal anti-inflammatory drug diclofenac on haemocyte parameters of the mussel Mytilus galloprovincialis and the clam Ruditapes philippinarum were investigated for the first time. Animals were maintained for one week (T0) in natural pH condition (8.1) and two reduced pH values (pH −0.4 units and pH −0.7 units). Bivalves were then exposed for additional 14 days (T1 and T2) to the three experimental pH values in both the presence and absence of environmentally realistic concentrations of diclofenac (0.05 and 0.50 μg/L). To assess potential impairment in immunosurveillance, haemocyte parameters (total haemocyte count, haemocyte volume and diameter, Neutral Red uptake, haemocyte proliferation and lysozyme activity) were measured after 7, 14 and 21 days of exposure to differing pH value or pH/diclofenac combinations. In both species, pH affected the whole haemocyte data set at all sampling times, influencing most of the parameters measured at T0 and T1 in clams, and at T2 in mussels. Conversely, in both species diclofenac affected the overall haemocyte response at T2 only. However, in R. philippinarum a higher number of haemocyte parameters were significantly influenced even at T1. A significant interaction between pH and diclofenac was mainly evident in mussels, affecting haemocyte size and lysozyme activity at both T1 and T2. Overall, the results obtained demonstrated that the experimental conditions tested can alter markedly haemocyte parameters in marine bivalves.

Continue reading ‘Seawater acidification and emerging contaminants: a dangerous marriage for haemocytes of marine bivalves’

Seawater acidification affects the immune enzyme activities of the Manila clam Ruditapes philippinarum

Ocean acidification leads to changes in physiological and immune responses of bivalves, but the effect on the immune enzyme activities of the Manila clam, Ruditapes philippinarum, when the pH is lower than the normal value has not been studied in detail. In this study, experiments were conducted to determine how pH (7.4, 7.7, 8.0) affects the immune enzyme activities in the gill and hemocytes of the Manila clam. Membrane stability and phagocytosis increased with decrease of pH from 8.0 to 7.7 and then decreased at pH 7.4. The total protein content in the hemocytes and gills decreased with decreasing pH. Lysozyme content in the hemocytes increased with decreasing pH, and the differences were significant among the different pH groups ( P < 0.05). Adenosine triphosphatase activity at pH 7.4 was significantly higher than in the other two groups, but no significant difference was observed between pH 7.7 and 8.0. Catalase activity decreased from pH 8.0 to 7.7 and then increased at pH 7.4, and the differences were significant among the experimental groups ( P < 0.05). These findings provide valuable information about the immune response of R. philippinarum to reduced water pH and insights for future research investigating exposure of bivalves to elevated CO2 conditions.

Continue reading ‘Seawater acidification affects the immune enzyme activities of the Manila clam Ruditapes philippinarum’

Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs

Predator-prey interactions often drive ecological patterns and are governed by factors including predator feeding rates, prey behavioral avoidance, and prey structural defenses. Invasive species can also play a large ecological role by disrupting food webs, driving local extinctions, and influencing evolutionary changes in prey defense mechanisms. This study documents a substantial reduction in the behavioral and morphological responses of multiple gastropod species (Nucella lapillus, N. ostrina, Urosalpinx cinerea) to an invasive predatory crab (green crab Carcinus maenas) under ocean acidification conditions. These results suggest that climate-related changes in ocean chemistry may diminish non-lethal effects of predators on prey responses including behavioral avoidance. While snails with varying shell mineralogies were similarly successful at deterring predation, those with primarily aragonitic shells were more susceptible to dissolution and erosion under high CO2 conditions. The varying susceptibility to predation among species with similar ecological roles could indicate that the impacts of invasive species like green crabs could be modulated by the ability of native and invasive prey to withstand ocean acidification conditions.

Continue reading ‘Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs’

Larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica) under different pH conditions

Changes in seawater pH in the culture environment have numerous effects on marine bivalves. To investigate the effect of pH on larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica), specimens were cultured under different experimental pH conditions (6.8, 7.2, 7.6, 8.0, 8.4, and 9.2). The pH range for optimal growth and development differed among different larval stages. However, significant changes in larval development (p < 0.5) relative to the control (pH 8.0) were detected at very high or low pH. The best hatching rate occurred at pH 7.6–8.8, and it was significantly lower (p < 0.5) at pH 6.8, 7.2, and 9.2. Larval survival was only 4% at pH 6.8. Growth rate of larvae increased with increasing pH and the optimal range was 8.0 to 8.8. This finding suggests that alkaline conditions favor growth and development of larvae and allow them to reach the metamorphic stage promptly. Prolonged metamorphosis was a common feature in larvae in the different experimental pH groups. pH below 7.6 and above 8.8 resulted in a significantly (p < 0.5) lower metamorphosis rate, suggesting that high acidity and alkalinity were deleterious to larval metamorphosis. Thus, the suitable pH range for metamorphosis was 8.0 to 8.8. Lower and higher pH also affected the digging behavior of geoduck clams, and the suitable pH range for burrowing was 7.2 to 8.8. Geoduck clams stopped burrowing in the sand at pH 6.8 and 9.2, possibly due to impairment of biological process caused by acidic and alkaline seawater. These findings provide valuable information about the larval and juvenile responses of P. japonica in variable pH.

Continue reading ‘Larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica) under different pH conditions’

Survival and respiration of green abalone (Haliotis fulgens) facing very short-term marine environmental extremes

The frequency and strength of extreme events are increasing due to climate change. These events have the potential to cause mass mortalities and recruitment failure in very short time scales. Here, we explored three relevant basic questions using green abalone: how the lethal levels of environmental variables (i.e. temperature, oxygen, and pH) change trough time, what the short-term synergistic effects of stressors are, and what the metabolic responses and recovery capacity are at this timescale. We observed that very short-term events are less likely to cause mass mortalities than events lasting for several days, that the relative importance of hyperthermia, hypoxia, and combined effects change through time, and that the respiration rate increased under hyperthermia and decreased under hypoxia and the combined effects, while hemocyanin concentration increased under hypoxia and decreased under hyperthermia and combined effects. Independently of the stressor, green abalone re-established their respiratory rate after the stress.

Continue reading ‘Survival and respiration of green abalone (Haliotis fulgens) facing very short-term marine environmental extremes’


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Ocean acidification in the IPCC AR5 WG II

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