Posts Tagged 'mollusks'

Acclimatization in a changing environment: linking larval and juvenile performance in the quahog Mercenaria mercenaria

Marine invertebrates in coastal communities are currently experiencing unprecedented, rapid environmental change. These symptoms of climate change and ocean acidification are projected to worsen faster than can be accommodated by evolutionary processes like adaptation via natural selection, necessitating investigations of alternative mechanisms that facilitate adaptive responses to environmental change. This dissertation posits that in the absence of adaptation, early development (larval) exposure to stressors can increase population tolerance by leveraging existing variation in the energy metabolism and host-microbial interactions. Focusing specifically on resiliency to acidification (low pH), hypoxia (low dissolved oxygen), and elevated temperature stress in the clam, Mercenaria mercenaria, this dissertation uses a combination of laboratory and field experiments in conjunction with next-generation sequencing and physiological assays to investigate the relationship between host health, microbial community structure, and environmental change.

Continue reading ‘Acclimatization in a changing environment: linking larval and juvenile performance in the quahog Mercenaria mercenaria’

Ocean acidification induces tissue-specific interactions with copper toxicity on antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818)


  • Cu and OA coexposures induce tissue-specific oxidative stress in clams.
  • OA exacerbates Cu toxicity and increases oxidative damage in tissues.
  • Gill is more vulnerable to oxidation than viscera with MDA and 8-OHdG as indicators.
  • PCAs usefully identify the contributions of biomarkers to antioxidant defences.
  • The results provide insights for assessing Cu toxicity under OA in wild bivalves.


Toxicity of contaminants in organisms under ocean acidification (OA) has attracted increasing attention in ecotoxicological studies. This study investigated how pCO2-driven OA affected waterborne copper (Cu) toxicity in antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818). Clams were continuously exposed to Cu at ambient relevant (0/no metal exposure, 10 and 50 μg L−1) and polluted-high (100 μg L−1) concentrations in unacidified (pH 8.10) and acidified (pH 7.70/moderate OA and 7.30/extreme OA) seawater for 21 days. Following coexposure, metal bioaccumulation and responses of antioxidant defence-related biomarkers to OA and Cu coexposure were investigated. Results showed that metal bioaccumulation was positively correlated with waterborne metal concentrations but was not notably influenced by OA conditions. Both Cu and OA affected the antioxidant responses to environmental stress. Additionally, OA induced tissue-specific interactions with Cu on antioxidant defences, varying with exposure conditions. In unacidified seawater, antioxidant biomarkers were activated to defend against oxidative stress induced by Cu and prevented clams from lipid peroxidation (LPO or MDA), but failed to defend against DNA damage (8-OHdG). OA exacerbated Cu toxicity in antioxidant defences and increased LPO levels in tissues. Gills and viscera adopted adaptive antioxidant defence strategies to manage oxidative stress, with the former being more vulnerable to oxidative stress than the latter. MDA and 8-OHdG were sensitive to OA and Cu exposure, respectively, and were useful bioindicators for assessing oxidative stress. Integrated biomarker response (IBR) and PCA can reflect the integrative responses of antioxidant biomarkers to environmental stress and illuminate the contributions of specific biomarkers to antioxidant defence strategies. The findings provided insights for understanding antioxidant defences against metal toxicity in marine bivalves under OA scenarios, which is essential into managing wild populations.

Continue reading ‘Ocean acidification induces tissue-specific interactions with copper toxicity on antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818)’

The clam before the storm: a meta analysis showing the effect of combined climate change stressors on bivalves

Impacts of a range of climate change on marine organisms have been analysed in laboratory and experimental studies. The use of different taxonomic groupings, and assessment of different processes, though, makes identifying overall trends challenging, and may mask phylogenetically different responses. Bivalve molluscs are an ecologically and economically important data-rich clade, allowing for assessment of individual vulnerability and across developmental stages. We use meta-analysis of 203 unique experimental setups to examine how bivalve growth rates respond to increased water temperature, acidity, deoxygenation, changes to salinity, and combinations of these drivers. Results show that anthropogenic climate change will affect different families of bivalves disproportionally but almost unanimously negatively. Almost all drivers and their combinations have significant negative effects on growth. Combined deoxygenation, acidification, and temperature shows the largest negative effect size. Eggs/larval bivalves are more vulnerable overall than either juveniles or adults. Infaunal taxa, including Tellinidae and Veneridae, appear more resistant to warming and oxygen reduction than epifaunal or free-swimming taxa but this assessment is based on a small number of datapoints. The current focus of experimental set-ups on commercially important taxa and families within a small range of habitats creates gaps in understanding of global impacts on these economically important foundation organisms.

Continue reading ‘The clam before the storm: a meta analysis showing the effect of combined climate change stressors on bivalves’

Ocean acidification impedes foraging behavior in the mud snail Ilyanassa obsoleta

Ocean acidification may diminish the response of many marine organisms to chemical cues that can be used to sense nearby food and predators, potentially altering community dynamics. We used a Y-maze choice experiment to investigate the impact of ocean acidification on the ability of mud snails (Ilyanassa obsoleta) to sense food cues in seawater. Mud snails have a well-adapted chemosensory system and play an important role in estuarine ecosystem functioning. Our results showed substantially diminished foraging success for the mud snail under acidified conditions, as snails typically moved towards the food cue in controls (pH 8.1) and away from it in acidified treatments (pH 7.6). These results, coupled with previous work, clearly demonstrate the magnitude at which ocean acidification may impair foraging efficiency, potentially resulting in severe alterations in future ecosystem dynamics.

Continue reading ‘Ocean acidification impedes foraging behavior in the mud snail Ilyanassa obsoleta’

Will ocean acidification affect the digestive physiology and gut microbiota of whelk Brunneifusus ternatanus?

To understand the physiological responses of the Brunneifusus ternatanus to future ocean acidification (OA), histology, enzyme activity and gut bacterial composition at different pH levels (Control: C group, pH 8.1; Exposure period: EP group, pH 7.3) for 28 days were studied under laboratory conditions. Microbiota composition was analyzed using 16S rRNA gene amplicon sequencing. Enzyme activities of trypsin (TRY), lipase (LPS), amylase (AMS), and lysozyme (LZM) were used as biochemical indicators, as well as weight gain rate (WGR), specific growth rate (SGR) as growth indicators. The stress caused by OA resulted in alterations to the intestine, including partially swollen and degranulated enterocytes and rough endoplasmic reticulum (RER). The relative abundance of the core phylum in the acidified group changed significantly, showing an increase in Tenericutes and a decrease in Proteobacteria. Firmicutes/Bacteroides ratio declined from 4.38 in the control group to 1.25 in the EP group. We found that the enzymes TRY, LPS, and AMS activities were inhibited at reduced pH, which was positively correlated with the dominant genera Mycoplasma and Bacteroides; while LZM activities showed a significant increment, but showing a strong negative correlation. Furthermore, both WG and SRG values showed a depression at low pH lever. These results suggest that if anthropogenic CO2 emissions continue to accelerate, OA could negatively impact the whelk’s health, compromising their growth performance and even survival. These findings will benefit the future risk assessments of OA or other related emerging environmental issues.

Continue reading ‘Will ocean acidification affect the digestive physiology and gut microbiota of whelk Brunneifusus ternatanus?’

Ocean acidification and warming modify stimulatory benthos effects on sediment functioning: an experimental study on two ecosystem engineers

Many macrofauna have a stimulatory effect on sediment functioning through their burrowing, feeding and irrigation activities. Here, we investigated the single and combined effect of ocean acidification and warming on the stimulatory effect of two key-species inhabiting sandy seabeds in the Southern Bight of the North Sea; the bivalve Abra alba and the polychaete Lanice conchilega. The species were separately incubated in natural sediment in the laboratory under ambient, low pH (pH: -0.3), warm (T: + 3°C) and mimicked climate change (pH: -0.3, T: +3°C) conditions. After six weeks of incubation, nutrient and oxygen exchange were measured at the sediment-water interface to estimate aerobic sediment metabolism and nitrogen cycling. Both species facilitate sediment community oxygen consumption, nitrification and denitrification under ambient conditions. The stimulatory effect of A. alba disappeared in a low pH environment and decreased over time in the warmer treatments along with increased mortality. In contrast, L. conchilega stimulated sediment biogeochemical cycling more when seawater becomes acidified (+ 8 to 41%, depending on the function) but warming had no effect. We explain these species-specific climate change effects by different behavioral and physiological coping strategies that cascade on to sediment biogeochemical cycling, especially through altered oxygenation the sediment matrix.

Continue reading ‘Ocean acidification and warming modify stimulatory benthos effects on sediment functioning: an experimental study on two ecosystem engineers’

Directional fabrication and dissolution of larval and juvenile oyster shells under ocean acidification

Biomineralization is one of the key biochemical processes in calcifying bivalve species such as oysters that is affected by ocean acidification (OA). Larval life stages of oysters are made of aragonite crystals whereas the adults are made of calcite and/or aragonite. Though both calcite and aragonite are crystal polymorphs of calcium carbonate, they have different mechanical properties and hence it is important to study the micro and nano structure of different life stages of oyster shells under OA to understand the mechanisms by which OA affects biomineralization ontogeny. Here, we have studied the larval and juvenile life stages of an economically and ecologically important estuarine oyster species, Crassostrea hongkongensis, under OA with focus over shell fabrication under OA (pHNBS 7.4). We also look at the effect of parental exposure to OA on larvae and juvenile microstructure. The micro and nanostructure characterization reveals directional fabrication of oyster shells, with more organized structure as biomineralization progresses. Under OA, both the larval and juvenile stages show directional dissolution, i.e. the earlier formed shell layers undergo dissolution at first, owing to longer exposure time. Despite dissolution, the micro and nanostructure of the shell remains unaffected under OA, irrespective of parental exposure history.

Continue reading ‘Directional fabrication and dissolution of larval and juvenile oyster shells under ocean acidification’

Ocean acidification stunts molluscan growth at CO2 seeps

Graphical abstract


  • Responses of molluscan growth to ocean acidification at CO2 seeps were studied.
  • Mussels near CO2 seeps grew significantly slower than those outside the seeps.
  • Mussels near and outside CO2 seeps exhibited differences in tissue carbon and nitrogen isotopic signatures.
  • Geochemical analysis indicated chemical shifts at the calcifying front in mussels near and outside CO2 seeps.


Ocean acidification can severely affect bivalve molluscs, especially their shell calcification. Assessing the fate of this vulnerable group in a rapidly acidifying ocean is therefore a pressing challenge. Volcanic CO2 seeps are natural analogues of future ocean conditions that offer unique insights into the scope of marine bivalves to cope with acidification. Here, we used a 2-month reciprocal transplantation of the coastal mussel Septifer bilocularis collected from reference and elevated pCO2 habitats to explore how they calcify and grow at CO2 seeps on the Pacific coast of Japan. We found significant decreases in condition index (an indication of tissue energy reserves) and shell growth of mussels living under elevated pCO2 conditions. These negative responses in their physiological performance under acidified conditions were closely associated with changes in their food sources (shown by changes to the soft tissue δ13C and δ15N ratios) and changes in their calcifying fluid carbonate chemistry (based on shell carbonate isotopic and elemental signatures). The reduced shell growth rate during the transplantation experiment was further supported by shell δ13C records along their incremental growth layers, as well as their smaller shell size despite being of comparable ontogenetic ages (5–7 years old, based on shell δ18O records). Taken together, these findings demonstrate how ocean acidification at CO2 seeps affects mussel growth and reveal that lowered shell growth helps them survive stressful conditions.

Continue reading ‘Ocean acidification stunts molluscan growth at CO2 seeps’

Seawater carbonate parameters function differently in affecting embryonic development and calcification in Pacific abalone (Haliotis discus hannai)

pH or pCO2 are usually taken to study the impact of ocean acidification on molluscs. Here we studied the different impact of seawater carbonate parameters on embryonic development and calcification of the Pacific abalone (Haliotis discus hannai). Early embryonic development was susceptible to elevated pCO2 level. Larvae hatching duration was positively and hatching rate was negatively correlated with the pCO2 level, respectively. Calcium carbonate (CaCO3) deposition of larval shell was found to be susceptible to calcium carbonate saturation state (Ω) rather than pCO2 or pH. Most larvae incubated in seawater with Ωarag = 1.5 succeeded in shell formation, even when seawater pCO2 level was higher than 3700 μatm and pHT was close to 7.4. Nevertheless, larvae failed to generate CaCO3 in seawater with Ωarag ≤ 0.52 and control level of pCO2, while seawater DIC level was lowered (≤ 852 μmol/kg). Surprisingly, some larvae completed CaCO3 deposition in seawater with Ωarag = 0.6 and slightly elevated DIC (2266 μmol/kg), while seawater pCO2 level was higher than 2700 μatm and pHT was lower than 7.3. This indicates that abalone may be capable of regulating carbonate chemistry to support shell formation, however, the capability was limited as surging pCO2 level lowered growth rate and jeopardized the integrity of larval shells. Larvae generated thicker shell in seawater with Ωarag = 5.6, while adult abalone could not deposit CaCO3 in seawater with Ωarag = 0.29 and DIC = 321 μmol/kg. This indicates that abalone may lack the ability to directly remove or add inorganic carbon at the calcifying sites. In conclusion, different seawater carbonate parameters play different roles in affecting early embryonic development and shell formation of the Pacific abalone, which may exhibit limited capacity to regulate carbonate chemistry.

Continue reading ‘Seawater carbonate parameters function differently in affecting embryonic development and calcification in Pacific abalone (Haliotis discus hannai)’

Ocean acidification, warming and feeding impacts on biomineralization pathways and shell material properties of Magallana gigas and Mytilus spp.


  • Mytilus spp. source environmental carbon into the shell aragonite under low pH.
  • In Mytilus spp. biomineralization pathways differ between calcite and aragonite.
  • M. gigas carbon sourcing remains similar maintaining calcite growth.
  • M. gigas mantle δ15N is lower in low pH reflecting algae nitrogen uptake.
  • Calcite biomineralization pathway differs between the two species under low pH.


Molluscs are among the organisms affected by ocean acidification (OA), relying on carbon for shell biomineralization. Metabolic and environmental sourcing are two pathways potentially affected by OA, but the circumstances and patterns by which they are altered are poorly understood. From previous studies, mollusc shells grown under OA appear smaller in size, brittle and thinner, suggesting an important alteration in carbon sequestration. However, supplementary feeding experiments have shown promising results in offsetting the negative consequences of OA on shell growth. Our study compared carbon uptake by δ13C tracing and deposition into mantle tissue and shell layers in Magallana gigas and Mytilus species, two economically valuable and common species. After subjecting the species to 7.7 pH, +2 °C seawater, and enhanced feeding, both species maintain shell growth and metabolic pathways under OA without benefitting from extra feeding, thus, showing effective acclimation to rapid and short-term environmental change. Mytilus spp. increases metabolic carbon into the calcite and environmental sourcing of carbon into the shell aragonite in low pH and high temperature conditions. Low pH affects M. gigas mantle nitrogen isotopes maintaining growth. Calcite biomineralization pathway differs between the two species and suggests species-specific response to OA.

Continue reading ‘Ocean acidification, warming and feeding impacts on biomineralization pathways and shell material properties of Magallana gigas and Mytilus spp.’

Climate change effects on marine species across trophic levels

Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. While there are numerous studies that have investigated the response of individual marine organisms to climate change, few studies have focused on differences in organismal responses across trophic levels. Such trophic differences in response to climate change may disrupt ecological interactions and thereby threaten marine ecosystem function. In addition, predation is known as a strong driver that impacts individuals and populations. Despite this, we still do not have a comprehensive understanding of how different trophic levels respond to climate change stressors, predation and their combined effects in marine ecosystems.

The main focus of this thesis is to identify whether marine trophic levels respond differently to climatic stressors and predation. To explore these questions, I have used a combination of traditional mesocosm experiments, together with a statistical method called meta-analysis. I initiated the research by study the responses of marine gastropods at two trophic levels to ocean acidification and predation using long-term mesocosm experiments together with a gastropod-specific meta-analyses. I focused on the amount of phenotypic plasticity in morphological traits of snails when exposed to the two stressors. In order to generalise and test these assumptions among a greater number of marine taxa, I used the meta-analysis approach to investigate the effects of ocean acidification and warming, as well as their combined effects on four marine trophic levels. Finally, to study the individual and combined effects of ocean acidification and predation with respect to inducible defences, I again applied a mesocosm experiment and used blue mussels as a model species.

By using long-term mesocosm experiments and the gastropod-specific meta-analysis on marine gastropods from two trophic levels, I showed that these trophic levels varied in their responses to both ocean acidification and predation. Gastropods at lower trophic levels exhibited greater phenotypic plasticity against predation, while those from higher trophic levels showed stronger tolerance to ocean acidification. Next, by using a meta-analysis, including a large number of species and taxa, examining the effects of ocean acidification and warming, I revealed that top-predators and primary producers were most tolerant to ocean acidification compared to other trophic levels. Herbivores on the other hand, were the most vulnerable trophic level against abiotic stress. Again, using the meta-analysis approach, but this time incorporating only factorial experimental data that included the interactive effects of ocean acidification and ocean warming, I showed that higher trophic levels again were the most tolerant trophic level, and herbivores being most sensitive, with respect to the combined effect of the two stressors. Contrary to previous discussions in the literature concerning multiple climate-related stressors, antagonistic and additive effects occurred most frequently, while synergistic effects were less common and which decreased with increasing trophic rank. Finally, by conducting a fully-factorial experiment using blue mussels, I found that mussels with previous experience contact with predator has developed greater inducible defences than ones without previous experience. However, levels of ocean acidification may mask predator cues, or obstruct shell material, and consequently disrupt blue mussels inducible defence from crab predation.

In summary, marine trophic levels respond differently to both biotic and climatic stressors. Higher trophic levels, together with primary producers, were often more robust against abiotic stress and may therefore be better prepared for future oceans compare species from lower trophic levels. These results may provide vital information for: implementing effective climate change mitigation, to understand which stressors to act on, and when and where to intervene for prioritizing conservation actions.

Continue reading ‘Climate change effects on marine species across trophic levels’

Ocean acidification drives gut microbiome changes linked to species-specific immune defence

Ocean acidification (OA) has important effects on the intrinsic phenotypic characteristics of many marine organisms. Concomitantly, OA can alter the extended phenotypes of these organisms by perturbing the structure and function of their associated microbiomes. It is unclear, however, the extent to which interactions between these levels of phenotypic change can modulate the capacity for resilience to OA. Here, we explored this theoretical framework assessing the influence of OA on intrinsic (immunological responses and energy reserve) and extrinsic (gut microbiome) phenotypic characteristics and the survival of important calcifiers, the edible oysters Crassostrea angulata and C. hongkongensis. After one-month exposure to experimental OA (pH 7.4) and control (pH 8.0) conditions, we found species-specific responses characterised by elevated stress (hemocyte apoptosis) and decreased survival in the coastal species (C. angulata) compared with the estuarine species (C. hongkongensis). Phagocytosis of hemocytes was not affected by OA but in vitro bacterial clearance capability decreased in both species. Gut microbial diversity decreased in C. angulata but not in C. hongkongensis. Overall, C. hongkongensis was capable of maintaining the homeostasis of the immune system and energy supply under OA. In contrast, C. angulata’s immune function was suppressed, and the energy reserve was imbalanced, which might be attributed to the declined microbial diversity and the functional loss of essential bacteria in the guts. This study highlights a species-specific response to OA determined by genetic background and local adaptation, shedding light on the understanding of host-microbiota-environment interactions in future coastal acidification.

Continue reading ‘Ocean acidification drives gut microbiome changes linked to species-specific immune defence’

Juvenile Atlantic sea scallop, Placopecten magellanicus, energetic response to increased carbon dioxide and temperature changes

This study assessed the energy budget for juvenile Atlantic Sea Scallop, Placopecten magellanicus, during a natural drop in temperature (15.6°C to 5.8°C) over an 8-week time period during the fall at three different enrichment levels of carbon dioxide (CO2). Every 2 weeks, individuals were sampled for ecophysiological measurements of feeding activity, respiration rate (RR) and excretion rate (ER) to enable the calculation of scope for growth (SFG) and atomic oxygen:nitrogen ratios (O:N). In addition, 36 individuals per treatment were removed for shell height, dry tissue weight (DTW) and dry shell weight (DSW). We found a significant decrease in feeding rates as CO2 increased. Those rates also were significantly affected by temperature, with highest feeding at 9.4°C. No significant CO2 effect was observed for catabolic energy processes (RR and ER); however, these rates did increase significantly with temperature. The O:N ratio was not significantly affected by CO2, but was significantly affected by temperature. There was a significant interaction between CO2 and temperature for ER and the O:N ratio, with low CO2 levels resulting in a U-shaped response that was not sustained as CO2 levels increased. This suggests that the independent effects of CO2 and temperature observed at low levels are different once a CO2 threshold is reached. Additionally, there were significant differences in growth estimators (shell height and DSW), with the best growth occurring at the lowest CO2 level. In contrast to temperature variations that induced a trade-off response in energy acquisition and expenditure, results from this research support the hypothesis that sea scallops have a limited ability to alter physiological processes to compensate for increasing CO2.

Continue reading ‘Juvenile Atlantic sea scallop, Placopecten magellanicus, energetic response to increased carbon dioxide and temperature changes’

The involvement of a novel calmodulin-like protein isoform from oyster Crassostrea gigas in transcription factor regulation provides new insight into acclimation to ocean acidification

Marine organisms need to adapt to improve organismal fitness under ocean acidification (OA). Recent studies have shown that marine calcifiers can achieve acclimation by stimulating calcium binding/signaling pathways. Here, a CaM-like gene (CgCaLP-2) from oyster Crassostrea gigas which typically responded to long-term CO2 exposure (two months) rather than short-term exposure (one week) was characterized. The cloned cDNA was 678 bp and was shorter than the retrieved sequence from NCBI (1125 bp). The two sequences, designated as CgCaLP-2-v1 and CgCaLP-2-v2, were demonstrated to be different splice variants by the genome sequence analysis. Western blotting analysis revealed two bands of 23 kD and 43 kD in mantle and hemocytes, corresponding to predicted molecular weight of CgCaLP-2-v1 and CgCaLP-2-v2, respectively. The isoform CgCaLP-2-v1 (the 23 kD band) was highly stimulated in response to long-term CO2 exposure (42-day and 56-day treatment) in hemocytes and mantle tissue. The fluorescence signal of CgCaLP-2 in mantle and hemocytes became more intensive after long-term CO2 exposure. Besides, in hemocytes, CgCaLP-2 presented a higher localization on the nuclear membrane after long-term CO2 exposure (56 d). The target gene network of CgCaLP-2 was predicted, and a transcription factor (TF) gene annotated as Homeobox protein SIX4 (CgSIX4) showed a similar expressive trend to CgCaLP-2 during CO2 exposure. Suppression of CgCaLP-2 via RNA interference significantly reduced the mRNA expression of CgSIX4. The results suggested that CgCaLP-2 might mediate the Ca2+-CaLP-TF signal transduction pathway under long-term CO2 exposure. This study serves as an example to reveal that alternative splicing is an important mechanism for generation multiple protein isoforms and thus shape the plastic responses under CO2 exposure, providing new insight into the potential acclimation ability of marine calcifiers to future OA.

Continue reading ‘The involvement of a novel calmodulin-like protein isoform from oyster Crassostrea gigas in transcription factor regulation provides new insight into acclimation to ocean acidification’

A novel approach effect of ocean acidification on oysters

We are pacing to a GHG free world to live in. Due to the escalated levels of carbon dioxide in the atmosphere, several living organisms are being affected. This is more intense for life under water. Carbon dioxide in the atmosphere gets dissolved in the ocean, leading to OCEAN ACIDIFICATION, reducing the pH of the ocean. This in return affects the ocean habitat. It makes calcium carbonate ions less available, which is a major building block for different species to build shells and skeletons. Due to the reduction of calcium carbonate ions in the ocean, the shells tend to dissolve. Oysters act as natural filters for the ocean, buffers for tides and their reefs serve as barriers to storms and tides, preventing erosion. Climate change and Ocean acidification has contributed to reduction of the species. This study aims to find out the optimum carbon dioxide, oysters’ metabolism to varying levels of carbon dioxide and alleviating the excess dissolved carbon dioxide.

Continue reading ‘A novel approach effect of ocean acidification on oysters’

Contrasting behavioural responses to ocean acidification and warming have the potential to disrupt herbivory


  • Global climate change has the potential to disrupt herbivore behaviours.
  • Current studies emphasise certain locations, life stage, phyla, and behaviours.
  • Behavioural experiments on invertebrate herbivores focus on grazing and movement.
  • Where there were effects, typically grazing increased while movement decreased.
  • Isolated effects of warming and acidification were often restricted when combined.


Global change has the potential to affect organisms and re-structure ecosystems where key species interactions, such as herbivory, are disrupted. The fastest ways individual herbivores – and therefore ecosystems – can respond to climate change is through shifts in behaviour. In marine habitats, environmental changes of particular concern in the future are ocean acidification and warming. Consequently, we reviewed the existing literature in this area of research, to identify if there were any over-arching trends or emerging patterns in behavioural responses of marine herbivores to ocean acidification and warming. We identified that while the body of research is growing, focus remains primarily on few locations (temperate areas), phyla (Mollusca, especially gastropods; Crustacea; Echinodermata), and behaviours (grazing rate, movement). Although representing a relatively narrow view of future herbivory, this review indicates that in many cases, the key behaviours of feeding and movement could be maintained under ocean acidification and warming. However, where change is observed, it is more likely grazing will be enhanced and movement impaired. If such patterns were to manifest under future climates, it would mean that the herbivores present would consume more yet there may be less of them as impaired movement and escape behaviours would have made them more vulnerable to predation. The exact responses will, however, likely be context-dependant. Therefore, we recommend future studies address the research gaps our review identified (i.e., a lack of understanding in tropical and polar regions, economically and ecologically important Crustacean and Echinoderm species, early life history stages, and more behavioural responses in addition to feeding and movement). Understanding the diversity of responses expected under varied contexts will be important to uncover trends in how marine invertebrates will behave under global change.

Continue reading ‘Contrasting behavioural responses to ocean acidification and warming have the potential to disrupt herbivory’

Differential effects of ocean acidification and warming on biological functioning of a predator and prey species may alter future trophic interactions


  • Multiple environmental stressors act upon multiple trophic levels.
  • Mollusc predator and prey respond differently to future climate scenarios.
  • Prey are negatively impacted physiologically and behaviourally.
  • Predators unaffected resulting in elevated predation risk for prey.
  • Potential for fundamental change in trophic interactions affecting biodiversity.


Independently, ocean warming (OW) and acidification (OA) from increased anthropogenic atmospheric carbon dioxide are argued to be two of the greatest threats to marine organisms. Increasingly, their interaction (ocean acidification and warming, OAW) is shown to have wide-ranging consequences to biological functioning, population and community structure, species interactions and ecosystem service provision. Here, using a multi-trophic experiment, we tested the effects of future OAW scenarios on two widespread intertidal species, the blue mussel Mytilus edulis and its predator Nucella lapillus. Results indicate negative consequences of OAW on the growth, feeding and metabolic rate of M. edulis and heightened predation risk. In contrast, Nucella growth and metabolism was unaffected and feeding increased under OAW but declined under OW suggesting OA may offset warming consequences. Should this differential response between the two species to OAW, and specifically greater physiological costs to the prey than its predator come to fruition in the nature, fundamental change in ecosystem structure and functioning could be expected as trophic interactions become disrupted.

Continue reading ‘Differential effects of ocean acidification and warming on biological functioning of a predator and prey species may alter future trophic interactions’

Sensitivity of the grooved carpet shell clam, Ruditapes decussatus (Linnaeus, 1758), to ocean acidification

This research investigated the possible impacts of ocean acidification on the grooved carpet shell clam Ruditapes decussatus as a model for commercially crucial marine bivalve species. Clams were collected from Lake Timsah on the Suez Canal coast, Ismailia, Egypt. They were then incubated in CO2-enriched seawater manipulated at four different CO2 concentrations: 420 ppm (ambient control) and 550, 750, and 1050 ppm. Calcification analysis was carried out using XRD and scanning electron microscope (SEM), highlighting a trend towards noticeable physical sensitivity to acidification. The antioxidant enzymatic activities [catalase (CAT)] were significantly different among different pCO2 (~ 20–23 µmol min−1 mg prot−1). Lipid peroxidation [malondialdehyde (MDA)] also showed a significant difference among treatments (0.21–0.23 nmol TBARS mg prot−1). Shell microstructure analysis showed periostracum distortion in the clam shell as pCO2 concentration increased at 1050 ppm. These results indicate that ocean acidification may exert an additional stress on bivalves through weakening their calcified shell making them more vulnerable to predators and affect their health and survival reducing production and economic value.

Continue reading ‘Sensitivity of the grooved carpet shell clam, Ruditapes decussatus (Linnaeus, 1758), to ocean acidification’

Effects of semidiurnal water column acidification and sediment presence on growth and survival of the bivalve Mya arenaria

In coastal environments, water column pH is affected by a variety of factors that result in lower and more variable pH in comparison to the open ocean. Consequently, it is critical to integrate variability in pH into laboratory experiments to better predict the response of coastal organisms to ocean acidification. For infaunal organisms, sediment can provide refuge from the water column conditions especially in coastal environments. As such, understanding how both water column conditions and the potential buffering abilities of sediment interact can provide insight into how infaunal organisms may respond to future oceanic conditions. Effects of pH variability on juvenile soft-shell clams (Mya arenaria; 2–11 mm in shell length), an ecologically and economically important species in the Bay of Fundy, Canada, were examined in a laboratory experiment. We manipulated pH through the addition of CO2 to seawater and exposed M. arenaria to three water treatments, no CO2 addition (mean ± sd; pH = 7.95 ± 0.06), semidiurnal intermittent CO2 addition (“on” pH =7.70 ± 0.13, “off” pH = 7.90 ± 0.11), and constant CO2 addition (pH = 7.73 ± 0.13). We found that M. arenaria final shell length, three mass metrics, and survival were negatively impacted by the constant CO2 addition treatment. Growth of juvenile M. arenaria only occurred in the presence of sediment, indicating the importance of sediment to M. arenaria, although sediment did not buffer the effects of constant CO2 addition. In the presence of sediment, the semidiurnal intermittent CO2 addition treatment did not negatively impact the growth of M. arenaria, indicating that it provided the clams with a recovery period. The similar growth rates of juvenile M. arenaria burrowed in sediment in the intermittent CO2 addition and control treatments suggests that M. arenaria may not be as negatively affected by future oceanic conditions as anticipated. This study demonstrated that pH variability can alter the response of benthic invertebrates to CO2 addition and thus this type of approach should be used to study other species of invertebrates.

Continue reading ‘Effects of semidiurnal water column acidification and sediment presence on growth and survival of the bivalve Mya arenaria’

RNAi silencing of the biomineralization gene perlucin impairs oyster ability to cope with ocean acidification

Calcifying marine organisms, including the eastern oyster (Crassostrea virginica), are vulnerable to ocean acidification (OA) because it is more difficult to precipitate calcium carbonate (CaCO3). Previous investigations of the molecular mechanisms associated with resilience to OA in C. virginica demonstrated significant differences in single nucleotide polymorphism and gene expression profiles among oysters reared under ambient and OA conditions. Converged evidence generated by both of these approaches highlighted the role of genes related to biomineralization, including perlucins. Here, gene silencing via RNA interference (RNAi) was used to evaluate the protective role of a perlucin gene under OA stress. Larvae were exposed to short dicer-substrate small interfering RNA (DsiRNA-perlucin) to silence the target gene or to one of two control treatments (control DsiRNA or seawater) before cultivation under OA (pH ~7.3) or ambient (pH ~8.2) conditions. Two transfection experiments were performed in parallel, one during fertilization and one during early larval development (6 h post-fertilization), before larval viability, size, development, and shell mineralization were monitored. Silenced oysters under acidification stress were the smallest, had shell abnormalities, and had significantly reduced shell mineralization, thereby suggesting that perlucin significantly helps larvae mitigate the effects of OA.

Continue reading ‘RNAi silencing of the biomineralization gene perlucin impairs oyster ability to cope with ocean acidification’

  • Reset


OA-ICC Highlights

%d bloggers like this: