Long-term exposure to elevated pCO2 more than warming modifies early-life shell growth in a temperate gastropod

Co-occurring global change drivers, such as ocean warming and acidification, can have large impacts on the behaviour, physiology, and health of marine organisms. However, whilst early-life stages are thought to be most sensitive to these impacts, little is known about the individual level processes by which such impacts take place. Here, using mesocosm experiments simulating ocean warming (OW) and ocean acidification (OA) conditions expected for the NE Atlantic region by 2100 using a variety of treatments of elevated pCO2 and temperature. We investigated their impacts on bio-mineralization, microstructure, and ontogeny of Nucella lapillus (L.) juveniles, a common gastropod predator that exerts important top-down controls on biodiversity patterns in temperate rocky shores. The shell of juveniles hatched in mesocosms during a 14 month long experiment were analysed using micro-CT scanning, 3D geometric morphometrics, and scanning-electron microscopy. Elevated temperature and age determined shell density, length, width, thickness, elemental chemistry, shape, and shell surface damages. However, co-occurring elevated pCO2 modified the impacts of elevated temperature, in line with expected changes in carbonate chemistry driven by temperature. Young N. lapillus from acidified treatments had weaker shells and were therefore expected to be more vulnerable to predation and environmental pressures such as wave action. However, in some instances, the effects of both higher CO2 content and elevated temperature appeared to have reversed as the individuals aged. This study suggests that compensatory development may therefore occur, and that expected increases in juvenile mortality under OA and OW may be counteracted, to some degree, by high plasticity in shell formation in this species. This feature may prove advantageous for N. lapillus community dynamics in near-future conditions.

Continue reading ‘Long-term exposure to elevated pCO2 more than warming modifies early-life shell growth in a temperate gastropod’

Effects of elevated pCO2 on crab survival and exoskeleton composition depend on shell function and species distribution: a comparative analysis of carapace and claw mineralogy across four porcelain crab species from different habitats

Elevated concentration of carbon dioxide (elevated pCO2) that cause reduced pH is known to influence calcification in many marine taxa, but how elevated pCO2 influences cation composition of mineralized structures is less well studied. To a large extent, the degree to which elevated pCO2 impacts mineralized structures is influenced by physiological adaptation of organisms to environments where low pH is routinely experienced. Here, we test the hypotheses that elevated pCO2 will differently impact the relative concentrations of divalent cations (Ca2+, Mg2+, Sr2+, and Mn2+) in four closely related species of porcelain crabs distributed across intertidal zone gradients. Cation composition of carapace and claw exoskeleton was determined using inductively coupled plasma mass spectrometry following 24-day exposures to pH/pCO2 levels of 8.0/418 and 7.4/1850 µatm during the intermoult period. Reduced pH/elevated pCO2 caused a 13–24% decrease of carapace [Ca2+] across all species, and species-specific responses in carapace and claw [Mg2+], [Sr2+] and [Mn2+] were observed. During a 24-day exposure, reduced pH/elevated pCO2 reduced survival probability in low-intertidal but not mid-intertidal species. Overall, the effect of reduced pH/elevated pCO2 on exoskeleton mineral composition was muted in mid-intertidal species relative to low-intertidal species, indicating that extant adaptation to the variable intertidal zone may lessen the impact of ocean acidification (OA) on maintenance of mineralized structures. Differences in responses to reduced pH/elevated pCO2among closely related species adds complexity to predictive inferences regarding the effects of OA.

Continue reading ‘Effects of elevated pCO2 on crab survival and exoskeleton composition depend on shell function and species distribution: a comparative analysis of carapace and claw mineralogy across four porcelain crab species from different habitats’

Minor impacts of reduced pH on bacterial biofilms on settlement tiles along natural pH gradients at two CO2 seeps in Papua New Guinea

Bacterial biofilms provide cues for the settlement of marine invertebrates such as coral larvae, and are therefore important for the resilience and recovery of coral reefs. This study aimed to better understand how ocean acidification may affect the community composition and diversity of bacterial biofilms on surfaces under naturally reduced pH conditions. Settlement tiles were deployed at coral reefs in Papua New Guinea along pH gradients created by two CO2 seeps. Biofilms on upper and lower tiles surfaces were sampled 5 and 13 months after deployment. Automated Ribosomal Intergenic Spacer Analysis was used to characterize 240 separate bacterial communities, complemented by amplicon sequencing of the bacterial 16S rRNA gene of 16 samples. Bacterial biofilms consisted predominantly of Alpha-, Gamma-, and Delta-proteobacteria, as well as Cyanobacteria, Flavobacteriia, and Cytophagia, whereas taxa that induce settlement of invertebrate larvae only accounted for a small fraction of the community. Bacterial biofilm composition was heterogeneous, with on average only ∼25% of operational taxonomic units shared between samples. Among the observed environmental parameters, pH was only weakly related to community composition (R2 ∼ 1%), and was unrelated to community richness and evenness. In contrast, biofilms strongly differed between upper and lower tile surfaces (contrasting in light exposure and grazing intensity). There also appeared to be a strong interaction between bacterial biofilm composition and the macroscopic components of the tile community. Our results suggest that on mature settlement surfaces in situ, pH does not have a strong impact on the composition of bacterial biofilms. Other abiotic and biotic factors such as light exposure and interactions with other organisms may be more important in shaping bacterial biofilms on mature surfaces than changes in seawater pH.

Continue reading ‘Minor impacts of reduced pH on bacterial biofilms on settlement tiles along natural pH gradients at two CO2 seeps in Papua New Guinea’

Ocean acidification as a driver of community simplification via the collapse of higher-order and rise of lower-order consumers

Increasing oceanic uptake of CO2 is predicted to drive ecological change as both a resource (i.e. CO2 enrichment on primary producers) and stressor (i.e. lower pH on consumers). We use the natural ecological complexity of a CO2 vent (i.e. a seagrass system) to assess the potential validity of conceptual models developed from laboratory and mesocosm research. Our observations suggest that the stressor-effect of CO2enrichment combined with its resource-effect drives simplified food web structure of lower trophic diversity and shorter length. The transfer of CO2 enrichment from plants to herbivores through consumption (apparent resource-effect) was not compensated by predation, because carnivores failed to contain herbivore outbreaks. Instead, these higher-order consumers collapsed (apparent stressor-effect on carnivores) suggesting limited trophic propagation to predator populations. The dominance of primary producers and their lower-order consumers along with the loss of carnivores reflects the duality of intensifying ocean acidification acting both as resource-effect (i.e. bottom-up control) and stressor-effect (i.e. top-down control) to simplify community and trophic structure and function. This shifting balance between the propagation of resource enrichment and its consumption across trophic levels provides new insights into how the trophic dynamics might stabilize against or propagate future environmental change.

Continue reading ‘Ocean acidification as a driver of community simplification via the collapse of higher-order and rise of lower-order consumers’

Heritability of behavioural tolerance to high CO2 in a coral reef fish is masked by nonadaptive phenotypic plasticity

Previous studies have demonstrated limited potential for acclimation of adversely affected olfactory behaviours in reef fishes under elevated CO2, indicating that genetic adaptation will be required to maintain behavioural performance in the future. Adaptation depends on the presence of heritable phenotypic variation in the trait, which may differ between populations and environments. We used parent–offspring regressions to estimate the heritability (h2) of variation in behavioural tolerance to high CO2 (754 μatm) in both field-collected and laboratory-reared families of Acanthochromis polyacanthus. Tolerance to elevated CO2 was measured by determining the behavioural response of individuals to chemical alarm cues. Both populations exhibited high heritability of olfactory behaviour phenotype (father–mid-offspring h2 = 0.56 & 0.65, respectively) when offspring were acutely exposed to high CO2 for 4 days. However, there was no heritability in the behavioural phenotype when juveniles were chronically exposed to high CO2 for 6 weeks in the laboratory-reared families. Parental exposure to high CO2 during the breeding season did not alter this relationship between heritability and length of juvenile exposure to high CO2. These results demonstrate that variation in behavioural tolerance to high CO2 is heritable, but adaptive potential may be constrained by a loss of phenotypic variation when juveniles permanently experience a high-CO2 environment, as will occur with rising CO2levels in the ocean.

Continue reading ‘Heritability of behavioural tolerance to high CO2 in a coral reef fish is masked by nonadaptive phenotypic plasticity’

A perspective for reducing environmental impacts of mussel culture in Algeria

Purpose

In Algeria, the Ministry of Fisheries and Halieutic Resources has designed a strategic plan for the development of marine aquaculture for the years 2015–2025, which aims at expanding the annual production of Mediterranean mussel from less than 150 metric tonnes year−1 in 2013 to 7600 metric tonnes year−1 in 2025. We used Life Cycle Assessment (LCA) for evaluating the environmental impact of suspended mussel culture in Algeria and suggest management practices which could reduce it.

Methods

In order to estimate the current and perspective impact of this industry, we (1) applied LCA to one of the few farms currently operating in Algeria and (2) investigated two management scenarios for the farms to be established in the future in the same coastal area. The first scenario (Comp_S) represents the continuity with the current situation, in which each farm is competing with the other ones and is therefore managing the production cycle independently. In the second scenario (Coop_S), mussel farms are grouped in an aquaculture management area and shared the same facilities for post-processing harvested mussels before sending them to the market. The midpoint-based CML-IA method baseline 2000 V 3.01 was employed using SimaPro software. Furthermore, we carried out a Monte Carlo simulation, in order to assess the uncertainty in the results.

Results and discussion

The analysis focused on impact categories related to acidification and global warming potential. We took into account the energy consumptions (electricity and vessel fuel), the rearing infrastructure, including longlines, and a building for stabling, grading, and packing the mussel. Electricity contributes with 38.1 and 31.8 % respectively to global warming potential (GWP) and acidification, while fuel consumption contributes with 19.5 % to GWP and 31.8 % to acidification. Results of this work are compared with other LCA studies recently carried out in France (Aubin and Fontaine 2014) and in Spain (Iribarren et al. 2010c).

Conclusions

The LCA results show that important reductions in environmental impacts could be attained if the mussel farming activity would be operated according to the cooperative scenario here proposed. In this case, the environmental benefits will be a reduction of 3150 MJ and 156 kg CO2 eq per metric tonne of mussel produced, compared with the alternative scenario. The results of this study suggest that LCA should be applied to the seafood production sector in Algeria, in order to identify best management practices.

Continue reading ‘A perspective for reducing environmental impacts of mussel culture in Algeria’

The short-term effects of elevated CO2 and ammonium concentrations on physiological responses in Gracilariopsis lemaneiformis (Rhodophyta)

Ocean acidification (OA) and coastal eutrophication affect coastal marine organisms. We studied the physiological responses of Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta) to increased concentrations of CO2 and NH4 +. Incubation treatments were applied at two different pH units (low, 7.5; high (control), 7.9) and three different NH4 + concentrations (low, 10; medium, 50; high, 100 μM). Growth, rates of photosynthetic oxygen evolution, and NH4 + uptake rates were affected by both elevated CO2 and NH4 + conditions. The changes in the pH of culture media were influenced by elevated CO2 or NH4 +treatments. However, chlorophyll fluorescence was affected only by the level of NH4 +. These results indicate that the physiological responses of G. lemaneiformis might be enhanced when the concentrations of CO2and NH4 + rise. Therefore, cultures of this alga could provide a good mitigation solution against ongoing problems with OA and coastal eutrophication.

Continue reading ‘The short-term effects of elevated CO2 and ammonium concentrations on physiological responses in Gracilariopsis lemaneiformis (Rhodophyta)’


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Ocean acidification in the IPCC AR5 WG II

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