Posts Tagged 'mollusks'

Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors

While early life-stage marine bivalves are vulnerable to ocean acidification, effects over successive generations are poorly characterized. The objective of this work was to assess the transgenerational effects of ocean acidification on two species of North Atlantic bivalve shellfish, Mercenaria mercenaria and Argopecten irradians. Adults of both species were subjected to high and low pCO2 conditions during gametogenesis. Resultant larvae were exposed to low and ambient pH conditions in addition to multiple, additional stressors including thermal stress, food-limitation, and exposure to a harmful alga. There were no indications of transgenerational acclimation to ocean acidification during experiments. Offspring of elevated pCO2-treatment adults were significantly more vulnerable to acidification as well as the additional stressors. Our results suggest that clams and scallops are unlikely to acclimate to ocean acidification over short time scales and that as coastal oceans continue to acidify, negative effects on these populations may become compounded and more severe.

Continue reading ‘Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors’

Latitudinal trends in shell production cost from the tropics to the poles

The proportion of body mass devoted to skeleton in marine invertebrates decreases along latitudinal gradients from large proportions in the tropics to small proportions in polar regions. A historical hypothesis—that latitudinal differences in shell production costs explain these trends—remains untested. Using field-collected specimens spanning a 79°N to 68°S latitudinal gradient (16,300 km), we conducted a taxonomically controlled evaluation of energetic costs of shell production as a proportion of the total energy budget in mollusks. Shell production cost was fairly low across latitudes at <10% of the energy budget and predominately <5% in gastropods and <4% in bivalves. Throughout life, shell cost tended to be lower in tropical species and increased slightly toward the poles. However, shell cost also varied with life stage, with the greatest costs found in young tropical gastropods. Low shell production costs on the energy budget suggest that shell cost may play only a small role in influencing proportional skeleton size gradients across latitudes relative to other ecological factors, such as predation in present-day oceans. However, any increase in the cost of calcium carbonate (CaCO3) deposition, including from ocean acidification, may lead to a projected ~50 to 70% increase in the proportion of the total energy budget required for shell production for a doubling of the CaCO3 deposition cost. Changes in energy budget allocation to shell cost would likely alter ecological trade-offs between calcification and other drivers, such as predation, in marine ecosystems.

Continue reading ‘Latitudinal trends in shell production cost from the tropics to the poles’

Dissolution of abiogenic and biogenic calcium carbonate under ocean acidification conditions

Under ocean acidification conditions, the chemistry of the seawater will change including a decrease in pH, a decrease in carbonate ion concentration and a decrease in the calcium carbonate saturation state of the water (Ω). This has implications for solid marine calcium carbonates including calcifying organisms and carbonate sediments. The dissolution kinetics of marine carbonates are poorly understood, therefore modelling of the future ocean under ocean acidification scenarios is hampered. The goal of this research was to provide an increased understanding of the kinetics of marine carbonate dissolution, including dependence of the dissolution rate of calcium carbonate mineral phases (calcite, calcite-aragonite, low Mg-calcite) on conditions relevant to ocean acidification, and then to apply this to biogenic samples (Pāua, kina and oyster). The effects of saturation state (Ω), surface area, and temperature were studied. Two methods were refined and used to collect and analyze the dissolution data – a pH-stat method and a pH free-drift method, with manipulation of the carbonate chemistry by addition of NaHCO3 and HCl. A LabVIEW® based program was developed for instrument control and automation and for data acquisition. The empirical equation R = k(1-Ω)n, was used to determine the reaction rates (R), the rate constants (k) and the reaction orders (n) for the each of the mineral phases and shellfish species.

Continue reading ‘Dissolution of abiogenic and biogenic calcium carbonate under ocean acidification conditions’

Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios

Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation however; the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats such as sand and mud flats, seagrass beds, exposed and protected shorelines, and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high/low oxygen and low/high CO2; varying pCO2 of 450 and 1300 ppm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allows us to evaluate respiration responses of species of contrasting habitats and life-history strategies to single and multiple stressors. Results show that the responses of the respiration were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will results in multiplicative effects and focus attention on alleviating hypoxia in the region.
Continue reading ‘Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios’

Metabolic response and thermal tolerance of green abalone juveniles (Haliotis fulgens: Gastropoda) under acute hypoxia and hypercapnia

Highlights

  • Assessment of the impacts of hypoxia and hypercapnia on thermal tolerance
  • Hypoxia induced a downshift in critical temperature.
  • Hypercapnia did not affect thermal tolerance.
  • Both drivers combined prompted a stronger narrowing of thermal tolerance.
  • Warming stress induced protein degradation under all experimental conditions.


Abstract

With ongoing climate change, rising ocean temperature is usually accompanied by falling oxygen levels (hypoxia) and increasing CO2 concentration (hypercapnia). Both drivers may impose constraints on physiological mechanisms that define thermal limits resulting in increased vulnerability towards warming in marine ectotherms. The present study aimed to detect differences in thermal tolerance by investigating the underlying metabolic responses in the green abalone (Haliotis fulgens) under conditions of hypoxia and hypercapnia. Juvenile abalones were exposed to a temperature ramp (+ 3 °C day− 1) under hypoxia (50% air saturation) and hypercapnia (~ 1000 μatm pCO2), both individually and in combination. Impacts on energy metabolism were assessed by analyzing whole animal respiration rates and metabolic profiles of gills and hepatopancreas via 1H NMR spectroscopy. While hypercapnia had a minor impact on the results of the temperature treatment, hypoxia strongly increased the vulnerability to warming, indicated by respiration rates falling below values expected from an exponential increase and by the onset of anaerobic metabolism suggesting a downward shift of the upper critical temperature. Warming under combined hypoxia and hypercapnia elicited a severe change in metabolism involving a strong accumulation of amino acids, osmolytes and anaerobic end products at intermediate temperatures, followed by declining concentrations at warmer temperatures. This matched the limited capacity to increase metabolic rate, loss of attachment and mortality observed under these conditions suggesting a strong narrowing of the thermal window. In all cases, the accumulation of free amino acids identified proteins as a significant energy source during warming stress.

Continue reading ‘Metabolic response and thermal tolerance of green abalone juveniles (Haliotis fulgens: Gastropoda) under acute hypoxia and hypercapnia’

Ocean acidification and pathogen exposure modulate the immune response of the edible mussel Mytilus chilensis

Highlights

  • Exposure to futuristic concentration of pCO2 modulates innate immune response.
  • After OA-stress, gene expression is partially counteracted after pathogen challenge.
  • pCO2 might trigger specific immune-related genes at early stages of infection.
  • Combination of OA and bacterial infection seems to have partial antagonistic effects.


Abstract

Ocean acidification (OA) is one of the main consequences of increasing atmospheric carbon dioxide (CO2), impacting key biological processes of marine organisms such as development, growth and immune response. However, there are scarce studies on the influence of OA on marine invertebrates’ ability to cope with pathogens. This study evaluated the single and combined effects of OA and bacterial infection on the transcription expression of genes related to antioxidant system, antimicrobial peptides and pattern recognition receptors in the edible mussel Mytilus chilensis. Individuals of M. chilensis were exposed during 60 days at two concentrations of pCO2 (550 and 1200 μatm) representing respectively current and future scenario of OA and were then injected with the pathogenic bacterium Vibrio anguillarum. Results evidenced an immunomodulation following the OA exposure with an up-regulation of C-type Lectin and Mytilin B and a down-regulation of Myticin A and PGRP. This immunomodulation pattern is partially counteracted after challenge with V. anguillarum with a down-regulation of the C-type lectin and Mytilin B and the up-regulation of Myticin A. In turn, these results evidence that pCO2-driven OA scenarios might triggers specific immune-related genes at early stages of infection, promoting the transcription of antimicrobial peptides and patterns recognition receptors. This study provides new evidence of how the immune response of bivalves is modulated by higher CO2 conditions in the ocean, as well one factor for the resilience of marine population upon global change scenarios.

Continue reading ‘Ocean acidification and pathogen exposure modulate the immune response of the edible mussel Mytilus chilensis’

Biochemical composition of turbinid snails and its sensitivity to ocean climate change

Information on the biochemical composition of under-utilised species, such as turban snails, is required to establish their nutritional quality, and improve consumer acceptance as a novel food source. Turbo militaris, Lunella undulata and L. torquata are large common gastropod species with overlapping distributions in eastern Australia. The edible foot tissue from these three species was analysed for comparison of their proximate composition, fatty acids and mineral elements. All species were found to have a high protein content and low lipid levels that are rich in polyunsaturated fatty acids (PUFAs), with a favourable ratio of omega–3/omega–6 PUFAs for human consumption. Turban snails also provide a good source of essential elements. To quantify the temporal changes in nutritional properties, L. undulata was collected monthly from the same site, Evans head, NSW from December 2013 to January 2015. Sex, shell sizes and gonadosomatic index (GSI) were recorded in order to investigate if these parameters influence the condition index (CI), meat yield (MY), proximate composition and trace elements of the edible foot tissue. The flesh of L. undulata can be considered nutritious and generally safe for human consumption all year round, but for the purpose of sustainable harvest, the peak spawning should be avoided to allow for successful reproduction. A manipulative experiment to investigate the effects of 38-day exposure to near-future ocean warming and acidification revealed that temperature alone affects the percentages of PUFAs in the foot tissue. Nevertheless, the main nutritional properties of high protein and low lipids dominated by PUFAs were consistently found in the Turbinidae. Toxic heavy metal elements remained well below the maximum allowed under Australia and New Zealand Food Standards. Based on their upper thermal limit, turban snails may be resilient to near-future ocean-warming, but they prefer lower temperatures, which could result in a southward retraction of the distribution of these species in NSW, Australia. Overall, this study shows that turban snails can provide a fisheries resource of similar quality to abalone, but ocean warming may influence the range of the target populations and the quality of lipids, but the product would be otherwise little-affected.

Continue reading ‘Biochemical composition of turbinid snails and its sensitivity to ocean climate change’


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Ocean acidification in the IPCC AR5 WG II

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