Posts Tagged 'laboratory'



Seasonal calcification of the coral Acropora digitifera from a subtropical marginal Okinawa reef under ocean acidification

Coral calcification is affected by the decrease in aragonite saturation state (Ωarag) caused by ocean acidification (OA). However, OA effects are modulated by other environmental factors such as seawater temperature, light intensity and nutrients. Considering that in subtropical coral reefs all these factors vary seasonally, it can be hypothesized that the magnitude of OA effects on coral physiology will also vary seasonally. We evaluated the seasonal coral calcification rate of a subtropical reef-building coral under OA conditions. We approached this aim by culturing Acropora digitifera under three different CO2 partial pressure (pCO2) conditions in three different seasons (summer, autumn and winter) under natural light and temperature conditions. Additionally, to predict future coral net G, the year-round seawater carbonate chemistry was measured on the coast of Okinawa Island, and the annual coral CaCO3production amount assessed considering seasonal changes in environmental conditions. Coral A. digitifera net calcification (net G) significantly differed among seasons, and summer net Gwas 1.7 and 2.7 times higher than autumn and winter, respectively. However, the impact of OA did not differ among seasons and the rate of net G decrease per unit Ωarag was 11.1%, 17.4% and 18.7% for summer, autumn and winter, respectively. The regression model indicated that net Gof A. digitifera is primarily affected by temperature, secondly by seawater Ωarag, while light intensity was not selected as an explanatory factor, and there was no interactive effect among the factors. The model predicts that the present annual A. digitifera net G in Okinawa Island reef (present mean annual pCO2: 382 μatm and Ωarag: 3.49) is about 0.3 g CaCO3 cm−2 y−1, and it will decrease by 20% with an increase of 500 μatm seawater pCO2 than the present condition. As reefs in high-latitude regions already have marginal positive net G, further decrease in annual CaCO3 production would be detrimental for the reef under conditions of climate change.

Continue reading ‘Seasonal calcification of the coral Acropora digitifera from a subtropical marginal Okinawa reef under ocean acidification’

Reduced nitrogenase efficiency dominates response of the globally important nitrogen fixer Trichodesmium to ocean acidification

The response of the prominent marine dinitrogen (N2)-fixing cyanobacteria Trichodesmium to ocean acidification (OA) is critical to understanding future oceanic biogeochemical cycles. Recent studies have reported conflicting findings on the effect of OA on growth and N2fixation of Trichodesmium. Here, we quantitatively analyzed experimental data on how Trichodesmium reallocated intracellular iron and energy among key cellular processes in response to OA, and integrated the findings to construct an optimality-based cellular model. The model results indicate that Trichodesmium growth rate decreases under OA primarily due to reduced nitrogenase efficiency. The downregulation of the carbon dioxide (CO2)-concentrating mechanism under OA has little impact on Trichodesmium, and the energy demand of anti-stress responses to OA has a moderate negative effect. We predict that if anthropogenic CO2 emissions continue to rise, OA could reduce global N2 fixation potential of Trichodesmium by 27% in this century, with the largest decrease in iron-limiting regions.

Continue reading ‘Reduced nitrogenase efficiency dominates response of the globally important nitrogen fixer Trichodesmium to ocean acidification’

Living in future ocean acidification, physiological adaptive responses of the immune systems of sea urchins resident at a CO2 vent system

Highlights

• Paracentrotus lividus living at CO2 vents was compared to those at two control sites.
• Sea urchins are adapted to life at vent site by altering immune cells metabolism.
• Vent animals show a rearrangement of defensive abilities and antioxidant processes.

Abstract

The effects of ocean acidification, a major anthropogenic impact on marine life, have been mainly investigated in laboratory/mesocosm experiments. We used the CO2 vents at Ischia as a natural laboratory to study the long-term effects of ocean acidification on the sea urchin Paracentrotus lividus population resident in low-pH (7.8 ± 0.2) compared to that at two control sites (pH 8.02 ± 0.00; 8.02 ± 0.01). The novelty of the present study is the analysis of the sea urchin immune cells, the sentinels of environmental stress responses, by a wide-ranging approach, including cell morphology, biochemistry and proteomics. Immune cell proteomics showed that 311 proteins were differentially expressed in urchins across sites with a general shift towards antioxidant processes in the vent urchins. The vent urchin immune cells showed higher levels of total antioxidant capacity, up-regulation of phagosome and microsomal proteins, enzymes of ammonium metabolism, amino-acid degradation, and modulation of carbon metabolism proteins. Lipid-hydroperoxides and nitric oxide levels were not different in urchins from the different sites. No differences in the coelomic fluid pH, immune cell composition, animal respiration, nitrogen excretion and skeletal mineralogy were observed. Our results reveal the phenotypic plasticity of the immune system of sea urchins adapted to life at vent site, under conditions commensurate with near-future ocean acidification projections.

Continue reading ‘Living in future ocean acidification, physiological adaptive responses of the immune systems of sea urchins resident at a CO2 vent system’

Thicker shells compensate extensive dissolution in brachiopods under future ocean acidification

Organisms with long generation times require phenotypic plasticity to survive in changing environments until genetic adaptation can be achieved. Marine calcifiers are particularly vulnerable to ocean acidification due to dissolution and a reduction in shell-building carbonate ions. Long-term experiments assess organisms’ abilities to acclimatise or even adapt to environmental change. Here we present an unexpected compensatory response to extensive shell dissolution in a highly calcium-carbonate-dependent organism after long-term culture in predicted end-century acidification and warming conditions. Substantial shell dissolution with decreasing pH posed a threat to both a polar (Liothyrella uva) and a temperate (Calloria inconspicua) brachiopod after 7 months and 3 months exposure, respectively, with more extensive dissolution in the polar species. This impact was reflected in decreased outer primary layer thickness in the polar brachiopod. A compensatory response of increasing inner secondary layer thickness, and thereby producing a thicker shell was exhibited by the polar species. Less extensive dissolution in the temperate brachiopod did not affect shell thickness. Increased temperature did not impact shell dissolution or thickness. Brachiopod ability to produce a thicker shell when extensive shell dissolution occurs suggests this marine calcifier has great plasticity in calcification providing insights into how similar species might cope under future environmental change.

Continue reading ‘Thicker shells compensate extensive dissolution in brachiopods under future ocean acidification’

Characterization, functional analysis, and expression levels of three carbonic anhydrases in response to pH and saline–alkaline stresses in the ridgetail white prawn Exopalaemon carinicauda

Carbonate alkalinity, salinity, and pH are three important stress factors for aquatic animals in saline–alkaline water. Carbonic anhydrases (CAs) catalyze the reversible reaction of CO2 reported to play an important role in the acid–base regulation in vertebrates. To explore the molecular mechanism of CAs efficacy in shrimp after their transfer into saline–alkaline water, the cDNAs of three CAs (EcCAc, EcCAg, and EcCAb) were cloned from Exopalaemon carinicauda. Sequence analysis showed that EcCAc and EcCAg both possessed a conserved α-CA domain and a proton acceptor site, and EcCAb contained a Pro-CA domain. Tissue expression analysis demonstrated that EcCAc and EcCAg were most abundantly in gills, and EcCAb was highly expressed in muscle. The cumulative mortalities remained below 25% under exposure to pH (pH 6 and pH 9), low salinity (5 ppt), or high carbonate alkalinity (5 and 10 mmol/L) after 72 h of exposure. However, mortalities increased up to 70% under extreme saline–alkaline stress (salinity 5 ppt, carbonate alkalinity 10 mmol/L, and pH 9) after 14 days of exposure. The EcCAc and EcCAg expressions in gills were significantly upregulated during the early period of pH and saline–alkaline stresses, while the EcCAb expressions showed no regular or large changes. The two-way ANOVA found significant interactions between salinity and carbonate alkalinity observed in EcCAc, EcCAg, and EcCAb expressions (p < 0.05). Furthermore, an RNA interference experiment resulted in increased mortality of EcCAc- and EcCAg-silenced prawns under saline–alkaline stress. EcCAc knockdown reduced expressions of Na+/H+ exchanger (EcNHE) and sodium bicarbonate cotransporter (EcNBC), and EcCAg knockdown reduced EcCAc, EcNHE, EcNBC, and V-type H+-ATPase (EcVTP) expressions. These results suggest EcCAc and EcCAg as important modulators in response to pH and saline–alkaline stresses in E. carinicauda.

Continue reading ‘Characterization, functional analysis, and expression levels of three carbonic anhydrases in response to pH and saline–alkaline stresses in the ridgetail white prawn Exopalaemon carinicauda’

Knockdown of carbonate anhydrase elevates Nannochloropsis productivity at high CO2 level

Highlights

• In the industrial oleaginous microalga Nannochloropsis oceanica, a cytosolic carbonic anhydrase (CA2) was identified as a key Carbon Concentrating Mechanism (CCM) component induced in response to lowered CO2 level.

• Knockdown of CA2 resulted in ~40% elevation of biomass accumulation rate under 5% CO2 (versus the wild type), which is reproducible across photobioreactor types and cultivation scales.

• The higher pH tolerance of CA2-knockdown mutant is underpinned by reduced biophysical CCM, sustained pH hemostasis, stimulated energy intake and enhanced photosynthesis.

• “Inactivation of CCM” is an effective strategy to generate hyper-CO2-assimilating and autonomously containable industrial microalgae for flue gas-based oil production.

Abstract

Improving acid tolerance is pivotal to the development of microalgal feedstock for converting flue gas to biomass or oils. In the industrial oleaginous microalga Nannochloropsis oceanica, transcript knockdown of a cytosolic carbonic anhydrase (CA2), which is a key Carbon Concentrating Mechanism (CCM) component induced under 100 ppm CO2 (very low carbon, or VLC), results in ∼45%, ∼30% and ∼40% elevation of photosynthetic oxygen evolution rate, growth rate and biomass accumulation rate respectively under 5% CO2 (high carbon, or HC), as compared to the wild type. Such high-CO2-level activated biomass over-production is reproducible across photobioreactor types and cultivation scales. Transcriptomic, proteomic and physiological changes of the mutant under high CO2 (HC; 5% CO2) suggest a mechanism where the higher pH tolerance is coupled to reduced biophysical CCM, sustained pH hemostasis, stimulated energy intake and enhanced photosynthesis. Thus “inactivation of CCM” can generate hyper-CO2-assimilating and autonomously containable industrial microalgae for flue gas-based oil production.

Continue reading ‘Knockdown of carbonate anhydrase elevates Nannochloropsis productivity at high CO2 level’

Role of temperature and carbonate system variability on a host-parasite system: implications for the gigantism hypothesis

Highlights

• Field and laboratory evidence support the parasite-induced gigantism hypothesis.

• Weight and thickness shell are influenced by the environmental factors and parasitism.

• Host-parasite interaction may be modulated by SST that interplay with carbonate system variability.

Abstract

Biological interactions and environmental constraints alter life-history traits, modifying organismal performances. Trematode parasites often impact their hosts by inducing parasitic castration, frequently correlated with increased body size in the host (i.e., gigantism hypothesis), which is postulated to reflect the re-allocation of energy released by the reduction in the reproductive process. In this study, we compared the effect of a trematode species on shell size and morphology in adult individuals of the intertidal mussels Perumytilus purpuratus (>20 mm) collected from two local populations of contrasting environmental regimes experienced in central-southern Chile. Our field data indicates that in both study locations, parasitized mussels evidenced higher body sizes (shell length, total weight and volume) as compared with non-parasitized. In addition, parasitized mussels from the southern location evidenced thinner shells than non-parasitized ones and those collected from central Chile, suggesting geographical variation in shell carbonate precipitation across intertidal habitats of the Chilean coast. In laboratory conditions, mussels collected from a local population in central Chile were exposed to two temperature treatments (12 and 18 °C). Parasitized mussels showed higher growth rates than non-parasitized, regardless of the seawater temperature treatments. However, the metabolic rate was not influenced by the parasite condition or the temperature treatments. Our field and laboratory results support the parasite-induced gigantism hypothesis, and suggest that both the thermal environment and geographic location explain only a portion of the increased body size, while the parasitic condition is the most plausible factor modulating the outcome of this host-parasite interaction.

Continue reading ‘Role of temperature and carbonate system variability on a host-parasite system: implications for the gigantism hypothesis’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,218,880 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book