Posts Tagged 'morphology'

Warming and acidification threaten glass sponge Aphrocallistes vastus pumping and reef formation

The glass sponge Aphrocallistes vastus contributes to the formation of large reefs unique to the Northeast Pacific Ocean. These habitats have tremendous filtration capacity that facilitates flow of carbon between trophic levels. Their sensitivity and resilience to climate change, and thus persistence in the Anthropocene, is unknown. Here we show that ocean acidification and warming, alone and in combination have significant adverse effects on pumping capacity, contribute to irreversible tissue withdrawal, and weaken skeletal strength and stiffness of A. vastus. Within one month sponges exposed to warming (including combined treatment) ceased pumping (50–60%) and exhibited tissue withdrawal (10–25%). Thermal and acidification stress significantly reduced skeletal stiffness, and warming weakened it, potentially curtailing reef formation. Environmental data suggests conditions causing irreversible damage are possible in the field at +0.5 °C above current conditions, indicating that ongoing climate change is a serious and immediate threat to A. vastus, reef dependent communities, and potentially other glass sponges.

Continue reading ‘Warming and acidification threaten glass sponge Aphrocallistes vastus pumping and reef formation’

In situ recovery of bivalve shell characteristics after temporary exposure to elevated pCO2

Ocean uptake of carbon dioxide (CO2) is causing changes in carbonate chemistry that affects calcification in marine organisms. In coastal areas, this CO2‐enriched seawater mixes with waters affected by seasonal degradation of organic material loaded externally from watersheds or produced as a response to nutrient enrichment. As a result, coastal bivalves often experience strong seasonal changes in carbonate chemistry. In some cases, these changes may resemble those experienced by aquacultured bivalves during translocation activities. We mimicked these changes by exposing juvenile hard clams (500 μm, Mercenaria mercenaria) to pCO2 in laboratory upwellers at levels resembling those already reported for northeastern U.S. estuaries (mean upweller pCO2 = 773, 1274, and 1838 μatm) and then transplanting to three grow‐out sites along an expected nutrient gradient in Narragansett Bay, Rhode Island (154 bags of 100 clams). Prior to the field grow‐out, clams exposed to elevated pCO2 exhibited larger shells but lower dry weight per unit volume (dw/V). However, percent increase in dw/V was highest for this group during the 27‐day field grow‐out, suggesting that individuals with low dw/V after the laboratory treatment accelerated accumulation of dw/V when they were transferred to the bay. Treatments also appeared to affect shell mineral structure and condition of digestive diverticula. Although treatment effects diminished during the field grow‐out, clams that were preexposed for several weeks to high pCO2 would likely have been temporarily vulnerable to predation or other factors that interact with shell integrity. This would be expected to reduce population recovery from short‐term exposures to high pCO2.

Continue reading ‘In situ recovery of bivalve shell characteristics after temporary exposure to elevated pCO2’

Ocean acidification inhibits initial shell formation of oyster larvae by suppressing the biosynthesis of serotonin and dopamine

Highlights

•5-HT and DA modulate shell formation in oyster larvae through TGF-β smad signaling pathway.

•5-HT and DA trigger the expression of tyrosinase and inhibit the expression of chitinase to form the initial shell.

•OA suppresses the biosynthesis of 5-HT and DA and the activation of TGF-β smad pathway.

•OA subverts the expression patterns of chitinase and tyrosinase and results in the failure of shell formation.

Abstract

Ocean acidification has severely affected the initial shell formation of marine bivalves during their larval stages. In the present study, it was found that dopamine (DA) content in early D-shape larvae was significantly higher than that in trochophore and D-shape larvae, while the serotonin (5-HT) content in early D-shape larvae and D-shape larvae was obviously higher than that in trochophore. Incubation of trochophore with 5-HT or DA could accelerate the formation of calcified shell, and the treatments with selective antagonists of receptors for 5-HT and DA (Cg5-HTR-1 and CgD1DR-1) obviously inhibited the formation of calcified shells. When oyster larvae were subjected to an experimental acidified treatment (pH 7.4), the biosynthesis of 5-HT and DA was inhibited, while the mRNA expression levels of the components in TGF-β pathway were significantly up-regulated in D-shape larvae. Moreover, the phosphorylation of TIR and the translocation of smad4 were hindered upon acidification treatments, and the expression patterns of chitinase and tyrosinase were completely reverted. These results collectively suggested that monoamine neurotransmitters 5-HT and DA could modulate the initial shell formation in oyster larvae through TGF-β smad pathway by regulating the expression of tyrosinase and chitinase to guarantee the chitin synthesis for shell formation. CO2-induced seawater acidification could suppress the biosynthesis of 5-HT and DA, as well as the activation of TGF-β smad pathway, which would subvert the expression patterns of chitinase and tyrosinase and cause the failure of initial shell formation in oyster early D-shape larvae.

Continue reading ‘Ocean acidification inhibits initial shell formation of oyster larvae by suppressing the biosynthesis of serotonin and dopamine’

Effect of ocean acidification and temperature on growth, survival, and shell performance of fluted giant clams (Tridacna squamosa)

This study aims to determine the effect of ocean acidification and temperature on growth, survival, and shell performance of fluted giant clam (Tridacna squamosa). Juvenile fluted giant clam put into an aquarium which is given a combination of CO2 pressure treatment (415, 1000 and 1800 ppm) and temperature (30, 32, and 34°C). Measuring the length, width and height of the shell perform in every two weeks for five times. CaCO3 content and shell strength was test at the end of the study. The best growth of shell length, shell width, and shell height in the treatment of CO2 concentrations of 415 ppm and temperatures of 30°C were 23.28 mm, 11.51 mm and 0.69 mm respectively. Survival live also obtained in the treatment of CO2 concentrations of 415 ppm and temperatures of 30°C and CO2 concentrations of 415 ppm and temperatures of 32°C each of 100%. The strength of the shell and CaCO3 content decreased in the treatment of CO2 concentration and high temperatures. Higher concentration of CO2 and increased temperature negatively affected the growth of length, width, survival of scales, reduced strength and the CaCO3 content of shell.

Continue reading ‘Effect of ocean acidification and temperature on growth, survival, and shell performance of fluted giant clams (Tridacna squamosa)’

Understanding patterns of bivalve vulnerability and resilience to ocean acidification: Insights from field studies, tank experiments and novel physiological studies

Anthropogenic greenhouse gas emissions, including carbon dioxide, are causing an unprecedented rate of global warming. Carbon dioxide emissions are additionally causing ocean acidification; a process that decreases the pH and carbonate saturation state of seawater. Ocean acidification is particularly stressful for marine calcifiers; organisms that build calcium carbonate shells or skeletons. Marine bivalves build calcium carbonate shells that they use as a support for their growing tissues, and as protection from predation. Bivalves are osmoconformers, and have limited mobility, meaning that they are particularly susceptible to the impacts of thermal stress. Bivalve fisheries generate billions of dollars to the US economy in annual revenue, therefore understanding their response to these two global change stressors is crucial for helping the communities that rely on these fisheries plan for global change. The following studies explore the response of commercially important bivalve species to ocean acidification and warming.

Continue reading ‘Understanding patterns of bivalve vulnerability and resilience to ocean acidification: Insights from field studies, tank experiments and novel physiological studies’

Novel reverse radioisotope labelling experiment reveals carbon assimilation of marine calcifiers under ocean acidification conditions

  1. Ocean acidification by anthropogenic carbon dioxide emissions is projected to depress metabolic and physiological activity in marine calcifiers. To evaluate the sensitivity of marine organisms against ocean acidification, the assimilation of nutrients into carbonate shells and soft tissues must be examined.
  2. We designed a novel experimental protocol, reverse radioisotope labelling, to trace partitioning of nutrients within a single bivalve species under ocean acidification conditions. Injecting CO2 gas, free from radiocarbon, can provide a large contrast between carbon dissolved in the water and the one assimilated from atmosphere. By culturing modern aquifer organisms in acidified seawater, we were able to determine differences in the relative contributions of the end members, dissolved inorganic carbon (DIC) in seawater and metabolic CO2, to shell carbonate and soft tissues.
  3. Under all pCO2 conditions (463, 653, 872, 1,137 and 1,337 μatm), radiocarbon (Δ14C) values of the bivalve Scapharca broughtonii shell were significantly correlated with seawater DIC values; therefore, shell carbonate was derived principally from seawater DIC. The Δ14C results together with stable carbon isotope (δ13C) data suggest that in S. broughtonii shell δ13C may reflect the kinetics of isotopic equilibration as well as end‐member contributions; thus, care must be taken when analysing end‐member contributions by a previous method using δ13C. The insensitivity of S. broughtonii to perturbations in pCO2 up to at least 1,337 µatm indicates that this species can withstand ocean acidification.
  4. Usage of radioisotope to dope for tracer experiments requires strict rules to conduct any operations. Yet, reverse radioisotope labelling proposing in this study has a large advantage and is a powerful tool to understanding physiology of aquifer organisms that can be applicable to various organisms and culture experiments, such as temperature, salinity and acidification experiments, to improve understanding of the proportions of nutrients taken in by marine organisms under changing environments.
Continue reading ‘Novel reverse radioisotope labelling experiment reveals carbon assimilation of marine calcifiers under ocean acidification conditions’

Metabolic recovery and compensatory shell growth of juvenile Pacific geoduck Panopea generosa following short-term exposure to acidified seawater

While acute stressors can be detrimental, environmental stress conditioning can improve performance. To test the hypothesis that physiological status is altered by stress conditioning, we subjected juvenile Pacific geoduck, Panopea generosa, to repeated exposures of elevated pCO2 in a commercial hatchery setting followed by a period in ambient common garden. Respiration rate and shell length were measured for juvenile geoduck periodically throughout short-term repeated reciprocal exposure periods in ambient (~550 μatm) or elevated (~2400 μatm) pCO2 treatments and in common, ambient conditions, 5 months after exposure. Short-term exposure periods comprised an initial 10-day exposure followed by 14 days in ambient before a secondary 6-day reciprocal exposure. The initial exposure to elevated pCO2 significantly reduced respiration rate by 25% relative to ambient conditions, but no effect on shell growth was detected. Following 14 days in common garden, ambient conditions, reciprocal exposure to elevated or ambient pCO2 did not alter juvenile respiration rates, indicating ability for metabolic recovery under subsequent conditions. Shell growth was negatively affected during the reciprocal treatment in both exposure histories; however, clams exposed to the initial elevated pCO2 showed compensatory growth with 5.8% greater shell length (on average between the two secondary exposures) after 5 months in ambient conditions. Additionally, clams exposed to the secondary elevated pCO2 showed 52.4% increase in respiration rate after 5 months in ambient conditions. Early exposure to low pH appears to trigger carryover effects suggesting bioenergetic re-allocation facilitates growth compensation. Life stage-specific exposures to stress can determine when it may be especially detrimental, or advantageous, to apply stress conditioning for commercial production of this long-lived burrowing clam.

Continue reading ‘Metabolic recovery and compensatory shell growth of juvenile Pacific geoduck Panopea generosa following short-term exposure to acidified seawater’


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Ocean acidification in the IPCC AR5 WG II

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