Archive for May, 2020



Irreversibility of marine climate change impacts under carbon dioxide removal

Artificial carbon dioxide removal (CDR) from the atmosphere has been proposed as a measure for mitigating climate change and restoring the climate system to a target state after exceedance (“overshoot”). This research investigates to what extent overshoot and subsequent recovery of a given cumulative CO2 emissions level by CDR leaves a legacy in the marine environment using an Earth system model. We use RCP2.6 and its extension to year 2300 as the reference scenario and design a set of cumulative emissions and temperature overshoot scenarios based on other RCPs. Our results suggest that the overshoot and subsequent return to a reference cumulative emissions level would leave substantial impacts on the marine environment. Although the changes in sea surface temperature, pH and dissolved oxygen are largely reversible, global mean values and spatial patterns of these variables differ significantly from those in the reference scenario when the reference cumulative emissions are attained.

Continue reading ‘Irreversibility of marine climate change impacts under carbon dioxide removal’

Pacific-wide pH snapshots reveal that high coral cover correlates with low, but variable pH

Ocean acidification (OA) is impairing the construction of coral reefs while simultaneously accelerating their breakdown. The metabolism of different reef organism assemblages alters seawater pH in different ways, possibly buffering or exacerbating OA impacts. In spite of this, field data relating benthic community structure and seawater pH are sparse. We collected pH time-series data snapshots at 10 m depth from 28 different reefs (n = 13 lagoon, n = 15 fore reef) across 22 Pacific islands, spanning 31° latitude and 90° longitude. Coincident with all deployments, we measured percent cover of the benthic community. On fore reefs, high coral cover (CC) negatively correlated with mean and minimum pH, but positively correlated with pH variability. Conversely, pH minima were positively correlated to coverage of coralline and turf algae. Benthic cover did not correlate with pH in lagoonal reefs. From 0%–100% CC, mean pH and aragonite saturation state (Ωarag ) declined −0.081 and −0.51, respectively, while declines in minimum values were greater (Δmin pH = −0.164, Δmin Ωarag = −0.96). Based upon previously published relationships, the mean pH decline from 0%–100% CC would depress coral calcification 7.7%–18.0% and increase biologically-mediated dissolution 13.5%–27.9%, with pH minima depressing dark coral calcification 14.4%–35.2% and increasing biologically-mediated dissolution 31.0%–62.2%. This spatially expansive dataset provides evidence that coral reefs with the highest coral cover may experience the lowest and most extreme pH values with OA.

Continue reading ‘Pacific-wide pH snapshots reveal that high coral cover correlates with low, but variable pH’

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’

External pH modulation during the growth of Vibrio tapetis , the etiological agent of Brown Ring Disease

Aims
Brown Ring Disease (BRD) is an infection of the Manila clam Ruditapes philippinarum due to the pathogen Vibrio tapetis . During BRD, clams are facing immunodepression and shell biomineralization alteration. In this paper, we studied the role of pH on the growth of the pathogen and formulated hypothesis on the establishment of BRD by V. tapetis .

Methods and Results
In this study, we monitored the evolution of pH during the growth of V. tapetis in a range of pH and temperatures. We also measured the pH of Manila clam hemolymph and extrapallial fluids during infection by V. tapetis . We highlighted that V. tapetis modulates the external pH during its growth, to a value of 7.70. During the development of BRD, V. tapetis also influences extrapallial fluids and hemolymph pH in vitro in the first hours of exposure and in vivo after 3 days of infection.

Conclusions
Our experiments have shown a close interaction between V. tapetis CECT4600, a pathogen of Manila clam that induces BRD, and the pH of different compartments of the animals during infection. These results indicate that that the bacterium, through a direct mechanism or as a consequence of physiological changes encountered in the animal during infection, is able to interfere with the pH of Manila clam fluids. This pH modification might promote the infection process or at least create an imbalance within the animal, that would favor its persistence. This last hypothesis should be tested in future experiment.

Significance and Impact of Study
This study is the first observation of pH modifications in the context of BRD and might orient future research on the fine mechanisms of pH modulation associated to BRD.

Continue reading ‘External pH modulation during the growth of Vibrio tapetis , the etiological agent of Brown Ring Disease’

Seasonal variability of the CO2 system in a large coastal plain estuary

The Chesapeake Bay, a large coastal plain estuary, has been studied extensively in terms of its water quality, and yet, comparatively less is known about its carbonate system. Here we present discrete observations of dissolved inorganic carbon (DIC) and total alkalinity from four seasonal cruises in 2016–2017. These new observations are used to characterize the regional CO2 system and to construct a DIC budget of the mainstem. In all seasons, elevated DIC concentrations were observed at the mouth of the bay associated with inflowing Atlantic Ocean waters, while minimum concentrations of DIC were associated with fresher waters at the head of the bay. Significant spatial variability of the partial pressure of CO2 was observed throughout the mainstem, with net uptake of atmospheric CO2 during each season in the upper mainstem and weak seasonal outgassing of CO2 near the outflow to the Atlantic Ocean. During the time frame of this study, the Chesapeake Bay mainstem was (1) net autotrophic in the mixed layer (net community production of 0.31‐mol C m−2 ·year−1 ) and net heterotrophic throughout the water column (net community production of −0.48‐mol C m−2 ·year−1), (2) a sink of 0.38‐mol C m−2 ·year−1 for atmospheric CO2, and (3) significantly seasonally and spatially variable with respect to biologically driven changes in DIC.

Continue reading ‘Seasonal variability of the CO2 system in a large coastal plain estuary’

Acidificación oceánica en organismos marinos (Audio in Spanish)

El cambio climático tiene muchísimas consecuencias a nivel mundial que alteran la dinámica de vida de la flora, la fauna, así como factores bióticos y abióticos. Una consecuencia de este fenómeno es la acidificación de los océanos. En esta edición de En la Academia, conversamos con la doctora Celeste Sánchez Noguera, quien abordará preguntas tales como ¿en qué organismos se enfoca esta investigación? o ¿cuáles son los más resistentes?, entre otras.

En la Academia se transmite los jueves a las 7:00 p.m. por la frecuencia 96.7 FM de Radio Universidad.

Invitada: Dra. Celeste Sánchez Noguera

Continue reading ‘Acidificación oceánica en organismos marinos (Audio in Spanish)’

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’

Graduate assistantship in eutrophication and coastal acidification

Graduate research assistantship is available to support a student pursuing M.S. or Ph. D. degree in the Department of Oceanography and Coastal Sciences, College of Coast and Environment, Louisiana State University, starting Fall 2020. LSU’s College of the Coast & Environment (CC&E) has been at the forefront of coastal and environmental issues for nearly a century. Interested candidates should have a B.S. or M.S. degree in environmental sciences, marine sciences, marine biology, geology, physical sciences or related fields.

The major focus of research for the selected student would be to work on a funded project to understand the impact of eutrophication and estuarine acidification on water quality and biology in coastal Louisiana.

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Ocean acidification, hypoxia and warming impair digestive parameters of marine mussels

Highlights

•Low pH, low DO and high temperature showed drastic effects on digestive enzyme activities.

•Low pH, low DO and high temperature synergistically reduced digestive enzyme activities.

•Lysozyme showed increased and then decreased activities with time.

•Combinations of low pH, low DO and high temperature showed more severe effects on digestive enzymes than single factors.

•Hypoxia and high temperature showed similar effects on digestive enzyme activities.

Abstract

Global change and anthropogenic activities have driven marine environment changes dramatically during the past century, and hypoxia, acidification and warming have received much attention recently. Yet, the interactive effects among these stressors on marine organisms are extremely complex and not accurately clarified. Here, we evaluated the combined effects of low dissolved oxygen (DO), low pH and warming on the digestive enzyme activities of the mussel Mytilus coruscus. In this experiment, mussels were exposed to eight treatments, including two degrees of pH (8.1, 7.7), DO (6, 2 mg/l) and temperature (30 °C and 20 °C) for 30 days. Amylase (AMS), lipase (LPS), trypsin (TRY), trehalase (TREH) and lysozyme (LZM) activities were measured in the digestive glands of mussels. All the tested stress conditions showed significant effects on the enzymatic activities. AMS, LPS, TRY, TREH showed throughout decreased trend in their activities due to low pH, low DO, increased temperature and different combinations of these three stressors with time but LZM showed increased and then decreased trend in their activities. Hypoxia and warming showed almost similar effects on the enzymatic activities. PCA showed a positive correlation among all measured biochemical parameters. Therefore, the fitness of mussel is likely impaired by such marine environmental changes and their population may be affected under the global change scenarios.

Continue reading ‘Ocean acidification, hypoxia and warming impair digestive parameters of marine mussels’

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’

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