Ocean acidification modulates expression of genes and physiological performance of a marine diatom

Ocean Acidification (OA) is known to affect various aspects of physiological performances of diatoms, but little is known about the underlining molecular mechanisms involved. Here, we show that in the model diatom Phaeodactylum tricornutum, the expression of key genes associated with photosynthetic light harvesting as well as those encoding Rubisco, carbonic anhydrase, NADH dehydrogenase and nitrite reductase, are modulated by OA (1000 μatm, pHnbs 7.83). Growth and photosynthetic carbon fixation were enhanced by elevated CO2. OA treatment decreased the expression of β-carbonic anhydrase (β-ca), which functions in balancing intracellular carbonate chemistry and the CO2 concentrating mechanism (CCM). The expression of the genes encoding fucoxanthin chlorophyll a/c protein (lhcf type (fcp)), mitochondrial ATP synthase (mtATP), ribulose-1, 5-bisphosphate carboxylase/oxygenase large subunit gene (rbcl) and NADH dehydrogenase subunit 2 (ndh2), were down-regulated during the first four days (< 8 generations) after the cells were transferred from LC (cells grown under ambient air condition; 390 μatm; pHnbs 8.19) to OA conditions, with no significant difference between LC and HC treatments with the time elapsed. The expression of nitrite reductase (nir) was up-regulated by the OA treatment. Additionally, the genes for these proteins (NiR, FCP, mtATP synthase, β-CA) showed diel expression patterns. It appeared that the enhanced photosynthetic and growth rates under OA could be attributed to stimulated nitrogen assimilation, increased CO2 availability or saved energy from down-regulation of the CCM and consequently lowered cost of protein synthesis versus that of non-nitrogenous cell components.

Continue reading ‘Ocean acidification modulates expression of genes and physiological performance of a marine diatom’

Sensitivity of sea urchin fertilization to pH varies across a natural pH mosaic

In the coastal ocean, temporal fluctuations in pH vary dramatically across biogeographic ranges. How such spatial differences in pH variability regimes might shape ocean acidification resistance in marine species remains unknown. We assessed the pH sensitivity of the sea urchin Strongylocentrotus purpuratus in the context of ocean pH variability. Using unique male–female pairs, originating from three sites with similar mean pH but different variability and frequency of low pH (pHT ≤ 7.8) exposures, fertilization was tested across a range of pH (pHT 7.61–8.03) and sperm concentrations. High fertilization success was maintained at low pH via a slight right shift in the fertilization function across sperm concentration. This pH effect differed by site. Urchins from the site with the narrowest pH variability regime exhibited the greatest pH sensitivity. At this site, mechanistic fertilization dynamics models support a decrease in sperm–egg interaction rate with decreasing pH. The site differences in pH sensitivity build upon recent evidence of local pH adaptation in S. purpuratus and highlight the need to incorporate environmental variability in the study of global change biology.

Continue reading ‘Sensitivity of sea urchin fertilization to pH varies across a natural pH mosaic’

Marine gametes in a changing ocean: Impacts of climate change stressors on fecundity and the egg

In marine invertebrates, the environmental history of the mother can influence fecundity and egg size. Acclimation of females in climate change stressors, increased temperature and low pH, results in a decrease in egg number and size in many taxa, with the exception of cephalopods, where eggs increase in size. With respect to spawned eggs, near future levels of ocean acidification can interfere with the eggs’ block to polyspermy and intracellular pH. Reduction of the extracellular egg jelly coat seen in low pH conditions has implications for impaired egg function and fertilization. Some fast generation species (e.g. copepods, polychaetes) have shown restoration of female reproductive output after several generations in treatments. It will be important to determine if the changes to egg number and size induced by exposure to climate change stressors are heritable.

Continue reading ‘Marine gametes in a changing ocean: Impacts of climate change stressors on fecundity and the egg’

Inorganic carbon and water masses in the Irminger Sea since 1991

The subpolar gyre region in the North Atlantic is a major sink for anthropogenic carbon. While the storage rates show large interannual variability related to atmospheric forcing, less is known about variability in the natural Dissolved Inorganic Carbon (DIC) and the combined impact of variations in the two components on the total DIC inventories. Here, data from 15 cruises in the Irminger Sea covering 1991–2015 were used to determine changes in total DIC and its natural and anthropogenic components in relation to the distribution and evolution of the main water masses. The inventory of DIC increased by 1.43 ± 0.17 mol m−2 yr−1 over the period, mainly driven by the increase in anthropogenic carbon (1.84 ± 0.16 mol m−2 yr −1), but partially offset by a loss of natural DIC (−0.57 ± 0.22 mol m−2 yr−1). Changes in the carbon storage rate can be driven by concentration changes in the water column, for example due to ageing of water masses, or by changes in the distribution of water masses with different concentrations, either by local formation or advection. A decomposition of the trends into their main drivers showed that variations of natural DIC inventories are mainly driven by changes in the layer thickness of the main water masses, while anthropogenic carbon is most affected by concentration changes. The storage rates of anthropogenic carbon are sensitive to data selection, while changes in DIC inventory show a robust signal on short timescales, associated with the strength of convection.

Continue reading ‘Inorganic carbon and water masses in the Irminger Sea since 1991’

Scientists study ocean absorption of human carbon pollution

Knowing the rate at which the oceans absorb carbon pollution is a key to understanding how fast climate change will occur.

As humans burn fossil fuels and release greenhouse gases, those gases enter the atmosphere where they cause increases in global temperatures and climate consequences such as more frequent and severe heat waves, droughts, changes to rainfall patterns, and rising seas. But for many years scientists have known that not all of the carbon dioxide we emit ends up in the atmosphere. About 40% actually gets absorbed in the ocean waters.

I like to use an analogy from everyday experience: the ocean is a little like a soda. When we shake soda, it fizzes. That fizz is the carbon dioxide coming out of the liquid (that is why sodas are called “carbonated beverages”). We’re doing the reverse process in the climate. Our carbon dioxide is actually going into the oceans.

The process of absorption is not simple – the amount of carbon dioxide that the ocean can hold depends on the ocean temperatures. Colder waters can absorb more carbon; warmer waters can absorb less. So, a prevailing scientific view is that as the oceans warm, they will become less and less capable of taking up carbon dioxide. As a result, more of our carbon pollution will stay in the atmosphere, exacerbating global warming. But it’s clear that at least for now, the oceans are doing us a tremendous favor by absorbing large amounts of carbon pollution.

Continue reading ‘Scientists study ocean absorption of human carbon pollution’

America’s coastal communities need a strong EPA leader, not Pruitt

Taylor Shellfish in Shelton,, WA (B. Kinney, Ocean Conservancy)

Taylor Shellfish in Shelton,, WA (B. Kinney, Ocean Conservancy)

It’s really quite simple. As the ocean absorbs more carbon emissions from the atmosphere, our ocean becomes more acidic. And the impacts are far-reaching. Just ask the shellfish growers and coastal businesses in the Pacific Northwest and across our country.

Yet Scott Pruitt, the Trump administration nominee to lead the Environmental Protection Agency, avoids acknowledging the existence – much less the impacts – of ocean acidification even when asked directly by Senators as part of his confirmation hearings in Washington D.C.

American businesses already know and have experienced the harsh reality of ocean acidification. In 2007, oyster farms and hatcheries in the Pacific Northwest suffered massive losses when close to 75% of the oyster larvae perished. Without these larvae or “oyster seed,” shellfish farms up and down the west coast did not have oysters to grow and sell the following year. Millions of dollars were lost.

Continue reading ‘America’s coastal communities need a strong EPA leader, not Pruitt’

Intertidal pool fish Girella laevifrons (Kyphosidae) shown strong physiological homeostasis but shy personality: The cost of living in hypercapnic habitats

Tide pools habitats are naturally exposed to a high degree of environmental variability. The consequences of living in these extreme habitats are not well established. In particular, little it is known about of the effects of hypercanic seawater (i.e. high pCO2 levels) on marine vertebrates such as intertidal pool fish. The aim of this study was to evaluate the effects of increased pCO2 on the physiology and behavior in juveniles of the intertidal pool fish Girella laevifrons. Two nominal pCO2 concentrations (400 and 1600 μatm) were used. We found that exposure to hypercapnic conditions did not affect oxygen consumption and absorption efficiency. However, the lateralization and boldness behavior was significantly disrupted in high pCO2 conditions. In general, a predator-risk cost of boldness is assumed, thus the increased occurrence of shy personality in juvenile fishes may result in a change in the balance of this biological interaction, with significant ecological consequences.

Continue reading ‘Intertidal pool fish Girella laevifrons (Kyphosidae) shown strong physiological homeostasis but shy personality: The cost of living in hypercapnic habitats’


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Ocean acidification in the IPCC AR5 WG II

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