Archive for November, 2016



NOAA research links human-caused CO2 emissions to dissolving sea snail shells off U.S. West Coast

photo-mooring-and-fairweather-from-2013-oa-cruise-noaa-111416-4480x2138-landscapeNovember 22, 2016 For the first time, NOAA and partner scientists have connected the concentration of human-caused carbon dioxide in waters off the U.S. Pacific coast to the dissolving of shells of microscopic marine sea snails called pteropods.

Commercially valuable fish such as salmon, sablefish and rock sole make the pteropod a major part of their diet.

“This is the first time we’ve been able to tease out the percentage of human-caused carbon dioxide from natural carbon dioxide along a large portion of the West Coast and link it directly to pteropod shell dissolution,” said Richard Feely, a NOAA senior scientist who led the research appearing in Estuarine, Coastal and Shelf Science. “Our research shows that humans are increasing the acidification of U.S. West Coast coastal waters, making it more difficult for marine species to build strong shells.”

Continue reading ‘NOAA research links human-caused CO2 emissions to dissolving sea snail shells off U.S. West Coast’

Indirect effects of climate changes on cadmium bioavailability and biological effects in the Mediterranean mussel Mytilus galloprovincialis

Despite the great interest in the consequences of climate change on the physiological functioning of marine organisms, indirect and interactive effects of rising temperature and pCO2 on bioaccumulation and responsiveness to environmental pollutants are still poorly explored, particularly in terms of cellular mechanisms. According to future projections of temperature and pH/pCO2, this study investigated the main cellular pathways involved in metal detoxification and oxidative homeostasis in Mediterranean mussels, Mytilus galloprovincialis, exposed for 4 weeks to various combinations of two levels of pH/pCO2 (8.2/∼400 μatm and 7.4/∼3000 μatm), temperature (20 and 25 °C), and cadmium addition (0 and 20 μg/L). Bioaccumulation was increased in metal exposed organisms but it was not further modulated by different temperature and pH/pCO2 combinations. However, interactions between temperature, pH and cadmium had significant effects on induction of metallothioneins, responses of the antioxidant system and the onset of oxidative damages, which was tissue dependent. Multiple stressors increased metallothioneins concentrations in the digestive gland revealing different oxidative effects: while temperature and cadmium enhanced glutathione-dependent antioxidant protection and capability to neutralize peroxyl radicals, the metal increased the accumulation of lipid peroxidation products under acidified conditions. Gills did not reveal specific effects for different combinations of factors, but a general stress condition was observed in this tissue after various treatments. Significant variations of immune system were mainly caused by increased temperature and low pH, while co-exposure to acidification and cadmium enhanced metal genotoxicity and the onset of permanent DNA damage in haemocytes. Elaboration of the whole biomarker data in a cellular hazard index, corroborated the synergistic effects of temperature and acidification which increased the toxicological effects of cadmium. The overall results confirmed that climate change could influence ecotoxicological effects of environmental contaminants, highlighting the importance of a better knowledge of cellular mechanisms to understand and predict responsiveness of marine organisms to such multiple stressors.

Continue reading ‘Indirect effects of climate changes on cadmium bioavailability and biological effects in the Mediterranean mussel Mytilus galloprovincialis’

The interactive effects of acidification, temperature stress, and food supply on the growth and survival of the forage fish, Menidia beryllina and Cyprinodon variegatus

The combustion of fossil fuels is increasing atmospheric CO2 concentrations and, in turn, acidifying and warming world oceans. A further consequence of warming oceans may be declines in the abundance of plankton. Some of these changes can already be observed in coastal oceans and may affect marine biota including forage fish which play a key role in marine food webs as key consumers of primary production and prey of fishery species. While these climate change stressors have previously been shown to negatively affect the performance of larval fish, the interactive effects of these multiple stressors on fish have yet to be explored. This thesis presents a series of experiments that examined the effects of changing temperature, pCO2, and food levels on the growth and survival of early life (embryo and larval) stages of two species of forage fish indigenous to the Northwest Atlantic Ocean, Menidia beryllina and Cyprinodon variegatus. These two fish species are a useful comparison as they lay pelagic and demersal eggs, respectively, and have been previously shown to be vulnerable and resistant to ocean acidification, respectively. Temperature had the strongest effect on the hatching rate, hatching success, survival, and growth of both fish species with higher temperatures yielding more rapid hatching and higher and lower temperatures leading to reduced growth and survival. In contrast, pCO2 and food levels had no effects on hatching, but elevated pCO2 and reduced food supplies significantly reduced the survival of larval M. beryllina. There were synergistically negative effects of elevated temperature and elevated pCO2 as well as low food supply and elevated pCO2 on larval fish. For example, larvae that were resistant to high pCO2 experienced elevated mortality when high pCO2 was experienced outside their thermal optimum. In other cases, elevated pCO2 resulted in smaller larvae at high, but not optimal, temperatures. Furthermore, larvae that were fed ad libitum were resistant to high pCO2 but experienced elevated mortality when exposed to high pCO2 and given a restricted diet. Such interactions evidence the importance of simultaneously considering effects of multiple stressors on larval fish rather than their individual effects as these outcomes could not have been predicted by observing each stressor individually and these stressors co-occur in estuaries. Collectively, this thesis demonstrates that the effects of multiple climate change stressors may interact to synergistically suppress the productivity of fisheries shallow coastal ecosystems. It is anticipated these effects will intensify through this century due to the intensification of climate change.

Continue reading ‘The interactive effects of acidification, temperature stress, and food supply on the growth and survival of the forage fish, Menidia beryllina and Cyprinodon variegatus’

Impact of low pH/high pCO2 on the physiological response and fatty acid content in diatom Skeletonema pseudocostatum

pCO2/pH perturbation experiments were carried out under two different pCO2 levels to evaluate effects of CO2-driven ocean acidification on semi-continuous cultures of the marine diatom Skeletonema pseudocostatum CSA48. Under higher pCO2/lowered pH conditions, our results showed that CO2-driven acidification had no significant impact on growth rate, chlorophyll-a, cellular abundance, gross photosynthesis, dark respiration, particulate organic carbon and particulate organic nitrogen between CO2-treatments, suggesting that S. pseudocostatum is adapted to tolerate changes of ~0.5 units of pH under high pCO2 conditions. However, dissolved organic carbon (DOC) concentration and DOC/POC ratio were significantly higher at high pCO2, indicating that a greater partitioning of organic carbon into the DOC pool was stimulated by high CO2/low pH conditions. Total fatty acids (FAs) were significantly higher under low pCO2 conditions. The composition of FAs changed from low to high pCO2, with an increase in the concentration of saturated and a reduction of monounsaturated FAs. Polyunsaturated FAs did not show significant differences between pCO2 treatments. Our results lead to the conclusion that the balance between negative or null effect on S. pseudocostatum ecophysiology upon low pH/high pCO2 conditions constitute an important factor to be considered in order to evaluate the global effect of rising atmospheric CO2 on primary productivity in coastal ocean. We found a significant decrease in total FAs, however no indications were found for a detrimental effect of ocean acidification on the nutritional quality in terms of essential fatty acids.

Continue reading ‘Impact of low pH/high pCO2 on the physiological response and fatty acid content in diatom Skeletonema pseudocostatum’

Increasing acidity dissolving ocean snails

The Pacific Ocean’s increasing acidity is dissolving the shells of tiny sea snails that are a vital food source for fish such as salmon and sole, according to new research by the National Oceanic and Atmospheric Administration.

The ocean’s changing chemistry is the result of carbon dioxide emissions from industry and agriculture. Increasing acidity means a reduction in carbonate ions, which the snails — known as pteropods — need to grow their shells.

“This is the first time we’ve been able to tease out the percentage of human-caused carbon dioxide from natural carbon dioxide along a large portion of the West Coast and link it directly to pteropod shell dissolution,” Richard Feely, a NOAA senior scientist, said in a statement.

Ocean acidification has been dubbed the “evil twin” of global warming because the same carbon dioxide emissions that cause climate change also dissolve into seawater, threatening the world’s oceans.

Continue reading ‘Increasing acidity dissolving ocean snails’

Molecular and physiological evidence of genetic assimilation to high CO2 in the marine nitrogen fixer Trichodesmium

Most investigations of biogeochemically important microbes have focused on plastic (short-term) phenotypic responses in the absence of genetic change, whereas few have investigated adaptive (long-term) responses. However, no studies to date have investigated the molecular progression underlying the transition from plasticity to adaptation under elevated CO2 for a marine nitrogen-fixer. To address this gap, we cultured the globally important cyanobacterium Trichodesmium at both low and high CO2 for 4.5 y, followed by reciprocal transplantation experiments to test for adaptation. Intriguingly, fitness actually increased in all high-CO2 adapted cell lines in the ancestral environment upon reciprocal transplantation. By leveraging coordinated phenotypic and transcriptomic profiles, we identified expression changes and pathway enrichments that rapidly responded to elevated CO2 and were maintained upon adaptation, providing strong evidence for genetic assimilation. These candidate genes and pathways included those involved in photosystems, transcriptional regulation, cell signaling, carbon/nitrogen storage, and energy metabolism. Conversely, significant changes in specific sigma factor expression were only observed upon adaptation. These data reveal genetic assimilation as a potentially adaptive response of Trichodesmium and importantly elucidate underlying metabolic pathways paralleling the fixation of the plastic phenotype upon adaptation, thereby contributing to the few available data demonstrating genetic assimilation in microbial photoautotrophs. These molecular insights are thus critical for identifying pathways under selection as drivers in plasticity and adaptation.

Continue reading ‘Molecular and physiological evidence of genetic assimilation to high CO2 in the marine nitrogen fixer Trichodesmium’

Scientists link humans to ocean acidification, sea snail shells ‘dissolving’

Elevated carbon dioxide levels in the Pacific Ocean are connected to human activity, according to a study from the federal government, and that acidification is causing the shells of a key microscopic sea snail to dissolve, a phenomenon that could affect other species in the ecosystem.

Research from the National Oceanic and Atmospheric Administration released Tuesday linked elevated human-caused carbon dioxide levels along the waters off the West Coast to “shell dissolution” among the microscopic sea snail known as pteropods.

The NOAA-backed study builds on past research that found when sea snail shells are damaged, it could affect their ability to swim and evade predators. The pteropod, roughly the size of the head of a pin, is an important research subject because its shell is particularly susceptible to ocean acidification, which could have widespread implications for marine life.

Continue reading ‘Scientists link humans to ocean acidification, sea snail shells ‘dissolving’’

Chemical and biological impacts of ocean acidification along the west coast of North America

The continental shelf region off the west coast of North America is seasonally exposed to water with a low aragonite saturation state by coastal upwelling of CO2-rich waters. To date, the spatial and temporal distribution of anthropogenic CO2 (Canth) within the CO2-rich waters is largely unknown. Here we adapt the multiple linear regression approach to utilize the GO-SHIP Repeat Hydrography data from the northeast Pacific to establish an annually updated relationship between Canth and potential density. This relationship was then used with the NOAA Ocean Acidification Program West Coast Ocean Acidification (WCOA) cruise data sets from 2007, 2011, 2012, and 2013 to determine the spatial variations of Canth in the upwelled water. Our results show large spatial differences in Canth in surface waters along the coast, with the lowest values (37–55 μmol kg−1) in strong upwelling regions off southern Oregon and northern California and higher values (51–63 μmol kg−1) to the north and south of this region. Coastal dissolved inorganic carbon concentrations are also elevated due to a natural remineralized component (Cbio), which represents carbon accumulated through net respiration in the seawater that has not yet degassed to the atmosphere. Average surface Canth is almost twice the surface remineralized component. In contrast, Canth is only about one third and one fifth of the remineralized component at 50 m and 100 m depth, respectively. Uptake of Canth has caused the aragonite saturation horizon to shoal by approximately 30–50 m since the preindustrial period so that undersaturated waters are well within the regions of the continental shelf that affect the shell dissolution of living pteropods. Our data show that the most severe biological impacts occur in the nearshore waters, where corrosive waters are closest to the surface. Since the pre-industrial times, pteropod shell dissolution has, on average, increased approximately 19–26% in both nearshore and offshore waters.

Continue reading ‘Chemical and biological impacts of ocean acidification along the west coast of North America’

The role of symbiotic algae in the formation of the coral polyp skeleton: 3-D morphological study based on X-ray microcomputed tomography

Symbiotic algae of primary polyps play an important role in calcification of coral skeletons. However, the function of the symbiotic algae, including the way they influence the physical features of their host skeleton under various conditions, is not well understood. We used X-ray microcomputed tomography to observe skeletal shape characteristics in symbiotic and aposymbiotic primary polyps of Acropora digitifera that were cultured at various temperature and pCO2 levels (temperature 27, 29, 33°C; pCO2 400, 800, 1000 µatm). Symbiotic polyps had a basal plate with a well-developed folding margin supporting the branched skeleton, whereas aposymbiotic ones did not. The features of the folding margin suggest that it might be the initial growth stage of the epitheca. In addition, three-dimensional (3-D) morphological measurements made by X-ray microcomputed tomography show that the branched skeletons of symbiotic primary polyps were taller than those of aposymbiotic ones, suggesting that zooxanthellae in coral primary polyps play a critical role in the height growth of skeletal branches. Furthermore, results of the temperature- and pCO2-controlled experiments suggest that global warming might greatly affect the activity of zooxanthellae, whereas ocean acidification might reduce calcification by damaging the coral host itself. Our findings provide new knowledge about the role of zooxanthellae in coral calcification.

Continue reading ‘The role of symbiotic algae in the formation of the coral polyp skeleton: 3-D morphological study based on X-ray microcomputed tomography’

The influence of Pacific Equatorial Water on fish diversity in the southern California Current System

The California Undercurrent transports Pacific Equatorial Water (PEW) into the Southern California Bight from the eastern tropical Pacific Ocean. PEW is characterized by higher temperatures and salinities, with lower pH, representing a source of potentially corrosive (aragonite, inline image) water to the region. We use ichthyoplankton assemblages near the cores of the California Current and the California Undercurrent to determine whether PEW influenced fish diversity. We use hydrographic data to characterize the interannual and seasonal variability of estimated pH and aragonite saturation with depth. Although there is substantial variability in PEW presence as measured by spice on the 26.25–26.75 isopycnal layer, as well as in pH and aragonite saturation, we found fish diversity to be stable over the decades 1985–1996 and 1999–2011. We detected significant difference in species structure during the 1998 La Niña period, due to reduced species evenness. Species richness due to rare species was higher during the 1997/1998 El Niño compared to the La Niña but the effect on species structure was undetectable. Lack of difference in the species abundance structure in the decade before and after the 1997/1999 ENSO event showed that the assemblage reverted to its former structure following the ENSO perturbation, indicating resilience. While the interdecadal species structure remained stable, the long tail of the distributions shows that species richness increased between the decades consistent with intrusion of warm water with more diverse assemblages into the southern California region.

Continue reading ‘The influence of Pacific Equatorial Water on fish diversity in the southern California Current System’


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