Acidification des oceans: Une menace que le Sénégal se doit d’étudier, de comprendre, et d’anticiper (in French)

La surpêche dans les eaux du Sénégal a reçu beaucoup d’attention, mais des menaces tout aussi importantes pèsent également sur les ressources marines dont les effets pervers peuvent s’avérer irréversibles pour nos sociétés. L’acidification des océans et les autres problèmes liés au dioxyde de carbone (CO2) représentent en effet un risque pour la biodiversité marine, les écosystèmes et la société humaine que le Sénégal se doit de bien prendre en compte pour une gestion durable de ses eaux marines.

L’augmentation des concentrations du CO2 atmosphérique liée aux activités humaines telles que la combustion des énergies fossiles a conduit à l’acidification d’environ 30 % des eaux océaniques de surface par rapport à l’époque préindustrielle. Les modifications chimiques induites par l’augmentation du CO2 dissous dans l’eau réduisent la disponibilité des composés chimiques essentiels à la formation des coquilles et des squelettes calcaires des organismes marins, notamment ceux des mollusques, des crustacés et des coraux.  La réduction de l’oxygène dissous et le réchauffement des océans sont deux facteurs importants également liés au CO2.

Continue reading ‘Acidification des oceans: Une menace que le Sénégal se doit d’étudier, de comprendre, et d’anticiper (in French)’

All aboard the carbon cruise

University of Miami students and researchers are blogging during a month-long expedition in the Gulf of Mexico to study ocean acidification.

An interdisciplinary and international team of scientists and students set sail aboard the NOAA (National Oceanic and Atmospheric Administration) ship Ronald H. Brown on Tuesday, July 18 for a 36-day expedition in the Gulf of Mexico.

The researchers – including graduate student Joletta Silva and two recent alumni, Emma Pontes and Leah Chomiak, from the University of Miami Rosenstiel School of Marine and Atmospheric Science – represent institutions from the United States, Mexico and Cuba.

The expedition, entitled the Gulf of Mexico Ecosystems and Carbon Cruise (GOMECC), is the third of such research cruises led by NOAA AOML (Atlantic Oceanographic and Meteorological Laboratory) for its Ocean Acidification Program to better understand how ocean chemistry along U.S. coasts is changing in response to ocean acidification. This cruise is the first that will explore Mexican waters of the Gulf of Mexico, and is considered to be the most comprehensive ocean acidification cruise to date in the region.

Continue reading ‘All aboard the carbon cruise’

Our oceans are becoming more acidic – what it means for marine life and what you can do

Oceans cover 70 percent of the earth’s surface and account for 97 percent of its water. They play a vital role in the natural carbon cycle and provides a home for over one million species of plants and animals, with another estimated nine million living in the depths left unexplored by humans. Billions of people rely on the ocean’s rich diversity of resources for survival, and its picturesque beauty provides a calming refuge and source of recreation for people around the world.

Plastic trash and other forms of pollution have turned the once pristine waters into a toxin-filled soup, but that’s not the only threat our oceans and marine life are facing. The earth’s levels of carbon dioxide, which the ocean absorbs from the atmosphere as part of the natural carbon cycle, have increased significantly. The excess carbon is lowering the pH levels of the oceans, causing acidification that is killing off coral reefs and threatening fish and other marine life.

Continue reading ‘Our oceans are becoming more acidic – what it means for marine life and what you can do’

Photoprotective responses in a brown macroalgae Cystoseira tamariscifolia to increases in CO2 and temperature

Global warming and ocean acidification are increasingly affecting coastal ecosystems, with impacts that vary regionally depending upon local biogeography. Ocean acidification drives shifts in seaweed community dominance that depend on interactions with other factors such as light and nutrients. In this study, we investigated the photophysiological responses in the brown macroalgae species Cystoseira tamariscifolia (Hudson) Papenfuss with important structural role in the coastal Mediterranean communities. These algae were collected in the Cabo de Gata-Nijar Natural Park in ultraoligotrophic waters (algae exposed under high irradiance and less nutrient conditions) vs. those collected in the La Araña beach in oligotrophic waters (algae exposed at middle nutrient and irradiance conditions) in the Mediterranean Sea. They were incubated in mesocosms, under two levels of CO2; ambient (400-500 ppm) and high CO2 (1200-1300 ppm), combined with two temperatures (ambient temperature; 20 °C and ambient temperature + 4 °C; 24 °C) and the same nutrient conditions of the waters of the origin of macroalgae. Thalli from two sites on the Spanish Mediterranean coast were significantly affected by increases in pCO2 and temperature. The carotenoids (fucoxanthin, violaxanthin and β-carotene) contents were higher in algae from oligotrophic than that from ultraoligotrophic water, i.e., algae collected under higher nutrient conditions respect to less conditions, increase photoprotective pigments content. Thalli from both locations upregulated photosynthesis (as Fv/Fm) at increased pCO2 levels. Our study shows that ongoing ocean acidification and warming can increase photoprotection and photosynthesis in intertidal macroalgae.

Continue reading ‘Photoprotective responses in a brown macroalgae Cystoseira tamariscifolia to increases in CO2 and temperature’

Influence of environmental conditions on the toxicokinetics of cadmium in the marine copepod Acartia tonsa

Marine and estuarine ecosystems are highly productive areas that often act as a final sink for several pollutants, such as cadmium. Environmental conditions in these habitats can affect metal speciation, as well as its uptake and depuration by living organisms. The aim of this study was to assess cadmium uptake and depuration rates in the euryhaline calanoid copepod Acartia tonsa under different pH, salinity and temperature conditions. Cadmium speciation did not vary with changing pH or temperature, but varied with salinity. Free Cd2+ ion activity increased with decreasing salinities resulting in increased cadmium concentrations in A. tonsa. However, uptake rate, derived using free Cd2+ ion activity, showed no significant differences at different salinities indicating a simultaneous combined effect of Cd2+ speciation and metabolic rates for osmoregulation. Cadmium concentration in A. tonsa and uptake rate increased with increasing pH, showing a peak at the intermediate pH of 7.5, while depuration rate fluctuated, thus suggesting that both parameters are mediated by metabolic processes (to maintain homeostasis at pH levels lower than normal) and ion competition at membrane binding sites. Cadmium concentration in A. tonsa, uptake and depuration rates increased with increasing temperature, a trend that can be attributed to an increase in metabolic energy demand at higher temperatures. The present study shows that cadmium uptake and depuration rates in the marine copepod A. tonsa is mostly affected by biological processes, mainly driven by metabolic mechanisms, and to a lesser extent by metal speciation in the exposure medium.

Continue reading ‘Influence of environmental conditions on the toxicokinetics of cadmium in the marine copepod Acartia tonsa’

Predation in high CO2 waters: prey fish from high-risk environments are less susceptible to ocean acidification

Most studies investigating the effects of anthropogenic environmental stressors do so in conditions that are often optimal for their test subjects, ignoring natural stressors such as competition or predation. As such, the quantitative results from such studies may often underestimate the lethality of certain toxic compounds. A well-known example of this concept is illustrated by the marked increase in the lethality of pesticides when larval amphibians are concurrently exposed to the odor of potential predators. Here, we investigated the interaction between background levels of environmental predation risk (high vs. low) and ocean acidification (ambient vs. elevated CO2) in 2 × 2 design. Wild-caught juvenile damselfish, Pomacentrus amboinensis, were exposed in the laboratory to the different risk and CO2 conditions for 4 days and released onto coral reef patches. Using a well-established field assay, we monitored the in situ behavior and mortality of the damselfish for 2 days. We predicted that juvenile fish exposed to elevated CO2 and high-risk conditions would display more severe behavioral impairments and increased mortality compared to fish exposed to elevated CO2 maintained under low-risk conditions. As expected, elevated CO2 exposure led to impaired antipredator responses and increased mortality in low-risk fish compared to ambient CO2 controls. However, we failed to find an effect of elevated CO2 on the behavior and survival of the high-risk fish. We hypothesized that the results may stem from either a behavioral compensation or a physiological response to high risk. Our results provide insights into the interactive nature of environmental and natural stressors and advance our understanding of the predicted effect of ocean acidification on aquatic ecosystems.

Continue reading ‘Predation in high CO2 waters: prey fish from high-risk environments are less susceptible to ocean acidification’

Ocean acidification alters the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and gene expression of a bivalve species, Sinonovacula constricta

Although the impacts of ocean acidification on fertilization, embryonic development, calcification, immune response, and behaviour have been well studied in a variety of marine organisms, the physiological and molecular mechanism manifesting acidification stress on behavioural response remains poorly understood. Therefore, the impacts of future ocean acidification scenarios (pH at 7.8, 7.6, and 7.4) on the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and expression of energy-producing-related genes of the razor clam Sinonovacula constricta were investigated in the present study. The results showed that elevated CO2 partial pressure ( pCO2) (pH at 7.6 and 7.4) led to a significant reduction in the digging depth of the razor clam. In addition, exposure to pCO2-acidified seawater depressed the metabolism and activity of Ca2+/Mg2+-ATPase, which may partially contribute to the reduced digging depth detected. Furthermore, the expression of energy-producing-related genes was generally induced by exposure to acidified seawater and could be accounted for by an increased energy demand under acidification stress. The results obtained suggest ocean acidification may exert a behavioural impact through altering physiological condition in the razor clam.

Continue reading ‘Ocean acidification alters the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and gene expression of a bivalve species, Sinonovacula constricta’


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Ocean acidification in the IPCC AR5 WG II

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