a news stream provided by the Ocean Acidification International Coordination Center (OA-ICC)
Une classe du collège Charles III a traduit de l’anglais et réalisé le doublage du dessin animé « Epoca », qui présente de manière accessible les dangers de l’acidification des océans, altérant le bon développement de certaines espèces. Le fruit de ce travail a été présenté au Musée Océanographique et dans les classes de la Principauté.
Greenhouse gases don’t just cause global warming… Meet a new threat: ocean acidification.
Cartoon on ocean acidification by Rosemary Mosco.
This study tested the hypothesis that the response of corals to temperature and pCO2 is consistent between taxa. Juvenile massive Porites spp. and branches of P. rus from the back reef of Moorea were incubated for 1 month under combinations of temperature (29.3 °C and 25.6 °C) and pCO2 (41.6 Pa and 81.5 Pa) at an irradiance of 599 μmol quanta m−2 s−1. Using microcosms and CO2 gas mixing technology, treatments were created in a partly nested design (tanks) with two between-plot factors (temperature and pCO2), and one within-plot factor (taxon); calcification was used as a dependent variable. pCO2 and temperature independently affected calcification, but the response differed between taxa. Massive Porites spp. was largely unaffected by the treatments, but P. rus grew 50% faster at 29.3 °C compared with 25.6 °C, and 28% slower at 81.5 Pa vs. 41.6 Pa CO2. A compilation of studies placed the present results in a broader context and tested the hypothesis that calcification for individual coral genera is independent of pH, [HCO3−], and [CO32−]. Unlike recent reviews, this analysis was restricted to studies reporting calcification in units that could be converted to nmol CaCO3 cm−2 h−1. The compilation revealed a high degree of variation in calcification as a function of pH, [HCO3−], and [CO32−], and supported three conclusions: (1) studies of the effects of ocean acidification on corals need to pay closer attention to reducing variance in experimental outcomes to achieve stronger synthetic capacity, (2) coral genera respond in dissimilar ways to pH, [HCO3−], and [CO32−], and (3) calcification of massive Porites spp. is relatively resistant to short exposures of increased pCO2, similar to that expected within 100 y.
The U.S. Geological Survey (USGS) partnership with the U.S. Coast Guard Ice Breaker Healy and its United Nations Convention Law of the Sea (UNCLOS) cruises has produced new synoptic data from samples collected in the Arctic Ocean and insights into the patterns and extent of ocean acidification. This framework of foundational geochemical information will help inform our understanding of potential risks to Arctic resources due to ocean acidification.
Continue reading ‘Studying ocean acidification in the Arctic Ocean’
We present over 900 carbonate system observations collected over four years (2007–2010) in the Western English Channel (WEC). We determined CO2 partial pressure (pCO2), Total Alkalinity (TA) and Dissolved Inorganic Carbon (DIC) along a series of 40 km transects, including two oceanographic stations (L4 and E1) within a sustained coastal observatory. Our data follow a seasonal pattern of CO2 undersaturation from January to August, followed by supersaturation in September-October and a return to near-equilibrium thereafter. This pattern is explained by the interplay of thermal and biological sinks in winter and spring-summer respectively, followed by the breakdown of stratification and mixing with deeper, high-CO2 water in autumn. The drawdown of DIC and inorganic N between March and June with a C:N ratio of 8.7–9.5 was consistent with carbon over-consumption during phytoplankton growth. Monthly mean surface pCO2 was strongly correlated with depth integrated chlorophyll a highlighting the importance of subsurface chlorophyll a maxima in controlling C-fluxes in shelf seas. Mixing of seawater with riverine freshwater in near-shore samples caused a reduction in TA and the saturation state of calcite minerals, particularly in winter. Our data show that the L4 and E1 oceanographic stations were small, net sinks for atmospheric CO2 over an annual cycle (−0.52±0.66 mol C m−2 y−1 and −0.62±0.49 mol C m−2 y−1 respectively).
Continue reading ‘Seasonal dynamics of the carbonate system in the Western English Channel’
The filamentous and diazotrophic cyanobacterium Nodularia spumigena plays a major role in the productivity of the Baltic Sea as it forms extensive blooms regularly. Under phosphorus limiting conditions Nodularia spumigena has a high enzyme affinity for dissolved organic phosphorus (DOP) by production and release of alkaline phosphatase. Additionally, it is able to degrade proteinaceous compounds by expressing the extracellular enzyme leucine aminopeptidase. As atmospheric CO2 concentrations are increasing, we expect marine phytoplankton to experience changes in several environmental parameters including pH, temperature, and nutrient availability. The aim of this study was to investigate the combined effect of CO2-induced changes in seawater carbonate chemistry and of phosphate deficiency on the exudation of organic matter, and its subsequent recycling by extracellular enzymes in a Nodularia spumigena culture. Batch cultures of Nodularia spumigena were grown for 15 days aerated with three different pCO2 levels corresponding to values from glacial periods to future values projected for the year 2100. Extracellular enzyme activities as well as changes in organic and inorganic compound concentrations were monitored. CO2 treatment–related effects were identified for cyanobacterial growth, which in turn was influencing exudation and recycling of organic matter by extracellular enzymes. Biomass production was increased by 56.5% and 90.7% in the medium and high pCO2 treatment, respectively, compared to the low pCO2 treatment and simultaneously increasing exudation. During the growth phase significantly more mucinous substances accumulated in the high pCO2 treatment reaching 363 μg Gum Xanthan eq l−1 compared to 269 μg Gum Xanthan eq l−1 in the low pCO2 treatment. However, cell-specific rates did not change. After phosphate depletion, the acquisition of P from DOP by alkaline phosphatase was significantly enhanced. Alkaline phosphatase activities were increased by factor 1.64 and 2.25, respectively, in the medium and high compared to the low pCO2 treatment. In conclusion, our results suggest that Nodularia spumigena can grow faster under elevated pCO2 by enhancing the recycling of organic matter to acquire nutrients.
Coccolithophores, a key phytoplankton group, are one of the best studied organisms with regard to the response to ocean acidification/carbonation. The biogenic production of calcareous coccoliths has made coccolithophores a promising group for paleoceanographic research aiming to reconstruct past environmental conditions. Recently, geochemical and morphological analyses of fossil coccoliths have gained increased interest in regard to changes in seawater carbonate chemistry. The cosmopolitan coccolithophore Emiliania huxleyi (Lohm.) Hay and Mohler was cultured over a range of pCO2 levels in controlled laboratory experiments under nutrient replete and nitrogen limited conditions. Measurements of photosynthetic activity and calcification revealed, as previously published, an increase in organic carbon production and a moderate decrease in calcification from ambient to elevated pCO2. The enhancement in particulate organic carbon production was accompanied by an increase in cell diameter. Coccolith volume was best correlated with the coccosphere/cell diameter and no significant correlation was found between coccolith volume and particulate inorganic carbon production rate. The conducted experiments revealed that the coccolith volume of E. huxleyi is variable with aquatic CO2 concentration within the tested range but appears to be a primary function of the coccosphere/cell diameter both under nitrogen limited and nutrient replete conditions. Comparing coccolith morphological and geometrical parameters like volume, mass and size to physiological parameters under controlled laboratory conditions is an important step to understand variations in fossil coccolith geometry.
Rhodoliths are nodules of non-geniculate coralline algae that occur in shallow waters (<150 m depth) subjected to episodic disturbance. Rhodolith beds stand with kelp beds, seagrass meadows, and coralline algal reefs as one of the world’s four largest macrophyte-dominated benthic communities. Geographic distribution of rhodolith beds is discontinuous, with large concentrations off Japan, Australia and the Gulf of California, as well as in the Mediterranean, North Atlantic, eastern Caribbean and Brazil. Although there are major gaps in terms of seabed habitat mapping, the largest rhodolith beds are purported to occur off Brazil, where these communities are recorded across a wide latitudinal range (2°N – 27°S). To quantify their extent, we carried out an inter-reefal seabed habitat survey on the Abrolhos Shelf (16°50′ – 19°45′S) off eastern Brazil, and confirmed the most expansive and contiguous rhodolith bed in the world, covering about 20,900 km2. Distribution, extent, composition and structure of this bed were assessed with side scan sonar, remotely operated vehicles, and SCUBA. The mean rate of CaCO3 production was estimated from in situ growth assays at 1.07 kg m−2 yr−1, with a total production rate of 0.025 Gt yr−1, comparable to those of the world’s largest biogenic CaCO3 deposits. These gigantic rhodolith beds, of areal extent equivalent to the Great Barrier Reef, Australia, are a critical, yet poorly understood component of the tropical South Atlantic Ocean. Based on the relatively high vulnerability of coralline algae to ocean acidification, these beds are likely to experience a profound restructuring in the coming decades.
Continue reading ‘Rhodolith beds are major CaCO3 bio-factories in the tropical South West Atlantic’
Manipulative studies have demonstrated that ocean acidification (OA) is a threat to coral reefs, yet no experiments have employed diurnal variations in pCO2 that are ecologically relevant to many shallow reefs. Two experiments were conducted to test the response of coral recruits (less than 6 days old) to diurnally oscillating pCO2; one exposing recruits for 3 days to ambient (440 µatm), high (663 µatm) and diurnally oscillating pCO2 on a natural phase (420–596 µatm), and another exposing recruits for 6 days to ambient (456 µatm), high (837 µatm) and diurnally oscillating pCO2 on either a natural or a reverse phase (448–845 µatm). In experiment I, recruits exposed to natural-phased diurnally oscillating pCO2 grew 6–19% larger than those in ambient or high pCO2. In experiment II, recruits in both high and natural-phased diurnally oscillating pCO2 grew 16 per cent larger than those at ambient pCO2, and this was accompanied by 13–18% higher survivorship; the stimulatory effect on growth of oscillatory pCO2 was diminished by administering high pCO2 during the day (i.e. reverse-phased). These results demonstrate that coral recruits can benefit from ecologically relevant fluctuations in pCO2 and we hypothesize that the mechanism underlying this response is highly pCO2-mediated, night-time storage of dissolved inorganic carbon that fuels daytime calcification.
Global climate and environmental change affect the biogeochemistry and ecology of aquatic systems mostly due to a combination of natural and anthropogenic factors. The latter became more and more important during the past few thousand years and particularly during the ‘Anthropocene’. However, although they are considered important in this respect as yet much less is known from tropical than from high latitude coasts. Tropical coasts receive the majority of river inputs into the ocean, they harbor a variety of diverse ecosystems and a majority of the population lives there and economically depends on their natural resources. This review delineates the biogeochemical response of coastal systems to environmental change and the interplay of natural and anthropogenic control factors nowadays and in the recent geological past with an emphasis on tropical regions. Weathering rates are higher in low than in high latitude regions with a maximum in the SE Asia/Western Pacific region. On a global scale the net effect of increasing erosion due to deforestation and sediment retention behind dams is a reduced sediment input into the oceans during the Anthropocene. However, an increase was observed in the SE Asia/Western Pacific region. Nitrogen and phosphorus inputs into the ocean have trebled between the 1970s and 1990s due to human activities. As a consequence of increased nutrient inputs and a change in the nutrient mix excessive algal blooms and changes in the phytoplankton community composition towards non-biomineralizing species have been observed in many regions. This has implications for foodwebs and biogeochemical cycles of coastal seas including the release of greenhouse gases. Examples from tropical coasts with high population density and extensive agriculture, however, display deviations from temperate and subtropical regions in this respect. According to instrumental records and observations the present-day biogeochemical and ecological response to environmental change appears to be on the order of decades. A sediment record from the Brazilian continental margin spanning the past 85,000 years, however, depicts that the ecosystem response to changes in climate and hydrology can be on the order of 1,000-2,000 years. The coastal ocean carbon cycle is very sensitive to Anthropocene changes in land-derived carbon and nutrient fluxes and increasing atmospheric carbon dioxide. As opposing trends in high latitude regions tropical coastal seas display increasing organic matter inputs and reduced calcification rates which have important implications for calcifying organisms and the carbon source or sink function of the coastal ocean. Particularly coral reefs which are thriving in warm tropical waters are suffering from ocean acidification. Nevertheless, they are not affected uniformly and the sensitivity to ocean acidification may vary largely among coral reefs. Therefore, the prediction of future scenarios requires an improved understanding of present and past responses to environmental change with particular emphasis put on tropical regions.
Ocean acidification, caused by elevated seawater carbon dioxide levels, may have a deleterious impact on energetic processes in animals. Here we show that high PCO2 can suppress metabolism, measured as oxygen consumption, in the pteropod, L. helicina forma antarctica, by ~20%. The rates measured at 180–380 µatm (MO2 = 1.25 M−0.25, p = 0.007) were significantly higher (ANCOVA, p = 0.004) than those measured at elevated target CO2 levels in 2007 (789–1000 µatm, = 0.78 M−0.32, p = 0.0008;). However, we further demonstrate metabolic plasticity in response to regional phytoplankton concentration and that the response to CO2 is dependent on the baseline level of metabolism. We hypothesize that reduced regional Chl a levels in 2008 suppressed metabolism and masked the effect of ocean acidification. This effect of food limitation was not, we postulate, merely a result of gut clearance and specific dynamic action, but rather represents a sustained metabolic response to regional conditions. Thus, pteropod populations may be compromised by climate change, both directly via CO2-induced metabolic suppression, and indirectly via quantitative and qualitative changes to the phytoplankton community. Without the context provided by long-term observations (four seasons) and a multi-faceted laboratory analysis of the parameters affecting energetics, the complex response of polar pteropods to ocean acidification may be masked or misinterpreted.
Une étude menée dans le Pacifique établit pour la première fois en milieu naturel le lien entre acidification et mortalité des naissains.
On connaissait les expériences menées en laboratoire, mais c’est la première fois que des chercheurs réussissent à montrer en milieu naturel l’effet néfaste de l’acidification des océans sur les huîtres. C’est ce que révèle une étude publiée dans la revue Limnology and Oceanography.
L’alerte remonte à 2007. Dans une des grandes écloseries d’huîtres de l’Oregon (États-Unis), fournissant les ostréiculteurs de la côte du Pacifique, les naissains ont commencé à dépérir. Les millions de bébés huîtres Crassostrea gigas, une fois plongés dans la mer, mouraient les uns après les autres. Une perte économique se comptant en millions de dollars.
Continue reading ‘L’acidification des océans nuit à la production des huîtres (in French)’
The detrimental effects of increasing atmospheric levels of carbon dioxide (CO2) and other greenhouse gases since the industrial revolution has led to a concerted international effort to control their release and abate the environmental and human health impacts. CO2 is removed from the atmosphere by photosynthesis of plants in the terrestrial environment and by aquatic sequestration. In the Middle East and other arid countries, terrestrial removal is minimal. The most likely removal pathway for CO2 in arid regions around the world is by aquatic sequestration. In the Middle East the major sink is the Arabian Gulf which leads to acidification of the marine environment. Biweekly pH concentration measurements in surface waters of the northern Arabian Gulf over a four year period in this study suggest that the Arabian Gulf waters are becoming increasingly acidic with time. Supporting evidence for increased CO2 sequestration comes from increased marine primary productivity over the past decade. Biological effects, such as coral bleaching, observed during this period suggest that urgent action is required to reverse the trend and protect marine life. The data highlight the fact that this semi-enclosed sea is undergoing a rapid degradation which may affect the oceanic chemistry and biogeochemical cycle much earlier than predicted for most oceanic waters.
Continue reading ‘Acidification in Arabian Gulf – Insights from pH and temperature measurements’
El proyecto propuesto desarrollará sistemas específicos para la medición de pH marino y CO2 atmosférico en la Costa del Garraf.
El aumento del contenido de CO2 en la atmósfera debido a las actividades antrópicas está provocando, a través del efecto invernadero y debido a que buena parte del CO2 emitido está siendo absorbido por los mares y océanos, una progresiva acidificación de sus aguas, lo cual tiene efectos devastadores para muchos organismos marinos.
Los sistemas de medición del pH marino y el CO2 atmosférico se implementarán en el observatorio OBSEA que, por sus características únicas, es especialmente idóneo para la toma de medidas en continuo a altas frecuencias de los diferentes parámetros de interés de una forma integrada.
Climate change, including ocean acidification (OA), presents fundamental challenges to marine biodiversity and sustained ecosystem health. We determined reproductive response (measured as naupliar production), cuticle composition and stage specific growth of the copepod Tisbe battagliai over three generations at four pH conditions (pH 7.67, 7.82, 7.95, and 8.06). Naupliar production increased significantly at pH 7.95 compared with pH 8.06 followed by a decline at pH 7.82. Naupliar production at pH 7.67 was higher than pH 7.82. We attribute the increase at pH 7.95 to an initial stress response which was succeeded by a hormesis-like response at pH 7.67. A multi-generational modelling approach predicted a gradual decline in naupliar production over the next 100 years (equivalent to approximately 2430 generations). There was a significant growth reduction (mean length integrated across developmental stage) relative to controls. There was a significant increase in the proportion of carbon relative to oxygen within the cuticle as seawater pH decreased. Changes in growth, cuticle composition and naupliar production strongly suggest that copepods subjected to OA-induced stress preferentially reallocate resources towards maintaining reproductive output at the expense of somatic growth and cuticle composition. These responses may drive shifts in life history strategies that favour smaller brood sizes, females and perhaps later maturing females, with the potential to profoundly destabilise marine trophodynamics.
Human beings start domesticating crops only 12,000 or so years ago. Written history begins about 5,000 years ago. The modern era dates from — when? — maybe 100-200 years ago. Perhaps it’s no surprise, then, that we have some difficulty internalizing the idea that our burning carbon has, already, set into motion dramatic changes to the entire planet’s environment, changes that will persist for 100,000 years, or more. One of these is ocean acidification. Dr. Bärbel Hönisch and her co-authors of the paper “The Geological Record of Ocean Acidification,” Science (2 March, 2012), show that the rate of change of ocean acidification is greater today, by at least an order of magnitude, than it has ever been during any period over the past 300,000,000 years. Rate of change, not absolute pH level, being what matters. The deep past includes, notably, a couple of rapid ocean acidification/mass extinction events. This therefore, not unreasonably, should be of concern. Thanks, Bärbel! Total runtime fifty minutes. Potius sērō quam nunquam.
À quel point l’acidification des océans menace-t-elle les organismes qui y vivent ? En Arctique, la fragilité d’un petit escargot planctonique, situé à la base de la chaîne alimentaire, préoccupe les biologistes.
Personne, il y a encore quatre ans, ne s’intéressait à ces minuscules escargots qui nagent dans l’océan Arctique : les ptéropodes Limacina helicina. Ils semblaient en effet si nombreux, atteignant par endroits plusieurs milliers d’individus par mètre carré, que leur sort ne suscitait aucune inquiétude. Une bonne nouvelle, car ces animaux représentent jusqu’à 90 % de la biomasse de zooplancton en Arctique. Mais c’était sans compter avec l’acidification des océans, qui résulte de la dissolution dans l’eau de mer d’une partie du dioxyde de carbone (CO2) atmosphérique : la coquille des ptéropodes est tout particulièrement sensible à ce phénomène. En avril 2012, cela vaudra à ces animaux une place de choix lors de la présentation finale des résultats du Programme de recherche européen sur l’acidification des océans (baptisé Epoca, selon son acronyme anglais), dédié à l’étude des conséquences de cette acidification (lire « L’acidification des océans sous surveillance », p. 81). Car selon son coordinateur, Jean-Pierre Gattuso, du laboratoire d’océanographie de Villefranche-sur-Mer : « Cette espèce est celle sur laquelle nous avons observé le plus d’effets négatifs dus à l’acidification. Ce qui permet de la considérer comme une espèce sentinelle de ce phénomène. » Explications en avant-première. Eaux de surface acides Chaque jour, les océans absorbent environ 22 millions de tonnes de CO2 émis par les activités humaines. Cela permet d’atténuer l’augmentation de l’effet de serre, mais avec un dommage collatéral : l’acidification des eaux de surface. Ainsi, le CO2 se dissout dans l’eau en formant des ions bicarbonates accompagnés d’ions hydrogène acidifiants. Résultat : depuis le début de la révolution industrielle, il y a deux cent cinquante ans, les eaux de surface s’acidifient. L’évolution de leur pH, l’unité de mesure de l’acidité, inversement corrélée à la concentration en ions hydrogène, le prouve. Entre la période préindustrielle et aujourd’hui, il est passé…
Continue reading ‘Le zooplancton sous la menace du climat (in French)’
Anthropogenically released CO2 is dissolving in the ocean, causing a decrease in bulk-seawater pH (ocean acidification). Projections indicate that the pH will drop 0.3 units from its present value by 2100 (ref. 1). However, it is unclear how the growth of plankton is likely to respond. Using simulations we demonstrate how pH and carbonate chemistry at the exterior surface of marine organisms deviates increasingly from those of the bulk sea water as organism metabolic activity and size increases. These deviations will increase in the future as the buffering capacity of sea water decreases with decreased pH and as metabolic activity increases with raised seawater temperatures. We show that many marine plankton will experience pH conditions completely outside their recent historical range. However, ocean acidification is likely to have differing impacts on plankton physiology as taxon-specific differences in organism size, metabolic activity and growth rates during blooms result in very different microenvironments around the organism. This is an important consideration for future studies in ocean acidification as the carbonate chemistry experienced by most planktonic organisms will probably be considerably different from that measured in bulk-seawater samples. An understanding of these deviations will assist interpretation of the impacts of ocean acidification on plankton of different size and metabolic activity.
Continue reading ‘Changes in pH at the exterior surface of plankton with ocean acidification’
A new study has found ocean acidification can affect the behaviour of baby corals in the Great Barrier Reef off Queensland.
University of Queensland (UQ) researchers have been analysing how ocean acidification affects the settlement of baby corals in the reef.
UQ Professor Peter Mumby says changes in the ocean are making the corals “stupid”.
“It implies that much of the biology of corals in terms of how they behave could be disrupted as the oceans change their chemistry,” he said.
Continue reading ‘Acidification threatens Barrier Reef coral: researchers’
Tillamook, Ore. — One of the Oregon coast’s biggest industries is being seriously threatened.
Recently, oyster hatcheries have seen a significant drop-off in production. During the last couple of years, researcher Alan Barton with the Whiskey Creek Shellfish Hatchery in Tillamook has been trying to figure out the reason behind the increase the high levels of acidity in the ocean. Oyster larvae are supposed to turn into this adult oyster, but researchers say the acidic ocean is a problem.
Continue reading ‘Researchers think they have reason for low oyster production figured out (video)’
