Archive for December, 2012

Spring plankton community structure and distribution in the north and south coasts of Sfax (Tunisia) after north coast restoration

The first phase of the Taparura Project aimed at restoring the north coast of Sfax (Tunisia), highly polluted by phosphate industry and uncontrolled phosphogypsum dumping. Before restoration of the north coast of Sfax, we investigated the state of the ecosystem in related coastal waters. To establish the impact of the Taparura Project, we conducted a similar study both after restoration. To discriminate natural changes over time, we extended the study to the south coast of Sfax, submitted to the same industrial pressure but not yet restored. The present study, conducted in May 2010 at 36 stations (18 on each coast, north and south), covered the spatial distribution of the microbial assemblage, nutrients, and abiotic parameters by collecting seawater samples at the surface and the water–sediment interface. Results revealed a striking difference between the two coasts regarding pH, with strong acidification of seawater in the south, likely generated by industrial activity. Suspended matter was higher in the north than in the south. Flow cytometry analysis of ultraphytoplankton (<10 μm) resolved six groups (Prochlorococcus, Synechococcus, nanoeukaryotes and three distinct subgroups within picoeukaryotes). In addition to these autotrophic groups, two unknown groups were characterised on the south coast. Heterotrophic prokaryotes were resolved into three groups, labelled LNA (low nucleic acid content), HNA1 and HNA2 (high nucleic acid content). Prochloroccocus, pico-nano-microphytoplankton, heterotrophic prokaryotes and ciliates were more abundant in the north, whereas Synechococcus and unknown species were more abundant in the south where chl a concentration was also higher. The results show that restoration had positive effects on the microbial assemblage of the north coast; they also highlight the strong acidification still prevalent in the south that may be responsible for the lower development of most phytoplankton groups and the occurrence of unknown species. The case for restoration of the city’s south coast is also reinforced.

Continue reading ‘Spring plankton community structure and distribution in the north and south coasts of Sfax (Tunisia) after north coast restoration’

Water quality is threatened by acidification

Water supply acidification can have drastic consequences for survival of some plant and animal species.

Key points

  • Humans burning of fossil fuels contribute to ocean acidification.
  • When fuels are burned, CO2 is produced. The ocean absorbs approximately 25% of the CO2 produced through the burning of fossil fuels.
  • The decreasing pH of the ocean through carbonic acid formation is known as ocean acidification.
  • New research suggests that the ocean’s pH will decrease by an additional .03 to 0.5 pH units before the end of the century.
  • Fossil fuel burning also creates a large amount of sulfur dioxides and nitrogen oxides. These compounds form strong acids when they react with water.
  • If sulfur dioxides and nitrogen oxides react with water in the air, a strong acid is formed and can fall to the ground as rain or snow. This is referred to as acid precipitation, which is when rain, snow, or fog has a pH of 5.2 or lower. A pH of 5.6 is normal for uncontaminated rain.

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Individual variability in reproductive success determines winners and losers under ocean acidification: a case study with sea urchins


Climate change will lead to intense selection on many organisms, particularly during susceptible early life stages. To date, most studies on the likely biotic effects of climate change have focused on the mean responses of pooled groups of animals. Consequently, the extent to which inter-individual variation mediates different selection responses has not been tested. Investigating this variation is important, since some individuals may be preadapted to future climate scenarios.

Methodology/principal findings

We examined the effect of CO2-induced pH changes (“ocean acidification”) in sperm swimming behaviour on the fertilization success of the Australasian sea urchin Heliocidaris erythrogramma, focusing on the responses of separate individuals and pairs. Acidification significantly decreased the proportion of motile sperm but had no effect on sperm swimming speed. Subsequent fertilization experiments showed strong inter-individual variation in responses to ocean acidification, ranging from a 44% decrease to a 14% increase in fertilization success. This was partly explained by the significant relationship between decreases in percent sperm motility and fertilization success at ΔpH = 0.3, but not at ΔpH = 0.5.

Conclusions and significance

The effects of ocean acidification on reproductive success varied markedly between individuals. Our results suggest that some individuals will exhibit enhanced fertilization success in acidified oceans, supporting the concept of ‘winners’ and ‘losers’ of climate change at an individual level. If these differences are heritable it is likely that ocean acidification will lead to selection against susceptible phenotypes as well as to rapid fixation of alleles that allow reproduction under more acidic conditions. This selection may ameliorate the biotic effects of climate change if taxa have sufficient extant genetic variation upon which selection can act.

Continue reading ‘Individual variability in reproductive success determines winners and losers under ocean acidification: a case study with sea urchins’

Comment l’acidification des océans monte en puissance (in French)

Encore peu connue du grand public, l’acidification des océans précipite, elle aussi, notre monde vers la fin d’une ère. Pour décrypter ses mécanismes, ses effets, et les solutions pour la réduire, l’Institut du développement durable et des relations internationales (Iddri) a réuni plusieurs experts autour d’un colloque, le 18 décembre à Paris.

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A land-to-ocean perspective on the magnitude, source and implication of DIC flux from major Arctic rivers to the Arctic Ocean

A series of seasonally distributed measurements from the six largest Arctic rivers (the Ob’, Yenisey, Lena, Kolyma, Yukon and Mackenzie) was used to examine the magnitude and significance of Arctic riverine DIC flux to larger scale C dynamics within the Arctic system. DIC concentration showed considerable, and synchronous, seasonal variation across these six large Arctic rivers, which have an estimated combined annual DIC flux of 30 Tg C yr−1. By examining the relationship between DIC flux and landscape variables known to regulate riverine DIC, we extrapolate to a DIC flux of 57 ± 9.9 Tg C yr−1 for the full pan-arctic basin, and show that DIC export increases with runoff, the extent of carbonate rocks and glacial coverage, but decreases with permafrost extent. This pan-arctic riverine DIC estimate represents 13–15% of the total global DIC flux. The annual flux of selected ions (HCO3, Na+, Ca2+, Mg2+, Sr2+, and Cl) from the six largest Arctic rivers confirms that chemical weathering is dominated by inputs from carbonate rocks in the North American watersheds, but points to a more important role for silicate rocks in Siberian watersheds. In the coastal ocean, river water-induced decreases in aragonite saturation (i.e., an ocean acidification effect) appears to be much more pronounced in Siberia than in the North American Arctic, and stronger in the winter and spring than in the late summer. Accounting for seasonal variation in the flux of DIC and other major ions gives a much clearer understanding of the importance of riverine DIC within the broader pan-arctic C cycle.

Continue reading ‘A land-to-ocean perspective on the magnitude, source and implication of DIC flux from major Arctic rivers to the Arctic Ocean’

A steep learning curve

Ocean acidification, caused by the uptake of anthropogenic carbon dioxide, is a significant stressor to marine life. Ulf Riebesell charts the rapid rise in ocean acidification research, from the discovery of its adverse effects to its entry into the political consciousness.

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Effects of ocean acidification on the ballast of surface aggregates sinking through the twilight zone

The dissolution of CaCO3 is one of the ways ocean acidification can, potentially, greatly affect the ballast of aggregates. A diminution of the ballast could reduce the settling speed of aggregates, resulting in a change in the carbon flux to the deep sea. This would mean lower amounts of more refractory organic matter reaching the ocean floor. This work aimed to determine the effect of ocean acidification on the ballast of sinking surface aggregates. Our hypothesis was that the decrease of pH will increase the dissolution of particulate inorganic carbon ballasting the aggregates, consequently reducing their settling velocity and increasing their residence time in the upper twilight zone. Using a new methodology for simulation of aggregate settling, our results suggest that future pCO2 conditions can significantly change the ballast composition of sinking aggregates. The change in aggregate composition had an effect on the size distribution of the aggregates, with a shift to smaller aggregates. A change also occurred in the settling velocity of the particles, which would lead to a higher residence time in the water column, where they could be continuously degraded. In the environment, such an effect would result in a reduction of the carbon flux to the deep-sea. This reduction would impact those benthic communities, which rely on the vertical flow of carbon as primary source of energy.

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The effects of ocean acidification and sea surface warming on the embryonic development of the opisthobranch gastropod Stylocheilus striatus

Anthropogenic increases in atmospheric CO2 compound the rates of long-term changes in the abiotic conditions of the Earth’s oceans. Because many physiological processes, including calcification rate, depend on these physical factors, there is mounting concern over how changes in temperature (T) and the CaCO3 saturation of seawater will affect marine organisms.  These effects may be particularly relevant during development— many organisms produce protective calcified structures critical for pelagic dispersal and larval survivability.  I investigated how unmitigated increases in oceanic pCO2 and temperature consistent with climate change predictions affect the embryonic development rate, hatching success, and veliger morphology of the opisthobranch gastropod,Stylocheilus striatus. Embryos were reared in four seawater treatments: 1) control (pH=8.02, T=27°C), 2) high-temperature (pH=8.02, T=31°C), 3) acidified(pH=7.67, T=27°C), 4) acidified high-temperature (pH=7.67, T=31°C). Development times increased under reduced pH conditions, but substantially decreased under high-temperature and acidified high-temperature treatments, with significant interaction between temperature and pH. The percentage of embryos that hatched into veligers significantly decreased in all three treatments (<70%reductionsin acidified high-temperature conditions).Larval shell size decreased in all three treatments— effects of acidification and temperature were synergistic, causing greater decreases in shell size with significant interaction in acidified high-temperature treatments. Additionally, there were observable deformities in the shell morphology of hatchlings incubated in decreased pH treatments— these deformities were exacerbated by temperature increases. Thus, my results indicate that oceanic conditions congruent with climate change predictions ca. 2100 suppress successful development in encapsulating gastropod embryos, potentially reducing their viability as pelagic larvae.

Continue reading ‘The effects of ocean acidification and sea surface warming on the embryonic development of the opisthobranch gastropod Stylocheilus striatus’

MRC update: marine work hours, ocean acidification…

San Juan County’s Marine Resources Committee meets on the first and third Wednesday of each month beginning at 8:30 a.m. in the community room in Islanders Bank Administration Building in Friday Harbor. December 5 topics included asking the state to extend the months in-water work is not allowed; ocean acidification and a pilot mussels program. Here are the minutes of that meeting.

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How many more Christmases for oysters? HKU Forum warns of ocean acidification and threat to marine life

Over this holiday season, many people in Southeast Asia enjoy the juicy, sweet and delicious oysters at the festive buffet. The day is soon coming when they may disappear from the menu altogether. South China Sea oysters and other seafood favorites are threatened. Man-made carbon dioxide taken up by the ocean is causing ocean acidification which is making it more difficult for shellfish to survive. The impact of ocean acidification on shellfish was recently observed when oyster production in the U.S. Pacific Northwest collapsed. This is economically significant when one considers that China produces over 80% of the world’s oysters.

Continue reading ‘How many more Christmases for oysters? HKU Forum warns of ocean acidification and threat to marine life’

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Ocean acidification in the IPCC AR5 WG II

OUP book