Archive for August, 2017

Iron sources alter the response of Southern Ocean phytoplankton to ocean acidification

The rise in anthropogenic CO2 and the associated ocean acidification (OA) will change trace metal solubility and speciation, potentially altering Southern Ocean (SO) phytoplankton productivity and species composition. As iron (Fe) sources are important determinants of Fe bioavailability, we assessed the effect of Fe-laden dust versus inorganic Fe (FeCl3) enrichment under ambient and high pCO2 levels (390 and 900 μatm) in a naturally Fe-limited SO phytoplankton community. Despite similar Fe chemical speciation and net particulate organic carbon (POC) production rates, CO2-dependent species shifts were controlled by Fe sources. Final phytoplankton communities of both control and dust treatments were dominated by the same species, with an OA-dependent shift from the diatom Pseudo nitzschia prolongatoides towards the prymnesiophyte Phaeocystis antarctica. Addition of FeCl3 resulted in high abundances of Nitzschia lecointei and Chaetoceros neogracilis under ambient and high pCO2, respectively. These findings reveal that both the characterization of the phytoplankton community at the species level and the use of natural Fe sources are essential for a realistic projection of the biological carbon pump in the Fe-limited pelagic SO under OA. As dust deposition represents a more realistic scenario for the Fe-limited pelagic SO under OA, unaffected net POC production and dominance of P. antarctica can potentially weaken the export of carbon and silica in the future.

Continue reading ‘Iron sources alter the response of Southern Ocean phytoplankton to ocean acidification’

Spatio-temporal variation of phytoplankton communities along a salinity and pH gradient in a tropical estuary (Brunei, Borneo, South East Asia)

Characterizing phytoplankton communities is essential to understanding the ecological functioning of pelagic marine systems. Nevertheless, our knowledge of phytoplankton communities is still inadequate for many tropical habitats, including estuaries. It is assumed that highly turbid tropical estuaries often experience acidification due to anthropogenic inputs, microbial degradation, run-off from acidic sulphate soils, and low buffer capacity characteristic for all estuarine systems. Here, we describe phytoplankton communities from the turbid, acidified, and euthrophised estuary of Brunei River (South East Asia). The four selected sampling stations represented gradients of salinity (0.4 – 28.5 PSU) and pH (5.87 – 8.06). A total of 26 microalgal families of phytoplankton (22 genera of diatoms, 7 of dinoflagellates, and 1 of ciliates) were recorded in the survey carried out over one year. The highest density was recorded at an intermediate station along the gradient (up to 9107 cells ml-1), whereas the lowest diversity was found at the least saline and most acidic station (7-1146 cells ml-1). Diatoms were a dominant component of the communities, with Nitzschia spp., Rhizosolenia spp., and Leptocylindrus sp. reaching the highest abundances. Salinity, pH and dissolved oxygen (DO) were positively correlated with the plankton abundances and typically declined landwards. Statistical analyses indicated that phytoplankton communities were strongly influenced by the effect of season (30 % of the total variance in phytoplankton data explained) and sampling site (20 %). The joint effect of pH and salinity and of pH and temperature explained 16.7 % and 17.5 % of the total observed variation, respectively.

Continue reading ‘Spatio-temporal variation of phytoplankton communities along a salinity and pH gradient in a tropical estuary (Brunei, Borneo, South East Asia)’

Alterations in microbial community composition with increasing fCO2: a mesocosm study in the eastern Baltic Sea (update)

Ocean acidification resulting from the uptake of anthropogenic carbon dioxide (CO2) by the ocean is considered a major threat to marine ecosystems. Here we examined the effects of ocean acidification on microbial community dynamics in the eastern Baltic Sea during the summer of 2012 when inorganic nitrogen and phosphorus were strongly depleted. Large-volume in situ mesocosms were employed to mimic present, future and far future CO2 scenarios. All six groups of phytoplankton enumerated by flow cytometry ( <  20 µm cell diameter) showed distinct trends in net growth and abundance with CO2 enrichment. The picoeukaryotic phytoplankton groups Pico-I and Pico-II displayed enhanced abundances, whilst Pico-III, Synechococcus and the nanoeukaryotic phytoplankton groups were negatively affected by elevated fugacity of CO2 (fCO2). Specifically, the numerically dominant eukaryote, Pico-I, demonstrated increases in gross growth rate with increasing fCO2 sufficient to double its abundance. The dynamics of the prokaryote community closely followed trends in total algal biomass despite differential effects of fCO2 on algal groups. Similarly, viral abundances corresponded to prokaryotic host population dynamics. Viral lysis and grazing were both important in controlling microbial abundances. Overall our results point to a shift, with increasing fCO2, towards a more regenerative system with production dominated by small picoeukaryotic phytoplankton.

Continue reading ‘Alterations in microbial community composition with increasing fCO2: a mesocosm study in the eastern Baltic Sea (update)’

“The Global Ocean Acidification Observing Network, GOA-ON: linking local information globally”, 2018 Ocean Sciences Meeting, Portland

Abstracts are due 6 September 2017!

Session Description: The Global Ocean Acidification Observing Network, GOA-ON (www.goa-on.org), was established in 2012 to serve scientific and policy needs by providing coordinated, worldwide information on ocean acidification and its ecological impacts.  The work of GOA-ON is guided by three high level goals: 1) to improve our understanding of global ocean acidification conditions; 2) to improve our understanding of ecosystem response to ocean acidification; and 3) to acquire and exchange the data and knowledge necessary to optimize the modeling of ocean acidification and its impacts. GOA-ON was organized by scientists for international coordination, with researchers from 66 countries now participating, has evolved to incorporate regional hubs for collaboration, and provides and promotes training and capacity building activities. By using consistent methods and networking data, GOA-ON enhances our understanding of the local expressions of this global process, thereby covering a range of spatial scales.

Continue reading ‘“The Global Ocean Acidification Observing Network, GOA-ON: linking local information globally”, 2018 Ocean Sciences Meeting, Portland’

Coral skeletons may resist the effects of acidifying oceans

Coral skeletons are the building blocks of diverse coral reef ecosystems, which has led to increasing concern over how these key species will cope with warming and acidifying oceans that threaten their stability.

New research from Pupa Gilbert, a professor of physics at the University of Wisconsin-Madison, provides evidence that at least one species of coral, Stylophora pistillata, and possibly others, build their hard, calcium carbonate skeletons faster, and in bigger pieces, than previously thought. Instead of slowly adding material molecule by molecule, the coral animal actively constructs large chunks of minerals that it adds to its growing skeleton, helping it grow much faster than it otherwise could, and with greater control.

The new research suggests that because the minerals are first formed inside the coral tissue, they may continue to do so even in acidifying oceans. If other coral species build their skeletons in a similar way, then the oceans could avoid a large-scale crisis in coral skeleton formation that scientists have worried would unravel reef ecosystems. Other stresses, like warmer waters and coral bleaching, still endanger coral, however.

The work is published this week (Aug. 28, 2017) in the Proceedings of the National Academy of Sciences. Collaborators from the University of Haifa and the Lawrence Berkeley National Laboratory contributed to the research.

Continue reading ‘Coral skeletons may resist the effects of acidifying oceans’

Amorphous calcium carbonate particles form coral skeletons

Whether coral skeleton crystals grow by attachment of ions from solution or particles from tissue determines (i) corals’ growth rate, (ii) how they survive acidifying oceans, and (iii) the isotopes in the crystals used for reconstructing ancient temperatures. Our data show that two amorphous precursors exist, one hydrated and one dehydrated amorphous calcium carbonate; that these are formed in the tissue as ∼400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally crystallize into aragonite. Since these particles are formed inside tissue, coral skeleton growth may be less susceptible to ocean acidification than previously assumed. Coral bleaching and postmortem dissolution of the skeleton will occur, but a calcification crisis may not.

Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya.

Continue reading ‘Amorphous calcium carbonate particles form coral skeletons’

Acid zone in Chesapeake Bay identified

A research team, led by University of Delaware professor Wei-Jun Cai, has identified a zone of water that is increasing in acidity in the Chesapeake Bay.

The team analyzed little studied factors that play a role in ocean acidification (OA)—changes in water chemistry that threaten the ability of shellfish such as oysters, clams and scallops to create and maintain their shells, among other impacts.

The U.S. Geological Survey defines pH as “a measure of how acidic or basic water is.” The pH scale ranges from 0-14, with 7 considered neutral. A pH less than 7 is acidic, while a pH greater than 7 is alkaline (basic). Battery acid, for example, might have a pH of 1, while Milk of Magnesia might have a pH of 10.

Changes in pH can tell scientists something about how the water chemistry is changing.

In their research, Cai and his colleagues discovered a “pH minimum zone” that occurs at a depth of approximately 10-15 meters (~30-50 feet) in the Chesapeake Bay. The pH in this zone is roughly 7.4, nearly 10 times higher in acidity (or a unit lower in pH) than what is found in surface waters, which have an average pH of 8.2.

“This study shows for the first time that the oxidation of hydrogen sulfide and ammonia from the bottom waters could be a major contributor to lower pH in coastal oceans and may lead to more rapid acidification in coastal waters compared to the open ocean,” said Cai, the paper’s lead author and an expert in marine chemistry and carbon’s movement through coastal waters.

Continue reading ‘Acid zone in Chesapeake Bay identified’

Seasonal pH and carbondioxide level as indicator of vulnerability of fresh and marine aquatic systems to climate change in Nigeria

Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans; raising concern over the current and future effects it may have on world climates. Certain changes are already evident but the impact of these changes on marine and coastal living resources is only poorly understood at this stage, particularly in sub-Saharan Africa. This study assessed seasonal dissolved carbon dioxide and pH of fresh and marine aquatic systems in Nigeria. Dissolved CO2 was non-significantly (p=0.07) higher in freshwater during the wet season (20±7ppm) compared to dry season (15 ± 1ppm), while in the marine system, dissolved CO2 level was significantly (p=0.02) higher (42±6ppm) during the dry season compared to the rainy season (31±5ppm). Mean pH values was significantly higher (p=0.003 and 0.05) in freshwater (6.8±0.8 and 6.9±0.2ppm) relative to marine (6.2±0.2 and 6.5±0.3ppm) during wet and dry seasons, respectively. The pH values were generally at the borderline of the acidic limit of the recommended pH values for aquaculture (6.5-9) during the two seasons. Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to a greater CO2 uptake by the oceans, acidification and consequently, saturation, thereby affecting the ocean’s continued ability to store CO2. This study therefore provides preliminary information on seasonal changes in CO2 and pH of fresh and marine systems in Nigeria; and their potential impacts on global climate and aquatic ecosystems.

Continue reading ‘Seasonal pH and carbondioxide level as indicator of vulnerability of fresh and marine aquatic systems to climate change in Nigeria’

Genome-wide mutation rate response to pH change in the coral reef pathogen Vibrio shilonii AK1

Recent application of mutation accumulation techniques combined with whole-genome sequencing (MA/WGS) has greatly promoted studies of spontaneous mutation. However, such explorations have rarely been conducted on marine organisms, and it is unclear how marine habitats have influenced genome stability. This report resolves the mutation rate and spectrum of the coral reef pathogen Vibrio shilonii, which causes coral bleaching and endangers the biodiversity maintained by coral reefs. We found that its mutation rate and spectrum are highly similar to those of other studied bacteria from various habitats, despite the saline environment. The mutational properties of this marine bacterium are thus controlled by other general evolutionary forces such as natural selection and genetic drift. We also found that as pH drops, the mutation rate decreases and the mutation spectrum is biased in the direction of generating G/C nucleotides. This implies that evolutionary features of this organism and perhaps other marine microbes might be altered by the increasingly acidic ocean water caused by excess CO2 emission. Nonetheless, further exploration is needed as the pH range tested in this study was rather narrow and many other possible mutation determinants, such as carbonate increase, are associated with ocean acidification.

Continue reading ‘Genome-wide mutation rate response to pH change in the coral reef pathogen Vibrio shilonii AK1’

Impacts of acidic oceans revealed for key Alaska fish and shellfish species (audio and text)

The chemistry showing that our oceans are becoming more acidic can’t be denied.  So how does all that absorption of increasing carbon dioxide affect some key Alaska fisheries?

“The direct effect of carbon dioxide increase may be the pH effect on the ability of a pollock or cod to grow or to have gas exchange across the gill membranes. It may be carbonate availability for a crab to build a shell directly.”
Bob Foy is director of the NOAA Fisheries lab at Kodiak. Other impacts, he says, affect fish behavior and senses.

“ A number of studies have shown that some species of fish lose the olfactory ability to find prey with lower pH. That’s going to be a problem, obviously.”
Then there are the food web effects –

“Pteropods are known to be severely affected by ocean acidification they also are one of the most important prey items for pink salmon.”

Ocean acidification impacts are a research focus of at the Kodiak NOAA lab. At a Sea Grant marine science symposium, Foy revealed years of test results on key Alaska species.

Continue reading ‘Impacts of acidic oceans revealed for key Alaska fish and shellfish species (audio and text)’


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