Seawater carbonate chemistry and shell length of Mediterranean pteropod Cavolinia inflexa larvae during experiments

Larvae of the Mediterranean pteropod Cavolinia inflexa were maintained at controlled pHT values of 8.1, 7.82 and 7.51, equivalent respectively to pCO2 levels of 380, 857 and 1713 µatm. At pHT 7.82 larvae exhibited malformations and lower shell growth, compared to the control condition. At pHT 7.51 the larvae did not make shells but were viable and showed a normal development. However, smaller shells or no shells will have both ecological (food web) and biogeochemical (export of carbon and carbonate) consequences. These results confirm that 1pteropods, as well as the species dependent upon them as a food resource, will be severely impacted by ocean acidification.

Seawater carbonate chemistry and processes during experiments with benthic foraminifera Ammonia tepida

Evidence of increasing concentrations of dissolved carbon dioxide, especially in the surface ocean and its associated impacts on calcifying organisms, is accumulating. Among these organisms, benthic and planktonic foraminifera are responsible for a large amount of the globally precipitated calcium carbonate. Hence, their response to an acidifying ocean may have important consequences for future inorganic carbon cycling. To assess the sensitivity of benthic foraminifera to changing carbon dioxide levels and subsequent alteration in seawater carbonate chemistry, we cultured specimens of the shallow water species Ammonia tepida at two concentrations of atmospheric CO2 (230 and 1900 ppmv) and two temperatures (10 °C and 15 °C). Shell weights and elemental compositions were determined. Impact of high and low pCO2 on elemental composition are compared with results of a previous experiment were specimens were grown under ambient conditions (380 ppvm, no shell weight measurements of specimen grown under ambient conditions are, however, available). Results indicate that shell weights decrease with decreasing [CO3], although calcification was observed even in the presence of calcium carbonate under-saturation, and also decrease with increasing temperature. Thus both warming and ocean acidification may act to decrease shell weights in the future. Changes in [CO3] or total dissolved inorganic carbon do not affect the Mg distribution coefficient. On the contrary, Sr incorporation is enhanced under increasing [CO3]. Implications of these results for the paleoceanographic application of foraminifera are discussed.

Seawater carbonate chemistry and conditions of Mytilus edulis extracellular body fluids and shell composition in a pH-treatment experiment: Acid-base status, trace elements and delta11B, 2012

Mytilus edulis were cultured for 3 months under six different seawater pCO2 levels ranging from 380 to 4000 µatm. Specimen were taken from Kiel Fjord (Western Baltic Sea, Germany) which is a habitat with high and variable seawater pCO2 and related shifts in carbonate system speciation (e.g., low pH and low CaCO3 saturation state). Hemolymph (HL) and extrapallial fluid (EPF) samples were analyzed for pH and total dissolved inorganic carbon (CT) to calculate pCO2 and [HCO3]. A second experiment was conducted for 2 months with three different pCO2 levels (380, 1400 and 4000 µatm). Boron isotopes (delta11B) were investigated by LA-MC-ICP-MS (Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry) in shell portions precipitated during experimental treatment time. Additionally, elemental ratios (B/Ca, Mg/Ca and Sr/Ca) in the EPF of specimen from the second experiment were measured via ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometry). Extracellular pH was not significantly different in HL and EPF but systematically lower than ambient water pH. This is due to high extracellular pCO2 values, a prerequisite for metabolic CO2 excretion. No accumulation of extracellular [HCO3] was measured. Elemental ratios (B/Ca, Mg/Ca and Sr/Ca) in the EPF increased slightly with pH which is in accordance with increasing growth and calcification rates at higher seawater pH values. Boron isotope ratios were highly variable between different individuals but also within single shells. This corresponds to a high individual variability in fluid B/Ca ratios and may be due to high boron concentrations in the organic parts of the shell. The mean delta11B value shows no trend with pH but appears to represent internal pH (EPF) rather than ambient water pH.

Seawater carbonate chemistry and calcification rate during mesocosm experiments with coral Montipora capitata, 2008

A long-term (10 months) controlled experiment was conducted to test the impact of increased partial pressure of carbon dioxide (pCO2) on common calcifying coral reef organisms. The experiment was conducted in replicate continuous flow coral reef mesocosms flushed with unfiltered sea water from Kaneohe Bay, Oahu, Hawaii. Mesocosms were located in full sunlight and experienced diurnal and seasonal fluctuations in temperature and sea water chemistry characteristic of the adjacent reef flat. Treatment mesocosms were manipulated to simulate an increase in pCO2 to levels expected in this century [midday pCO2 levels exceeding control mesocosms by 365 ± 130 µatm (mean ± sd)]. Acidification had a profound impact on the development and growth of crustose coralline algae (CCA) populations. During the experiment, CCA developed 25% cover in the control mesocosms and only 4% in the acidified mesocosms, representing an 86% relative reduction. Free-living associations of CCA known as rhodoliths living in the control mesocosms grew at a rate of 0.6 g buoyant weight per year while those in the acidified experimental treatment decreased in weight at a rate of 0.9 g buoyant weight per year, representing a 250% difference. CCA play an important role in the growth and stabilization of carbonate reefs, so future changes of this magnitude could greatly impact coral reefs throughout the world. Coral calcification decreased between 15% and 20% under acidified conditions. Linear extension decreased by 14% under acidified conditions in one experiment. Larvae of the coral Pocillopora damicornis were able to recruit under the acidified conditions. In addition, there was no significant difference in production of gametes by the coral Montipora capitata after 6 months of exposure to the treatments.

Seawater carbonate chemistry and biological processes during experiments with a Sea Star Crassaster papposus, 2010

Ocean acidification (OA) is believed to be a major threat for near-future marine ecosystems, and that the most sensitive organisms will be calcifying organisms and the free-living larval stages produced by most benthic marine species. In this respect, echinoderms are one of the taxa most at risk. Earlier research on the impact of near-future OA on echinoderm larval stages showed negative effects, such as a decreased growth rate, increased mortality, and developmental abnormalities. However, all the long-term studies were performed on planktotrophic larvae while alternative life-history strategies, such as nonfeeding lecithotrophy, were largely ignored. Here, we show that lecithotrophic echinoderm larvae and juveniles are positively impacted by ocean acidification. When cultured at low pH, larvae and juveniles of the sea star Crossaster papposus grow faster with no visible affects on survival or skeletogenesis. This suggests that in future oceans, lecithotrophic species may be better adapted to deal with the threat of OA compared with planktotrophic ones with potentially important consequences at the ecosystem level. For example, an increase in populations of the top predator C. papposus will likely have huge consequences for community structure. Our results also highlight the importance of taking varying life-history strategies into account when assessing the impacts of climate change, an approach that also provides insight into understanding the evolution of life-history strategies.

Seawater carbonate chemistry and biological processes of Sepia officinalis during experiments, 2010

Acidification of ocean surface waters by anthropogenic carbon dioxide (CO2) emissions is a currently developing scenario that warrants a broadening of research foci in the study of acid-base physiology. Recent studies working with environmentally relevant CO2 levels, indicate that some echinoderms and molluscs reduce metabolic rates, soft tissue growth and calcification during hypercapnic exposure. In contrast to all prior invertebrate species studied so far, growth trials with the cuttlefish Sepia officinalis found no indication of reduced growth or calcification performance during long-term exposure to 0.6 kPa CO2. It is hypothesized that the differing sensitivities to elevated seawater pCO2 could be explained by taxa specific differences in acid-base regulatory capacity. In this study, we examined the acid-base regulatory ability of S. officinalis in vivo, using a specially modified cannulation technique as well as 31P NMR spectroscopy. During acute exposure to 0.6 kPa CO2, S. officinalis rapidly increased its blood [HCO3] to 10.4 mM through active ion-transport processes, and partially compensated the hypercapnia induced respiratory acidosis. A minor decrease in intracellular pH (pHi) and stable intracellular phosphagen levels indicated efficient pHi regulation. We conclude that S. officinalis is not only an efficient acid-base regulator, but is also able to do so without disturbing metabolic equilibria in characteristic tissues or compromising aerobic capacities. The cuttlefish did not exhibit acute intolerance to hypercapnia that has been hypothesized for more active cephalopod species (squid). Even though blood pH (pHe) remained 0.18 pH units below control values, arterial O2 saturation was not compromised in S. officinalis because of the comparatively lower pH sensitivity of oxygen binding to its blood pigment. This raises questions concerning the potentially broad range of sensitivity to changes in acid-base status amongst invertebrates, as well as to the underlying mechanistic origins. Further studies are needed to better characterize the connection between acid-base status and animal fitness in various marine species.

Seawater carbonate chemistry and biological processes of Emiliania huxleyi (PML B92/11) during experiments, 2011

The present study investigates the combined effect of phosphorous limitation, elevated partial pressure of CO2 (pCO2) and temperature on a calcifying strain of Emiliania huxleyi (PML B92/11) by means of a fully controlled continuous culture facility. Two levels of phosphorous limitation were consecutively applied by renewal of culture media (N:P = 26) at dilution rates (D) of 0.3 d- and 0.1 d-1. CO2 and temperature conditions were 300, 550 and 900 µatm pCO2 at 14 °C and 900 µatm pCO2 at 18 °C. In general, the steady state cell density and particulate organic carbon (POC) production increased with pCO2, yielding significantly higher concentrations in cultures grown at 900 µatm pCO2 compared to 300 and 550 µatm pCO2. At 900 µatm pCO2, elevation of temperature as expected for a greenhouse ocean, further increased cell densities and POC concentrations. In contrast to POC concentration, C-quotas (pmol C cell-1) were similar at D = 0.3 d-1 in all cultures. At D = 0.1 d-1, a reduction of C-quotas by up to 15% was observed in the 900 µatm pCO2 at 18 °C culture. As a result of growth rate reduction, POC:PON:POP ratios deviated strongly from the Redfield ratio, primarily due to an increase in POC. Ratios of particulate inorganic and organic carbon (PIC:POC) ranged from 0.14 to 0.18 at D = 0.3 d-1, and from 0.11 to 0.17 at D = 0.1 d-1, with variations primarily induced by the changes in POC. At D = 0.1 d-1, cell volume was reduced by up to 22% in cultures grown at 900 µatm pCO2. Our results indicate that changes in pCO2, temperature and phosphorus supply affect cell density, POC concentration and size of E. huxleyi (PML B92/11) to varying degrees, and will likely impact bloom development as well as biogeochemical cycling in a greenhouse ocean.

Seawater carbonate chemistry and biological processes during experiments with common cuttlefish Sepia officinalis, 2010

Ocean acidification and associated changes in seawater carbonate chemistry negatively influence calcification processes and depress metabolism in many calcifying marine invertebrates. We present data on the cephalopod mollusc Sepia officinalis, an invertebrate that is capable of not only maintaining calcification, but also growth rates and metabolism when exposed to elevated partial pressures of carbon dioxide (pCO2). During a 6 wk period, juvenile S. officinalis maintained calcification under ~4000 and ~6000 ppm CO2, and grew at the same rate with the same gross growth efficiency as did control animals. They gained approximately 4% body mass daily and increased the mass of their calcified cuttlebone by over 500%. We conclude that active cephalopods possess a certain level of pre-adaptation to long-term increments in carbon dioxide levels. Our general understanding of the mechanistic processes that limit calcification must improve before we can begin to predict what effects future ocean acidification will have on calcifying marine invertebrates.

Seawater carbonate chemistry and severe tissue damage in Atlantic cod larvae under increasing ocean acidification, 2012

Ocean acidification, caused by increasing atmospheric concentrations of CO2, is one of the most critical anthropogenicthreats to marine life. Changes in seawater carbonate chemistry have the potential to disturb calcification, acid-base regulation, blood circulation and respiration, as well as the nervous system of marine organisms, leading to long-term effects such as reduced growth rates and reproduction. In teleost fishes, early life-history stages are particularly vulnerable as they lack specialized internal pH regulatory mechanisms. So far, impacts of relevant CO2concentrations on larval fish have been found in behaviour and otolith size, mainly in tropical, non-commercial species. Here we show detrimental effects of ocean acidification on the development of a mass-spawning fish species of high commercial importance. We reared Atlantic cod larvae at three levels of CO2, (1) present day, (2) end of next century and (3) an extreme, coastal upwelling scenario, in a long-term ( 2.5 1/2 months) mesocosm experiment. Exposure to CO2 resulted in severe to lethal tissue damage in many internal organs, with the degree of damage increasing with CO2 concentration. As larval survival is the bottleneck to recruitment, ocean acidification has the potential to act as an additional source of natural mortality, affecting populations of already exploited fish stocks.

Seawater carbonate chemistry and biological processes during experiments with common cuttlefish Sepia officinalis, 2008

Ocean acidification and associated changes in seawater carbonate chemistry negatively influence calcification processes and depress metabolism in many calcifying marine invertebrates. We present data on the cephalopod mollusc Sepia officinalis, an invertebrate that is capable of not only maintaining calcification, but also growth rates and metabolism when exposed to elevated partial pressures of carbon dioxide (pCO2). During a 6 wk period, juvenile S. officinalis maintained calcification under ~4000 and ~6000 ppm CO2, and grew at the same rate with the same gross growth efficiency as did control animals. They gained approximately 4% body mass daily and increased the mass of their calcified cuttlebone by over 500%. We conclude that active cephalopods possess a certain level of pre-adaptation to long-term increments in carbon dioxide levels. Our general understanding of the mechanistic processes that limit calcification must improve before we can begin to predict what effects future ocean acidification will have on calcifying marine invertebrates.

Seawater carbonate chemistry and calcification of Lophelia pertusa during experiments, 2009

The cold-water coral Lophelia pertusa is one of the few species able to build reef-like structures and a 3-dimensional coral framework in the deep oceans. Furthermore, deep cold-water coral bioherms may be among the first marine ecosystems to be affected by ocean acidification. Colonies of L. pertusa were collected during a cruise in 2006 to cold-water coral bioherms of the Mingulay reef complex (Hebrides, North Atlantic). Shortly after sample collection onboard these corals were labelled with calcium-45. The same experimental approach was used to assess calcification rates and how those changed due to reduced pH during a cruise to the Skagerrak (North Sea) in 2007. The highest calcification rates were found in youngest polyps with up to 1% d-1 new skeletal growth and average rates of 0.11±0.02% d-1±S.E.). Lowering pH by 0.15 and 0.3 units relative to the ambient level resulted in calcification being reduced by 30 and 56%. Lower pH reduced calcification more in fast growing, young polyps (59% reduction) than in older polyps (40% reduction). Thus skeletal growth of young and fast calcifying corallites suffered more from ocean acidification. Nevertheless, L. pertusa exhibited positive net calcification (as measured by 45Ca incorporation) even at an aragonite saturation state below 1.

FE simulation and experimental tests of high-strength structural bolts under tension

Experimental tests have been completed for high-strength 8.8 bolts for studying their mechanical performance subjected to tensile loading. As observed from these tests, failure of structural bolts has been identified as in one of two ways: threads stripping and necking of the threaded portion of the bolt shank, which is possibly due to the degree of fit between internal and external threads. Following the experimental work, a numerical approach has been developed for demonstration of the tensile performance with proper consideration of tolerance class between bolts and nuts. The degree of fit between internal and external threads has been identified as a critical factor affecting failure mechanisms of high-strength structural bolts in tension, which is caused by the machining process. In addition, different constitutive material laws have been taken into account in the numerical simulation, demonstrating the entire failure mechanism for structural bolts with different tolerance classes in their threads. It is also observed that the bolt capacities are closely associated with their failure mechanisms.

Computational and experimental study of the behavior of cyano-based ionic liquids in aqueous solution

The solvation of cyano- (CN-) based ionic liquids (ILs) and their capacity to establish hydrogen bonds (H-bonds) with water was studied by means of experimental and computational approaches. Experimentally, water activity data were measured for aqueous solutions of ILs based on 1-butyl-3-methylimidazolium ([BMIM](+)) cation combined with one of the following anions: thiocyanate ([SCN](-)), dicyanamide ([DCA](-)), or tricyanomethanide ([TCM](-)), and of 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][TCB]). From the latter data, water activity coefficients were estimated showing that [BMIM][SCN] and [BMIM][DCA], unlike [BMIM][TCM] and [EMIM][TCB], are able to establish favorable interactions with water. Computationally, the conductor like screening model for real solvents (COSMO-RS) was used to estimate the water activity coefficients which compare well with the experimental ones. From the COSMO-RS results, it is suggested that the polarity of each ion composing the ILs has a strong effect on the solvation phenomena. Furthermore, classical molecular dynamics (MD) simulations were performed for obtaining an atomic level picture of the local molecular neighborhood of the different species. From the experimental and computational data it is showed that increasing the number of CN groups in the ILs' anions does not enhance their ability to establish H-bonds with water but decreases their polarities, being [BMIM][DCA] and [BMIM][SCN] the ones presenting higher propensity to interact.

Arsenic Geochemitry in Warm Spring Ponds: New Field and Experimental Results

Silver Bow Creek (SBC) flows into the Warm Springs Ponds Operable Unit (WSPOU), where various containment cells are used to precipitate copper and other metals (e.g., Cd, Cu, Mn, Pb, Zn). Lime is added seasonally to increase the pH and assist in removal of metals from the water column. Although the WSPOU is effective at removing copper and other cationic trace metals, concentrations of dissolved arsenic exiting the facility are often above the site specific standard, 20 20 ug/L, during low-flow periods each summer and fall. This thesis is a continuation of arsenic geochemistry studies by Montana Tech in the WSPOU. Field work focused on Pond 3, the largest and first in the series of treatment ponds. Shallow groundwater was sampled from 8 PVC piezometers located near the south end of Pond 3. Three sediment pore-water diffusion samplers (“peepers”) were also deployed at the south end of Pond 3 to examine vertical gradients in chemistry in the top 25 cm of the pond sediment. In general, the pH and Eh values of the shallow groundwater and sediment pore-water were less than in the pond water. Concentrations of arsenic were generally higher in subsurface water, and tended to pass through a maximum (up to 530 g/L) about 10 cm below the sediment-water interface. In the peeper cells, there was a strong positive correlation between dissolved As and dissolved Fe, and an inverse correlation with sulfate. Therefore, the zone of arsenic release corresponds to a zone of bacterial Fe and sulfate reduction in the shallow, organic-rich sediment. Redox speciation of arsenic shows that arsenate (As(V)) is dominant in the pond, and arsenite (As(III)) is dominant in the subsurface water. A series of laboratory experiments with pH adjustment were completed using SBC water collected near the inlet to the WSPOU as well as water and shallow sediment collected from Pond 3. Water ± sediment mesocosms were set up in 1-L Nalgene bottles (closed system) or a 20-L aquarium (open system), both with continuous stirring. The pH of the mesocosm was adjusted by addition of NaOH or HNO3 acid. The closed system provided better pH control since the water was not in contact with the atmosphere, which prevented exchange of carbon dioxide. In both the closed and open systems, dissolved arsenic concentrations either decreased or stayed roughly the same with increase in pH to values > 11. Therefore, the release of dissolved As into the treatment ponds in low-flow periods is not due to changes in pH alone. All of these results support the hypothesis that the arsenic release in WSPOU is linked to microbial reduction of ferric oxide minerals in the organic-rich sediment. Upwards diffusion of dissolved As from the sediment pore-water into the pond water is the most likely explanation for the increase in As concentration of the WSPOU in low-flow periods.