CO2-acidified Seawater Research Articles

Response of CRH system in brain and gill of marine medaka to seawater acidification.

Corticotropin-releasing hormone (CRH) is mainly secreted by the hypothalamus to regulate stress when environmental factors change. Gills contact with water directly and may also secrete CRH to maintain local homeostasis. Ocean acidification changes water chemical parameters and is becoming an important environmental stressor for marine fish. The response of brain and gill CRH systems to ocean acidification remains unclear. In this study, marine medaka were exposed to CO2-acidified seawater (440ppm, 1000ppm, and 1800ppm CO2) for 2h, 4h, 24h, and 7 d, respectively. At 2h and 4h, the expression of crh mRNA in gills increased with increasing CO2 concentration. Crh protein is expressed mainly in the lamellae cells. crhbp and crhr1 expression also increased significantly. However, at 2h and 4h, acidification caused little changes in these genes and Crh protein expression in the brain. At 7 d, Crh-positive cells were detected in the hypothalamus; moreover, Crh protein expression in the whole brain increased. It is suggested that CRH autocrine secretion in gills is responsible for local acid-base regulation rather than systemic mobilization after short-term acidification stress, which may help the rapid regulation of body damage caused by environmental stress.

Independent effects of seawater pH and high PCO2 on olfactory sensitivity in fish: possible role of carbonic anhydrase.

Ocean acidification may alter olfactory-driven behaviour in fish by direct effects on the peripheral olfactory system; olfactory sensitivity is reduced in CO2-acidified seawater. The current study tested whether this is due to elevated PCO2 or the consequent reduction in seawater pH and, if the former, the possible involvement of carbonic anhydrase, the enzyme responsible for the hydration of CO2 and production of carbonic acid. Olfactory sensitivity to amino acids was assessed by extracellular multi-unit recording from the olfactory nerve of the gilthead seabream (Sparus aurata L.) in normal seawater (pH ∼8.2), and after acute exposure to acidified seawater (pH ∼7.7) but normal PCO2 (∼340 µatm) or to high PCO2 seawater (∼1400 µatm) at normal pH (∼8.2). Reduced pH in the absence of elevated PCO2 caused a reduction in olfactory sensitivity to l-serine, l-leucine, l-arginine and l-glutamine, but not l-glutamic acid. Increased PCO2 in the absence of changes in pH caused reduced olfactory sensitivity to l-serine, l-leucine and l-arginine, including increases in their threshold of detection, but had no effect on sensitivity to l-glutamine and l-glutamic acid. Inclusion of 1 mmol l-1 acetazolamide (a membrane-permeant inhibitor of carbonic anhydrase) in the seawater reversed the inhibition of olfactory sensitivity to l-serine caused by high PCO2 Ocean acidification may reduce olfactory sensitivity by reductions in seawater pH and intracellular pH (of olfactory receptor neurones); the former by reducing odorant-receptor affinity, and the latter by reducing the efficiency of olfactory transduction. The physiological role of carbonic anhydrase in the olfactory receptor neurones remains to be explored.

Gene expression correlated with delay in shell formation in larval Pacific oysters (Crassostrea gigas) exposed to experimental ocean acidification provides insights into shell formation mechanisms

BackgroundDespite recent work to characterize gene expression changes associated with larval development in oysters, the mechanism by which the larval shell is first formed is still largely unknown. In Crassostrea gigas, this shell forms within the first 24 h post fertilization, and it has been demonstrated that changes in water chemistry can cause delays in shell formation, shell deformations and higher mortality rates. In this study, we use the delay in shell formation associated with exposure to CO2-acidified seawater to identify genes correlated with initial shell deposition.ResultsBy fitting linear models to gene expression data in ambient and low aragonite saturation treatments, we are able to isolate 37 annotated genes correlated with initial larval shell formation, which can be categorized into 1) ion transporters, 2) shell matrix proteins and 3) protease inhibitors. Clustering of the gene expression data into co-expression networks further supports the result of the linear models, and also implies an important role of dynein motor proteins as transporters of cellular components during the initial shell formation process.ConclusionsUsing an RNA-Seq approach with high temporal resolution allows us to identify a conceptual model for how oyster larval calcification is initiated. This work provides a foundation for further studies on how genetic variation in these identified genes could affect fitness of oyster populations subjected to future environmental changes, such as ocean acidification.

Effects of reduced pH and elevated pCO2 on sperm motility and fertilisation success in blood clam, Tegillarca granosa

ABSTRACTAlthough it has been shown that ocean acidification generally has a negative impact on fertilisation success of broadcast spawning marine organisms, whether induced fertilisation success reduction is a consequence of elevated pCO2 or decreased pH remains unclear. Therefore, the impacts of HCl- and CO2-induced acidified seawater on sperm motility and gametes fertilisation capability of a broadcast spawning bivalve species, Tegillarca granosa were investigated in the present study. The results showed that the fertilisation capability of both gametes was significantly reduced in either HCl- or CO2-acidified seawater. In addition, significant impacts on sperm motility were observed in the group exposed to CO2-acidified seawater, suggesting that this parameter is sensitive to pCO2 instead of solely pH value. The differences between the two seawater acidification manipulating methods may be due to the intrinsic difference in diffusion capability of CO2 and protons.

Response of antioxidant defense system in copepod Calanus sinicus Brodsky exposed to CO2-acidified seawater

Marine zooplankton responds sensitively to elevated seawater CO2 concentration. However, the underlying physiological mechanisms have not been studied well. We therefore investigated the effects of elevated CO2 concentration (0.08%, 0.20%, 0.50% and 1.00%) on antioxidant defense components, as well as two detoxification enzymes of Calanus sinicus (copepod). The results showed that glutathione peroxidase (GPx) activity exposed to CO2-acidified seawater was significantly stimulated while other antioxidant components, including glutathione-S-transferase (GST) activity, superoxide dismutase (SOD) activity decreased significantly with reduced glutathione (GSH) level and GSH/oxidized glutathione (GSSG) value. CO2-acidified seawater exhibited stimulatory effects on adenosine triphosphatase (ATPase) activity and acetylcholinesterase (AchE) activity was inhibited. Moreover, the results of principal component analysis indicated that 75.93% of the overall variance was explained by the first two principal components. The elevated CO2 concentration may affect the metabolism and survivals of copepods through impacts these enzymes activities. Further studies are needed to focus on the synergistic effects of elevated CO2 concentration and other environmental factors on copepods.

Juvenile Antarctic rockcod (Trematomus bernacchii) are physiologically robust to CO2-acidified seawater.

To date, numerous studies have shown negative impacts of CO2-acidified seawater (i.e. ocean acidification, OA) on marine organisms, including calcifying invertebrates and fishes; however, limited research has been conducted on the physiological effects of OA on polar fishes and even less on the impact of OA on early developmental stages of polar fishes. We evaluated aspects of aerobic metabolism and cardiorespiratory physiology of juvenile emerald rockcod, ITALIC! Trematomus bernacchii, an abundant fish in the Ross Sea, Antarctica, to elevated partial pressure of carbon dioxide ( ITALIC! PCO2 ) [420 (ambient), 650 (moderate) and 1050 (high) μatm ITALIC! PCO2 ] over a 1month period. We examined cardiorespiratory physiology, including heart rate, stroke volume, cardiac output and ventilation rate, whole organism metabolism via oxygen consumption rate and sub-organismal aerobic capacity by citrate synthase enzyme activity. Juvenile fish showed an increase in ventilation rate under high ITALIC! PCO2compared with ambient ITALIC! PCO2 , whereas cardiac performance, oxygen consumption and citrate synthase activity were not significantly affected by elevated ITALIC! PCO2 Acclimation time had a significant effect on ventilation rate, stroke volume, cardiac output and citrate synthase activity, such that all metrics increased over the 4week exposure period. These results suggest that juvenile emerald rockcod are robust to near-future increases in OA and may have the capacity to adjust for future increases in ITALIC! PCO2 by increasing acid-base compensation through increased ventilation.

Elevated CO2 induces a bloom of microphytobenthos within a shell gravel mesocosm.

The geological storage of carbon dioxide (CO2) is expected to be an important component of future global carbon emission mitigation, but there is a need to understand the impacts of a CO2 leak on the marine environment and to develop monitoring protocols for leakage detection. In the present study, sediment cores were exposed to CO2-acidified seawater at one of five pH levels (8.0, 7.5, 7.0, 6.5 and 6.0) for 10 weeks. A bloom of Spirulina sp. and diatoms appeared on sediment surface exposed to pH 7.0 and 7.5 seawater. Quantitative PCR measurements of the abundance of 16S rRNA also indicated an increase within the pH 7.0 and 7.5 treatments after 10 weeks incubation. More detailed analysis of the microbial communities from the pH 7.0, 7.5 and 8.0 treatments confirmed an increase in the relative abundance of Spirulina sp. and Navicula sp. sequences, with changes in the relative abundance of major archaeal and bacterial groups also detected within the pH 7.0 treatment. A decreased flux of silicate from the sediment at this pH was also detected. Monitoring blooms of microphytobenthos may prove useful as an indicator of CO2 leakage within coastal areas.

Species-specific differences in thermal tolerance may define susceptibility to intracellular acidosis in reef corals

It is widely acknowledged that temperature stress affects an organism’s sensitivity to ocean acidification and vice versa, yet it is not clear how the two are mechanistically linked. Here, we induced thermal stress in two coral species with differing bleaching susceptibilities to measure how a reduction in photosynthetic performance impacts intracellular pH (pHi) regulation in the symbiotic dinoflagellates (Symbiodinium sp.) and their host coral cells. Our hypothesis was that thermally induced photosynthetic dysfunction in the symbiont would prevent the efficient removal of additional CO2, lowering its buffering capacity and thus increasing the host cell’s susceptibility to intracellular acidosis. To test this, we exposed Pocillopora damicornis (a thermally sensitive coral) and Montipora capitata (a thermally resilient coral) to four different temperature treatments (23.8, 25.5, 28 and 31 °C) for 1 week. We then isolated intact symbiotic coral endodermal cells, placed them in a live-cell chamber attached to a confocal microscope and bathed them in CO2-acidified seawater (~pH 7.6) for 30 min, before measuring the light-adapted pHi of both the host cell and its symbiont. Cells isolated from P. damicornis were more prone to cellular acidosis (declines in pHi of 11 and 8 % in host and symbiont, respectively, at 31 °C relative to 23.8 °C) than cells isolated from M. capitata (5 and 4 %, respectively). These results highlight the important role of Symbiodinium productivity (in addition to a range of physico-chemical factors such as skeletal morphology and tissue pigmentation) in determining the sensitivity of corals to rising sea surface temperatures and ocean acidification.

Effects of Elevated Carbon Dioxide (CO2) Concentrations on Early Developmental Stages of the Marine Copepod Calanus finmarchicus Gunnerus (Copepoda: Calanoidae)

Ocean acidification poses an ongoing threat to marine organisms, and early life stages are believed to be particularly sensitive. The boreal calanoid copepod Calanus finmarchicus seasonally dominates the standing stock of zooplankton in the northern North Sea and North Atlantic, and due to its size and abundance is considered an ecological key species linking energy from primary producers to higher trophic levels. To examine whether the early stages of C. finmarchicus are particularly vulnerable to elevated levels of CO2, eggs and nauplii were subjected to different levels of CO2-acidified seawater for 1 wk. The first experiment, with eggs as the starting point, revealed no marked effect on hatching success, but a significant reduction in nauplii survival during incubation at 8800 ppm CO2. In addition, a significant decrease in ontogenetic development rate during incubation at 8800 ppm CO2 was observed in this experiment. In the second experiment, where third-stage nauplii represented the starting point, no significant effects on ontogenetic development and survival following exposure to pCO2 ≥ 7700 ppm were observed. Data suggest that the two first nauplii stages, which are fed endogenously, may be more vulnerable and therefore likely to represent the “bottleneck” for this species in a more acidic ocean. However, the absence of significant effects in the most sensitive stages during exposure to 2800 ppm CO2, a level that is well above worst-case scenario predictions for year 2300 (approximately 2000 ppm CO2), suggests that this species may be generally robust to direct effects of ocean acidification.

Aerobic scope fails to explain the detrimental effects on growth resulting from warming and elevated CO2 in Atlantic halibut

As a consequence of increasing atmospheric CO2, the world's oceans are becoming warmer and more acidic. Whilst the ecological effects of these changes are poorly understood, it has been suggested that fish performance including growth will be reduced mainly as a result of limitations in oxygen transport capacity. Contrary to the predictions given by the oxygen- and capacity-limited thermal tolerance hypothesis, we show that aerobic scope and cardiac performance of Atlantic halibut (Hippoglossus hippoglossus) increase following 14-16 weeks exposure to elevated temperatures and even more so in combination with CO2-acidified seawater. However, the increase does not translate into improved growth, demonstrating that oxygen uptake is not the limiting factor for growth performance at high temperatures. Instead, long-term exposure to CO2-acidified seawater reduces growth at temperatures that are frequently encountered by this species in nature, indicating that elevated atmospheric CO2 levels may have serious implications on fish populations in the future.

Medium-term exposure of the North Atlantic copepod <i>Calanus finmarchicus</i> (Gunnerus, 1770) to CO<sub>2</sub>-acidified seawater: effects on survival and development

Abstract. The impact of medium-term exposure to CO2-acidified seawater on survival, growth and development was investigated in the North Atlantic copepod Calanus finmarchicus. Using a custom developed experimental system, fertilized eggs and subsequent development stages were exposed to normal seawater (390 ppm CO2) or one of three different levels of CO2-induced acidification (3300, 7300, 9700 ppm CO2). Following the 28-day exposure period, survival was found to be unaffected by exposure to 3300 ppm CO2, but significantly reduced at 7300 and 9700 ppm CO2. Also, the proportion of copepodite stages IV to VI observed in the different treatments was significantly affected in a manner that may indicate a CO2-induced retardation of the rate of ontogenetic development. Morphometric analysis revealed a significant increase in size (prosome length) and lipid storage volume in stage IV copepodites exposed to 3300 ppm CO2 and reduced size in stage III copepodites exposed to 7300 ppm CO2. Together, the findings indicate that a pCO2 level ≤2000 ppm (the highest CO2 level expected by the year 2300) will probably not directly affect survival in C. finmarchicus. Longer term experiments at more moderate CO2 levels are, however, necessary before the possibility that growth and development may be affected below 2000 ppm CO2 can be ruled out.

Acute extracellular acid–base disturbance in the burrowing sea urchin Brissopsis lyrifera during exposure to a simulated CO2 release

We tested the hypothesis that as infaunal organisms are regularly exposed to elevated CO2, burrowing sea urchins will demonstrate a lower sensitivity to massive CO2 release than has previously been recorded for epifaunal organisms. Infaunal urchins Brissopsis lyrifera were exposed to CO2 acidified sea water (nominal pH 7.8 (control), 7.3, 6.5 and 5.9; T=10°C, S=34) for 12h and aspects of their extracellular acid–base balance measured every 2h. In common with epifaunal urchins B. lyrifera exhibited an uncompensated respiratory acidosis in its extracellular fluid, but was more sensitive to CO2 acidification than epifaunal urchins. The lower extracellular pH of B. lyrifera may indicate a higher metabolism than epifaunal urchins and this could explain the heightened sensitivity of this species to elevated CO2. Thus, the results of this present study do not support our original hypothesis. Instead we suggest an alternative hypothesis that as infaunal organisms are exposed naturally to high levels of CO2, they may already be closer to the limits of their physiological performance. Thus any further CO2 increase could compromise their function. As a result of this sensitivity, infaunal urchins may be more at risk from an accidental release of CO2 from geological sub-seabed storage sites, or from the deliberate injection of CO2 into deep water masses, than their epifaunal counterparts.

End of century ocean warming and acidification effects on reproductive success in a temperate marine copepod

We examined how predicted end of century ocean warming and acidification scenarios affected the incidence of apoptosis in the eggs and nauplii of the copepod Calanus helgolandicus. Offspring viability was not affected by 1000 ppm CO2-acidified seawater, whereas the effects of 2 and 4°C warming were dependent upon the batch of eggs used; warming increased viability in the second batch. This context-dependency highlights the need for cautious interpretation and application of data from individual climate-change studies.

Impact of ocean acidification on benthic and water column ammonia oxidation

Ammonia oxidation is a key microbial process within the marine N-cycle. Sediment and water column samples from two contrasting sites in the English Channel (mud and sand) were incubated (up to 14 weeks) in CO2-acidified seawater ranging from pH 8.0 to pH 6.1. Additional observations were made off the island of Ischia (Mediterranean Sea), a natural analogue site, where long-term thermogenic CO2 ebullition occurs (from pH 8.2 to pH 7.6). Water column ammonia oxidation rates in English Channel samples decreased under low pH with near-complete inhibition at pH 6.5. Water column Ischia samples showed a similar though not statistically significant trend. However, sediment ammonia oxidation rates at all three locations were not affected by reduced pH. These observations may be explained by buffering within sediments or low-pH adaptation of the microbial ammonia oxidizing communities. Our observations have implications for modeling the future impact of ocean acidification on marine ecosystems.

Impact of CO2-acidified seawater on the extracellular acid–base balance of the northern sea urchin Strongylocentrotus dröebachiensis

We investigated the effect of five day exposure to CO2-acidified sea water treatments (pHNBS=7.89 [control], 7.44, 7.16 and 6.78, T=9.5°C) on the extracellular acid–base balance of the northern sea urchin Strongylocentrotus dröebachiensis. In each case there was an uncompensated respiratory acidosis which increased in intensity with decreasing environmental pH. This was very similar to results for another sea urchin species, Psammechinus miliaris (8d exposure, T=15°C). However, there were some important differences in the response to low seawater pH between the two urchin species S. dröebachiensis and P. miliaris. At the lowest pH tested (6.78) there was a metabolic component to this acidosis recorded (correlated with a significant increase in l-lactate) in S. dröebachiensis but not P. miliaris. The acidosis was accompanied by a very small, but significant increase in coelomic fluid calcium. Also the water used in our study was (controlling for pH) markedly undersaturated with respect to carbonate compared with that used in the Psammechinus study, highlighting the need for the environmental context to be assessed in future comparative studies.

Short-term exposure to hypercapnia does not compromise feeding, acid–base balance or respiration ofPatella vulgatabut surprisingly is accompanied by radula damage

The effect of short-term (5 days) exposure to CO2-acidified seawater (year 2100 predicted values, ocean pH = 7.6) on key aspects of the function of the intertidal common limpetPatella vulgata(Gastropoda: Patellidae) was investigated. Changes in extracellular acid–base balance were almost completely compensated by an increase in bicarbonate ions. A concomitant increase in haemolymph Ca2+and visible shell dissolution implicated passive shell dissolution as the bicarbonate source. Analysis of the radula using SEM revealed that individuals from the hypercapnic treatment showed an increase in the number of damaged teeth and the extent to which such teeth were damaged compared with controls. As radula teeth are composed mainly of chitin, acid dissolution seems unlikely, and so the proximate cause of damage is unknown. There was no hypercapnia-related change in metabolism (O2uptake) or feeding rate, also discounting the possibility that teeth damage was a result of a CO2-related increase in grazing. We conclude that although the limpet appears to have the physiological capacity to maintain its extracellular acid–base balance, metabolism and feeding rate over a 5 days exposure to acidified seawater, radular damage somehow incurred during this time could still compromise feeding in the longer term, in turn decreasing the top-down ecosystem control thatP. vulgataexerts over rocky shore environments.

Effect of CO<sub>2</sub>-related acidification on aspects of the larval development of the European lobster, <i>Homarus gammarus</i> (L.)

Abstract. Oceanic uptake of anthropogenic CO2 results in a reduction in pH termed "Ocean Acidification" (OA). Comparatively little attention has been given to the effect of OA on the early life history stages of marine animals. Consequently, we investigated the effect of culture in CO2-acidified sea water (approx. 1200 ppm, i.e. average values predicted using IPCC 2007 A1F1 emissions scenarios for year 2100) on early larval stages of an economically important crustacean, the European lobster Homarus gammarus. Culture in CO2-acidified sea water did not significantly affect carapace length of H. gammarus. However, there was a reduction in carapace mass during the final stage of larval development in CO2-acidified sea water. This co-occurred with a reduction in exoskeletal mineral (calcium and magnesium) content of the carapace. As the control and high CO2 treatments were not undersaturated with respect to any of the calcium carbonate polymorphs measured, the physiological alterations we record are most likely the result of acidosis or hypercapnia interfering with normal homeostatic function, and not a direct impact on the carbonate supply-side of calcification per se. Thus despite there being no observed effect on survival, carapace length, or zoeal progression, OA related (indirect) disruption of calcification and carapace mass might still adversely affect the competitive fitness and recruitment success of larval lobsters with serious consequences for population dynamics and marine ecosystem function.

The effect of CO2 acidified sea water and reduced salinity on aspects of the embryonic development of the amphipod Echinogammarus marinus (Leach)

We investigated the effect of CO2 acidified sea water (S=35, 22 and 10PSU) on embryonic development of the intertidal amphipod Echinogammarus marinus (Leach). Low pH, but not low salinity (22PSU), resulted in a more protracted embryonic development in situ although the effect was only evident at low salinity. However reduced salinity, not pH, exerted a strong significant effect, on numbers and calcium content of hatchlings. Females exposed to low salinity (10PSU) did not carry eggs through to hatching. There was no significant difference in the number of viable hatchlings between females cultured in 22 and 35PSU but the exoskeleton of the juveniles at 22PSU contained significantly less calcium. Ocean acidification may affect aspects of E. marinus development but exposure to realistic low salinities appear, in the short term, to be more important in impacting development than exposure to CO2 acidified sea water at levels predicted for 300years time.

Effects of CO2-induced seawater acidification on the health of Mytilus edulis

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 37:215-225 (2008) - DOI: https://doi.org/10.3354/cr00765 Effects of CO2-induced seawater acidification on the health of Mytilus edulis A. Beesley*, D. M. Lowe, C. K. Pascoe, S. Widdicombe Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth, Devon PL1 3DH, UK *Email: abee@pml.ac.uk ABSTRACT: The impact of CO2-acidified seawater (pH 7.8, 7.6, or 6.5, control = pH 8) on the health of Mytilus edulis was investigated during a 60 d mesocosm experiment. Mussel health was determined using the neutral red retention (NRR) assay for lysosomal membrane stability and from histopathological analysis of reproductive, digestive and respiratory tissues. Seawater acidification was shown to significantly reduce mussel health as measured by the NRR assay, and it is suggested that this impact is due to elevated levels of calcium ions (Ca2+) in the haemolymph, generated by the dissolution of the mussels’ calcium carbonate shells. No impact on tissue structures was observed, and it is concluded that M. edulis possess strong physiological mechanisms by which they are able to protect body tissues against short-term exposure to highly acidified seawater. However, these mechanisms come at an energetic cost, which can result in reduced growth during long-term exposures. Consequently, the predicted long-term changes to seawater chemistry associated with ocean acidification are likely to have a more significant effect on the health and survival of M. edulis populations than the short-lived effects envisaged from CO2 leakage from sub-seabed storage. Ocean acidification could reduce the general health status of this commercially and ecologically important marine species. KEY WORDS: Mytilus edulis · Ocean acidification · Seawater pH · Lysosomes · Neutral red retention assay Full text in pdf format PreviousNextCite this article as: Beesley A, Lowe DM, Pascoe CK, Widdicombe S (2008) Effects of CO2-induced seawater acidification on the health of Mytilus edulis. Clim Res 37:215-225. https://doi.org/10.3354/cr00765 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 37, No. 2-3. Online publication date: October 16, 2008 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2008 Inter-Research.

Unification of the deterministic and statistical approaches for predicting localized corrosion damage. I. Theoretical foundation

In this paper, we provide an alternative, more general theoretical basis for damage function analysis (DFA), by drawing an analogy between the growth of a pit and the movement of a particle. In contrast to our previous formulation of DFA, which was developed specifically for enabling the damage function for localized corrosion to be calculated from the point defect model for passivity breakdown, the coupled environment pitting model for pit growth, and the theory of prompt and delayed repassivation, the new formulation readily incorporates any theories or models (deterministic or empirical) for these stages in the development of a pit. We show that the new formulation leads to the original expressions for the damage functions for active (living) and passivated (dead) pits, and hence for the differential and integral damage functions, as were obtained from the original theory. We also describe the unification of deterministic (damage function analysis, DFA) and empirical, statistical (extreme value statistics, EVS) methods for predicting the development of localized corrosion damage on metal surfaces. In particular, we have devised a means of estimating the central and scale parameters of EVS directly from DFA in a “first principles” manner, as well as from fitting the EVS distribution function to experimental data for short times, in order to predict the extreme value distributions at longer times. The techniques have been evaluated on EVS data for the pitting of manganese steel in CO 2-acidified seawater and for the pitting of aluminum in tap water. Finally, we outline the generalization of pit nucleation, as described by the point defect model, for external conditions that depend on time.