Ocean acidification (OA) poses a global threat to marine biodiversity. The rise in atmospheric carbon dioxide (CO2) concentration, resulting from anthropogenic activities, is responsible for the increase in the dissolved state of this gas in the oceans. The consequent changes in pH and seawater carbonate chemistry are responsible for the disruption of several biological processes (e.g. impairing survival and the maintenance of fitness-enhancing, physiological and behavioural, mechanisms) in certain marine groups. Disruption at the individual level, can originate negative cascading effects at higher levels of biological organization (i.e. populations and communities), which in turn can alter the underlying dynamics that control an ecosystem’s structure and overall function. Current theories suggest that marine organisms might be able to maintain their performance in future OA conditions, either through acclimation or through evolutionary adaptation. Surprisingly, the effects of prolonged high-CO2 exposure in crustaceans are still poorly known. The present dissertation investigates, for the first time, the transgenerational effects (i.e. over two generations) of ocean acidification in the physiology, behaviour (e.g. male mate-attraction) and reproductive traits (e.g. female investment, fecundity, mate-guarding and embryonic development) of the gammarid amphipod Gammarus locusta. Significant effects of ocean acidification were found for most reproductive traits. Although OA may initially stimulate female investment, transgenerational exposure led to an overall reduction in egg number and fecundity. The duration of mate-guarding behaviours was also diminished under high-CO2 exposure. Individuals from the second generation (F1) exhibited metabolic depression (i.e. reduced oxygen consumption rates), and males also displayed a reduced ability to accurately identify and track the origin of female scent cues, thus hinting at a possible disruption of chemosensory abilities. Overall, negative transgenerational (i.e. parental) effects were observed for all reproductive traits, as well as survival, in the acidified lineage. The present findings suggest that exposure to a future ocean acidification scenario will likely lead to a reduction in the fitness of the natural populations of G. locusta.
Archive for January, 2018
Transgenerational responses of a gammarid amphipod to ocean acidification: effects on reproductive traits, mate detection and metabolism
Published 25 January 2018 Science ClosedTags: biological response, crustaceans, laboratory, mortality, North Atlantic, performance, physiology, reproduction, respiration
The effects of ocean acidification on Oregon Coast estuaries as well as oyster and Dungeness crab fisheries will be on the agenda when Dr. George Waldbusser addresses the Thursday, Feb. 1, meeting of the The MidCoast Watersheds Council in Newport.
Waldbusser is an associate professor in the College of Earth, Ocean and Atmospheric Sciences at Oregon State University with expertise is in seafloor ecology and biogeochemistry.
Changing ocean conditions: new council to mitigate effects
Published 25 January 2018 Media coverage Closed
Jeremy C. Ruark / The News Guard
Oregon’s new Coordinating Council on Ocean Acidification and Hypoxia (OAH) will host its first meeting from 10 a.m.to 3 p.m. on Thursday, Jan. 25, at the Hatfield Marine Science Center’s Guin Library, 2030 Marine Science Drive in Newport.
A full agenda for the meeting and supporting materials are available online at oregonocean.info.
Oregon lawmakers created the OAH Council through the passage of Senate Bill 1039 last year to look for ways to better understand, adapt to and mitigate the effects of changing ocean conditions. The state has already seen the effects of ocean acidification on its prized shellfish industry after annual die-offs of juvenile oysters at the Whiskey Creek Shellfish Hatchery started in 2007. Oregon has also seen the effects of intensifying hypoxia events, which have been implicated in die-offs of crabs and other marine life over the past two decades.
Continue reading ‘Changing ocean conditions: new council to mitigate effects’
Environmental influences on synthetic and biogenic calcium carbonate in aragonite-calcite sea conditions
Published 24 January 2018 Science ClosedTags: biogeochemistry, biological response, chemistry, laboratory, morphology
Ocean chemistry has oscillated throughout Earth history to favour the dominant non-biogenic polymorph of calcium carbonate (CaCO3) to be either calcite or aragonite (Sandberg, 1983). Throughout the Phanerozoic these oscillations have occurred to facilitate aragonite-dominant conditions three times and calcite-dominant conditions twice. These aragonite-calcite seas conditions have previously been viewed as a global phenomenon where conditions fluctuate over time, but not in space, and represent the main environmental context in which the evolution of CaCO3 biomineralisation has occurred (Stanley and Hardie, 1998). CaCO3 is one of the most widely distributed minerals in the marine environment, occurring throughout geological history, both biogenically and non-biogenically (Lowenstam and Weiner, 1989). Marine non-biogenic precipitates are commonly found as carbonate ooids, sedimentary cements and muds (Nichols, 2009). Biogenic CaCO3 is formed via biomineralisation in calcifying organisms (Lowenstam and Weiner, 1989; Allemand et al., 2004), and is much more abundant than the non-biogenic forms. Although CaCO3 is abundant, it only accounts for a small proportion of the global carbon budget. Biogenic CaCO3 is representative of a larger proportion of the global carbon budget than non-biogenically formed CaCO3 (Berelson et al., 2007). The main driving force controlling the precipitation of CaCO3 polymorphs is the Mg:Ca molar ratio of seawater (Morse et al., 2007). However, other parameters such as temperature (Burton and Walter, 1984; Morse et al, 1997; Balthasar and Cusack, 2015), pCO2 (Lee and Morse, 2010), and SO4 (Morse et al., 2007) are also known to influence CaCO3 polymorph formation but are often overlooked in the context of aragonite-calcite seas. Fluctuations in these parameters of Mg:Ca ratio, SO42+ and pCO2 of seawater have been suggested to cause shifts in original composition of non-biogenic marine carbonates, and in turn viewed as the main driving mechanisms facilitating the switch between aragonite and calcite dominance (Morse et al., 1997; Lee and Morse, 2010; Bots et al., 2011). Specifically the influence of temperature is important because it is likely to result in aragonite-calcite sea conditions to vary spatially (Balthasar and Cusack, 2015). Today marine temperatures are changing across the latitudes due to environmental factors. Global CO2 levels have increased significantly since industrialisation (Doney et al., 2009), with 33% entering the oceans and reducing pH (Raven et al., 2005) accelerating climate change (IPCC, 2013) and influencing marine calcification (Fitzer et al., 2014a; 2015b; Bach, 2015; Zhao et al., 2017). Strong links between the carbon cycle and climate change observed in the rock record give evidence that environmental changes such as pCO2 and global warming have impacts on calcification and marine biota (Hönish et al., 2012). The first objective was to determine the influence of Mg:Ca ratio, temperature and water movement on the first-formed precipitates of non-biogenic CaCO3 precipitation yielded via a continuous addition technique experiments (Chapter 3). CaCO3 precipitation was induced by continuously adding bicarbonate to a bulk solution of known Mg:Ca ratio (1,2 or 3), and fixed salinity of 35 (practical salinity scale), at 20°C and 30ºC in still conditions, and then repeated with the solution being shaken at 80rpm mimicking more natural marine conditions. The mineralogy and crystal morphology of precipitates was determined using Raman Spectroscopy and Scanning Electron Microscopy. Results in Chapter 3 indicated that polymorphs co-precipitate, with the ratio of aragonite to calcite increasing with increased Mg:Ca ratio and elevated temperature. The main difference between still and shaken conditions was that overall, more crystals of aragonite compared to calcite precipitate in shaking conditions. The crystal size is less influenced in aragonite, but calcite crystals were smaller. These results contradict current views on aragonite-calcite seas as spatially homogenous ocean states need to be re-examined to include the effect of temperature on the spatial distribution of CaCO3 polymorphs. Examining polymorph growth under these experimental constraints allows us to gain a better understanding of how temperature and Mg:Ca together control non-biogenic aragonite and calcite precipitation providing a more realistic environmental framework in which to evaluate the evolution of biomineralisation. To further this work, the same continuous addition technique was used with the presence of sulphate in the mother solution (Chapter 4). Sulphate being the 4th most common marine ion (Halvey et al., 2012) and known to have an influence on mineralogy (Kontrec et al., 2004). The presence of sulphate increase the aragonite to calcite proportion formed compared to sulphate-free conditions (Chapter 4). Elevated temperature with sulphate further increased the proportion of aragonite to calcite facilitated (Chapter 4). In the presence of sulphate the main difference between sulphate-free environments and those with sulphate environments was: in still conditions the presence of sulphate increased the crystal number more than the crystal size at 20°C; at 30°C or in shaken conditions the presence of sulphate increased the crystal size of aragonite to calcite much more than it had influence on the crystal number. Non-biogenically the influence of sulphate lowered the threshold of Mg:Ca ratio that the switch between calcite and aragonite would be facilitated at (Bots et al., 2011). This would have implications for marine calcification as pure calcite seas would become very rare and imply that organisms would be forming calcified hard parts out with the supported mineralogies. Biogenic application of these results is complex however as organisms often have the ability to select aragonite as their main polymorph for their own functional requirements (Weiner and Dove, 2003). The growth parameters of non-biogenic polymorph formations grown from artificial seawater can be used to understand how organism control can influence the polymorph formation under similar conditions (Kawano et al., 2009). Assessing the elemental composition of mussel shells grown under know conditions of temperature and pCO2 allowed the environmental influences on mineralogy be assessed under possible the projected changes in climate forecast to occur by 2100 by IPCC (2013). Prior to this research, no study had used Mytilus edulis shell elemental composition to test the influence of aragonite-calcite sea conditions on mineralogy. This research compiles a detailed source of information on the constraints from environmental sources such as temperature and pCO2, on the elemental concentrations within shell formation and what potential changes could occur in response to a changing marine environment (Chapter 5). Here elevated temperature significantly increased the concentration of magnesium in calcite, but did not influence the magnesium concentration of aragonite unless combined with elevated pCO2. The concentrations of sulphur in calcite were significantly decreased at elevated pCO2 or combined increased temperature and pCO2 as concentrations of sodium were found to be increased under these conditions. In aragonite the concentrations of both sulphur and sodium were significantly different under all scenarios. Strontium did not yield any significant results in this research in either calcite or aragonite. Results observed indicate that the shell elemental concentrations are influenced differently in aragonite or calcite, and further influenced by environmental conditions based on the original mineralogy. This suggests that physiological mechanisms under the constraints of increased temperature and pCO2 can override the seawater chemistry influences of aragonite-calcite seas impacting on mineralogy. This research allows comparison of how non-biogenic and biogenic CaCO3 formation is influenced by seawater chemistry and environmental parameters to determine the dominant mineralogy. Increased temperature in both formations has shown to increase the impact of magnesium on calcite enabling the facilitation of aragonite. However, magnesium has influence on biogenic aragonite in extreme combined conditions of elevated temperature and pCO2. This work indicates that CaCO3 formation is complex and requires a multi-variable approach to understanding the mechanisms that facilitate the dominant mineralogy. By including variables such as temperature, this research suggests that aragonite-calcite seas conditions do not facilitate globally homogeneous switches in mineralogy, but the mineralogy is indeed influenced on latitudinal scales by other factors that influence the mechanisms involved.
Effects of CO2 enrichment on benthic primary production and inorganic nitrogen fluxes in two coastal sediments
Published 24 January 2018 Science ClosedTags: biogeochemistry, biological response, BRcommunity, laboratory, photosynthesis, physiology, primary production, sediment, South Pacific
Ocean acidification may alter the cycling of nitrogen in coastal sediment and so the sediment–seawater nitrogen flux, an important driver of pelagic productivity. To investigate how this perturbation affects the fluxes of NOX− (nitrite/nitrate), NH4+ and O2, we incubated estuarine sand and subtidal silt in recirculating seawater with a CO2-adjusted pH of 8.1 and 7.9. During a 41-day incubation, the seawater kept at pH 8.1 lost 97% of its NOX− content but the seawater kept at pH 7.9 lost only 18%. Excess CO2 increased benthic photosynthesis. In the silt, this was accompanied by a reversal of the initial NOX− efflux into influx. The estuarine sand sustained its initial NOX− influx but, by the end of the incubation, released more NH4+ at pH 7.9 than at pH 8.1. We hypothesise that these effects share a common cause; excess CO2 increased the growth of benthic microalgae and so nutrient competition with ammonia oxidising bacteria (AOB). In the silt, diatoms likely outcompeted AOB for NH4+ and photosynthesis increased the dark/light fluctuations in the pore water oxygenation inhibiting nitrification and coupled nitrification/denitrification. If this is correct, then excess CO2 may lead to retention of inorganic nitrogen adding to the pressures of increasing coastal eutrophication.
Greenland tidal pools as hot spots for ecosystem metabolism and calcification
Published 24 January 2018 Science ClosedTags: biogeochemistry, biological response, BRcommunity, calcification, chemistry, field, North Atlantic, primary production
The hypothesis that Arctic tidal pools provide environmental conditions suitable for calcifiers during summer, thereby potentially providing refugia for calcifiers in an acidifying Arctic Ocean, was tested on the basis of measurements conducted during two midsummers (2014 and 2016) in tidal pools colonised by a community composed of macroalgae and calcifiers in Disko Bay, Greenland (69° N). The tidal pools exhibited steep diurnal variations in temperature from a minimum of about 6 °C during the night to a maximum of almost 18 °C in the afternoon, while the temperature of the surrounding shore water was much lower, typically in the range 3 to 8 °C. O2 concentrations in the tidal pools were elevated relative to those in the adjacent open waters, by up to 11 mg O2 L−1, and exhibited heavy super-saturation (up to > 240%) during daytime emersion, reflecting intense and sustained photosynthetic rates of the tidal macroalgae. The intense photosynthetic activity of the seaweeds resulted in the drawdown of pCO2 concentrations in the pools during the day to levels down to average (±SE) values of 66 ± 18 ppm, and a minimum recorded value of 14.7 ppm, corresponding to pH levels as high as 8.69 ± 0.08, as compared to CO2 levels of 256 ± 4 and pH levels of 8.14 ± 0.01 in the water flooding the pools during high tide. The corresponding Ωarag reached 5.04 ± 0.49 in the pools as compared to 1.55 ± 0.02 in the coastal waters flooding the pools. Net calcification averaged 9.6 ± 5.6 μmol C kg−1 h−1 and was strongly and positively correlated with calculated net ecosystem production rates, which averaged 27.5 ± 8.6 μmol C kg−1 h−1. Arctic tidal pools promote intense metabolism, creating conditions suitable for calcification during the Arctic summer, and can, therefore, provide refugia from ocean acidification to vulnerable calcifiers as extended periods of continuous light during summer are conducive to suitable conditions twice a day. Meroplankton larvae are exposed to ocean acidification until they settle in vegetated tidal pools, where they benefit from the protection offered by the “macroalgae-carbonate saturation state” interaction favouring calcification rates.
Continue reading ‘Greenland tidal pools as hot spots for ecosystem metabolism and calcification’
Stylophora pistillata in the Red Sea demonstrate higher GFP fluorescence under ocean acidification conditions
Published 24 January 2018 Science ClosedTags: biological response, corals, laboratory, molecular biology, physiology, Red Sea
Ocean acidification is thought to exert a major impact on calcifying organisms, including corals. While previous studies have reported changes in the physiological response of corals to environmental change, none have described changes in expression of the ubiquitous host pigments—fluorescent proteins (FPs)—to ocean acidification. The function of FPs in corals is controversial, with the most common consideration being that these primarily regulate the light environment in the coral tissue and protect the host from harmful UV radiation. Here, we provide for the first time experimental evidence that increased fluorescence of colonies of the coral Stylophora pistillata is independent of stress and can be regulated by a non-stressful decrease in pH. Stylophora pistillata is the most abundant and among the most resilient coral species in the northern Gulf of Eilat/Aqaba (GoE/A). Fragmented “sub-colonies” (n = 72) incubated for 33 days under three pH treatments (ambient, 7.9, and 7.6), under ambient light, and running seawater showed no stress or adverse physiological performance, but did display significantly higher fluorescence, with lower pH. Neither the average number of planulae shed from the experimental sub-colonies nor planulae green fluorescent protein (GFP) expression changed significantly among pH treatments. Sub-colonies incubated under the lower-than-ambient pH conditions showed an increase in both total protein and GFP expression. Since extensive protein synthesis requires a high level of transcription, we suggest that GFP constitutes a UV protection mechanism against potential RNA as well as against DNA damage caused by UV exposure. Manipulating the regulation of FPs in adult corals and planulae, under controlled and combined effects of pH, light, and temperature, is crucial if we are to obtain a better understanding of the role played by this group of proteins in cnidarians.
Healthy staghorn coral. Researchers at The Ohio State University and their colleagues have demonstrated the effect of rising temperatures and ocean acidification on the health of corals’ natural microbes — the natural coral ‘microbiome.’ Credit: The Ohio State University
If this winter finds you stressed out and fighting a sinus infection, then you know something of what coral will endure in the face of climate change.
They don’t have sinuses, but these colorful aquatic animals do actually make mucus—”coral snot” is a thing—and the balance of different species of bacteria living in their mucus is very important, because it functions as an ad hoc immune system, keeping the coral healthy by keeping unfriendly bacteria at bay.
In a study appearing in the journal PLOS ONE, researchers at The Ohio State University and their colleagues have demonstrated how two separate effects of climate change combine to destabilize different populations of coral microbes—that is, unbalance the natural coral “microbiome”—opening the door for bad bacteria to overpopulate corals’ mucus and their bodies as a whole.
Continue reading ‘How climate change weakens coral ‘immune systems’’
Marine vegetation can mitigate ocean acidification, study finds
Published 24 January 2018 Press releases Closed
Study authors Nyssa Silbiger, then a UCI postdoctoral researcher, and UCI graduate student Laura Elsberry (standing) survey tide-pool communities at Corona del Mar State Beach. Credit: Cascade Sorte / UCI
Marine plants and seaweeds in shallow coastal ecosystems can play a key role in alleviating the effects of ocean acidification, and their robust population in shoreline environments could help preserve declining shellfish life, according to a study by University of California, Irvine ecologists.
In a new study on the Pacific Coast, Nyssa Silbiger, former UCI postdoctoral researcher, and Cascade Sorte, assistant professor of ecology & evolutionary biology, determined that marine plants and seaweeds decrease the acidity of their surroundings through photosynthesis. Their findings suggest that maintaining native seawater vegetation could locally lessen the acidifying effects of rising CO2 levels on marine animals who are sensitive to ocean pH, which has declined since preindustrial times.
Continue reading ‘Marine vegetation can mitigate ocean acidification, study finds’
Carbonate system parameters of an algal-dominated reef along West Maui
Published 23 January 2018 Science ClosedTags: algae, biogeochemistry, biological response, BRcommunity, calcification, chemistry, corals, field, North Pacific, primary production, respiration
Constraining coral reef metabolism and carbon chemistry dynamics are fundamental for understanding and predicting reef vulnerability to rising coastal CO2 concentrations and decreasing seawater pH. However, few studies exist along reefs occupying densely inhabited shorelines with known input from land-based sources of pollution. The shallow coral reefs off Kahekili, West Maui, are exposed to nutrient-enriched, low-pH submarine groundwater discharge (SGD) and are particularly vulnerable to the compounding stressors from land-based sources of pollution and lower seawater pH. To constrain the carbonate chemistry system, nutrients and carbonate chemistry were measured along the Kahekili reef flat every 4 h over a 6-d sampling period in March 2016. Abiotic process – primarily SGD fluxes – controlled the carbonate chemistry adjacent to the primary SGD vent site, with nutrient-laden freshwater decreasing pH levels and favoring undersaturated aragonite saturation (Ωarag) conditions. In contrast, diurnal variability in the carbonate chemistry at other sites along the reef flat was driven by reef community metabolism. Superimposed on the diurnal signal was a transition during the second sampling period to a surplus of total alkalinity (TA) and dissolved inorganic carbon (DIC) compared to ocean end-member TA and DIC measurements. A shift from net community production and calcification to net respiration and carbonate dissolution was identified. This transition occurred during a period of increased SGD-driven nutrient loading, lower wave height, and reduced current speeds. This detailed study of carbon chemistry dynamics highlights the need to incorporate local effects of nearshore oceanographic processes into predictions of coral reef vulnerability and resilience.
Continue reading ‘Carbonate system parameters of an algal-dominated reef along West Maui’
Functional spatial contextualisation of the effects of multiple stressors in marine bivalves
Published 23 January 2018 Science ClosedTags: biological response, individualmodeling, laboratory, modeling, mollusks, morphology, multiple factors, oxygen, performance, physiology, reproduction
Many recent studies have revealed that the majority of environmental stressors experienced by marine organisms (ocean acidification, global warming, hypoxia etc.) occur at the same time and place, and that their interaction may complexly affect a number of ecological processes. Here, we experimentally investigated the effects of pH and hypoxia on the functional and behavioural traits of the mussel Mytilus galloprovincialis, we then simulated the potential effects on growth and reproduction dynamics trough a Dynamic Energy Budget (DEB) model under a multiple stressor scenario. Our simulations showed that hypercapnia had a remarkable effect by reducing the maximal habitat size and reproductive output differentially as a function of the trophic conditions, where modelling was spatially contextualized. This study showed the major threat represented by the hypercapnia and hypoxia phenomena for the growth, reproduction and fitness of mussels under the current climate change context, and that a mechanistic approach based on DEB modelling can illustrate complex and site-specific effects of environmental change, producing that kind of information useful for management purposes, at larger temporal and spatial scales.
Pteropods counter mechanical damage and dissolution through extensive shell repair
Published 22 January 2018 Science ClosedTags: dissolution, morphology, zooplankton
The dissolution of the delicate shells of sea butterflies, or pteropods, has epitomised discussions regarding ecosystem vulnerability to ocean acidification over the last decade. However, a recent demonstration that the organic coating of the shell, the periostracum, is effective in inhibiting dissolution suggests that pteropod shells may not be as susceptible to ocean acidification as previously thought. Here we use micro-CT technology to show how, despite losing the entire thickness of the original shell in localised areas, specimens of polar species Limacina helicina maintain shell integrity by thickening the inner shell wall. One specimen collected within Fram Strait with a history of mechanical and dissolution damage generated four times the thickness of the original shell in repair material. The ability of pteropods to repair and maintain their shells, despite progressive loss, demonstrates a further resilience of these organisms to ocean acidification but at a likely metabolic cost.
Interactive effects of temperature, CO2 and nitrogen source on a coastal California diatom assemblage
Published 22 January 2018 Science ClosedTags: abundance, biological response, BRcommunity, community composition, laboratory, multiple factors, North Pacific, nutrients, otherprocess, physiology, phytoplankton, temperature
Diatoms are often considered to be a single functional group, yet there is a great deal of morphological, genetic and ecological diversity within the class. How these differences will translate into species-specific responses to rapid changes in the ocean environment resulting from climate change and eutrophication is currently poorly understood. We investigated the response of a natural diatom-dominated assemblage in coastal California waters to interactions between the variables nitrogen source (nitrate and urea), temperature (19 and 23°C) and CO2 (380 and 800 ppm) in a factorial experimental matrix using continuous culture (ecostat) methods. The community included diatoms of the cosmopolitan genera Pseudo-nitzschia and Chaetoceros, as well as Leptocylindrus and Cylindrotheca. Our results demonstrate strong interactive effects of these variables on community composition; notably, nitrogen source alone and nitrogen and CO2 together had a much greater influence on diatom community structure at 23°C compared with 19°C. In addition, warming and acidification interactions significantly increased cellular quotas of the neurotoxin domoic acid produced by Pseudo-nitzschia multiseries. In general, the effects observed for the factors tested differed significantly between the various diatom genera in this assemblage, suggesting potentially divergent responses of some of these ecologically and biogeochemically important phytoplankton taxa to interactions between global-scale and local-scale anthropogenic stressors in a changing ocean.
Seasonal variation in aragonite saturation in surface waters of Puget Sound – a pilot study
Published 22 January 2018 Science ClosedTags: chemistry, field, North Pacific
A pilot study of sampling, using monthly marine flights over spatially distributed stations, was conducted with the aim to characterize the carbonate system in Puget Sound over a full year-long period. Surface waters of Puget Sound were found to be under-saturated with respect to aragonite during October–March, and super-saturated during April–September. Highest pCO2 and lowest pH occurred during the corrosive October–March period. Lowest pCO2 and highest pH occurred during the super-saturated April–September period. The monthly variations in pCO2 , pH, and aragonite saturation state closely followed the variations in monthly average chlorophyll a. Super-saturated conditions during April–September are likely strongly influenced by photosynthetic uptake of CO2 during the phytoplankton growing season. The relationship between phytoplankton production, the carbonate system, and aragonite saturation state suggests that long-term trends in eutrophication processes may contribute to trends in ocean acidification in Puget Sound.
Autonomous optofluidic chemical analyzers for marine applications: insights from the submersible autonomous moored instruments (SAMI) for pH and pCO2
Published 19 January 2018 Science ClosedTags: chemistry, methods
The commercial availability of inexpensive fiber optics and small volume pumps in the early 1990’s provided the components necessary for the successful development of low power, low reagent consumption, autonomous optofluidic analyzers for marine applications. It was evident that to achieve calibration-free performance, reagent-based sensors would require frequent renewal of the reagent by pumping the reagent from an impermeable, inert reservoir to the sensing interface. Pumping also enabled measurement of a spectral blank further enhancing accuracy and stability. The first instrument that was developed based on this strategy, the Submersible Autonomous Moored Instrument for CO2 (SAMI-CO2), uses a pH indicator for measurement of the partial pressure of CO2 (pCO2). Because the pH indicator gives an optical response, the instrument requires an optofluidic design where the indicator is pumped into a gas permeable membrane and then to an optical cell for analysis. The pH indicator is periodically flushed from the optical cell by using a valve to switch from the pH indicator to a blank solution. Because of the small volume and low power light source, over 8,500 measurements can be obtained with a ~500 mL reagent bag and 8 alkaline D-cell battery pack. The primary drawback is that the design is more complex compared to the single-ended electrode or optode that is envisioned as the ideal sensor. The SAMI technology has subsequently been used for the successful development of autonomous pH and total alkalinity analyzers. In this manuscript, we will discuss the pros and cons of the SAMI pCO2 and pH optofluidic technology and highlight some past data sets and applications for studying the carbon cycle in aquatic ecosystems.
Combined effects of ocean acidification and nutrient levels on the photosynthetic performance of Thalassiosira (Conticribra) weissflogii (Bacillariophyta)
Published 19 January 2018 Science ClosedTags: biological response, growth, laboratory, multiple factors, nutrients, photosynthesis, phytoplankton
The purpose of this study was to investigate the effects of ocean acidification and nutrient level on the growth and photosynthetic performance of the diatom Thalassiosira (Conticribra) weissflogii. Cells were exposed to varying levels of CO2 [current CO2 (LC), 400 μatm; high CO2 (HC), 1000 μatm] and nutrients, with NO3− and PO43− concentrations enriched, respectively, at 50 μmol l−1 and 5 μmol l−1 [high nutrient (HN)], 20 μmol l−1 and 2 μmol l−1 [mid-level nutrient (MN)] and 10 μmol l−1 and 1 μmol l−1 [low nutrient (LN)]. After acclimatization for over 20 generations, no significant differences in growth rates were observed between LC and HC cultures under both HN and LN conditions; whereas, HC significantly reduced the growth rate under MN conditions. Lower nutrient loading significantly inhibited the growth rates of both LC and HC cultures; whereas, HC (but not LC) significantly decreased chlorophyll a and carotenoid contents in LN treatments. HC conditions significantly increased maximum relative electron transport rates (rETRmax) and saturating light intensity (Ik) of HN cultures, with rETRmax showing a positive relationship with growth rates stimulated by nutrient enrichments. The maximum (Fv/Fm) and effective quantum yield (Yield) were all inhibited under LN conditions, with the greatest reduction in Yield observed under LC conditions, corresponding to the highest nonphotochemical quenching, lowest light use efficiency (α) and lowest rETRmax. Based on these results, ocean acidification and nutrient availability may influence photosynthetic performance in T. weissflogii individually or interactively, with the future growth of marine diatoms mediated by these codependent environmental drivers.
Senator Murkowski, worried for coastal communities, is trying to assess ocean acidification (video)
Published 19 January 2018 Media coverage ClosedWASHINGTON (Gray DC) – Our coastlines could be in harm’s way. Not because of a storm or a tidal wave, but because of ocean acidification. Carbon dioxide emissions are changing the chemistry of our oceans which could have a negative impact on coastlines and economies. Senator Lisa Murkowski (R-AK) is looking for answers to this growing problem. She says we need to find out how vulnerable our communities are. Continue reading ‘Senator Murkowski, worried for coastal communities, is trying to assess ocean acidification (video)’
Seasonal variability of the carbonate system and coccolithophore Emiliania huxleyi at a Scottish Coastal Observatory monitoring site
Published 18 January 2018 Science ClosedTags: abundance, biological response, chemistry, field, morphology, North Atlantic, otherprocess, phytoplankton
- • There is a “knowledge gap” on carbonate chemistry in inshore waters.
- • Stonehaven coastal carbonate system shows a strong variability at short-time and year-to-year scales.
- • Occurrence of E. huxleyi morphotypes shows a repeated seasonal pattern.
- • E. huxleyi in situ calcification seems not to be affected by carbonate chemistry.
- • Seasonality in E. huxleyi morphotypes should be considered when interpreting sporadic cruises data.
Lack of information about carbonate chemistry in inshore waters is a ‘knowledge gap’ in assessing the impacts of changing carbonate chemistry on the marine environment. Assessing the response of calcifying phytoplankton to this changing carbonate chemistry requires a greater understanding of temporal variation. This study provides a description of the variability of carbonate parameters at a monitoring site in the eastern coast of Scotland. Four-years of monthly data were analysed to assess the diversity, abundance and morphometrics of coccolithophores in relation to carbonate chemistry and environmental variables. The seasonality in carbonate parameters reflected the seasonal cycle in phytoplankton activity, with higher total alkalinity concentrations and pH and lower dissolved inorganic carbon concentrations during the growing season. The dominant coccolithophore at the site was Emiliania huxleyi which showed a clear seasonal pattern, being more abundant in mid-summer when warmer and nutrient-depleted conditions restricted the annual diatom bloom. This study revealed the presence of three morphotypes of E. huxleyi, type A, type A overcalcified (type AO) and type B, which were seasonally distributed throughout the year. The less calcified form was mainly observed in spring while heavily calcified morphotypes overlapped during summer. Autumn and winter months were dominated by the most calcified form (type AO). These results indicate that the seasonal pattern of E. huxleyi morphotypes was not related to the carbonate concentration at the site. This study reflects the strong interannual variability in carbonate chemistry and the complexity associated with coccolithophore calcification, and highlights the need of long-term data to understand the potential impact of ocean acidification on calcifying phytoplankton.
pH gradients in the diffusive boundary layer of subarctic macrophytes
Published 18 January 2018 Science ClosedTags: algae, physiology
Highly productive macrophytes produce diurnal and seasonal cycles in CO2 concentrations modulated by metabolic activity, which cause discrepancies between pH in the bulk water and near seaweed blades, especially when entering the diffusion boundary layer (DBL). Calcifying epiphytic organisms living in this environment are therefore exposed to a different pH environment than that of the water column. To evaluate the actual pH environment on blade surfaces, we measured the thickness of the DBL and pH gradients within it for six subarctic macrophytes: Fucus vesiculosus, Ascophyllum nodosum, Ulva lactuca, Zostera marina, Saccharina longicruris, and Agarum clathratum. We measured pH under laboratory conditions at ambient temperatures (2–3 °C) and slow, stable flow over the blade surface at five light intensities (dark, 30, 50, 100 and 200 µmol photons m−2 s−1). Boundary layer thickness ranged between 511 and 1632 µm, while the maximum difference in pH (∆pH) between the blade surface and the water column ranged between 0.4 ± 0.14 (average ± SE; Zostera) and 1.2 ± 0.13 (average ± SE; Ulva) pH units. These differences in pH are larger than predictions for pH changes in the bulk water by the end of the century. A simple quadratic model best described the relationship between light intensity and maximum ∆pH, pointing at relatively low optimum PAR of between 28 and 139 µmol photons m−2 s−1 to reach maximum ∆pH. Elevated pH at the blade surface may provide chemical “refugia” for calcifying epiphytic organisms, especially during summer at higher latitudes where photoperiods are long.
Continue reading ‘pH gradients in the diffusive boundary layer of subarctic macrophytes’
Dynamic changes in carbonate chemistry in the microenvironment around single marine phytoplankton cells
Published 18 January 2018 Science ClosedTags: physiology, phytoplankton
Photosynthesis by marine diatoms plays a major role in the global carbon cycle, although the precise mechanisms of dissolved inorganic carbon (DIC) uptake remain unclear. A lack of direct measurements of carbonate chemistry at the cell surface has led to uncertainty over the underlying membrane transport processes and the role of external carbonic anhydrase (eCA). Here we identify rapid and substantial photosynthesis-driven increases in pH and [CO32−] primarily due to the activity of eCA at the cell surface of the large diatom Odontella sinensis using direct simultaneous microelectrode measurements of pH and CO32− along with modelling of cell surface inorganic carbonate chemistry. Our results show that eCA acts to maintain cell surface CO2 concentrations, making a major contribution to DIC supply in O. sinensis. Carbonate chemistry at the cell surface is therefore highly dynamic and strongly dependent on cell size, morphology and the carbonate chemistry of the bulk seawater.
