720 research outputs found
Approaches and tools to manipulate the carbonate chemistry
Although the chemistry of ocean acidifi cation is very well understood (see chapter 1), its impact on marine organisms and ecosystems remains poorly known. The biological response to ocean acidifi cation is a recent field
of research, the fi rst purposeful experiments have only been carried out as late as the 1980s (Agegian, 1985)
and most were not performed until the late 1990s. The potentially dire consequences of ocean acidifi cation
have attracted the interest of scientists and students with a limited knowledge of the carbonate chemistry and
its experimental manipulation. Perturbation experiments are one of the key approaches used to investigate
the biological response to elevated p(CO2). Such experiments are based on measurements of physiological or
metabolic processes in organisms and communities exposed to seawater with normal and altered carbonate chemistry. The basics of the carbonate chemistry must be understood to perform meaningful CO2 perturbation experiments (see chapter 1). Briefl y, the marine carbonate system considers
€ CO2 ∗(aq) [the sum of CO2 and H2CO3], € HCO3 −, € CO3 2−,
H+, € OH− , and several weak acid-base systems of which borate-boric acid (€ B(OH)4 − , B(OH)3) is the most
important. As discussed by Dickson (chapter 1), if two components of the carbonate chemistry are known, all
the other components can be calculated for seawater with typical nutrient concentrations at given temperature,
salinity, and pressure. One of the possible pairs is of particular interest because both components can be
measured with precision, accuracy, and are conservative in the sense that their concentrations do not change
with temperature or pressure. Dissolved inorganic carbon (DIC) is the sum of all dissolved inorganic carbon
species while total alkalinity (AT) equals € [HCO3 − ] + 2
€ [CO3 2− ] + € [B(OH)4 − ] + € [OH− ] - [H+] + minor components, and refl ects the excess of proton acceptors over proton donors with respect to a zero level of protons (see chapter 1 for a detailed defi nition). AT is determined by the titration of seawater with a strong acid and thus can also be regarded as a measure of the buffering capacity. Any changes in any single component of the carbonate system will lead to changes in several, if not all, other components. In other words, it is not possible to vary a single component of the carbonate system while keeping all other components constant. This interdependency
in the carbonate system is important to consider when performing CO2 perturbation experiments.
To adjust seawater to different p(CO2) levels, the carbonate system can be manipulated in various ways that
usually involve changes in AT or DIC. The goal of this chapter is (1) to examine the benefi ts and drawbacks of
various manipulation methods used to date and (2) to provide a simple software package to assist the design
of perturbation experiments
Response of the Arctic Pteropod Limacina helicina to projected future environmental conditions
Thecosome pteropods (pelagic mollusks) can play a key role in the food web of various marine ecosystems. They are a food source for zooplankton or higher predators such as fishes, whales and birds that is particularly important in high latitude areas. Since they harbor a highly soluble aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The effect of changes in the seawater chemistry was investigated on Limacina helicina, a key species of Arctic pelagic ecosystems. Individuals were kept in the laboratory under controlled pCO2 levels of 280, 380, 550, 760 and 1020 matm and at control (0uC) and elevated (4uC) temperatures. The respiration rate was unaffected by pCO2 at control temperature, but significantly increased as a function of the pCO2 level at elevated temperature. pCO2 had no effect on the gut clearance rate at either temperature. Precipitation of CaCO3, measured as the incorporation of 45Ca, significantly declined as a function of pCO2 at both temperatures. The decrease in calcium carbonate precipitation was highly correlated to the aragonite saturation state. Even though this study demonstrates that pteropods are able to precipitate calcium carbonate at low aragonite saturation state, the results support the current concern for the future of Arctic pteropods, as the production of their shell appears to be very sensitive to decreased pH. A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems
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Synthesis, x-ray structure and anion binding properties of a cryptand-like hybrid calixpyrrole
The novel cryptand in/out-3, containing two tripyrrolemethane units briged by three 1,3- diisopropylidenbenzene arms was readily synthesized by a convergent three-step synthesis. It binds fluoride by inclusion with excellent selectivity with respect to a number of other tested anions. The structure of the free receptor and that of its fluoride complex were investigated in solution by NMR spectroscopy. The solid state X-ray structure of the free cryptand 3 was also determined
Preface "Arctic ocean acidification: pelagic ecosystem and biogeochemical responses during a mesocosm study"
The growing evidence of potential biological impacts
of ocean acidification affirms that this global change phenomenon
may pose a serious threat to marine organisms
and ecosystems. Whilst ocean acidification will occur everywhere,
it will happen more rapidly in some regions than in
others. Due to the high CO2 solubility in the cold surface
waters of high-latitude seas, these areas are expected to experience
the strongest changes in seawater chemistry due to
ocean acidification. This will be most pronounced in the Arctic
Ocean. If atmospheric pCO2 levels continue to rise at
current rates, about 10% of the Arctic surface waters will
be corrosive for aragonite by 2018 (Steinacher et al., 2009).
By 2050 one-half of the Arctic Ocean will be sub-saturated
with respect to aragonite. By the end of this century corrosive
conditions are projected to have spread over the entire
Arctic Ocean (Steinacher et al., 2009). In view of these
rapid changes in seawater chemistry, marine organisms and
ecosystems in the Arctic are considered particularly vulnerable
to ocean acidification. With this in mind, the European
Project on Ocean Acidification (EPOCA) chose the Arctic
Ocean as one of its focal areas of research
A dataset for investigating socio-ecological changes in Arctic fjords
The collection of in situ data is generally a costly process, with the
Arctic being no exception. Indeed, there has been a perception that the
Arctic is lacking in situ sampling; however, after many years of concerted effort and
international collaboration, the Arctic is now rather well sampled, with many
cruise expeditions every year. For example, the GLODAP (Global Ocean Data Analysis Project) product has a greater
density of in situ sampling points within the Arctic than along the Equator. While
this is useful for open-ocean processes, the fjords of the Arctic, which
serve as crucially important intersections of terrestrial, coastal, and
marine processes, are sampled in a much more ad hoc process. This is not to say
they are not well sampled but rather that the data are more difficult to
source and combine for further analysis. It was therefore noted that the
fjords of the Arctic are lacking in FAIR (findable, accessible,
interoperable, and reusable) data. To address this issue, a single dataset
has been created from publicly available, predominantly in situ data from seven study
sites in Svalbard and Greenland. After finding and accessing the data from a
number of online platforms, they were amalgamated into a single project-wide
standard, ensuring their interoperability. The dataset was then uploaded to
PANGAEA so that it can be findable and reusable in the future. The
focus of the data collection was driven by the key drivers of change in
Arctic fjords identified in a companion review paper. To demonstrate the
usability of this dataset, an analysis of the relationship between the
different drivers was performed. Via the use of an Arctic biogeochemical
model, these relationships were projected forward to 2100 via Representative Carbon Pathways (RCPs) 2.6, 4.5, and 8.5. This dataset is a work in progress, and as new datasets containing
the relevant key drivers are released, they will be added to an updated
version planned for the middle of 2024.
The dataset (Schlegel and Gattuso, 2022) is available on PANGAEA at
https://doi.org/10.1594/PANGAEA.953115.
A live version is available at the FACE-IT WP1 site and can be accessed by clicking the “Data
access” tab: https://face-it-project.github.io/WP1/ (last access: 17 August 2023).</p
Impact of ocean acidification on a key Arctic pelagic mollusc (Limacina helicina)
Thecosome pteropods (shelled pelagic molluscs) can play an important role in the food web of various ecosystems and play a key role in the cycling of carbon and carbonate. Since they harbor an aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The impact of changes in the carbonate chemistry was investigated on Limacina helicina, a key species of Arctic ecosystems. Pteropods were kept in culture under controlled pH conditions corresponding to pCO2 levels of 350 and 760 μatm. Calcification was estimated using a fluorochrome and the radioisotope 45Ca. It exhibits a 28% decrease at the pH value expected for 2100 compared to the present pH value. This result supports the concern for the future of pteropods in a high-CO2 world, as well as of those species dependent upon them as a food resource. A decline of their populations would likely cause dramatic changes to the structure, function and services of polar ecosystems
Evaluation of data-based estimates of anthropogenic carbon in the Arctic Ocean
The Arctic Ocean is particularly vulnerable to ocean acidification, a process that is mainly driven by the uptake of anthropogenic carbon (Cant) from the atmosphere. Although Cant concentrations cannot be measured directly in the ocean, they have been estimated using data-based methods such as the transient time distribution (TTD) approach, which characterizes the ventilation of water masses with inert transient tracers, such as CFC-12. Here, we evaluate the TTD approach in the Arctic Ocean using an eddying ocean model as a test bed. When the TTD approach is applied to simulated CFC-12 in that model, it underestimates the same model's directly simulated Cant concentrations by up to 12%, a bias that stems from its idealized assumption of gas equilibrium between atmosphere and surface water, both for CFC-12 and anthropogenic CO2. Unlike the idealized assumption, the simulated partial pressure of CFC-12 (pCFC-12) in Arctic surface waters is undersaturated relative to that in the atmosphere in regions and times of deep-water formation, while the simulated equivalent for Cant is supersaturated. After accounting for the TTD approach's negative bias, the total amount of Cant in the Arctic Ocean in 2005 increases by 8% to 3.3 ± 0.3 Pg C. By combining the adjusted TTD approach with scenarios of future atmospheric CO2, it is estimated that all Arctic waters, from surface to depth, would become corrosive to aragonite by the middle of the next century even if atmospheric CO2 could be stabilized at 540 ppm
Pelagic metabolism of the Scheldt estuary measured by the oxygen method on an annual scale
Pelagic gross primary production (GPP), community respiration (CR) and nitrification were measured in the turbid Scheldt Estuary by the oxygen Winkler method from January to December 2003 at monthly intervals (EUROTROPH EU project). Five stations along the estuary were investigated, corresponding to a salinity (S) range of 0-25. Water was sampled and incubated until sunset in 60 ml glass bottles stored in a 5 compartment incubator kept at in situ temperature by flowing water. Irradiance was controlled in each compartment by filters having a shading capacity ranging from 0 to 100%. In order to estimate the oxygen consumption due to the respiration and nitrification processes, samples were incubated, in the dark compartment, with and without addition of nitrification inhibitors. Net community production (NCP) was most of the time negative in the estuary with values ranging from -275 to +31mmol O2.m-2.d-1 and the lowest values were found near Antwerp (S = 2). Strong pelagic GPP and positive NCP rates were observed in the freshwater part during summer with a maximal value in June (+373mmol O2.m-2.d-1), corresponding to an increase of the O2 concentration and a decrease of the partial pressure of CO2 (pCO2) in the water column during this period. Nitrification contributes 5 to 60% of the oxygen consumption in the water column with highest values measured in the inner part of the estuary due to high ammonium and suspended matter concentrations. Assuming a C/O2 molar ratio of 0.07, we estimated that nitrification represents on an annual scale 35% of organic matter production at salinity 2 which is consistent with previous estimates. NCP rates measured in 2003 are among the lowest reported in the literature and confirm the strong heterotrophic status of the Scheldt Estuary
Computer Controlled Solid State Lighting Assembly to Emulate Diurnal Cycle and Improve Circadian Rhythm Control
A light system can simultaneously emulate more than one different diurnal cycle to individually improve circadian rhythm control for more than one observer by having each light fixture autonomously self-controlled. Each light fixture is mountable in respective locations to individually treat respective observers. Each light fixture includes one or more light elements mounted to a housing and are controllable to emit a selected light intensity at a selected light temperature. A micro controller is contained in the housing and includes memory containing instructions for one or more automatic diurnal cycle protocols. The micro controller is in communication with the memory and the one or more light elements to execute the instructions to configure the light fixture to vary the light intensity and the light temperature of the emitted light
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