Posts Tagged 'field'



Net community production and carbon exchange from winter to summer in the Atlantic Water inflow to the Arctic Ocean

The eastern Fram Strait and area north of Svalbard, are influenced by the inflow of warm Atlantic water, which is high in nutrients and CO2, influencing the carbon flux into the Arctic Ocean. However, these estimates are mainly based on summer data and there is still doubt on the size of the net ocean Arctic CO2 sink. We use data on carbonate chemistry and nutrients from three cruises in 2014 in the CarbonBridge project (January, May, and August) and one in Fram Strait (August). We describe the seasonal variability and the major drivers explaining the inorganic carbon change (CDIC) in the upper 50 m, such as photosynthesis (CBIO), and air-sea CO2 exchange (CEXCH). Remotely sensed data describes the evolution of the bloom and net community production. The focus area encompasses the meltwater-influenced domain (MWD) along the ice edge, the Atlantic water inflow (AWD), and the West Spitsbergen shelf (SD). The CBIO total was 2.2 mol C m–2 in the MWD derived from the nitrate consumption between January and May. Between January and August, the CBIO was 3.0 mol C m–2 in the AWD, thus CBIO between May and August was 0.8 mol C m–2. The ocean in our study area mainly acted as a CO2 sink throughout the period. The mean CO2 sink varied between 0.1 and 2.1 mol C m–2 in the AWD in August. By the end of August, the AWD acted as a CO2 source of 0.7 mol C m–2, attributed to vertical mixing of CO2-rich waters and contribution from respiratory CO2 as net community production declined. The oceanic CO2 uptake (CEXCH) from the atmosphere had an impact on CDIC between 5 and 36%, which is of similar magnitude as the impact of the calcium carbonate (CaCO3, CCALC) dissolution of 6–18%. CCALC was attributed to be caused by a combination of the sea-ice ikaite dissolution and dissolution of advected CaCO3 shells from the south. Indications of denitrification were observed, associated with sea-ice meltwater and bottom shelf processes. CBIO played a major role (48–89%) for the impact on CDIC.

Continue reading ‘Net community production and carbon exchange from winter to summer in the Atlantic Water inflow to the Arctic Ocean’

Effects of long-term exposure to reduced pH conditions on the shell and survival of an intertidal gastropod

Highlights

• Prolonged exposures to high pCO2 can severely affect Phorcus sauciatus shell.

• No effects of high pCO2 were found on size-frequency or population density of P. sauciatus.

• Shells from reduced pH sites exhibited a higher shell aspect ratio and greater percentages of shell dissolution and break.

• Shells from high pCO2 areas exhibited changes in mechanical strength.

• Similar desiccation tolerance was found among contrasting environment populations.

Abstract

Volcanic CO2 vents are useful environments for investigating the biological responses of marine organisms to changing ocean conditions (Ocean acidification, OA). Marine shelled molluscs are highly sensitive to changes in seawater carbonate chemistry. In this study, we investigated the effects of reduced pH on the intertidal gastropod, Phorcus sauciatus, in a volcanic CO2 vent off La Palma Island (Canary Islands, North East Atlantic Ocean), a location with a natural pH gradient ranging from 7.0 to 8.2 over the tidal cycles. Density and size-frequency distribution, shell morphology, shell integrity, fracture resistance, and desiccation tolerance were evaluated between populations from control and CO2 vent sites. We found no effects of reduced pH on population parameters or desiccation tolerance across the pH gradient, but significant differences in shell morphology, shell integrity, and fracture resistance were detected. Individuals from the CO2 vent site exhibited a higher shell aspect ratio, greater percentages of shell dissolution and break, and compromised shell strength than those from the control site. Our results highlight that long-term exposure to high pCO2 can negatively affect the shell features of P. sauciatus but may not have a significant effect on population performance. Moreover, we suggest that loss of shell properties could lead to changes in predator-prey interactions.

Continue reading ‘Effects of long-term exposure to reduced pH conditions on the shell and survival of an intertidal gastropod’

Geochemical characterization of highly diverse hydrothermal fluids from volcanic vent systems of the Kermadec intraoceanic arc

During the R/V Sonne cruise SO253 in 2016/2017, hydrothermal vent sites along the Kermadec intraoceanic arc were sampled for hydrothermal fluids at four active volcanoes: Macauley, Haungaroa, Brothers and Rumble III, respectively. Water depths ranged between 290 m and 1700 m. A new vent field was discovered at Haungaroa. The samples were taken from diffuse-flow sites as well as from white and black smokers – rich in metals and gases – with discharge temperatures as high as 311 °C. Their fluid composition is very variable but basically divides into two types: one that indicates distinct magmatic input and another that shows evidence for intense water-rock interaction under hot, acidic conditions.

Fluid samples from Macauley, the shallowest sampling site (~300 m), had Fe concentrations as high as 1.7 mM, Al concentrations up to 122 μM and H2S up to 10 mM at a pH of only 1.2. At Brothers, the deepest sampling site (down to 1600 m), we identified two different fluid types: 1) A magmatically-influenced type at the Upper and Lower Cone with highest temperatures of 115 °C, up to 95.6 mM Mg (the highest Mg concentration measured in fluids from intraoceanic arc systems so far), elevated SO42− (76.9 mM), high H2S (5.0 mM), but Fe concentrations of only 15 μM and 2) A fluid with low Mg (5.4 mM), low H2S (1.1 mM), temperatures reaching 311 °C and high Fe contents (12.4 mM) at the Upper Caldera and NW Caldera Wall, typical of a black smoker fluid. Chloride concentrations in all fluids were similar, or highly enriched when compared to seawater (e.g. up to 787 mM, brine fluids), with also one low-chlorinity vapor-phase fluid sample recovered, indicating that phase separation is occurring at Brothers. Unusual highly elevated Mg concentrations in fluids from the Brothers Lower Cone (95.6 mM, compared to 53.2 mM in ambient seawater) combined with highly elevated concentrations of SO42− (76.9 mM, compared to 29.0 mM in ambient seawater) indicate dissolution of Mg- and SO42−-bearing minerals in the subsurface, such as caminite.

Our data show how highly diverse and variable island arc systems can be with respect to their fluid chemistry, both spatially and temporally. It adds to the still limited data set of arc systems compared to mid-ocean ridges and supplies an important contribution towards a better understanding of geochemical processes along arc volcanoes.

The higher range in fluid chemistry together with shallower water depth implies that the fluids from intraoceanic arcs may contribute a significant fraction of dissolved metals not only to the global oceanic biogeochemical cycle but also into the photic zone, the area of highest bioproductivity.

Continue reading ‘Geochemical characterization of highly diverse hydrothermal fluids from volcanic vent systems of the Kermadec intraoceanic arc’

Prediction of pH value by multi-classification in the Weizhou Island area

Ocean acidification is changing the chemical environment on which marine life depends. It causes a decrease in seawater pH and changes the water quality parameters of seawater. Changes in water quality parameters may affect pH, a key indicator for assessing ocean acidification. Therefore, it is particularly important to study the correlation between pH and various water quality parameters. In this paper, several water quality parameters with potential correlation with pH are investigated, and multiple linear regression, softmax regression, and support vector machine are used to perform multi-classification. Most importantly, experimental data were collected from Weizhou Island, China. The classification results show that the pH has a strong correlation with salinity, temperature, and dissolved oxygen. The prediction accuracy of the classification is good, and the correlation with dissolved oxygen is the most significant. The prediction accuracies of the three methods for multi-classifiers based on the above three factors reach 87.01%, 87.77%, and 89.04%, respectively.

Continue reading ‘Prediction of pH value by multi-classification in the Weizhou Island area’

Features of the regional balance of inorganic carbon of marine ecosystems under anthropogenic pressure (in Russian)

The global changes in the biogeochemical structure of the oceans, which are most pronounced on a regional scale, caused by an increase in the flow of carbon into aquatic ecosystems as a result of increased releases from the atmosphere, coastal sources, primary production and destruction processes in the marine environment, make the issues of sharing the influence of the natural climatic and anthropogenic factors. For a quantitative assessment and analysis of the degree of influence of factors leading to the transformation of the natural carbon cycle, it is necessary to restore its budget, which is determined by the intake and removal of carbon, as well as the processes that result in its redistribution between different forms. The paper estimates the carbon budget for the ecosystem of the Sevastopol Bay (Black Sea), as well as analyzes the contribution of the anthropogenic component according to many years of research (2007–2018) of hydrochemical and geochemical characteristics. The results of studying the carbonate system of bottom sediments are presented: the vertical profile of the total dissolved inorganic carbon, alkalinity and pH, as well as the ratio between dissolved inorganic carbon and alkalinity. It has been established that the oxidation of organic matter occurs predominantly under anaerobic conditions. The values ​​of the flux of total dissolved inorganic carbon ( J TCO2 ) at the water-bottom boundary are directed from the bottom sediments to the bottom layer of water and are J T CO2 = 0.42 … 0.61 mol / (m 2 ∙ year). An analysis of the various components of the inorganic carbon budget showed that the largest role is played by anthropogenic sources, whose contribution is at least 75% of the total inorganic carbon supply. By the value of the total stock of dissolved inorganic carbon and its removal to the open sea, it was suggested that the time for the complete renewal of the waters of the Sevastopol Bay is 2 years 4 months.

Continue reading ‘Features of the regional balance of inorganic carbon of marine ecosystems under anthropogenic pressure (in Russian)’

Little evidence of adaptation potential to ocean acidification in sea urchins living in “future ocean” conditions at a CO2 vent

Ocean acidification (OA) can be detrimental to calcifying marine organisms, with stunting of invertebrate larval development one of the most consistent responses. Effects are usually measured by short‐term, within‐generation exposure, an approach that does not consider the potential for adaptation. We examined the genetic response to OA of larvae of the tropical sea urchin Echinometra sp. C. raised on coral reefs that were either influenced by CO2 vents (pH ~ 7.9, future OA condition) or nonvent control reefs (pH 8.2). We assembled a high quality de novo transcriptome of Echinometra embryos (8 hr) and pluteus larvae (48 hr) and identified 68,056 SNPs. We tested for outlier SNPs and functional enrichment in embryos and larvae raised from adults from the control or vent sites. Generally, highest FST values in embryos were observed between sites (intrinsic adaptation, most representative of the gene pool in the spawned populations). This comparison also had the highest number of outlier loci (40). In the other comparisons, classical adaptation (comparing larvae with adults from the control transplanted to either the control or vent conditions) and reverse adaptation (larvae from the vent site returned to the vent or explanted at the control), we only observed modest numbers of outlier SNPs (6–19) and only enrichment in two functional pathways. Most of the outliers detected were silent substitutions without adaptive potential. We conclude that there is little evidence of realized adaptation potential during early development, while some potential (albeit relatively low) exists in the intrinsic gene pool after more than one generation of exposure.

Continue reading ‘Little evidence of adaptation potential to ocean acidification in sea urchins living in “future ocean” conditions at a CO2 vent’

Characterization of a novel autonomous analyzer for seawater total alkalinity: results from laboratory and field tests

High‐quality seawater total alkalinity (AT) measurements are essential for reliable ocean carbon and acidification observations. Well‐established manual multipoint potentiometric titration methods already fulfill these requirements. The next step in the improvement of these observations is the increase of the spatial and temporal measuring resolution with minimal personnel and instrumental effort. For this, a rapid, automated underway analyzer meeting the same high requirements as the traditional method is necessary. In this study, we carried out a comprehensive characterization of the flow‐through analyzer CONTROS HydroFIA® TA (Kongsberg Maritime Contros GmbH, Kiel, Germany) for automated seawater AT measurements in the laboratory and in field with overall more than 5000 measurements. Under laboratory conditions, the analyzer featured a precision of ± 1.5 μmol kg−1 and an accuracy of ± 1.0 μmol kg−1, combined in an uncertainty of 1.6 – 2.0 μmol kg−1. High precision (± 1.1 μmol kg−1) and accuracy (−0.3 ± 2.8 μmol kg−1), and low uncertainty (2.0 – 2.5 μmol kg−1) were also achieved during field trials of 4 and 6 weeks duration. Although a linear drift appears to be the typical behavior of the system, this can be corrected for by regular reference measurements giving consistent measurement results. Another advantage of regular reference measurements is the early detection of any kind of malfunction due to its direct impact on the measurement performance. Based on the present study, recommendations for automated long‐term deployments are provided in order to gain optimal performance characteristics, aiming at the requirements for AT measurements.

Continue reading ‘Characterization of a novel autonomous analyzer for seawater total alkalinity: results from laboratory and field tests’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book