Temperature differentially affects the persistence of polyunsaturated aldehydes in seawater

2013 ◽  
Vol 10 (5) ◽  
pp. 403 ◽  
Author(s):  
Ana Bartual ◽  
María J. Ortega
Keyword(s):  
Organic Compounds ◽  
Rapid Growth ◽  
Algal Blooms ◽  
Seawater Temperature ◽  
Phytoplankton Species ◽  
Surrounding Water ◽  
Unicellular Algae ◽  
The Stability ◽  
Polyunsaturated Aldehydes ◽  
Water Depths

Environmental context Diatoms, unicellular algae that live suspended in the water column, can undergo periods of rapid growth, called blooms. When these algal blooms die, organic compounds including polyunsaturated aldehydes are released to the surrounding water with currently unknown ecological effects. Here we demonstrate that temperature differentially affects the persistence of three major polyunsaturated aldehydes produced by diatoms, and we quantify the removal rates from seawater of these compounds. Abstract Polyunsaturated aldehydes (PUAs) are volatile compounds commonly released into the environment by different fresh and seawater phytoplankton species. Diatoms are among the main producers of these metabolites in seawater. The release of these metabolites in seawater is known to be wound-activated as a consequence of predation or cell lysis. Hence, the interaction of phytoplankton species that produce PUAs with other marine organisms is being thoroughly investigated. However, the stability of these compounds in seaweater once they are released and their persistence under different environmental conditions have never been quantified. In this work, we reveal an important effect of seawater temperature on the persistence of dissolved 2E,4E/Z-decadienal (DECA), 2E,4E/Z-octadienal (OCTA) and 2E,4E/Z-heptadienal (HEPTA) in seawater at the nanomolar scale. These three aldehydes were more persistent at 10°C than at either 15 or 20°C. Half lives of OCTA and HEPTA were reduced from 200h at 10°C to 80h at 15°C and 60h at 20°C. In addition, DECA was consistently more persistent than OCTA and HEPTA at the three temperatures assayed. This dependence of the persistence of dissolved PUAs on seawater temperature could determine a differential effect of equivalent PUA concentrations on the diversity and plankton community’s structure at different water depths, seasons or latitudes.

Role of single-celled organisms in mucilage formation on the shores of Büyükada Island (the Marmara Sea)

2010 ◽  
Vol 91 (4) ◽  
pp. 771-781 ◽  
Author(s):  
Neslıhan Balkis ◽  
Hakan Atabay ◽  
Irfan Türetgen ◽  
Serhat Albayrak ◽  
Hüsamettın Balkis ◽  
...  
Keyword(s):  
Membrane Filtration ◽  
Skeletonema Costatum ◽  
Seawater Temperature ◽  
Sampling Period ◽  
N:P Ratio ◽  
Cell Number ◽  
Species Number ◽  
Sampling Point ◽  
Marmara Sea ◽  
Phytoplankton Species

This study was implemented to determine the environmental factors and causative organisms of the recent mucilage formation in the Marmara Sea. Samples were taken during the study from 7 different depths (0.5–30 m) of one sampling point of the Büyükada Island shore between January and June 2008. As a result, 62 phytoplankton species belonging to 5 different groups were identified. Dinoflagellates were dominant in terms of species number, and diatoms in terms of cell number. In January and February, mucilage formation was very dense, where 5 phytoplankton species (Clindrotheca closterium, Pseudo-nitzschiasp.,Skeletonema costatum, Thalassiosira rotula(Bacillariophyceae) andGonyaulax fragilis(Dinophyceae)) were reported as dominant organisms. Among them,Gonyaulax fragilishas never been reported in the Marmara Sea previously, thus that organism appeared firstly with the formation of dense mucilage and then when the mucilage decayed in May and June 2008,G. fragilisdisappeared. Autofluorescent single-celled organisms were classified in three groups depending on their cell sizes (>20 μm, >2 μm, >0.2 μm) by membrane filtration and total count of bacteria were determined by epifluorescence microscope after dying with DAPI. The highest total bacteria was recorded in April at 25 m depth (6655 ± 44.4 cells ml−1) while the lowest count was in June at 0.5 m depth (1077 ± 26.1 cells ml−1). The seawater temperature ranged between 7.0 and 21.5°C, salinity between 20.9 and 37.4 ppt and dissolved oxygen amount between 2.75 and 12.75 mg l−1. The chlorophyll-aamount ranged between 0.10 and 6.35 μg l−1, the higher values were recorded in January at 15 m depth (6.35 μg l−1) and in April at 10 m depth (4.89 μg l−1). Among the nutrients, the amounts of nitrite + nitrate-N varied between 0.02 and 7.67 μg-at N l−1, phosphate-P between 0.11 and 0.96 μg-at P l−1and silicate-Si between 0.37 and 8.93 μg-at Si l−1. The highest values were determined at a deeper layer where nutrients are accumulated. On the other hand, the N:P ratio interval was found as 0.1–11.3, Si:P ratio as 2.92–52.33 and N:Si ratio as 0.01–1.10 during the sampling period. Nitrogen was the limiting nutrient and the silica amount was enough to enable the development of diatoms.

Theoretical Study on Thermal Hazardous Properties of C18H10O11 and C18H18O7 Organic Peroxides

2013 ◽  
Vol 787 ◽  
pp. 301-305
Author(s):  
Yun Bo He ◽  
Wei Wang ◽  
Shi Xiong Wang ◽  
Xiang Jun Yang ◽  
Hong Guo
Keyword(s):  
Molecular Structure ◽  
Thermal Decomposition ◽  
Quantum Chemistry ◽  
Organic Compounds ◽  
Theoretical Study ◽  
Organic Peroxides ◽  
Quantum Chemistry Calculation ◽  
The Past ◽  
Chemistry Calculation ◽  
The Stability

The thermal decomposition of organic peroxides are widely used as coagulant for organic compounds, however, its thermal hazardous characteristics have already caused serious accidents in chemical industries, which limited its application in much more strict conditions. Organic peroxides of C18H10O11 and C18H18O7 are two new candidates fitted for industrial explosive. However, as we best known there is little reports available on the geometry structure in the past decades. In this work, by means of quantum chemistry calculation, the relation of safety with molecular structure of C18H10O11 and C18H18O7 are discussed. The molecules with more activity O and the activity part more dispersedly exhibit higher stable, and the configuration has good safety. All the energy of molecule b is higher than that of molecule a. The stability of different configurations are 6a>7a>8a>9a>5a>1a>4a>3a=2a and 1b>7b>5b>6b>4b>2b>3b>8b, respectively, suggesting the structures of 6a,3a,2a,1b,8b exhibit high safety.

FORMIC ACID AS A SOLVENT FOR OZONIZATION INVESTIGATIONS

1940 ◽  
Vol 18b (1) ◽  
pp. 30-34 ◽  
Author(s):  
Rodger M. Dorland ◽  
Harold Hibbert
Keyword(s):  
Formic Acid ◽  
Ethyl Acetate ◽  
Organic Compounds ◽  
Aromatic Nucleus ◽  
Carboxyl Group ◽  
The Stability

The use of formic acid as a solvent in ozonization investigations has been developed and its suitability demonstrated by experiments on organic compounds of known structure. This solvent shows a remarkable tendency to protect the aldehyde from oxidation to the carboxyl group. The stability of the aromatic nucleus to ozone is apparently somewhat greater in this solvent than in ethyl acetate.

Mineral Redox Buffers and The Stability of Organic Compounds Under Hydrothermal Conditions

1996 ◽  
Vol 432 ◽  
Author(s):  
J. S. Seewald
Keyword(s):  
Organic Compounds ◽  
Active Species ◽  
Hydrothermal Systems ◽  
Hydrothermal Conditions ◽  
Sulfur Species ◽  
Sedimentary Environments ◽  
Mineral Assemblages ◽  
Catalytically Active ◽  
Chemical Conditions ◽  
The Stability

AbstractOrganic compounds play an integral role in numerous geochemical process in subsurface environments. To evaluate factors that regulate the stability of ethane, ethene, propane, and propene in hydrothermal systems a series of experiments were conducted at 300 to 325°C and 350 bars. The experiments contained the mineral assemblages pyrite-pyrrhotite-magnetite, hematite-magnetite-pyrite, and hematite-magnetite to buffer fO2, aH2(aq) and aH2S(aq) at geologically reasonable values.Results of the experiments suggest that under appropriate physical and chemical conditions, metastable redox dependent thermodynamic equilibrium involving liquid water and inorganic iron-bearing mineral assemblages may regulate the relative abundance of short chain alkanes and their corresponding alkenes. In addition, alkenes represent an important intermediary in the conversion of n-alkanes to methane and oxidized species such as carbon dioxide, ketones alcohols, and organic acids.The rates of redox dependent organic reactions during the experiments were strongly influenced by the presence of sulfur. Under relatively oxidizing conditions greater catalytic activity due to the presence of dissolved sulfur species was observed. Fluid speciation calculations suggest that oxidized aquous sulfur compounds represent the catalytically active species.These results suggest that redox conditions and the presence or absence of dissolved sulfur species in natural sedimentary environments may strongly influence the stability of hydrocarbons. Accordingly, models used to predict the stability of oil and the formations of natural gas need to account for chemical processes that involve both organic and inorganic sedimentary components.

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