Total Pigment Research Articles

Evaluation of eco-friendly anticorrosive pigments for paints in service conditions

The performance of different replacements for chromates was studied. The anticorrosive properties of seven phosphate-based pigments, a calcium-exchange silica and a ferrite were assessed by electrochemical techniques and formulating solvent-borne paints with epoxy and alkyd resins. Paints contained 30% by volume of anticorrosive pigment, with respect to the total pigment content. The anticorrosive performance of paints was evaluated by accelerated tests (salt spray chamber) and electrochemical essays (corrosion potential and ionic resistance). Outdoor exposure tests were carried out in an urban-industrial environment during 8 years. The anticorrosive performance of the tested paints showed that there is not a clear relationship between the laboratory tests and the outdoors exposition and that none of them, by themselves can predict the behaviour of the paint under service. However, electrochemical essays with pigments may give an orientation about pigment performance in anticorrosive paints. As a general rule, if the pigment reduces notably steel corrosion rate and generates a rather high apparent polarization resistance a good anticorrosive performance may be expected.

Tailored ferrites‐kaolin anticorrosive hybrid pigments in solvent‐based paints for protection of cold‐rolled steel

PurposeThe purpose of this paper is to determine a new easy route to obtain high performance and economic anticorrosive hybrid pigments based on kaolin and ferrite. The new route is based on depositing a surface layer of an expensive efficient anticorrosive pigment (ferrite) on a bulk of cheap extender pigment (kaolin). The combination of these pigments can add improved properties to the new pigment different from each of its individual components. These improved properties lead to imparting new properties to paint films containing these prepared pigments.Design/methodology/approachThe new prepared hybrid pigments contain different concentrations of deposited ferrite on kaolin surface, are determined using X‐ray fluorescence analysis to estimate the concentration of each element in the pigments. The pigments are characterised using different spectro‐photometric and analytical methods to prove the deposition of the shell layer and elucidate the structure of their particles. Then, they are incorporated in anticorrosive paint formulations, where their presence in these formulations is between 50 and 75 per cent of the total pigments in the paint formula. A model of the mechanism of protection to the metal substrate is presented.FindingsThe results show that the presence of these hybrid pigments imparts excellent corrosion protection to steel substrates, in spite of their different concentrations and loadings in the paint films.Practical implicationsThese pigments can be applied in other polymer composites, e.g. rubber and plastics as filler and reinforcing agent.Originality/valuePrepared pigments are eco‐friendly and can replace other hazardous pigments (e.g. chromates) – also it can replace original ferrite pigments. These pigments can compensate for the presence of other known pigments in markets successfully. The main advantage of these pigments is that they combine both the properties of their counter‐parts, and they are of lower cost than the original inhibitive pigment (ferrite). Also, they can be applied in other industries other than paints, e.g. paper, rubber and plastics composites.

Identification and Characterization of Purple Pigment-Producing Actinomycete Strain*

An actinomycete, named strain LK-178, was isolated from an alkaline soil sample in Henan, China. It produced grayish-white aerial mycelium and purple diffusible pigment on Gause’s synthetic agar. Microscopic observation revealed that it produced straight chain of cylindrical spores. It was primarily identified as genus Streptomyces according to its morphological, physiological and biochemical characteristics. The 16S rRNA gene sequence of strain LK-178 shared the highest similarity (99.0%) with that of S. bikiniensis AB208713. The phylogenetic tree of strain LK-178 was derived with NJ and analyzed with bootstraping. The result demonstrated that it belonged to S. bikiniensis. The test on antimicrobial activities showed that it had ability against the Gram-positive, Gram-negative bacteria and fungi. The UV- VIS spectrometry and chemical analysis revealed that the pigment producted by this strain was stable, total relative color value of the pigment was as high as 147 U/mL and total pigment yield reached 13.4 g/L.

Laser-induced fluorescence emission (LIFE) from Lake Fryxell (Antarctica) cryoconites

AbstractLaser-induced fluorescence emission (LIFE) images were obtained in situ from a 27 cm long ice core at Lake Fryxell, Antarctica. The excitation was accomplished with a simple 532 nm green laser pen light, and the fluorescence images were captured with a small compact digital camera. The targets for the experiment were mm-scale cryoconite assemblages found in the ice covers of this perennially frozen Antarctic lake. The fluorescence response originates from photo-pigments in cyanobacteria-dominated cryoconite assemblages with phycoerythrin (PE) exhibiting the optimal target cross section. This inexpensive, low-mass, low-energy method avoids manipulation of the in situ habitat and individual target organisms and does not disturb the microbial community or the surrounding ice matrix. We establish the correlation between fluorescence intensity and PE concentration. We show that cryoconite fluorescence response does not appear to decrease with depth in the ice cover, in agreement with similar findings at Lake Untersee, a perennially ice-covered lake in Dronning Maud Land, Antarctica. Optical reflection and refraction events at the air/ice interface can complicate quantitative estimates of total pigment concentrations. Laser targeting of a single mm-scale cryoconite can result in multiple neighboring excitation events secondary to reflection and refraction phenomena in the multiple air/ice interface of the bubbles surrounding the primary target.

Influence of impurities and hull content in material for pressing on sensory quality cold-pressed sunflower oil

This paper analyzes influence of different percentage of impurities and hull in the material for pressing on sensory quality (appearance, smell, taste, aroma and colour) of edible nonrefined sunflower oil. It has been concluded that simultaneous presence of impurities and hull in the starting material, especially presence of bigger quantities of impurities, has a rather negative effect on sensory quality of sunflower oil, made by cold pressing on a screw press. Apart from sensory analysis, the effect of impurities and hull on oil colour has also been identified by transparency determining, i.e. content of total pigments - carotenoids and chlorophyll. It has been concluded that presence of bigger quantities of impurities and hull cause the increase of content of both carotenoids and chlorophyll, and at the same time, decrease of transparency value in cold-pressed sunflower oil.

Photoinactivation of Escherichia coli on acrylic paint formulations using fluorescent light

The composition of acrylic paints containing TiO2 photocatalyst was evaluated in terms of bacterial inactivation using Escherichia coli (ATCC8739), during irradiation with fluorescent light. Paint formulations containing photocatalyst and photocatalyst plus extenders were prepared as films. Complete bacterial inactivation was obtained within 96 h for simple paint formulations containing photocatalyst at different loadings (15–80% of total pigment volume concentration). The addition of extenders such as silica and talc to the paint formulation did not affect the efficacy of bacterial inactivation. However, the use of CaCO3 as extender reduced the photocatalytic activity of the paint. This is attributed to reduced contact between the microorganism and the nanoparticles when CaCO3 is present, especially at concentrations higher than 40%. Results show the importance of careful paint formulation to enable activation of photocatalyst for E. coli killing under fluorescent light.

Effect of dehydration on some physiological aspects of shade and light grown plant species using detached leaves

Detached leaves were used to study the effect of hydration on some physiological aspects in shade (Syngonium podophyllum) as well as light grown (Lycopersicon esculentum Mill) plant species. In addition, these two plants were used to investigate the role of light to accelerate the effect of dehydration on peroxidase activity and chlorophyll degradation. Relative water content of both tomato and S. podophyllum (nephtytis) decreased drastically in three days under dehydration condition. Tomato leaves are thicker and fleshier than those of nephtytis; it may explain why the reduction in relative water content of tomato was higher than that of nephtytis, especially under dark condition. In three days, the reduction in total pigments of nephtytis was higher than those of tomato, especially under light condition. Both plant species showed reduction in total carbohydrate and protein contents resulted from the reduction of insoluble fractions. Under dehydration condition, both plant species showed disappearance (high in nephtytis) or appearance (high in tomato) of some polypeptides. In both plant species, increase of the soluble carbohydrate and protein fractions, enhance the peroxidase activity and expression of new polypeptides were three mechanisms to avoid the negative effects of dehydration but they were not enough to regulate the oxidative risks exerted by three days dehydration.

Chemical compositions and characteristics of farm raised giant catfish ( Pangasianodon gigas) muscle

Proximate composition, chemical and physical properties of dorsal, ventral and lateral line cuts of farm raised giant catfish were determined. Protein, fat and ash content of the different cuts averaged 16.88, 4.45 and 1.24 g/100 g, respectively. Dorsal contains higher protein concentrations (19 g/100 g) than other two parts ( p < 0.05). Ventral showed the highest hydroxyproline content (0.83 mg/g). Differences in lipid composition and fatty acid profiles were found among different cuts with highest phospholipids in the dorsal and highest triglyceride in both ventral and lateral line ( p < 0.05). All the meat cuts contained high saturated fatty acid, followed by mono- and polyunsaturated fatty acid. High muscle hardness and toughness was found in the dorsal than that in the ventral ( p > 0.05). The highest content of myoglobin and total pigment in lateral line resulted in the highest redness index ( a*/b*) of this part. Three major nitrogenous compositions classified based on solubility in giant catfish muscle were myofibrillar, sarcoplasmic and alkaline soluble proteins.

EVALUATION OF RED CABBAGE ANTHOCYANIN PIGMENTS AND ITS POTENTIAL USES AS ANTIOXIDANT AND NATURAL FOOD COLORANTS

Anthocyanins derived from red cabbage were extracted, and identified by using HPLC. These pigments are used as alternative natural red colorants in some processed foods i.e.; hard candy; jelly and ice sherbets. They are also effect of using as natural antioxidant on sunflower oil. Red cabbage has 90.5 mg anthocyanin /100 gm on fresh weights. Where the major constituents were cyaniding-3-diglucoside-5-glucoside (80%) and cyanidin 3, 5 diglucoside (20%) with HPLC. The best carrier for red cabbage anthocyanin pigment was found to be dextrin followed by cellulose, soluble starch and glucose respectively. On the other hand, color and higher pigment stability of anthocyanin derived from red cabbage were in acidic condition at pH ranged between 1.0 to 4.0 and in temperatures ranged between 40 to 80oC. Meanwhile, the degradation of anthocyanin being 10% of total pigments after 180 min at 100oC. Antioxidant activities of red cabbage anthocyanin were assessed by determining peroxide value on sunflower oil during 7 days at 60oC. Sunflower oil contained 200 ppm red cabbage extract showed lower peroxide value being (9.92) than using 200 ppm synthetic antioxidant (BHT) (10.12) meq/Kg. Analysis of variance for sensory evaluation of prepared hard candy, jelly and ice sherbets indicated that, hard candy, jelly contained 0.10% and ice sherbets contained 0.20% red cabbage anthocyanin pigments revealed the highest score of color, taste, odor and overall acceptability similar with synthetic color (carmine).

Effect of iron on growth, biochemical composition and paralytic shellfish poisoning toxins production of Alexandrium tamarense

Effects of iron (Fe) on growth, biochemical composition and paralytic shellfish poisoning (PSP) toxins production of Alexandrium tamarense were studied. Under Fe-limited conditions (1 nmol L −1 Fe), the alga exhibited a low specific growth rate (0.076 ± 0.017 d −1, n = 3) that was nearly a half of that under Fe-replete conditions (1 μmol L −1 Fe, 0.137 ± 0.00752 d −1, n = 4), and the cell density on day 21 (8210 cells mL −1) was also less than a half of that under Fe-replete conditions (2 × 10 4 cells mL −1). At the same time, total pigment, chlorophyll a (Chl a), protein, carbohydrate contents per cell and Chl a/carotenoid ratio decreased. In contrast, the PSP toxins content and the PSP toxicity per cell of the alga increased remarkably. Under Fe-limited conditions, total PSP toxins content and relative toxicity of alga were 2.55- and 2.54-fold of those under Fe-replete conditions, respectively. In addition, the profiles of PSP toxins also changed notably. The cellular content of gonyautoxin 1 + 4 (GTX1 + 4) increased for 5.6-fold along with the decrease of saxitoxin (STX) and gonyautoxin 2 + 3 (GTX2 + 3) contents contrasting to that under Fe-replete conditions. It suggested that the availability of Fe might effectively control the growth and toxic production of the alga and thereby influence the toxic effect of these harmful bloom events.

Effects of fibre orientation, myoglobin redox form, and postmortem storage on NIR tissue oximeter measurements of beef longissimus muscle

To determine near-infrared tissue oximeter responses to muscle fibre orientation, display time, and surface colour differences of beef longissimus lumborum steaks, beef loins were cut into steaks either perpendicular or parallel to the muscle fibre orientation. Surface colour differences were created by packaging steaks in vacuum (VAC), 80% O 2 and 20% CO 2 modified atmosphere packaging (HiOx MAP), polyvinyl chloride film overwrap (PVC), and HiOx MAP converted to PVC (HiOx-PVC) after 2 days. Changes in surface colour and subsurface pigments during display (0, 2, 4, 10, and 15 days at 2 °C) were characterized by using a reflectance-spectrophotometer and a near-infrared tissue oximeter, respectively. Fibre orientation, storage, and packaging affected ( P < 0.05) colour, total pigment, deoxymyoglobin, and oxymyoglobin content. Tissue oximetry measurements appear to have potential for real-time monitoring of myoglobin redox forms and oxygen status of packaged meat, but fibre orientation needs to be controlled.

New approach in studies of microalgal cell lysis

AbstractA new approach to the studies of the microalgal cell lysis by utilizing a combination of two complementary methods is presented. Delayed fluorescence (DF) is a measure of the living algal biomass, detecting only cells with active photosynthesis. Thermal lens spectrometry (TLS) detects the total pigment amount released from lysed cells. Both methods select for photosynthetic organisms, reducing possible background from other sources (e.g. heterotrophic bacteria, zooplankton, and abiotic substances). The DF/TLS method was tested with a laboratory Skeletonema costatum culture exposed to a geometric dilution series of the lysing factor poly- APS. The exposure resulted in similar EC50 values for DF intensity, TLS and dissolved esterase activity of 0.8±0.2, 1.77±0.35, and 1.25±0.1 mg poly-APS l−1, respectively. The combined DF/TLS method enabled a rapid evaluation of the living vs. dead cells without any sample pretreatment or manipulation.

Quinoid pigments from the sea urchin Toxopneustes pileolus

Many studies of the sea urchin Toxopneustes pileolus (Lamarck) are dedicated to toxic compounds released from various organs, especially the pedicellariae [1]. However, its pigments have not yet been studied. Quinoid pigments of the spinochrome are a distinguishing feature of this class of echinoderms and impart color to the testae and spines as the Ca and Mg salts [2]. The set of spinochromes for a certain species of sea urchin is not random but is determined by the maternal side [3]. Nevertheless, the color is variable and can differ not only in different populations [4] but also over several days in an individual [5] or from the effect of various factors [6]. These facts have not yet been fully explained. Although these compounds exhibit antimicrobial [7] and anti-oxidant [8] properties, their functions are apparently not limited to these. We investigated pigments of T. pileolus collected near Nya Chang Bay of the South China Sea during the 30th expedition of the SRS Academic Oparin. The color of the sea urchins varied from pale-blue to brownish-green although the pedicellariae of all were pale-rose. We selected one representative from each of three differently colored groups of sea urchins, pale-blue, green, and brownish-green. The remaining specimens (20) were combined to obtain a total pigment extract by collecting from them beforehand air-dried pedicellariae (∼3 g). Before pigments were extracted the testae with spines were first washed with EtOH and n-BuOH. Spinochromes were extracted exhaustively with n-BuOH, decomposing the material with dilute HCl. The resulting extract was washed with water to remove HCl, evaporated, and chromatographed several times over KSK silica gel with elution by benzene with a gradient of increasing acetone content. Pure compounds were purified further over Sephadex LH-20 using CHCl3:EtOH (4:1) to afford 1 (12 mg), 2 (2 mg), and 3 (52 mg). These were identified by comparing their UV, mass, and NMR spectra with the literature [2] and with those of known spinochrome samples that were isolated by us earlier from Strongylocentrotus nudus [9] as spinochromes A, C, and B, respectively. Only spinochrome A was observed in pedicellariae of this species of sea urchin. The composition and ratio of spinochromes in representatives of the various color groups were determined in extracts obtained as described above except for the use of Et2O as the extractant. Spinochromes were separated from the resulting extracts by saturated NaHCO3 solution and were again transferred to an Et2O solution by acidifying the extract with HCl. The extract was washed with H2O to remove HCl, dried over Na2SO4, evaporated, and analyzed by TLC and HPLC using spinochromes isolated during this work as references. Differently colored testae and spines contained all three spinochromes observed in the total extract from this species. Spinochrome B dominated (>97 and 86.4%) in green and brownish-green specimens, respectively. Spinochromes A and C made up 0.5% for the green specimens. The brownish tone was imparted to the animals by higher contents of these compounds, 6.7 and 4.2%, respectively. The main component in extracts from pale-blue specimens was spinochrome A. Spinochromes B and C were present in trace quantities. These results and those from a single study in the literature [4] indicate that the pigment compositions of testae and spines of sea urchins are characteristic of a species. However, color variability in individuals is determined by the quantitative ratio of spinochromes.

THE EFFECT OF WATER AND POTASSIUM SUPPLEMENT ON YIELD AND LYCOPENE CONTENT OF PROCESSING TOMATO

THE EFFECT OF WATER AND POTASSIUM SUPPLEMENT ON YIELD AND LYCOPENE CONTENT OF PROCESSING TOMATO

Spatial variability in organic material sinking export in the Hudson Bay system, Canada, during fall

Spatial variations in the sinking export of organic material were assessed within the Hudson Bay system (i.e., Hudson Bay, Hudson Strait and Foxe Basin) during the second oceanographic expedition of ArcticNet, on board the CCGS Amundsen in early fall 2005. Sinking fluxes of particulate organic material were measured using short-term free-drifting particle interceptor traps deployed at 50, 100 and 150 m for 8–20 h at eight stations. Measurements of chlorophyll a (chl a), pheopigments (pheo), particulate organic carbon (POC), biogenic silica (BioSi), protists, fecal pellets and bacteria were performed on the collected material. In parallel, sea surface salinity and temperature were determined at 121 stations in the Hudson Bay system. Three hydrographic regions presenting different sedimentation patterns were identified based on average surface salinity and temperature. Hudson Strait was characterized by a marine signature, with high salinity (average=32.3) and low temperature (average=2.1 °C). Eastern Hudson Bay was strongly influenced by river runoff and showed the lowest average salinity (26.6) and highest average temperature (7.6 °C) of the three regions. Western Hudson Bay showed intermediate salinity (average=29.4) and temperature (average=4.4 °C). Sinking fluxes of total pigments (chl a+pheo: 3.37 mg m −2 d −1), diatom-associated carbon (19.8 mg m −2 d −1) and BioSi (50.2 mg m −2 d −1) at 50 m were highest in Hudson Strait. Eastern Hudson Bay showed higher sinking fluxes of total pigments (0.52 mg m −2 d −1), diatom-associated carbon (3.29 mg m −2 d −1) and BioSi (36.6 mg m −2 d −1) compared to western Hudson Bay (0.19, 0.05 and 7.76 mg m −2 d −1, respectively). POC sinking fluxes at 50 m were low and relatively uniform throughout the Hudson Bay system (50.0–76.8 mg C m −2 d −1), but spatial variations in the composition of the sinking organic material were observed. A large part (37–78%) of the total sinking POC was unidentifiable by microscopic observation and was qualified as amorphous detritus. Considering only the identifiable material, the major contributors to the POC sinking flux were intact protist cells in Hudson Strait (28%), fecal pellets in eastern Hudson Bay (52%) and bacteria in western Hudson Bay (17%). A significant depth-related attenuation of the POC sinking fluxes (average loss between 50 and 150 m=32%) and a significant increase in the BioSi:POC ratio (average increase between 50 and 150 m=76%) were observed in Hudson Strait and eastern Hudson Bay. For all other sinking fluxes and composition ratios, we found no statistically significant difference with depth. These results show that during fall, the sinking export of total POC from the euphotic zone remained fairly constant throughout the Hudson Bay system, whereas other components of the organic sinking material (e.g., chl a, BioSi, fecal pellets, protist cells) showed strong spatial variations.

Magnetic Fields Induce Changes in Photosynthetic Pigments Content in Date Palm (Phoenix dactylifera L.) Seedlings

Growth, development and plants productivity are usually affected by photosynthetic pigments activity. Magnetic fields are known to induce biochemical changes and could be used as a stimulator for growth related reactions including affecting photosynthetic pigments. The impact of magnetic field strengths on chlorophyll and carotenoids were investigated in this study through the use of date palm (Phoenix dactylifera L.) seedlings. To study the effects of magnetic treatments on photosynthetic pigments, date palm seedlings were exposed to magnetic fields in two experiments. In the first experiment, seedlings were treated with static magnetic field at three levels of (10, 50 and 100 mT) and different durations (30, 60, 180, 240 and 360 min). At the second experiment, seedlings were treated with alternating magnetic field at 1.5 T for different durations (1, 5, 10 and 15 min). The photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids and total pigments) were assayed using spectrophotometric methods. Results indicated that pigments content (chlorophyll a, chlorophyll b, carotenoids and total pigments) was significantly increased under static magnetic field. The highest measurements were recorded at 100 mT, after 360 min of exposure. On the other hand, alternating magnetic field has decreased photosynthetic pigments content after 10 min of treatment with 1.5 T. Low magnetic field doses had a simulative effect on photosynthetic pigments whereas high doses had a negative effect. Chlorophyll a and carotenoids were more affected than chlorophyll b. Magnetic fields treatment could be used to enhance plant growth and productivity.

Photoautotrophic community changes in Lagunillo del Tejo (Spain) in response to lake level fluctuation: Two centuries of sedimentary pigment records

Lagunillo del Tejo is a small doline lake in a karstic region of the Iberian Ranges (central-eastern Spain) that undergoes significant lake level fluctuation in response to changing aquifer influxes. In order to assess changes in the primary producer community in the lake over the last two centuries and to elucidate whether these were conditioned by climatic variability, photosynthetic pigments and their derivatives were extracted from the sediments and the data analysed using multivariate statistical techniques. Quantitative variations in total pigment concentrations through the sedimentary sequence are considered a result of changes in sedimentation rate, largely due to lake level fluctuation. Rapid lowering of the level results in an increase in detritic mineral matter eroded from the sides of the lake, which accumulates in the sediment and dilutes the organic matter content in the corresponding sediment layers. On the other hand, shifts in the relative abundances of the different pigments suggest the development of two different primary producer communities: (i) planktonic, comprising cyanobacteria, chlorophytes, cryptophytes and purple sulfur bacteria and (ii) primary producers related to the littoral environment, mostly submerged macrophytes. These two communities showed alternating relative importance over the last two centuries, as a biotic response to lake level fluctuation during wet and dry periods, respectively.

PHYSIOLOGICAL AND BIOCHEMICAL EFFECTS OF UV-RADIATION AND SODIUM DODECYL SULPHATE (SDS) MUTAGENS ON GROWTH AND METABOLISM OF GARLIC PLANTS

The effects of enhanced UVA (320-380), UVC (280nm) and SDS, as mutagenic substances, on growth parameters and certain metabolic changes, during vegetative and flowering growth stages of garlic (Allium sativum var. Seds 40) were investigated. Root length, shoot length, fresh mass, dry mass accumulation and leaf area in garlic, treated with UV- radiation (A and C), and SDS (0.1 M and 0.3 M) as mutagenic substances, throughout the entire period of the experiment, showed significant variable changes below the control levels. Photosynthetic pigments (chl a, chl b, carotenoids, total chl a+b, and total pigment) contents of the variously treated garlic plants showed significant changes as compared with control plants throughout the duration of the experiment. The ratio of chl a / b showed variable changes in UV- and SDS- treated plants in relation to control. UV- absorbing compounds (total phenolic compounds and anthocyanins contents) of the UV- and SDS- treated garlic plants, showed significant increase above the control levels during vegetative and flowering growth stages. As compared with control nucleic acid levels, nucleic acid contents (DNA and RNA) of UV- and SDS- treated plants, at vegetative and flowering growth stages, showed significant decrease.

EFFECT OF SALICYLIC ACID ON PHOTOSYNTHESIS AND SOME ANTIOXIDANT ENZYMES OF STRESSED SCENEDESMUS OBLIQUUS CULTURES

This study followed the effect of salicylic acid on growth criteria, photosynthetic pigments, photosynthesis, respiration, proline and the activities of some antioxidant enzymes of stressed Scenedesmus obliquus cultured for 7 days. The growth criteria (cell number and dry weight) and total pigments ofnon- stressed and stressed Scenedesmus obliquus cultures were significantly increased, when the algal cultures were subjected to 200 mM NaCl and treated with 100and 200 ppm of salicylic acid. Also, Photosynthesis (oxygen evolution), respiration (dark oxygen uptake), proline, amino acids and catalase enzyme of non- salinized and salinized Scenedesmus obliquus cultured were significantly increased, when the algal cultures were subjected to 200 mM NaCl and treated with 100and 200 ppm of salicylic acid. However, both respiration (oxygen uptake) , lipid peroxidation as termed (malondialdhyde) and peroxidase were significantly decreased, when the algal cultures were subjected to 200 mM NaCl and treated with 400 ppm of salicylic. These values were compared with that of the control cultures.

Sedimentary pigments on the Pakistan margin: Controlling factors and organic matter dynamics

Abstract Sedimentary pigments can provide information on various aspects of benthic processes and biogeochemistry. In this study, sediments from sites at depths of 140 to 1850 m spanning the Pakistan margin oxygen minimum zone (OMZ), and representing dramatic contrasts in depositional conditions and benthic communities, were analysed for pigment yields and compositions. This has allowed a rare consideration of how different factors, including oxygen concentration, organic matter (OM) supply and biological activity (e.g., degree of bioturbation) may influence sedimentary pigment distribution in a continental margin environment. It has also allowed one of the first efforts to study the impact of biological activity on pigment concentrations in the natural environment, rather than in a microcosm setting. Total extractable surface sediment pigment concentrations showed a range of ∼1.5–49 μg g −1 of dry sediment. The pigment suite was dominated by pheophytin and pheophorbide (which together constituted ∼75% of total pigments), with minor amounts of chlorophyll- a , alloxanthin, diatoxanthin, zeaxanthin and β-carotene. Low oxygen concentration appeared to influence pigment abundance by increasing the concentration of refractory pigments ultimately buried. In addition, maximal pigment abundances were associated with minimal amounts of sediment mixing by macrofauna, and at one site macrofaunal digestion may have altered the relative dominance of the different pheopigments. In contrast, the lack of a marked increase in pigment concentrations after the summer monsoon plus the lack of a correlation between pigment concentration and water depth suggest that OM supply plays a relatively small role in controlling sedimentary pigments. Pigment concentrations and suites, together with modelled decay half-lives (∼0.8–15 years), suggest that in general OM on the Pakistan margin, despite the low oxygen concentrations and monsoon-driven productivity, is surprisingly degraded compared to that on other continental margins with OM-rich sediments. As an exception to this general situation, pigment suites appeared to be relatively “fresh” (i.e., contained more labile components) compared to those found on the Oman margin of the Arabian Sea, but overall concentrations were lower. This is consistent with the higher oxygen concentrations, productivity and macrofaunal abundances found on the western margin of the Arabian Sea. Principle component analysis of pigment suites showed that they correlated with an amino-acid-based degradation index (DI). Thus, the pigment composition of marine sediments is related to, and may serve as an indicator of, the state of decay of sedimentary OM.