Distribution of biogenic silica and particulate organic matter in coastal and oceanic surface waters off the South Shetland Islands in summer

Biogenic silica (BSi), lithogenic silica (LSi), particiulate organic carbon (POC) and nitrogen (PON), and chlorophyll a (Chl a) concentration levels were measured in the surface waters (<100 m) off the northern coast of the South Shetland Islands in summer 1991. High concentration levels of BSi and LSi were recorded in the oceanic area and the coastal area, respectively. However, marked regional differences were not observed for POC, PON and Chl a concentrations. The mean BSi/POC atomic ratio (±SD) in the oceanic area (0.27±0.17) was 6 times that in the coastal area (0.045±0.020), except for the bloom situation (0.19±0.029). In contrast, the mean POC/PON atomic ratio was not significantly different in the coastal area (5.9±1.4) and the oceanic area (5.2±1.7). Nitzschia spp. were the dominant diatoms in the oceanic area but not in the coastal area. High BSi/POC ratios have been reported for blooms dominated by Nitzschia spp. even in the coastal regions of the Antarctic Ocean. The area difference in the BSi/POC ratios was probably related to the difference in species composition of phytoplankton and not to regional contrast. This species contributes significantly to high BSi/POC ratios in the Antarctic Ocean.     

Ingestion of particulate matter by the outer surface cells of the mollusc mantle

A study of the ingestion of particulate matter from the pallial space located between the shell and the outer surface of the mantle of Isognomon alatus and Pinctada radiata was undertaken with the aid of the electron microscope. For this purpose colloidal thorium dioxide (thorotrast) was introduced into the pallial space for periods of 1–5 days after which time the mantle was excised and prepared for examination with the electron microscope. After 24 hours thorotrast micelles were observed in the pallial space, on the surface of the microvilli, in small pinocytotic vesicles between the bases of the microvilli, in vacuoles undergoing coalescence and finally in large dense bodies (lysosomes). Amoebocytes in the pallial space also participate in the removal of particulate matter in a manner similar to that described for the surface epithelium. During active ingestion the Golgi apparatus changes from a vesicular to a lamellar form. The method of ingestion observed in the surface epithelia and the amoebocytes is similar to the ingestion of protein and other particulate material reported for a variety of vertebrate tissues.     

Phytoplankton productivity in turbid waters

Many of the freshwater areas in the world are turbid, due tosuspended inorganic particles. The euphotic depth of the shallowturbid impoundment, Wuras Dam, varies between 0.3–1.3m. This results in a compressed production profile where accuratemeasurements become difficult. Tubes of various lengths havebeen used and usually render higher rates, when compared todiscrete bottle incubations. A tube the depth of the euphoticzone confines the phytoplankton in the light and the rates measuredrepresent the maximal possible under the prevailing conditions.Longer tubes include an aphotic portion and give an idea ofthe magnitude of respiration losses. The depth of the mixinglayer appears to be especially important in turbid systems asthe time spent in the dark, relative to the light is of greatimportance and may be the most important regulating factor insuch waters. ^*This paper is the result of a study made at the Group for AquaticPrimary Productivity (GAP), Second International Workshop heldat the National Oceanographic Institute, Haifa, Israel in April–May1984.     

The role of phytoplankton in the removal of arsenic by sedimentation from surface waters

The role of phytoplankton in the removal of arsenic (As) by particle adsorption and sedimentation was investigated in Moira Lake, Canada. Sampling water and suspended particles over one year illustrated significant variation in As partitioning between particulate and aqueous phases, but failed to establish a correlation between the partition coefficient, K _d, and indicators of phytoplankton biomass. A highly significant inverse logarithmic relationship was noted between K _d and the concentration of suspended particles (log K _d = 5.1 – 1.4 log SS; p = 0.0001) in an apparent demonstration of the particle concentration effect (O' Connor & Connolly, 1980).Particle deposition, measured by means of sediment traps, appeared to include a substantial component of resuspended surficial sediment making sediment trap results unreliable for quantifying the removal of substances from the water column. The As concentration of particles from deep traps deployed during late summer and early fall exceeded the As concentrations of suspended particles and surficial sediment, and may indicate that a highly contaminated nepheloid layer acts as a temporary sink for As.     

Sources and fluxes of particulate organic matter in shallow coastal waters characterized by summer macroaggregate formation

The origin and temporal variation in composition of sedimented particulate organic matter (POM) in the Gulf of Trieste (northern Adriatic) was studied over the year with special reference to the composition and sedimentation of macroaggregates in summer of 1991 using sediment traps.Suspended and sedimented POM, comprising a minor part of the largely inorganic total particulate matter, was prevalently of marine origin and composed mostly of humic substances followed by carbohydrates and proteins. Seasonal variations of particulate proteins and carbohydrates were correlated with variations of phytoplankton biomass. New production, occurring in late spring as a consequence of massive riverine inputs of N, Si and P nutrients in the surface layer of the Gulf, produced high particulate carbohydrate and protein concentrations. Subsequent depletion of introduced nutrients caused the decrease of particulate protein concentration but not that of particulate carbohydrate. The prolonged plankton biosynthesis of carbohydrates successively produced marine snow and later macroaggregates. The macroaggregates were characterized by ¹³C value of –19.9. and their carbohydrates were mostly composed of glucose followed in decreasing order by mannose, fructose, galactose, arabinose, ribose, xylose and fucose, suggesting a prevalent origin from phytoplankton structural heteropolysaccharides. Sedimentation of particulate organic constituents in the summertime, characterized by the massive presence of macroaggregates in the surface layer above the pycnocline, was the highest at a depth of 10 m at the end of this phenomenon, about six weeks after its first appearance. Sedimented macroaggregates were clearly traced by a characteristic ¹³C signal and higher carbohydrate concentrations. The monosaccharide composition was influenced by selective degradation in the water column. Sedimented POM in the bottom layer was, on the other hand, more affected by sediment resuspension. The mean yearly decrease of particulate protein-C and carbohydrate-C by 40–50% in the water column between the depths of 10 and 20 m indicates the preferential utilization of these constituents by microorganisms. The decrease of particulate humic-C is probably more the result of the export of particulate matter from the Gulf. This study also indicates that the macroaggregate formation has little impact on the annual C and N budget in such coastal areas.     

Real-time measurement of particulate matter deposition in the lung

Abstract

Air pollution and cigarette smoke are recognized health risks. A method was developed for the measurement of the deposition fraction (DF) of polydisperse particulate matter (PM) in human airways. Ten normal volunteers [three females, age range 18–67 years, mean age (SD) 43.9 (14)] made single breath exhalations after inhalation to total lung capacity. The exhaled breath was diverted to a multichannel laser diffraction chamber where the particulate profiler measured 0.3–1.0-µm particles. DF was inversely related to expiration flow-rate, 0.69 (0.02) at 4 l min^?1 and 0.5 (0.01) at 13 l min^?1, respectively (p<0.05), and was influenced by the inhalation flow-rate [0.70 (0.02) at 3 l min^?1 and 0.59 (0.02) at 13 l min^?1, respectively (p<0.05)], while no differences were found between nasal and oral inhalation (0.68 (0.05) versus 0.67 (0.06), p>0.05). Higher breath holding times were associated with elevated DF [0.74 (0.02) at 20 s, and 0.62 (0.05) without breath holding (p<0.01)]. When the expiratory flow was controlled and the breath hold time standardized, DF was reproducible (CV?=?4.85%). PM can be measured in the exhaled breath and its DF can be quantified using a portable device. These methods may be useful in studies investigating the health effects of air pollution and tobacco smoke.     

The role of oligochaetes in the management of waters

To better understand the role of an aquatic oligochaete in the management of water quality, it was determined if oligochaetes were representative of water quality, if indices based on oligochaetes were widely applicable to access water quality, and if oligochaete assemblages were related to environmental factors other than organic pollution. It was found that if only one monitoring sample a year was taken in December, about 73% of the more common species were collected. Seasonality did not seem to affect the taxa collected except for forms in low presence, e.g., Nais. Several indices we used were not applicable to regulated streams. Oligochaete ordination procedures revealed only a partial picture of the environmental conditions of regulated streams.     

厦门近岸海域大型底栖动物次级生产力

于2013年5月和11月在厦门近岸海域设置67个站位进行大型底栖动物定量调查,运用Brey(1990)经验公式对该海域的次级生产力进行估算。结果表明:该海域大型底栖动物年均总次级生产力P和P/B值分别为4.6±10.1 g AFDW·m-2·a-1和1.0±0.4a-1,软体动物和多毛类为该海域P值的主要贡献类群,秋季的P值略高于春季,同安湾的P值明显高于大嶝海域、九龙江口、厦门外海域和围头湾。相关性分析显示,该海域次级生产力与沉积物有机质含量以及水体底温呈显著相关,底质类型以及采砂、航道清淤、环境污染等人类活动干扰也是影响次级生产力分布的主要因素。     

Intestinal absorption of particulate matter.

Evidence for and against the movement of intact particulates across the normal intestinal mucosa is reviewed. The effects of type of particulate and age of animal are considered. Small particulates unquestionably enter the gut-associated lymphoid tissues of adult animals and are engulfed by macrophages. Published evidence also favors the conclusion that small particulates are taken into absorptive cells of adults by an endocytotic mechanism. The evidence for passage of particulates between intestinal absorptive cells or into villus tips at the extrusion zone is not yet conclusive.     

The responses of lake waters to organic matter additions

The increase of inorganic nitrogen subsequent to the addition of organic matter was investigated in replicate lake-water aliquots. Two experiments used freshly killed bacteria as the organic addition. In both, inorganic nitrogen in the water column increased only after a lag period following the organic addition, and only if the amount of organic matter added exceeded a threshold value. Two other experiments used freshly killed algae as the organic addition; in these, neither the lag period nor the threshold value were seen. A qualitative explanation for these observations is offered.     

Real-time measurement of particulate matter deposition in the lung.

Air pollution and cigarette smoke are recognized health risks. A method was developed for the measurement of the deposition fraction (DF) of polydisperse particulate matter (PM) in human airways. Ten normal volunteers [three females, age range 18-67 years, mean age (SD) 43.9 (14)] made single breath exhalations after inhalation to total lung capacity. The exhaled breath was diverted to a multichannel laser diffraction chamber where the particulate profiler measured 0.3 - 1.0-microm particles. DF was inversely related to expiration flow-rate, 0.69 (0.02) at 4 l min-1 and 0.5 (0.01) at 13 l min-1, respectively (p<0.05), and was influenced by the inhalation flow-rate [0.70 (0.02) at 3 l min-1 and 0.59 (0.02) at 13 l min-1, respectively (p<0.05)], while no differences were found between nasal and oral inhalation (0.68 (0.05) versus 0.67 (0.06), p>0.05). Higher breath holding times were associated with elevated DF [0.74 (0.02) at 20 s, and 0.62 (0.05) without breath holding (p<0.01)]. When the expiratory flow was controlled and the breath hold time standardized, DF was reproducible (CV = 4.85%). PM can be measured in the exhaled breath and its DF can be quantified using a portable device. These methods may be useful in studies investigating the health effects of air pollution and tobacco smoke.     

Anaerobic degradation kinetics of particulate organic matter in untreated and sonicated sewage sludge: role of the inoculum

Degradation kinetics of particulate matter in anaerobic digestion of secondary sludge, untreated and sonicated, was investigated by carrying out batch tests at different feed/inoculum ratio (F/I) (in the range of 0.1-4.0). Particulate COD degradation data were analysed using the four equations most widely utilized to model the hydrolysis process and the related kinetic parameters were evaluated. The increase of F/I results in a correspondent increase of the process rate up to one order of magnitude in the investigated interval for both untreated and sonicated sludge. The maximum step increase is observed in the range of 0.1-2.0 while for F/I varying from 2.0 to 4.0 only a modest enhancement of the process kinetics is detected. The effect of sonication on kinetics is not appreciable at low F/I, due to the low fraction of fed sludge and to the consequent strong substrate limitation, whereas at high F/I a slight increase is evidenced.     

Concentrations of particulate matter in the North Frisian Wadden Sea

The amount of particulate matter for different size classes was determined in the North Frisian Wadden Sea over a period of 10 months from November 1973 to August 1974. Particle volume, particulate organic carbon and phaeopigment concentrations decrease with advancing season, reaching minima in June. It is concluded that concentrations of particulate matter including chlorophyll were sufficiently high throughout the study period to support the growth and reproduction of appendicularia which abundantly occur in the Wadden Sea.     

Temporal and spatial variations in phytoplankton productivity in surface waters of a warm-temperate,monomictic lake in New Zealand

Surface phytoplankton productivity measurements were carried out in morphologically complex Lake Rotoiti with the objective of defining variations between sites and seasons, and the dominant environmental drivers of these variations. Measurements were carried out monthly at two depths at each of three morphologically diverse stations for 1 year throughout the lake. Productivity at the surface of the shallow embayment was significantly higher in most months of the year compared with the surface of the other two stations but there were no significant differences from September to December 2004. There were no relationships between measured environmental variables and primary productivity or specific production. Inorganic nutrient concentrations at the surface of the shallow station were low throughout the whole year but at the other two stations they showed a typical pattern for monomictic lakes of higher levels during winter mixing and declining concentrations during thermal stratification. The high variability between sites found in this study indicates that it is important to account for local differences in productivity in morphologically diverse lakes, and that whole lake productivity estimates may vary greatly depending on the location and depth of productivity measurements.     

Ambient particulate matter induces alveolar epithelial cell cycle arrest: role of G1 cyclins

We hypothesized that the ambient air pollution particles (particulate matter; PM) induce cell cycle arrest in alveolar epithelial cells (AEC). Exposure of PM (25microg/cm(2)) to AEC induced cells cycle arrest in G1 phase, inhibited DNA synthesis, blocked cell proliferation and caused decrease in cyclin E, A, D1 and Cyclin E- cyclin-dependent kinase (CDK)-2 kinase activity after 4h. PM induced upregulation of CDK inhibitor, p21 protein and p21 activity in AEC. SiRNAp21 blocked PM-induced downregulation of cyclins and AEC G1 arrest. Accordingly, we provide the evidence that PM induces AEC G1 arrest by altered regulation of G1 cyclins and CDKs.     

The role of phytochelates in plant growth and productivity

Plants require minimal amounts of certain metals (Zn,Fe,Cu,etc) for optimal growth and productivity, but excess of these metals leads to cell death. When growth is limited by metal excess or metal deficiency plants respond by synthesizing nonproteinogenic chelating substances. Phytosiderophores are secreted by roots of iron deficient grasses and are important in providing sufficient Fe for normal growth. In response to growth-inhibitory levels of heavy metals plants synthesize metal-binding phytochelatins which detoxify excess metals. Biostimulants such as humic substances and oligomers of lactic acid have properties in common with both phytosiderophores and phytochelatins. The word phytochelates is proposed as a generic term to cover substances that affect plant growth by acting as chelating agents.     

Quality of suspended fine particulate matter in the Little Tennessee River

Hydrobiologia - Fine particulate organic matter is a major food resource in southeastern river food webs, but natural variability in the quality of this resource has not been assessed. We measured...     

The use of sedimentation field-flow fractionation to study suspended particulate matter

The current and potential uses of sedimentation field-flow fractionation (SdFFF) for characterizing suspended particulate matter (SPM) from natural waters is reviewed. Suitable sample preparation methods and run conditions are given which enable the particle size distribution of aquatic SPM to be determined. Samples collected from different natural waters display quite distinct differences in the shape of their particle size distribution.One of the major advantages of this high resolution separation technique is that fractions of specific size ranges can be collected for characterization by other analytical methods. This has been illustrated in this work with scanning electron microscopy and EDAX elemental analysis data. The potential to extend this approach using other characterization techniques such as inductively coupled-plasma mass spectrometry and X-ray diffraction is discussed.A method has been developed for combining adsorption experiments with SdFFF separations that enables the distributions of both the amount adsorbed and the surface adsorption density across the SPM size range to be determined with good resolution. This approach is illustrated by the adsorption of the herbicide glyphosate to two estuarine SPM samples.