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PubMed2006

Changes in active bacterial communities before and after dredging of highly polluted Baltic Sea sediments.

Bacteria residing in sediments have key functions in the marine food web. However, it has been difficult to correlate the identity and activity of bacteria in sediments due to lack of appropriate methods beyond cultivation-based techniques. Our aim was to use a combination of molecular approaches, bromodeoxyuridine incorporation and immunocapture, terminal restriction fragment length polymorphism, and cloning and sequencing of 16S rRNA genes to assess the composition of growing bacteria in Baltic Sea sediments. The study site was a highly polluted area off the Swedish coast. The sediments were sampled in two consecutive years, before and after remediation, by dredging of the top sediments. Levels of polyaromatic hydrocarbons (PAHs), mercury, and polychlorinated biphenyls were dramatically reduced as a result of the cleanup project. The compositions of growing members of the communities were significantly different at the two sampling periods. In particular, members from the class Deltaproteobacteria and genus Spirochaeta were more dominant before dredging, but members of the classes Gammaproteobacteria and the Flavobacteria represented the most dominant growing populations after dredging. We also cultivated isolates from the polluted sediments that could transform the model PAH compound, phenanthrene. Some of these isolates were confirmed as dominant growing populations by the molecular methods as well. This suite of methods enabled us to link the identity and activity of the members of the sediment communities.

Archaea↗
PubMed1999

Pelagic-benthic coupling of nucleic acids in an abyssal location of the northeastern Atlantic Ocean.

Spatial and temporal changes in sedimentary nucleic acid concentrations in an abyssal locality of the northeastern Atlantic Ocean were investigated in relation to fluxes of nucleic acids produced in the photic layer. Sediment trap material, collected between 1996 and 1998 at depths of 1,000, 3,000, and 4,700 m, and sediment samples were analyzed for DNA and RNA content. Nucleic acid concentrations in the sediments were very high and displayed significant temporal changes, whereas mesoscale variability was low. DNA and RNA concentrations generally displayed opposite temporal patterns, which are likely to be dependent on the nature and characteristics of DNA and RNA molecules. Nucleic acid fluxes were high and displayed clear seasonal changes apparently coupled with seasonal pulses of primary production. However, while median values of DNA fluxes were relatively similar in all sediment traps, median values of RNA fluxes almost doubled from the 1,000- to the 4,700-m depth, suggesting differences in the metabolic activity of microbes associated with sinking particles. Significant relationships between DNA concentrations in the sediments and DNA fluxes and between RNA concentrations and RNA fluxes, indicating the presence of a clear pelagic-benthic coupling of particulate nucleic acids, were observed. The benthic system investigated was not steady state since we estimated that, from September 1996 to October 1998, nucleic acid concentration in the sediments decreased by about 165 mg of DNA m(-2). Vertical profiles revealed a significant decrease in DNA concentration with depth in the sediments, reaching an asymptotic value of about 5 microg g(-1). This DNA fraction constitutes a pool of potentially refractory DNA (accounting for 16 to 40% of the total DNA pool) that might be buried in the sediments.

DNA↗
PubMed2003

Anaerobic ammonium oxidation measured in sediments along the Thames estuary, United Kingdom.

Until recently, denitrification was thought to be the only significant pathway for N(2) formation and, in turn, the removal of nitrogen in aquatic sediments. The discovery of anaerobic ammonium oxidation in the laboratory suggested that alternative metabolisms might be present in the environment. By using a combination of (15)N-labeled NH(4)(+), NO(3)(-), and NO(2)(-) (and (14)N analogues), production of (29)N(2) and (30)N(2) was measured in anaerobic sediment slurries from six sites along the Thames estuary. The production of (29)N(2) in the presence of (15)NH(4)(+) and either (14)NO(3)(-) or (14)NO(2)(-) confirmed the presence of anaerobic ammonium oxidation, with the stoichiometry of the reaction indicating that the oxidation was coupled to the reduction of NO(2)(-). Anaerobic ammonium oxidation proceeded at equal rates via either the direct reduction of NO(2)(-) or indirect reduction, following the initial reduction of NO(3)(-). Whether NO(2)(-) was directly present at 800 micro M or it accumulated at 3 to 20 micro M (from the reduction of NO(3)(-)), the rate of (29)N(2) formation was not affected, which suggested that anaerobic ammonium oxidation was saturated at low concentrations of NO(2)(-). We observed a shift in the significance of anaerobic ammonium oxidation to N(2) formation relative to denitrification, from 8% near the head of the estuary to less than 1% at the coast. The relative importance of anaerobic ammonium oxidation was positively correlated (P < 0.05) with sediment organic content. This report of anaerobic ammonium oxidation in organically enriched estuarine sediments, though in contrast to a recent report on continental shelf sediments, confirms the presence of this novel metabolism in another aquatic sediment system.

Anaerobiosis↗
PubMed2004

Metal dynamics of plant litter of Spartina alterniflora and Phragmites australis in metal-contaminated salt marshes. Part 1: Patterns of decomposition and metal uptake.

To investigate the decay rate and metal uptake in litter from two species of wetland plants, leaves and stems of senescent Spartina alterniflora and Phragmites australis (P) were obtained from the Hackensack Meadowlands (NJ, USA) in October 1998, and their initial metal contents were determined. Two types of S. alterniflora were obtained, one set from a natural site (NS) and one from a restored site (RS). Leaves and stems were placed in separate litterbags, and samples of each type were reciprocally transplanted into each of the three collection sites (NS, RS, and P) as well as in the laboratory, where they were alternately dried and wetted. Litterbags were retrieved from the field at four six-month intervals and after one year from the laboratory. Annual decay coefficients were greater for leaves than for stems. Stems of P. australis initially decomposed more slowly (37-63% remaining) than those of S. alterniflora (23-53 % remaining), but after two years, decay was comparable (8-40% remaining for both species). Decomposition was slower at the RS site than at the other field sites, and it was slowest in the laboratory. Metal concentrations initially were lower in stems than in leaves, and Cr, Pb, and Zn were lower in P. australis than in S. alterniflora. In the field, large increases (10- to 100-fold) in metal concentrations rapidly obliterated any initial differences between plant species. Metal concentrations in leaves rose more quickly and remained greater than in stems. For example, Cu approached 300 microg/g in leaves but was less than 200 microg/g in stems. In contrast to the modest rise in metal concentrations in the leaf tissue at the more contaminated RS site (Zn rose to approximately 200 microg/g in sediments containing approximately 400 microg/g), Cu and Zn concentrations in leaf litter at the P and NS sites increased to levels exceeding those in the surrounding sediment (Zn rose to approximately 500 microg/g in sediments containing approximately 200 microg/g). Temporal changes in metal pools (grams of metal per litterbag) were not discernable because of the negative correlation of mass remaining and metal concentrations as well as because of the great variability of metal concentrations within each treatment. Decomposition and the accumulation of metals may be influenced more by differences between tissue types than by species or sediment metal concentrations.

Chromium↗
PubMed1998

A study of keratinolytic fungi in mountain sediments. I. Hair-baiting data.

Sediments form mountain streams in Brenna (Beskid Slaski) were examined for keratinolytic fungi. A rare psychrophilic dermatophyte, Keratinophyton ceretanicus, occurred abundantly in the sediments. The qualitative and qualitative compositions of keratinolytic fungi depended on the water contamination with sewage and on the contents of plant organic material, small mineral particles and salts in the sediments.

Arthrodermataceae↗
PubMed2001

Development and evaluation of a mathematical model for the study of sediment-related water quality issues.

A mathematical model (Sediment-Transport-Associated Nutrient Dynamics-STAND) has been developed for the study of sediment-associated water quality issues. The model is intended to simulate changes of water composition associated with sediment behavior. It has a 3-level structure. The first level accounts for the hydraulics of open-channel flow. The second computes sediment transport potential and actual rates based on the information provided by the first level. A non-equilibrium approach is used. In the third level, changes of nutrient concentrations along a studied river are computed with the consideration of nutrient transport, adsorption/desorption, and release. In order to calibrate the model, field data were collected from the Oconee River, a major tributary of the Altamaha River in Georgia, USA. Two stations, approximately 17 km distant from each other, were established along the river for the purpose of data collection. Observations of the river's hydraulics, suspended sediment, and water quality (mainly orthophosphate, nitrate, temperature, specific conductivity, oxidation-reduction potential, dissolved oxygen, and pH) were collected at the two stations. Another data set collected along a major tributary of the Yellow River in China was also used for calibration of the model's hydraulics and sediment transport parts. Calibration and validation results are encouraging, which suggests STAND may be a useful tool for the thorough study and understanding of nutrient dynamics associated with sediment behaviour.

Computer Simulation↗
PubMed2003

Disturbances to metal partitioning during toxicity testing of iron(II)-rich estuarine pore waters and whole sediments.

Metal partitioning is altered when suboxic estuarine sediments containing Fe(II)-rich pore waters are disturbed during collection, preparation, and toxicity testing. Experiments with model Fe(II)-rich pore waters demonstrated the rates at which adsorptive losses of Cd, Cu, Ni, Mn, Pb, and Zn occur upon exposure to air. Experiments with Zn-contaminated estuarine sediments demonstrated large and often unpredictable changes to metal partitioning during sediment storage, removal of organisms, and homogenization before testing. Small modifications to conditions, such as aeration of overlying waters, caused large changes to the metal partitioning. Disturbances caused by sediment collection required many weeks for reestablishment of equilibrium. Bioturbation by benthic organisms led to oxidation of pore-water Fe(II) and lower Zn fluxes because of the formation of Fe hydroxide precipitates that adsorb pore-water Zn. For five weeks after the addition of organisms to sediments, Zn fluxes increased slowly as the organisms established themselves in the sediments, indicating that the establishment of equilibrium was not rapid. The results are discussed in terms of the dynamic nature of suboxic, Fe(II)-rich estuarine sediments, how organisms perturb their environment, and the importance of understanding chemistry in toxicity testing with whole sediments or pore water. Recommendations are provided for the handling of sediments for toxicity testing.

Ferrous Compounds↗
PubMed2003

Correlations of extractable heavy metals with organic matters in contaminated river sediments.

In southern Taiwan, almost all the main rivers have been contaminated by anthropogenic heavy metals and organic matters. The main pollution sources include agricultural, industrial, and domestic activities. River sediments potentially have large capacities to accumulate heavy metals and organic matters when the river water flows through it. The sediments sampled from high contaminated river (the Yenshui River) and moderately contaminated rivers (the Tsengwen, Chishui, Potzu, and Peikang Rivers) were used to realize correlations between each kind of aqua regia extractable heavy metals (Co, Cr, Cu, Zn, Ni, Pb, Mn, and Fe) and organic matters in vertical sediment cores. Organic matters and aqua regia extractable heavy metal concentrations, analyzed by strong acid-digested extraction, were determined in vertical profile segments from downstream sediments of the five rivers. Sum of six aqua regia extractable heavy metals (Co, Cr, Cu, Zn, Ni, and Pb) were below 3,000 mg/kg in sediments of the Yenshui River, and below 500 mg/kg in the other four rivers' sediments. Strongly positive correlations (r = 0.83-0.95) between each kind of aqua regia extractable heavy metals and organic matters (concentration range between 0.6 to 3.8%) were observed in sediments of the Yenshui River. The slopes of the linear regressive lines approximated the average metal complexation ratios with organic matters in the sediments. In sediments of the other four rivers, smaller positive correlation coefficients between aqua regia extractable heavy metals and organic matters (below 2.6%) were observed. The complexation ratios derived from the four moderately polluted river sediments were smaller than those derived from the highly contaminated river sediments, indicating that the importance of organic matters in the accumulation of heavy metals in river sediments.

Environmental Monitoring↗
PubMed2005

[Effects of overlying water properties on sorption of organic pollutants in sediments].

By the method of orthogonal experiment, this paper studied the effects of overlying water temperature, pH, ionic strength, and dissolved organic carbon (DOC) on the sorption of phenanthrene and pentachlorophenol (PCP) in sediments. The results showed that temperature was the main factor affecting the sorption behavior of phenanthrene, with the trend of partition coefficient (Kd) decreased with temperature. For PCP, its Kd was the smallest at 20 degrees C, and its sorption was decreased with pH. The DOC content of overlying water slightly decreased the Kd of phenanthrene and PCP, and ionic strength only increased the Kd of PCP slightly. The sorption capacity of organic pollutants in sediment was mainly determined by the properties of organic pollutants and sediments.

Adsorption↗
PubMed2000

PIXE study of Cuban quaternary paleoclimate geological samples and speleothems.

PIXE elemental analysis of sediments, speleothems, and other geological formations related to the karst of the Sierra de San Carlos is presented. The similarity of the elemental composition of the sediments studied, as well as the alluvial regime which created them, indicate their common origin at each location. The Sr/Ca concentration ratio of a stalactite indicates that the average atmospheric temperature 12,000 and 18,000 years B.P. was colder than that of 6000 years B.P.

Calcium↗
PubMed1997

Effect of river and wetland sediments on toxicity of metolachlor.

Metolachlor is a preplant, preemergent herbicide applied to corn and soybean fields. Agricultural runoff after application can cause the herbicide to enter into natural waters. The objective of this study was to determine the effect of river and wetland sediments on the toxicity of metolachlor. Sediments from a river and a wetland (separately) were mixed with Ottawa sand (0, 25, 50, 75, and 100%). Metolachlor (in water) and sediment were mixed in an orbital shaker for 8 hr; the mixture was centrifuged, and the supernatant liquid was tested for toxicity (EC50%) using the marine luminescent bacteria Vibrio fischeri (Microtox). The toxicity (EC50%) of metolachlor with the river sediment was 64.61. Metolachlor after interaction with the wetland sediment demonstrated no toxicity possibly due to increased adsorption on the higher amount of organic matter (10 times) and clay (3.5 times) present in the wetland sediment than the river sediment.

Acetamides↗