Increase In Sulfide Concentration Research Articles

Sulfide perturbation of NOM-bearing oxic environments induces dark •OH production

The photo-irradiation of natural organic matter (NOM) is a well-documented pathway of •OH production in surface waters. Using humic acid (HA) as a model compound, we show that the perturbation of NOM-bearing oxic environments by naturally occurring reduced species, sulfide, contributes to •OH production under dark conditions. Sulfide concentration had a more prominent influence on •OH production than HA. When HA was controlled at 16 mM C under oxic and neutral pH conditions, the increase of sulfide concentration from 0 to 5 mM increased the cumulative •OH concentration from <2 to 72.2 μM within 120 min. When sulfide was maintained at 2.5 mM, the increase of HA concentration from 0 to 16 mM C increased the cumulative •OH concentration from <0.6 to 44.8 μM. •OH accumulation showed good consistency with sulfide removal and O2 consumption. O2 consumption increased with increasing HA concentration at a fixed sulfide concentration, and also increased with increasing sulfide concentration at a fixed HA concentration. UV–Vis and FTIR characterizations suggested that the reduced HA moieties resulting from sulfide interaction with HA acted as the redox-active moieties responsible for •OH production. Additionally, 3DEEM fluorescence suggested the reaction of sulfide with oxic HA as a partially reversible reduction-oxidation process with production of labile HA fluorophoric intermediates. Our findings implicate that the perturbation of NOM-bearing oxic environments by sulfide, i.e., from the discharge of anoxic groundwater, springs, seafloor black smokers, and hydrothermal vents, is another important source of •OH in natural environments in addition to photo-irradiation.

An indirect electrochemical method for aqueous sulfide determination in freshwaters using a palladium chelate as a selective sensor

Sulfide anion is a highly toxic and corrosive compound and its presence above the threshold concentrations (i.e. μmol L−1) in freshwaters may indicate environmental pollution. Besides, the increase in sulfide concentration results in modifications of the organoleptic proprieties of water and air. Many analytical methodologies have been designed for aqueous sulfide quantification, however, due to the high reactivity and instability of sulfide, the pursue of a simple, sensitive, selective, and portable analytical method is still a current demand. In this study, an indirect electrochemical method for the determination of sulfide based on its interaction with a palladium complex – bis(2-aminobenzoate) palladium(II) – acting as a selective chemosensor is described. The reaction leads to the demasking of the electroactive ligand 2-aminobenzoic acid (i.e. anthranilic acid) and square wave voltammetry is employed to monitor its concentration using a glassy carbon electrode (GCE). Experimental conditions were optimized and the reaction was performed in Britton-Robinson (BR) buffer at pH 5 for 4 min, providing the higher magnitude of the analytical signal. A linear relation (r2 > 0.99) from 3 to 30 μmol L−1 of sulfide was obtained with a limit of detection of 0.10 μmol L−1. Recovery experiments using freshwater samples spiked with sulfide revealed overall satisfactory results for the limit concentration levels permitted by regulatory agencies. Therefore, the proposed methodology shows advantages in terms of portability, selectivity, sensitivity, low-cost, and easiness-to-use enabling monitoring of sulfide in a variety of waters.

Synergistic approach to control reservoir souring in the moderately thermophilic oil fields of western India

Souring, the increase in sulfide concentration in production fluid, exists in the moderately high temperature oil fields of western India located in state of Rajasthan. The source water for oil production is taken from an underground aquifer that has high salinity and sulfate concentration. The reduction of this sulfate to sulfide was initiated above-ground when this source water was mixed with produced water. Current research revealed that high temperature (55 °C) and low salinity are the factors that influence souring in these fields. It was observed that the microbial community of the produced water has a significant proportion of thermophilic SRB and the active sulfate reduction takes place only after produced water was mixed with source water for reinjection. To stop sulfate reduction at these sites, six combinations of biocides and metabolic inhibitors were screened. Out of these combinations, nitrate and benzalkonium chloride (BAC) showed a maximum synergistic inhibitory effect on SRB growth.

H2S removal from sour water in a combination system of trickling biofilter and biofilter

Desulfurization of sour water was investigated in a combination system of trickling biofilter (BTF) and biofilter (BF) filled with ceramic packing materials. A critical elimination capacity (EC) of 251.93 g S m−3 h−1 was obtained for the BTF/BF system during a stepwise increase of sulfide concentration from 10 to 60 g S m−3. This stepwise increment of loading rate also led to critical ECs of 176.21 and 478.88 g S m−3 h−1 for BTF and BF, respectively. A dynamic model describing biological H2S removal from sour water in the BTF/BF was developed and calibrated by a set of experimental data. The model includes the main processes occurring in the BTF/BF such as mass transfer between phases, diffusion and biological reaction inside the biofilm. The model also considers the intermediate (elemental sulfur) production/consumption and sulfate formation through the different oxidation pathways. The model validation was performed under a starvation period and a dynamic H2S loading period. A sensitivity analysis was carried out to evaluate the relative importance of the key parameters on the performance of the BTF/BF system. Sensitivity analysis showed that the BTF performance is more affected by the parameters related to H2S mass transfer.

Synergistic effect between cavitation erosion and corrosion for various copper alloys in sulphide-containing 3.5% NaCl solutions

Cavitation erosion-corrosion (CE-C) behaviour of various copper alloys for ship propellers were investigated in sulphide-containing 3.5% NaCl solutions. Results indicate that the CE-C resistance remarkably decreases with increase in sulphide concentration for cast and friction stir processed nickel-aluminum bronzes. CE increases the current density by approximately two orders of magnitude and causes a positive potential shift when the sulphide concentration exceeds 50 ppm. The synergistic effect between CE and corrosion contributes greatly to CE-C degradation in sulphide solutions. However, the CE-C behaviour is insensitive to sulphide concentration for manganese-aluminum bronze and manganese brass. In all solutions, CE causes a positive potential shift and increases the current density by less than one order of magnitude. Mechanical attack dominates the CE-C damage.

Operando sulfur speciation during sulfur poisoning-regeneration of Ru/SiO2 and Ru/Al2O3 using non-resonant sulfur Kα1,2 emission.

A periodic oxidative regeneration of a sulfur-poisoned methanation catalyst is an alternative to the expensive state-of-the-art process of syngas cleaning using wet scrubbers. Here we have employed operando X-ray emission spectroscopy (XES) to study sulfur speciation on Ru/SiO2 and Ru/Al2O3 during methanation in the presence of H2S and subsequent regeneration in dilute O2 at 360 °C. XES allowed us to obtain semi-quantitative sulfur speciation and to monitor changes in the absolute sulfur concentration. It was established that Al2O3, in contrast to SiO2, forms sulfite/sulfate species by reacting with SO2, which is released from the poisoned Ru surface upon oxidative treatment. The concentration of sulfite/sulfate species is reduced upon switching the feed to H2/CO while no simultaneous increase in sulfide concentration is observed. For both catalysts, the regenerative treatment removes adsorbed sulfur as SO2 only partially, which we propose is the main reason for the incomplete activity recovery of the poisoned catalyst after regeneration.

Accelerating effects of humin on sulfide-mediated azo dye reduction

As an important fraction of humic substances, humin has been found capable of stimulating bioreduction reactions. However, whether humin could promote abiotic reduction and the effects of coexisting soluble humic substance and insoluble mineral remained unsolved. In this study, a humin sample was isolated from a paddy soil. Cyclic voltammetry, electron paramagnetic resonance, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses of the humin indicated the existence of redox-active quinone moieties and other oxygen-containing groups. The humin could be reduced by sulfide and its presence stimulated the abiotic reduction of acid red 27 (AR27) and four other azo dyes by sulfide. In the presence of 100–1000 mg/L intact humin, the sulfide-mediated AR27 reduction efficiency in 7 d was enhanced from 56.3% to 92.5%. The stimulating behavior of intact humin was observed for 100–300 mg/L AR27 and increased with the increase of sulfide concentration (1.2–3.0 mM). Much higher stimulating effects were found with the presence of humin pre-reduced by sulfide. Moreover, for sulfide-mediated AR27 reduction, the coexistence of humin (500 mg/L) and humic acid (10–30 mg/L) or Wyoming sodium-montmorillonite (SWy-2, 1–4 g/L) led to better promotion activities than the presence of single component. And synergistic promotion of sulfide-mediated AR27 reduction was observed with coexisting humin and SWy-2 due to enhanced Fe(II) production. These findings extended our understanding of the influence of humin on reductive transformation of pollutants in the environment.

The response of sulfur dioxygenase to sulfide in the body wall of Urechis unincinctus.

BackgroundIn some sedimentary environments, such as coastal intertidal and subtidal mudflats, sulfide levels can reach millimolar concentrations (2–5 mM) and can be toxic to marine species. Interestingly, some organisms have evolved biochemical strategies to overcome and tolerate high sulfide conditions, such as the echiuran worm, Urechis unicinctus. Mitochondrial sulfide oxidation is important for detoxification, in which sulfur dioxygenase (SDO) plays an indispensable role. Meanwhile, the body wall of the surface of the worm is in direct contact with sulfide. In our study, we chose the body wall to explore the SDO response to sulfide.MethodsTwo sulfide treatment groups (50 µM and 150 µM) and a control group (natural seawater) were used. The worms, U. unicinctus, were collected from the intertidal flat of Yantai, China, and temporarily reared in aerated seawater for three days without feeding. Finally, sixty worms with similar length and mass were evenly assigned to the three groups. The worms were sampled at 0, 6, 24, 48 and 72 h after initiation of sulfide exposure. The body walls were excised, frozen in liquid nitrogen and stored at −80 °C for RNA and protein extraction. Real-time quantitative RT-PCR, enzyme-linked immunosorbent assay and specific activity detection were used to explore the SDO response to sulfide in the body wall.ResultsThe body wall of U. unicinctus consists of a rugal epidermis, connective tissue, outer circular muscle and middle longitudinal muscle. SDO protein is mainly located in the epidermis. When exposed to 50 µM sulfide, SDO mRNA and protein contents almost remained stable, but SDO activity increased significantly after 6 h (P < 0.05). However, in the 150 µM sulfide treatment group, SDO mRNA and protein contents and activity all increased with sulfide exposure time; significant increases all began to occur at 48 h (P < 0.05).DiscussionAll the results indicated that SDO activity can be enhanced by sulfide in two regulation mechanisms: allosteric regulation, for low concentrations, and transcription regulation, which is activated with an increase in sulfide concentration.

Response of gut health and microbiota to sulfide exposure in Pacific white shrimp Litopenaeus vannamei

Sulfide is a natural and widely distributed toxicant. It can be commonly found on the interface between water and sediment in the aquatic environment. The Pacific white shrimp Litopenaeus vannamei starts life in the benthic zone soon after the mysis stage, an early stage of post larvae. Therefore, L. vannamei is inevitably affected by exposure to sulfide released from pond sediment. This study explored the toxicant effect of different concentrations of sulfide on the intestinal health and microbiota of Pacific white shrimp by monitoring the change of expression of inflammatory, immune related cytokines, and the structure of the intestinal microbiota. The gut histology, expressions of inflammatory and immune related cytokines (tumor necrosis factor-alpha, C-type lectin 3, myostatin and heat shock transcription factor 1), and the microbiota were determined in L. vannamei after exposure to 0 (control), 425.5 (1/10 LC 50–96 h), and 851 μg/L (1/5 LC 50–96 h) of sulfide for 21 days. With the increase of sulfide concentration, intestinal injury was aggravated and the inflammatory and immune related cytokines generated a range of reactions. The expression of myostatin (MSTN) was significantly down-regulated by the concentration of sulfide exposure. No difference in the expression of heat shock transcription factor 1 (HSF1) was found between the control and shrimp exposed to 425.5 μg/L, but significantly higher HSF1 expression was found in shrimp exposed to 851 μg/L of sulfide. Significantly higher values of tumor necrosis factor-alpha (TNF-α) and C-type lectin 3 (CTL3) were found in the shrimp exposed to 425.5 μg/L of sulfide compared to the control, but a lower value was found in the shrimp exposed to 851 μg/L (P < 0.05). Sulfide also changed the intestinal microbial communities. The abundance of pathogenic bacteria, such as Cyanobacteria, Vibrio and Photobacterium, increased significantly with exposure to the increasing concentration of sulfide. The abundance of some anti-stress bacteria, such as Chlorobi and Fusobacterium, increased. Nitrospirae which can alleviate nitrite toxicity decreased. Microbacterium, Parachlamydia, and Shewanella were all commonly found and down-regulated in both sulfide groups, which is associated with an adaptation to sulfide stimulation. This study indicates that chronic exposure to sub-lethal levels of sulfide could lead to damage of the gut structure, stimulate the response of the inflammatory and immune systems, and shape the structure of the gut microbiota in L. vannamei.

Effects of Sodium Thiosulfate and Sodium Sulfide on the Corrosion Behavior of Carbon Steel in an MDEA-Based CO2 Capture Process

The corrosion behavior of carbon steel has been tested in the presence of sodium thiosulfate and sodium sulfide in an MDEA-based CO2 capture system using electrochemical methods, weight loss measurements and surface analysis. The results of electrochemical measurements revealed that both thiosulfate and sulfide showed corrosion resistance properties to carbon steel corrosion. The corrosion resistance for the system with thiosulfate increased with concentration, while the system with sulfide yielded better corrosion resistance to carbon steel at lower concentrations as increase in sulfide concentration decreased the corrosion resistance. The corrosion inhibition behaviors for both systems at 0.05 M salt concentrations were confirmed by weight loss measurement, and the solution with sodium sulfide exhibited a better inhibition with time.

Performance and Influencing Factors of Dissimilatory Nitrate Reduction to Ammonium Process by the Strain Desulfovibrio sp. CMX

The process of dissimilatory nitrate reduction to ammonium (DNRA) plays an important role in the presence and conversion of ammonium ions in nature. However, the influencing factors and mechanisms of DNRA process in sulfate-reducing bacteria (SRB) have not yet been identified. The ability, influencing factors and mechanisms of DNRA was investigated in Desulfovibrio sp. CMX isolated previously in our laboratory. The results showed that the production rate of ammonium reached 85.8% and 97.3% respectively with NO3- and NO2- (10 mmol·L-1) as the sole electron donor and nitrogen source. Meanwhile, there was no by-products such as N2 and N2O. Then the effects of different extra nitrogen sources and initial concentrations of sulfate and sulfide on DNRA process were also investigated. As a result, extra nitrogen, yeast extract, could promote DNRA process by improving both growth and metabolism of the strain. In another study, sulfate promoted the nitrate reduction stage while inhibited the nitrite reduction. Overall, the DNRA process by Desulfovibrio sp. CMX was inhibited by sulfate. In addition, both the growth and two stages of the DNRA process were inhibited in the presence of sulfide. Dose effect of sulfide was observed. Inhibition was enhanced with the increase of sulfide concentration. It's noticeable that the inhibition on nitrate reduction was stronger than the inhibition on nitrite reduction with 6 mmol·L-1 of sulfide, leading to the lower reduction rate of nitrate than that of nitrite. In this condition, no accumulation of nitrite was observed in the system.

Influence factors on stress corrosion cracking of P110 tubing steel under CO2 injection well annulus environment

Stress corrosion cracking (SCC) behavior of P110 tubing steel in simulated CO2 injection well annulus environments was investigated through three-point bent tests, potentiodynamic polarization and EIS measurements. The results demonstrate that SCC of P110 tubing steel could occur in acidulous simulated environment, and the sensitivity of SCC increases with the decrease of pH, as well as increase of sulfide concentration and total environmental pressure. Both anodic dissolution and hydrogen embrittlement make contributions to the SCC. Adequate concentration of corrosion inhibitor can inhibit the occurrence of SCC on account of the inhibition of localized anodic dissolution and cathodic hydrogen evolution.

Activity Variation of Phanerochaete chrysosporium under Nanosilver Exposure by Controlling of Different Sulfide Sources.

Due to the particular activation and inhibition behavior of silver nanoparticles (AgNPs) on microbes at various concentrations, it’s crucial to exploit the special concentration effect in environment. Here, we studied the viability variation of Phanerochaete chrysosporium (P. chrysosporium) under exposure to citrate-coated AgNPs (Citrate-AgNPs) in the presence of different sulfide sources (an inorganic sulfide, NaHS and an organic sulfide, thioacetamide (TAA)). The results indicated that both NaHS and TAA can promote activation of P. chrysosporium by Citrate-AgNPs at a higher concentration, which was initial at toxic level. Treatment with various concentrations of Citrate-AgNPs (0–9 mg/L) demonstrated a maximum activation concentration (MAC) at 3 mg/L. With the increase in sulfide concentration, MAC transferred to higher concentration significantly, indicating the obvious “toxicity to activation” transformation at a higher concentration. Ag+ testing exhibited that variations in sulfide-induced Ag+ concentration (3−7 μg/L Ag+) accounted for the “toxicity to activation” transformation. In addition, the similar results were observed on antibacterial application using Escherichia coli as the model species. Based on the research results, the application of this transformation in improving antibacterial activity was proposed. Therefore, the antibacterial activity of AgNPs can be controlled, even at concentration, via adjusting for the sulfide concentration.

Response of Removal Rates to Various Organic Carbon and Ammonium Loads in Laboratory‐Scale Constructed Wetlands Treating Artificial Wastewater

High levels (92 and 91%) of organic carbon were successfully removed from artificial wastewater by a laboratory-scale constructed wetland under inflow loads of 670 mg/m2 x d (100 mg/d) and 1600 mg/m2d (240 mg/d), respectively. Acidification to pH 3.0 was observed at the low organic carbon load, which further inhibited the denitrification process. An increase in carbon load, however, was associated with a significant elevation of pH to 6.0. In general, sulfate and nitrate reduction were relatively high, with mean levels of 87 and 90%, respectively. However, inhibition of nitrification was initiated with an increase in carbon loads. This effect was probably a result of competition for oxygen by heterotrophic bacteria and an inhibitory effect of sulfide (S2) toxicity (concentration approximately 3 mg/L). In addition, numbers of healthy stalks of Juncus effusus (common rush) decreased from 14 000 to 10 000/m2 with an increase of sulfide concentration, indicating the negative effect of sulfide toxicity on the wetland plants.

Fluorescence properties of nanosized sulfides

The absorption spectra of nanosized sulfides and selenides (ZnS, CdS, CuS, Cu2S, AgS, In2S3, SnS, PbS, Sb2S3, FeS, CoS, NiS, CdSe, and Ag2Se) showed one absorption band with a maximum at wave-lengths shorter than 300 nm. The UV fluorescence spectra of all of these nanosized sulfides in a polyvinyl alcohol film contained maxima at 380–440 nm. Nanosized sulfides are thus characterized by a very large (up to 15000 cm−1) Stokes shift of fluorescence. In a polyvinyl alcohol film, a decrease in the concentration of cadmium sulfide from 0.05 to 0.002 M led to a threefold increase in the fluorescence intensity. The dependence of the degree of fluorescence buildup on the sulfide concentration is nearly linear. An increase in sulfide concentration to more than 5 × 10−3 M in solution led to a complete coagulation of particles.

Competitive, Microbially-Mediated Reduction of Nitrate with Sulfide and Aromatic Oil Components in a Low-Temperature, Western Canadian Oil Reservoir

Fields from which oil is produced by injection of sulfate-bearing water often exhibit an increase in sulfide concentration with time (souring). Nitrate added to the injection water lowers the sulfide concentration by the action of sulfide-oxidizing, nitrate-reducing bacteria (SO-NRB). However, the injected nitrate can also be reduced with oil organics by heterotrophic NRB (hNRB). Aqueous volatile fatty acids (VFAs; a mixture of acetate, propionate, and butyrate) are considered important electron donors in this regard. Injection and produced waters from a western Canadian oil field with a low in situ reservoir temperature (30 degrees C) had only 0.1-0.2 mM VFAs. Amendment of these waters with nitrate gave therefore only partial reduction. More nitrate was reduced when 2% (v/v) oil was added, with light oil giving more reduction than heavy oil. GC-MS analysis of in vitro degraded oils and electron balance considerations indicated that toluene served as the primary electron donor for nitrate reduction. The differences in the extent of nitrate reduction were thus related to the toluene content of the light and heavy oil (30 and 5 mM, respectively). Reduction of nitrate with sulfide by SO-NRB always preceded that with oil organics by hNRB, even though microbially catalyzed kinetics with either electron donor were similar. Inhibition of hNRB by sulfide is responsible for this phenomenon. Injected nitrate will thus initially be reduced with sulfide through the action of SO-NRB. However, once sulfide has been eliminated from the near-injection wellbore region, oil organics will be targeted by the action of hNRB. Hence, despite the kinetic advantage of SO-NRB, the nitrate dose required to eliminate sulfide from a reservoir depends on the concentration of hNRB-degradable oil organics, with toluene being the most important in the field under study. Because the toluene concentration is lower in heavy oilthan in light oil, nitrate injection into a heavy-oil-producing field of low temperature is more likely to succeed in containing souring.

Effect of sulfur-containing compounds onBacilluscellulosome-associated ‘CMCase’ and ‘Avicelase’ activities

The isolation of cellulosomes from clostridial sources has been extensively studied; however, the isolation of cellulosomes from facultative soil anaerobes of the family Bacillaceae is not as well characterized. The Bacillus cellulosome (celluloxylanosome) essentially consists of two complex components: C-I and C-II. This multi-component complex enables Bacillus to degrade a variety of carbonaceous compounds as it is composed of several enzymes, such as cellulases, xylanases and other degradative enzymes. The cellulosomal cellulases from Bacillus megaterium were purified using cellulose affinity chromatography, followed by Sepharose 4B gel filtration chromatography. The objective of this investigation was to establish the effect of sulfate and sulfide on cellulosomal 'cellulase' activity. An increase in sulfide concentration led to a general enhancement of cellulosomal-associated cellulolytic activity, whereas an increase in sulfate concentration resulted in an inhibition of the cellulosome-associated cellulolytic activity.

ATP-sulphurylase: An enzymatic marker for biological sulphate reduction?

Adenosine triphosphate-sulphurylase (ATPS) plays a major role in dissimilatory sulphate reduction. In this study, the level of ATPS activity was monitored in a time course study using a biosulphidogenic batch bioreactor system. A coincident decrease in ATPS activity with a decline in sulphate concentration and an increase in sulphide concentration as biosulphidogenesis proceeded was observed. Flask studies further showed sulphate to be stimulatory to ATPS, while sulphide proved to be inhibitory. The effect of ions (Ca 2+, Cl −, Fe 2+ and Zn 2+) on the ATPS activity was also investigated. Most of the ions studied (Ca 2+, Cl − and Fe 2+) were stimulatory at lower concentrations (40–120 mg/l) but proved toxic at higher concentrations (>120 mg/l). In contrast, Zn 2+ was inhibitory even at low concentrations (⩾40 mg/l). ATPS may potentially be used as an enzymatic marker for biological sulphate reduction in sulphate-rich wastewaters and natural environments (anaerobic systems such as soils and sediments found in freshwater and marine systems), providing all residual sulphide and interfering ions are removed using a simple preparative step.

Climatic and Anthropogenic Variations in the Sulfide Distribution in the Black Sea

Information on the depth of the sulfide onset in the Black Sea has been analyzed for the period 1910–1995. Correlation between the depth of the sulfide onset and the density structure of the layer of the main pycnocline is significant for the entire period covered. Correlation coefficients (R) between the depth of the sulfide onset and the position of isopycnal surfaces in the layer of the main pycnocline vary, on average, 0.71–0.88. The average value of density (σt) at the depth of sulfide onset, defined as a sulfide concentration equal to 3 μM, is close to 16.17. Oscillations in the average depth of the sulfide onset range over 24 m and indicate that a steady-state trend does not occur. The period of these oscillations may occur over a century timescale. The dataset for the period 1960–1995 has been used to analyze temporal variations in concentrations of sulfide inside the anoxic zone of the Black Sea. The results of isopycnal analysis demonstrate that possible temporal variations in the average position of sulfide onset versus density (σt) scale do not exceed 0.15, which is close to the limit of uncertainties for data obtained before 1988. In contrast, a prominent increase in sulfide concentration, as well as nutrient levels, within the anoxic zone is shown and is related to anthropogenic impact.

Effects of anoxic and sulfidic conditions on cyanobacteria and macrozoobenthos in shallow coastal sediments of the Southern Baltic Sea

In the eulittoral zone of Hiddensee Island (southern coast of the Baltic Sea) abiotic parameters, especially oxygen and sulfide concentrations in the sediment, and the structure and distribution of the macrozoobenthic community were investigated during four sampling periods in 1992. In the following year, anoxia and high sulfidic conditions were generated experimentally by covering the sediment surface with dark PVC-foils. Changes of oxygen, sulfide concentrations and microprofiles, as well as the response of the cyanobacterial and macrozoobenthic communities were studied continuously over two weeks. One final sampling was conducted after 138 days of cover. The macrozoobenthic community of the study area was characterized by low diversity and high species abundance. It was dominated by species with high resistance to anoxia and sulfide (e.g. the ostracod Cyprideis torosa), with high mobility (e.g. the amphipod Corophium volutator) and opportunistic features (e.g. the oligochaete Paranais litoralis). The experimental cover caused anoxic conditions after one day and a general increase in sulfide concentrations in the sediment for the whole experiment. The cyanobacterial coenosis, mainly composed of highly tolerant organisms, well adapted to high sulfide concentrations (e.g. Lyngbya aestuarii, Oscillatoria spec.) showed first responses after 12 days of anoxia. Less tolerant species without adaptation mechanisms against sulfide (e.g. Calothrix spec.) disappeared first. After long-term anoxia (138 days) 50% of the species were still present. The same pattern could be shown for macrobenthos, though the community was affected much earlier. After a successive dropout of more sensitive macrobenthic species (e.g. Corophium volutator), the macrozoobenthic association became monospecific after 12 days with only Cyprideis torosa surviving the anoxic and sulfidic conditions. However, both communities seem well adapted to temporal small-scale anoxia and high sulfide concentrations frequently occurring in these shallow coastal habitats of the Southern Baltic Sea.