Station S1 Research Articles

Depth-dependent and seasonal variability in archaeal community structure in the subarctic and subtropical western North Pacific

Archaea represent an important component of marine picoplankton. Marine archaeal communities are generally dominated by Marine Group I (MGI) and Marine Group II (MGII), which are affiliated to the phyla Thaumarchaeota and Euryarchaeota. We used pyrosequencing-based analysis of archaeal 16S rRNA genes to investigate archaeal community composition throughout the water column (0–5000 m) at the subarctic (station K2) and subtropical (station S1) stations in western North Pacific. Sampling was conducted on four occasions between 2010 and 2011 to examine seasonal variability in community composition. Four phylogenetic groups (MGI-α, MGI-γ, MGII-α, and MGII-β) belonging to Thaumarchaeota and Euryarchaeota were found throughout the water column, but the relative abundance of each group varied depending on depth. In the surface water, archaeal communities displayed marked seasonal variability at both stations, whereas in deeper waters (300–5000 m), temporal variability in community composition was less evident. Sequences similar to those of the uncultured Marine Benthic Group A, to date found only in marine sediments, were detected throughout the water column at station S1.

Structure and dynamics of the planktonic diatom community in the Iguassu River, Paraná State, Brazil.

The evaluation of abiotic and biotic variables can provide information for understanding the structure and function of lotic systems. To obtain this information, measurements of 15 chemical and physical variables and of phytoplankton were conducted at two sampling stations. The present study aims to evaluate the temporal and spatial variation of planktonic diatoms in terms of abiotic variables and the trophic level of the river water and to select diatom species as descriptors of the physical and chemical conditions of the water upstream (S1) and downstream (S2) of the Iguassu River over an annual cycle. Sampling station S1 was classified as oligotrophic to mesotrophic, and S2 was classified as ultra-oligotrophic to oligotrophic. A total of 98 diatom species distributed among 39 genera was recorded, showing no dominant species but 36 abundant species. Although the differences of chemical and physical variables between S1 and S2 were limited to greater turbulence and turbidity, processes triggered by heavy rainfall exerted a significant influence on community structure, and a temporal change in composition was observed. At the end of the dry period, due to the recovery of nutrients and high transparency, there was an abundance of Cocconeis placentula var. lineata. In the rainy period, with increased turbulence and turbidity processes resulting from higher rainfall, there was an abundance of Aulacoseira granulata var. granulata.

Primary productivity at the time-series stations in the northwestern Pacific Ocean: is the subtropical station unproductive?

A comparative study of primary productivity in the northwestern Pacific Ocean was conducted at time-series stations K2 and S1 in the nutrient-rich subarctic gyre and oligotrophic subtropical gyre, respectively. The estimated annual means of net primary production (NPP) at the two stations were virtually identical: 292 mg C m−2 day−1 at K2 and 303 mg C m−2 day−1 at S1, whereas the annual mean of gross primary production (GPP) at S1 was 1.5 times that at K2. NPP was very much limited by the supply of nutrients, typified by nitrate at S1, although it was enhanced during winter due to mitigation of nutrient limitation. The NPP/GPP ratios were remarkably lower at S1 during the spring-to-autumn time interval than in winter. The reduced NPP/GPP ratio means that photosynthetically assimilated carbon was lost at a higher rate via respiration and extracellular release of dissolved organic carbon (DOC). The carbon loss (difference between GPP and NPP) was higher at S1 than at K2, probably because of the enhanced respiration due to the relatively high temperature throughout the year, as well as the enhanced DOC release by nutrient limitation. The released DOC should be accounted for as primary production, because it contributes to oceanic biogeochemistry in a manner similar to the photosynthesized compounds. Consequently, total primary production, the sum of NPP and DOC release, was higher at S1 than at K2.

Composition and distribution of planktonic ciliates in the southern South China Sea during late summer: Comparison between surface and 75 m deep layer

Ciliates are very important components in most marine ecosystem. They are trophic link between the microbial food web and grazing food chain. In this study, ciliates were collected from 11 sites in the southern South China Sea (SCS) during August 25 to September 28, 2011. Their composition and distribution at the surface and 75 m deep depth of the ocean were studied. A total of 30 species belonging to 22 genera were identified, and 22 species of 15 genera were Tintinnids. Eutintinnus fraknoii and E. stramentus were the most common species. The other dominants were strombidiids ciliates including Strombidium conicum and S. globosaneum, which were followed by the tide form, Mesodinium pulex. Ciliates abundance ranged from 46 ind L-1 to 368 ind L-1 in the open sites, 46–368 ind L-1 at surface and 73–198 ind L-1 at 75 m deep layer. In the Yongshu reef, ciliates abundance ranged from 167 ind L-1 to 365 ind L-1 in the water column, similar to that in Sanya coral reef waters. Ciliates composition showed obvious difference between surface and 75 m deep layer at station S2 (P < 0.05), while no similar result was observed at other sites. At 75 m deep layer, salinity was negatively related to mixed layer depth (P < 0.05), but positively to chlorophyll a concentration (P < 0.05), indicating that the change of vertical mixing in water column influenced vertical distribution of ciliates in the southern SCS.

Seasonal changes in the mesozooplankton biomass and community structure in subarctic and subtropical time-series stations in the western North Pacific

Seasonal changes in mesozooplankton biomass and their community structures were observed at time-series stations K2 (subarctic) and S1 (subtropical) in the western North Pacific Ocean. At K2, the maximum biomass was observed during the spring when primary productivity was still low. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 1.39 (day) and 2.49 (night) g C m−2 and 4.00 (day) and 3.63 (night) g C m−2, respectively. Mesozooplankton vertical distribution was bimodal and mesopelagic peak was observed in a 200- to 300-m layer; it mainly comprised dormant copepods. Copepods predominated in most sampling layers, but euphausiids were dominant at the surface during the night. At S1, the maximum biomass was observed during the spring and the peak timing of biomass followed those of chlorophyll a and primary productivity. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 0.10 (day) and 0.21 (night) g C m−2 and 0.47 (day) and 0.26 (night) g C m−2, respectively. Copepods were dominant in most sampling layers, but their mean proportion was lower than that in K2. Mesozooplankton community characteristics at both sites were compared with those at other time-series stations in the North Pacific and with each other. The annual mean primary productivities and sinking POC fluxes were equivalent at both sites; however, mesozooplankton biomasses were higher at K2 than at S1. The difference of biomasses was probably caused by differences of individual carbon losses, population turnover rates, and trophic structures of communities between the two sites.

Coupled 1-D physical–biological model study of phytoplankton production at two contrasting time-series stations in the western North Pacific

A vertical one-dimensional physical–biological model is applied to clarify the mechanisms controlling the seasonality and interannual variability of primary production in the surface layer at two contrasting time-series stations, K2 (in the subarctic gyre) and S1 (in the subtropical gyre), in the western North Pacific. Using forcing based on realistic atmospheric and oceanic data, the model reproduces seasonal differences in the degree to which different controlling factors affect primary production between these two stations, primarily as a result of differences in the physical environment. At station K2, light intensity is an important factor controlling primary production in summer. After April, the mixed layer depth (MLD) becomes shallow, resulting in higher average light intensity, and the water column remains stratified until September; these sustain high primary production during this period. In contrast, at station S1, the supply of nutrients via entrainment is vital to sustaining production, because light intensity remains sufficient throughout the year. In summer, the relationship between nutricline depth and euphotic layer is a controlling factor. The simulations forced by the different atmospheric conditions for each year, respectively, show different MLD. In the 2012 simulation, the deep winter MLD (200 m) enhances primary production in the surface layer as compared to the other two years (2010 and 2011) simulations.

Macrobenthic Community Structure as A Bio-Indicator for the Assessment of Coastal Water Pollution In Greater Noakhali-Bangladesh

Present study was aimed for the partial judgement of coastal water pollution and accordingly the abundance, diversity as well as the species composition of macrobenthic communities on the sediment of 3 selected stations were carried out following standard methods during January to March, 2015 in Noakhali, Bangladesh. 14 families under 4 major groups yielded a total of 5481 ind./m2 with a mean density of 609 ± 445 ind./m2 during the study. The highest and the lowest number of taxa were identified in January (10) and February (6) respectively during the study period. On the other hand, monthly diversity profile of microbenthic communities showed clear difference in the diversity of all stations which is compatible to the other published results of macrobenthic animal as well. Based on the calculated results from Shannon-Wiener index of microbenthic species diversity (H′), the present study might be considered as heavily polluted in February (H′ = 0.9202) and moderately polluted in January (H′ = 1.514) and in March (H′ = 1.571). On the other hand, The Margalef’s index of benthic macro-invertebrates at station S1 (0.4501) was lowest in February and at station S1 (1.096) was highest. Therefore, the research output revealed that the abundance and diversity of macrobenthic animal community might be good indicators to assess the aquatic environmental pollution as the selected study area fall under the category of more or less polluted.

Effect of Flower Farm Effluents on Diversity and Composition of Macro Invertebrates in Marura Wetland

Wetlands are important sites for biological conservation due to their rich biodiversity which possess high productivity. They also offer shelter to many organisms and offers services such as water purification and flood control. However, biodiversity in wetlands has been reduced due to human activities that cause pollution like, flower farm effluents which are discharged directly to wetlands or river systems. Four water quality parameters; DO, BOD, pH, TDS, TSS and macro-invertebrates composition were investigated at four different stations (S1, S2, S3, S4) adjacent to Equator Flower Farm along the Marura wetland. PAST program was used to calculate diversity indices and richness in the macroinvertebrates communities. Station S2 had the highest temperature (22.6°C), whereas S4 had the lowest temperature (19.6°C). The pH value did not vary along the stations (8.3-6.3). The DO level fluctuated along the river, station S1 had highest level of 3.6 m/l and lowest station S3 had 0.8mg/l. TSS and TDS did not show significant variations, while BOD levels varied with different stations. The highest value of TN was recorded at Station 3 (0.33±0.045mgl-1). There was no significant difference (p=0.055) in three stations (S1, S2, S4) except S3. In total 10 orders, 30 genera and 30 families of macroinvertebrates were identified. The orders; Odonata, Coleoptera, Hemiptera and Diptera were the main macroinvertebrates found in all station, while the members of orders; Ephemeroptera, Trichoptera, Oligochaeta Mollusca, Gnathobellidae and Isopoda were few in all sampling stations. Station S2 and S4 had the highest species diversity compared to station S1 and S3 which had the lowest diversity. DO, BOD and temperature were found to have a significant effect on abundance and composition of benthic organisms with S3 having less abundance due to its proximity to the flower farm.

Substratum as Determining Factor for the Distribution of Benthic Macroinvertebrate Fauna in a River Ecosystem

Present study was focused on the Ken river for determination of the distribution of benthic macroinvertebrate fauna with respect to substrate variation. The invertebrate samples were collected during December 2003 to March 2004 at four different stations by lifting of stones and sieving of clay–silt substratum from 0.09 m2 area. The collected samples were preserved in 5 % formalin and identified at family level. The count data was used to determine the density and composition of benthic macroinvertebrate fauna. Total mean density decreased from station S1 to S3 but increased at S4 and differed significantly among the stations. The maximum density was found in the stony substratum (boulder and cobble) as compared to small particle size (pebble, gravel and sand). The fauna was predominated by insects at stations S1 (84 %), S2 (90 %) and S3 (93 %), while reduced at S4 (48 %). Neoephemeridae and Caenidae were abundant taxa in boulder–cobble and cobble–pebble substrate, respectively. Leptophlebiidae, Baetidae and Hydropsychidae were abundant at pebble–gravel substrate and Thiaridae–Chironomidae–Nephthydae were abundant in silt–clay substrate. Principal component analysis also indicated the above observation. Canonical correspondence analysis at each station indicated that substratum (abiotic and biotic) was responsible for the distribution of benthic macroinvertebrate fauna in the Ken. Functionally, the collector insects dominate the fauna, at all the four stations because of substratum as well as the continuous source of particulate organic matter in the river.

A Multidisciplinary Assessment of River Surface Water Quality in Areas Heavily Influenced by Human Activities.

The present study could serve as a multidisciplinary approach for the assessment of river surface water quality with the use of chemical and biological methods. Specifically, physicochemical parameters, heavy metals, and pesticides were measured in water samples from three different stations (sampling station S1, S2, and S3) along Asopos River (Greece). In parallel, algal species (primary producers)-such as Scenedesmus rubescens and Chlorococcum sp.; consumer invertebrate species, such as the fairy shrimp Thamnocephalus platyurus and the rotifer Brachionus calyciflorus; as well as human lymphocytes-were exposed to those samples for assessing their toxic and genotoxic/mutagenic effects. According to the results, although the values of almost all of the physicochemical parameters tested, heavy metals (zinc, cadmium, lead, and mercury) and pesticides were lower than or within the respective environmental quality standards, thus offering no clear evidence for their natural or anthropogenic origin. Values recorded for nickel, chromium, hexavalent chromium, and malathion represent a typical case of mixed influence from natural and anthropogenic enrichments. In contrast, the algal growth arrest, the acute toxic effects on the freshwater invertebrates, and the increased micronuclei frequencies observed in human lymphocytes showed the presence of human-derived hazardous substances, which were hardly determinable with the use of conventional chemical methods. Given that the presence of priority pollutants in river surface waters, heavily burdened by anthropogenic activities, could give no clear evidence for their biological risk, the results of the present study showed that chemical and biological assays should be applied in parallel, thus serving as a reliable tool for the assessment of river water quality.

Comparison of sinking particles in the upper 200 m between subarctic station K2 and subtropical station S1 based on drifting sediment trap experiments

Drifting sediment trap experiments were conducted during various seasons to elucidate the characteristics of particles sinking through the upper 200 m of the water column in the western Pacific at subarctic station K2 and subtropical station S1. The sinking particle flux increased when primary productivity was high at each station, during June–July at K2 and during February at S1. Biogenic opal (Opal) and CaCO3 were the major components of the fluxes at K2 and S1, respectively. Contrary to the expectation of a high flux at the eutrophic station K2 and low flux at the oligotrophic station S1, the annual average organic carbon fluxes at 100 m were comparable at both stations: 62.7 mg C m−2 day−1 at K2 and 56.1 mg C m−2 day−1 at S1. The similarity of the fluxes was perhaps a reflection of the unexpectedly high primary production at S1. At K2, the organic carbon export ratio (organic carbon flux/primary productivity) was significantly and negatively correlated with primary production and tended to decrease with depth. The magnitude of the rate of attenuation of the organic carbon flux with depth was larger at S1 than at K2. This rate of attenuation tended to decrease and increase with primary production at K2 and S1, respectively. The explanation for these patterns may be that the flux of labile organic carbon at relatively shallow depths decreased with increasing primary production at K2, and zooplankton grazing pressure increased with increasing primary productivity at S1.

Pollution biomonitoring in the Bizerte lagoon (Tunisia), using combined chemical and biomarker analyses in grass goby, Zosterisessor ophiocephalus (Teleostei, Gobiidae)

In this study, biological responses and contaminant levels in biological tissues were investigated in grass goby fish specimens (Zosterisessor ophiocephalus) collected from five stations in a moderately polluted ecosystem, namely the Bizerte lagoon on the north coast of Tunisia. The following biomarkers were measured: muscular acetylcholinesterase (AChE), hepatic ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), catalase (CAT), lipoperoxidation (TBARS), condition factor (CF), and hepatosomatic index (HSI). These measurements were taken in parallel with the content of Organochlorine pesticides (OCPs), Polychlorinated biphenyls (PCBs), Polycyclic aromatic hydrocarbons (PAHs) and trace metals (As, Cr, Cu, Mn, Pb, V, Zn, Ag, Cd, Co and Ni) in muscle tissue. Total PAH concentrations ranged from 20.09 ± 0.68 to 105.77 ± 42.58 ng g−1 dw, PCB from 33.19 ± 6.25 to 126.28 ± 7.37 ng g−1 dw, OCP from 11.26 ± 1.62 to 19.17 ± 2.06 ng g−1 dw, and metals from 107.83 ± 1.83 to 187.21 ± 2.00 mg/kg dw. The highest levels of pollutants and biomarkers were observed at station S1, located in the Bizerte channel. Elevated EROD, GST and CAT activities, as well as TBARS levels in liver were positively correlated with tissue contaminant levels at station S1. Significant negative correlations were also found between hexachlorobenzene (HCB) and dichlorodiphenyltrichloroethane (DDTs) body burden with AChE activity in muscle at station S2. The integration of biological responses and contaminant tissue content indicated that certain areas of the Bizerte lagoon, notably station S1, are significantly impacted by various human activities, which likely represent a threat for aquatic wildlife. On the basis of these results, and due to its ecological characteristics, the grass goby appears a suitable indicator species for pollution biomonitoring in coastal marine areas along the Mediterranean Sea.

Spatial and seasonal variation of potential toxic elements in Adocia pigmentifera, seawater and sediment from Rameswaram, southeast coast of India

The concentrations of potential toxic elements (PTEs) such as cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) were measured in five different stations of Rameswaram (RM) coast, Gulf of Mannar (GoM), India, in coastal waters in sediments and tissues of Adocia pigmentifera. Concentration of PTEs (Cd, Cu, Pb and Zn) was found to be highest in sediments followed by A. pigmentifera and seawater samples collected from the different stations of RM coast. The pattern of accumulation of PTEs in the three sample types is of the following order Zn < Pb < Cu < Cd. The seasonal variation of these PTEs also followed the same pattern. One-way analysis of variance (ANOVA) with Tukey’s HSD post hoc test has revealed significant differences among stations S1–S4 when compared with the station S5 which is considered as the reference site. Correlation coefficient study showed no significant correlation in the concentration of PTEs in A. pigmentifera, seawater and sediment samples. The concentration of all the PTEs in different sample types has exceeded the FAO/WHO/sediment background values, except for the concentration of Zn in A. pigmentifera and sediment sample, which did not exceed the limits. The contamination factor (CF) and geoaccumulation index (I geo) values indicated significant contamination of PTEs in the sediments from different stations of RM coast, India. Variations found between the sample types during the studies could be due to changes in levels of pollution discharge over time, availability of PTEs for adsorption as well as variations in the sampling season. Increasing urban sprawl and release of effluents both from domestic and industrial sources are the main sources of pollution at RM coast and are the prime reasons for the loss of existing diverse ecosystem.

A multibiomarker approach to the assessment of pollution impacts in two Baltic Sea coastal areas in Sweden using caged mussels (Mytilus trossulus)

Blue mussels (Mytilus trossulus) were transplanted in cages for three months in two Swedish coastal areas in the Bothnian Sea (northern Baltic Sea) to investigate the interactions between analysed environmental chemicals and biological responses. A wide array of biological parameters (biomarkers) including antioxidant and biotransformation activity, geno-, cyto- and neurotoxic effects, phagocytosis, bioenergetic status and heart rate were measured to detect the possible effects of contaminants. Integrated Biomarker Response index and Principal Component Analysis performed on the individual biological response data were able to discriminate between the two study areas as well as the contaminated sites from their respective local reference sites. The two contaminated sites outside the cities of Sundsvall (station S1) and Gävle (station G1) were characterised by different biomarker response patterns. Mussels at station S1 showed a low condition index, increased heart rate recovery time and phagocytosis activity coinciding with the highest tissue concentrations of some trace metals, polycyclic aromatic hydrocarbons and organotins. At station G1 the highest organochlorine pesticide concentration was recorded as well as elevations in glutathione S-transferase activity, thiamine content and low lysosomal membrane stability. Significant variability in the geno- and cytotoxic responses and bioenergetic status was also observed at the different caging stations. The results obtained suggest that different chemical mixtures present in the study areas cause variable biological response patterns in organisms.

In vitro and in vivo toxicities of sediment and surface water in an area near a major steel industry of Korea: Endocrine disruption, reproduction, or survival effects combined with instrumental analysis

The influence of industrial and/or municipal contaminant inputs on the aquatic environment of Pohang, Korea was investigated, with a focus on bioassay combined with instrumental analysis. Pohang is the most heavily populated city in Gyeongsangbuk-do province of Korea, with more than half a million residents, and also hosts the nation's biggest steel manufacturer and related industries. Sediment (n=15) and surface water samples (n=17) were collected from Hyeongsan River which runs across the Pohang city, in two separate events, i.e., June 2010 and February 2011. Sediment samples were first Soxhlet-extracted (raw extract) and were measured for estrogenicity using H295R cell line, and also analyzed for alkylphenols (APs), bisphenol A (BPA), PAHs, and PCBs. For sediment samples which exhibited greatest effects in the cell line, further fractionation was performed into non-polar, mid-polar, and polar portions. In surface water samples, heavy metals were also analyzed. Among 15 sediment samples, station S2 near the steel industry complex and station M3 near the municipal area showed the greatest sex hormone changes, and these changes were generally explained by the fractions which contained APs and BPA. Principal component analysis (PCA) however suggests that chemicals that were not analyzed in the present study would better explain endocrine disruption capacity of sediments. In water samples, adverse effects on hatchability and growth of Japanese medaka fish, and on Daphnia reproduction were noted following exposure to six water samples collected from stations near industrial and municipal areas. Several heavy metals and nonylphenol (NP) concentrations exceeded surface water quality guidelines, suggesting adverse effects of contamination inputs from both industrial and municipal activities. Observed estrogenicities in stations such as S2 and M3 warrant further investigations on longer term ecosystem impacts near industrial and municipal areas. The levels of major organic chemicals in sediments are quite comparable to those reported in ~10years ago, emphasizing a need for source control.

English

&nbsp; There has been a serious concern about declining water quality in the rivers and streams since 1960. Wide varities of pollutants have been reported to cause deterioration of water quality in rivers. Tungabhadra River in Karnataka is an important tributary of Krishna. It has a drainage area of 71,417&nbsp;sq. km out of which 57,671 sq. km area lies in the state of Karnataka. The river covers the distance of 293 km in the state. This river is considered as life line of this area, which fulfills the needs of hundreds of villages, situated at both sides of the river. The study was conducted to measure its various physico-chemical and bacteriological parameters including levels of algal community. Pollution in water bodies may indicate the environment of algal nutrients in water. They may also function as indicators of pollution. Hence, the present investigation is an attempt to know the pollution load through algal indicators in Tungabhadra river of Karnataka near Harihar town. The study has been conducted from May 2004 to April 2005. The water and algal samples were collected at regular intervals of 15 days at four stations for one year. The most tolerant genera and species of four groups of algae namely, Chlorophyceae, Bacilariophyceae, Cyanophyceae and Euglenophyceae indicate that total algal population is 17,7159 o/L in station S3; which has the influence of industrial pollution from Harihar Polyfibre and Grasim industry situated on the bank of the river; which are discharging its treated effluent to this river. The population of algal species is 75,849 o/L at station S1, 68,056 o/L station S2&nbsp;and 38,915 o/L station S4. The correlation and inter correlation among the physico-chemical parameters along with phytoplankton groups have been made. The results obtained are tabulated and discussed. &nbsp; Key words:&nbsp;Tungabhadra River, dynamics, phytoplankton, succession

Distribution and ecological risk of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in surface sediments from the Bizerte lagoon, Tunisia

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in 18 surface sediment samples collected from Bizerte lagoon, Tunisia. The total concentrations of ten PCBs (∑PCBs) and of four OCPs (∑OCPs) in the sediments from this area ranged from 0.8 to 14.6 ng g(-1) dw (average value, 3.9 ng g(-1) dw) and from 1.1 to 14.0 ng g(-1) dw (average value, 3.3 ng g(-1) dw), respectively. Among the OCPs, the range of concentrations of dichlorodiphenyltrichloroethane and its metabolites (DDTs) and hexachlorobenzene (HCB) were 0.3-11.5 ng g(-1) dw (1.9 ng g(-1) dw) and 0.6-2.5 ng g(-1) dw (1.4 ng g(-1) dw), respectively. Compositional analyses of the POPs indicated that PCB 153, 138 and 180 were the predominant congeners accounting for 60 % of the total PCBs. In addition, p,p'-DDT was found to be the dominant DDTs, demonstrating recent inputs in the environment. Compared with some other regions of the world, the Bizerte lagoon exhibited low levels of PCBs and moderate levels of HCB and DDTs. The high ratios ΣPCBs/ΣDDTs indicated predominant industrial versus agricultural activities in this area. According to the established guidelines for sediment quality, the risk of adverse biological effects from such levels of OCPs and PCBs, as recorded at most of the study sites, was insignificant. However, the higher concentrations in stations S1 and S3 could cause biological damage.

Response of Epilithic Diatom Communities to Downstream Nutrient Increases in Castelhano Stream, Ven&amp;#226;ncio Aires City, RS, Brazil

The Castelhano Stream Hydrographic Basin, located in the city of Venancio Aires, RS, Brazil, shows an area of 675.3 km2, highlighting the Castelhano Stream as their main water course. The stream is the main responsiblity for the local water supply; however, there are no published studies in the literature regarding their water quality. In this context, the present research aimed to assess the water quality of Castelhano Stream in terms of organic pollution and eutrophication, applying the Biological Water Quality Index (BWQI), which uses epilithic diatoms communities as bioindicators. Biological samples were collected at three sampling stations along the stream in the months of September, November and December 2012. The results showed 81 identified species, distributed in 30 genera. The water pollution levels detected ranged from “strong” (66.7%) and “very strong” (33.3%), with differences in species composition between sampling stations. The sampling station S1 in the upper reaches was characterized by the presence of indicative species of acidophilus and lentic environments with large amounts of organic matter. The sampling stations S2 and S3, in the intermediate and lower reaches, respectively, showed a substitution of species in the community, with the presence of highly tolerant taxa to organic pollution and eutrophication. The high pollution levels detected along the basin are related to the nutrients and high organic load originating from livestock, domestic and industrial waste, as well as excess fertilizers and agricultural inputs used in farming. The results demonstrate the necessity to implement mitigation measures to contain the processes of organic pollution and eutrophication detected due to the dangers offered to public health and the environment.

Three-year survey of sulfate-reducing bacteria community structure in Carnoulès acid mine drainage (France), highly contaminated by arsenic

A 3-year survey on sulfate-reducing bacteria (SRB) was conducted in the waters of the arsenic-rich acid mine drainage (AMD) located at Carnoulès (France) to determine the influence of environmental parameters on their community structure. The source (S5 station) exhibited most extreme conditions with pH lowering to ~1.2; iron, sulfate, and arsenic concentrations reaching 6843, 29 593, and 638 mg L(-1), respectively. The conditions were less extreme at the downstream stations S1 (pH ~3.7; iron, sulfate, and arsenic concentrations of 1114, 4207, and 167 mg L(-1), respectively) and COWG (pH ~3.4; iron, sulfate, and arsenic concentrations of 854, 3134, and 110 mg L(-1), respectively). SRB community structures were characterized by terminal restriction fragment length polymorphism and library analyses based on dsrAB genes. The predominant dsrAB sequences detected were most similar to the family Desulfobulbaceae. Additionally, certain phylotypes could be related to spatio-temporal fluctuations of pH, iron, and arsenic species. For example, Desulfohalobiaceae-related sequences were detected at the most acidic sample (pH 1.4) with high iron and arsenic concentrations (6379 and 524 mg L(-1), respectively). New dsrAB sequences, with no isolated representatives, were found exclusively in COWG. This study gives new insights on SRB community dynamics in AMD systems.

Effects of simulated natural and massive resuspension on benthic oxygen, nutrient and dissolved inorganic carbon fluxes in Loch Creran, Scotland

The effect of repeated natural resuspension on benthic oxygen consumption and the effect of natural and massive resuspension on oxygen consumption and fluxes of phosphate, silicate, ammonium and dissolved inorganic carbon (DIC) were studied at two stations (S1 and S2) in a Scottish sea loch. Station S11 had organically enriched sediment and station S1 had lower organic content in the sediment. The fluxes were measured in situ using the Göteborg benthic lander. Natural resuspension, simulating resuspension events due to strong wind, waves or currents, and massive resuspension, simulating resuspension due to e.g. trawling or dredging, were created inside the incubation chambers by regulating the stirring of the incubated overlying water or by retracting and shaking the incubated sediment. Natural resuspension showed clear effects on the oxygen consumption at station S11, where it increased with an average of 12.8 (standard error (s.e.) 0.17) and 7.7 (s.e. 0.12) mmolm−2d−1 during the first and second incubations, respectively. At station S1 there was no clear effect of natural resuspension on the oxygen consumption. Massive resuspension increased the oxygen consumption on S1 with an average of 608 (standard deviation (sd) 366) mmolm−2d−1 and on S11 with an average of 2396 (sd 2265) mmolm−2d−1. The fluxes of ammonium, phosphate and silicate were affected by the massive resuspension in 50, 14 and 33% of the chambers, respectively, on station S11. However, in the majority of the cases there were no effects on the nutrient and DIC fluxes of massive resuspension. The absolute concentrations of DIC, ammonium and silicate did however instantly increase with an average of 419 (sd 297), 48 (sd 27) and 6.9 (sd 3.7) μM, respectively, at S11 upon massive resuspension. The concentrations of phosphate decreased instantly with an average of 0.2 (sd 0.1) μM. On station S1 there were effects only on the ammonium and silicate concentrations, which increased with 0.8 (sd 0.3) and 1.13 (sd 0.36) μM, respectively. The large increase in oxygen consumption due to massive resuspension indicates that activities like e.g. trawling and dredging that take place in areas where water exchange occurs infrequently may lead to oxygen depletion in bottom water, which in turn might affect the ecological balance. Silicate, ammonium and DIC can be released due to massive resuspension and contribute to increased algal blooms in surface waters.