Anthropogenic effects on greenhouse gas (CH4 and N2O) emissions in the Guadalete River Estuary (SW Spain).

Coastal areas are subject to a great anthropogenic pressure because more than half of the world's population lives in its vicinity causing organic matter inputs, which intensifies greenhouse gas emissions into the atmosphere. Dissolved concentrations of CH4 and N2O have been measured seasonally during 2013 in the Guadalete River Estuary, which flows into the Cadiz Bay (southwestern Spanish coast). It has been intensely contaminated since 1970. Currently it receives wastewater effluents from cities and direct discharges from nearby agriculture crop. Eight sampling stations have been established along 18 km of the estuary. CH4 and N2O were measured using a gas chromatograph connected to an equilibration system. Additional parameters such as organic matter, dissolved oxygen, nutrients and chlorophyll were determinate as well, in order to understand the relationship between physicochemical and biological processes. Gas concentrations increased from the River mouth toward the inner part, closer to the wastewater treatment plant discharge. Values varied widely within 21.8 and 3483.4 nM for CH4 and between 9.7 and 147.6 nM for N2O. Greenhouse gas seasonal variations were large influenced by the precipitation regime, masking the temperature influence. The Guadatete Estuary acted as a greenhouse gas source along the year, with mean fluxes of 495.7 µmol m(-2)d(-1) and 92.8 µmol m(-2)d(-1) for CH4 and N2O, respectively.

Aerobic biodegradation of linear alkylbenzene sulfonates and sulfophenylcarboxylic acids for different salinity values by means of continuous assays.

Aerobic biodegradation of linear alkylbenzene sulfonates (LAS) and sulfophenylcarboxylic acids (SPCs) in water, at different salinity values, has been studied. Three experiments have been carried out employing a staircase model system with continuous dosage of LAS to the system and using concentrations of LAS of the same order as those detected in littoral waters receiving urban wastewater discharges. LAS biodegradation was observed to be almost complete (showing a great extent), and in all cases exceeds 98.4%. At the very low concentration values of LAS utilized in the experiments, no significant variations in the biodegradation of LAS due to the effect of the different salinity values assayed were observed. The biodegradation intermediates detected for all the cases were sulfophenylcarboxylic acids with carboxylic chains of between five and 13 carbon atoms. The detection of C13-SPC (which is only produced by C13-LAS) confirms the existence of omega-oxidation. The total disappearance of SPCs in all cases indicates that mineralization of LAS at the concentrations tested was complete.

Toxicity of copper in natural marine picoplankton populations.

Standard microalgae toxicity tests should be able to establish responses in real ecosystems. Natural marine picoplankton samples collected during the months of March, June, August, October 2007 and January 2008, where exposed to 72 h copper toxicity tests. Results analysed by flow cytometry distinguished two groups, with different cytometric characteristics that can match with two of Synechococcus populations. EC(50) values for these two populations resulted low, ranging from 0.62 to 26.28 microg L(-1), this converts copper in a very powerful contaminant and Synechococcus in one of the most sensitive groups of phytoplankton. Differences in EC(50) values for a same population can be related to the month of collection including different initial cellular densities and oceanographic parameters that can affect the picoplankton's tolerance and distribution.

A multivariate assessment of sediment contamination in dredged materials from Spanish ports.

This paper summarises the performance of simple multivariate exploratory analyses to investigate on their potential application for dredged material characterization and management. The data from 25 sampling stations located at 7 different Spanish ports, produced a matrix consisting of 300 observations on 10 variables: the metals Cd, Cu, Cr, Hg, Ni, Pb and Zn, the metalloid As, the sum of PAHs and PCB congeners, and the proportion of fines and organic matter content. The cluster analysis was suitable to separate the sediments according to the extent of contamination while the PCA indicated that the data was defined by two principal factors: a first one that accounts for 56.4% of the total variance, describing the metallic contaminants except Ni and Cr, and a second one that accounts for 14.4% of the total variance describing the organic contaminants PAHs and PCBs. The use of these two simple and untutored multivariate techniques seems a cost-effective approach for future pre-dredging investigations in the studied areas providing useful information for dredged material characterization and management with little additional effort.

Effect of linear alkylbenzene sulfonate (LAS) and atrazine on marine microalgae.

Five marine microalgae (Tetraselmis chuii, Rhodomonas salina, Chaetoceros sp., Isochrysis galbana (T-iso) and Nannochloropsis gaditana), in the same biovolume quantity, were exposed to 72h growth-inhibition tests with atrazine and LAS. In all cases, the inhibition effect of atrazine was higher than that of LAS up to two orders of magnitude higher in the case of T. chuii. In a second part of the study, initial cellular densities for each microalga strain and fixed organic compound concentration were varied, and results show density has a clear influence in growth inhibition tests. Finally, the sum of all data obtained in the study was expressed in terms of "toxic cellular quota" (mass of chemical substance per cell). The result was a sigmoid curve with a good fit, including the two main factors in toxicity tests, initial cellular density and contaminant concentration. This toxic cellular quota exhibits a general tendency to increase with cell volume/size.

Direct comparison of amphipod sensitivities to dredged sediments from Spanish ports.

The sensitivity of the benthic amphipod species Ampelisca brevicornis and Corophium volutator to dredged sediments was compared through simultaneous testing on the standard 10 days sediment toxicity test. The results of mortality obtained for 22 harbor sediments sampled at several Spanish ports were studied together with the physico-chemical characteristics of the samples to obtain the incidence of toxicity in terms of dredged material categories and to identify possible differences in the amphipod mortality results when using one or another test species. The results showed a similar incidence of toxicity for medium-high and highly contaminated sediments for both amphipod species, similar to that obtained through the comparison of the chemical concentrations measured in sediments with the single limit values used in Spain for dredged material characterization and management. On the contrary, C. volutator presented a higher mortality and a higher incidence of toxicity when exposed to low and medium-low contaminated sediments, which may have been caused by the lower sensitivity of A. brevicornis when exposed to sediments from its natural environment. When compared to other amphipod species used for whole sediment toxicity assessment, both amphipod species used in this study reported slightly higher sensitivities although these differences could have been associated to the different set of chemical compounds considered when characterizing the sediment samples. In this sense, the amphipod mortality results were better predicted through the use of mean quotients than just by comparing the measured chemical concentrations with the single limit values used in Spain, which indicates that the toxic response of both species was caused by the cocktail of contaminants present in the sediments. Finally, the correlation analysis identified a higher association between A. brevicornis mortality and the metallic contaminants while C. volutator was more correlated with the organic micro-pollutants. Despite these differences, the results indicate that Ampelisca brevicornis can be used as test organism for dredged material characterization when enough individuals of other recommended species such as Corophium volutator are not available.

Liquid versus solid phase bioassays for dredged material toxicity assessment.

Since 1994 the results of the analyses of key chemical compounds (trace metals, polychlorinated biphenyls and polycyclic aromatic hydrocarbons) and the comparison with the corresponding sediment quality guidelines (SQGs) are used in decision-making for dredged material management in Spain. Nonetheless in the last decades a tiered testing approach is promoted for assessing the physical and chemical characteristics of dredged sediments and their potential biological effects in the environment. Bioassays have been used for sediment toxicity assessment in Spain but few or no experiences are reported on harbour sediments. We studied the incidence of toxicity in the 7 d bioassay using rotifers (Brachionus plicatilis) and the 48 h bioassay using sea urchin (Paracentrotus lividus) embryos over a series of experiments employing 22 different elutriates. The relative performance of this exposure phase was not comparable to data on the 10-d acute toxicity test using the burrowing amphipod Corophium volutator and the polychaete Arenicola marina, carried out on the whole sediments. These results evidence the importance of the exposure route and the test selected in decision-making, as the toxicity registered for the undiluted elutriates was largely due to the different solubility of sediment-bound contaminants. This work and other studies indicate that for many sediments, a complete battery of test is recommended together with physico-chemical analyses to decide whether dredged sediments are suitable for open water disposal or not.

Simulating a heavy metal spill under estuarine conditions: effects on the clam Scrobicularia plana.

We describe the effect of heavy metals Zn, Cd, Pb and Cu on the induction of methallothioneins on the clam Scrobicularia plana along a salinity gradient simulated under laboratory conditions. The clams were exposed to constant heavy metal concentrations in a dynamic estuary simulator during a 15-day assay to investigate possible induction of metal-binding proteins in them. The concentration of heavy metals in water was analysed. Clams were analysed for methallothionein concentrations. The speciation of Zn, Cd, Pb and Cu along the salinity gradient was modelled. Zn showed the highest concentrations and its prevalent species was the free ion. Intersite differences have been observed in methallothionein concentration and related to the salinity gradient. It seems that synthesis of methallothioneins is the result of physiological forces acting in concert with the changes in the chemical speciation of metals, owing to the trace metals uptake is controlled by means of an interaction of physiology and physicochemistry.

Sediment quality in the Guadalquivir estuary: lethal effects associated with the Aznalcóllar mining spill.

Monitoring from 1998 to 2001 has assessed the impact of the Aznalcóllar mining spill on the sediment quality in the Guadalquivir estuary. Chemical analysis has been completed with biological effects measured in different organisms. The toxicity of sediments obtained from dilutions of toxic mud and from environmental stations affected by the accidental spill was tested using the amphipod Ampelisca brevicornis and the clam Scrobicularia plana. The results obtained show that amphipods are more sensitive to the accidental spill than the clams. A dilution of clean sediment by more than 1.8% of toxic mud produced 100% mortality of amphipods. In GR2 station is detected toxicity to amphipods but not to clams. The rest of the environmental stations show no toxicity. Toxicity to amphipods in GR2 station decreased along time (from 50% to 60% of mortality in 1998 to 10 to 15% in 2001) and it can be associated with a recovery of the areas impacted by the accidental spill.

Sediment quality in the Guadalquivir estuary: sublethal effects associated with the Aznalcóllar mining spill.

As a complementary assessment of the impact of the Aznalcóllar mining spill on the Guadalquivir estuary two different sediment toxicity tests using fish (Solea senegalensis) and clams (Scrobicularia plana) were performed. The histopathological alterations by recording lesions at 15 and 30 days in fish to the gills, liver, gut and kidney and at 14 days in clams to the gills and gut were used to determine the adverse effects associated with the contaminants bound to sediments. The lesions measured at different tissues in both organisms show that the enrichment of heavy metals from the mining spill stressed some areas in the ecosystem of the estuary. The comparison of these effects with those lethal effects detected in the same samples using a multivariate analysis approach permits to identify the adverse effects associated with the accidental spill on the estuary. The incidence of the impact, located in specific areas of the estuary show an acute effect related to the spill.

The behaviour of heavy metals from the Guadalquivir estuary after the Aznalcóllar mining spill: field and laboratory surveys.

The spill at 'Los Frailes' caused a large input of metals into the riverine, estuarine and coastal ecosystems. Metal behaviour in natural waters can be studied both by performing field measurements, and by undertaking laboratory simulation experiments. Here is described the behaviour of the heavy metals Zn, Cd, Pb and Cu in the Guadalquivir estuary using incubation experiments and the results compared to those obtained during field assessments. If the toxic waste water had been discharged untreated into the environment, it could have raised the heavy metal concentrations in the estuary water to high values, such as 20.65 microM for Zn and 40 x 10(-3) microM for Cd. These values are several times higher than those obtained in samples collected in the area during the monitoring of the early impact. The metals present a non-conservative behaviour, with a high loss to waters of low salinity values.

Evaluating the heavy metal contamination in sediments from the guadalquivir estuary after the Aznalcóllar mining spill (SW Spain): a multivariate analysis approach.

The Doñana National Park is one of the most important Natural Reserves in west Europe. The park and the Guadalquivir estuary were impacted by the release of 5 million cubic meters of acid waste from the processing of pyrite ore. Here are presented a multivariate analysis approach to evaluate the extension and the magnitude of the accidental spill on the estuarine sediments. Sediments were used to analyze 6 different metals (Fe, Mn, Zn, Cd, Pb, Cu). Also the concentration of the metals in the different geochemical sediment fractions were determined as a means of assessing the potential impact of the acid water from the mine. The analysis of the results obtained permits to establish that the impact of the accident was acute on the ecosystem due to the set up of a treatment plan in June 1998 and to the high hydrodynamic of the estuary that absorb the early impact. Chronic contamination by Cu was also detected during the monitoring of the impact of the accident in the estuary but this did not appear to be related to the accidental spill. Because the likelihood of long term adverse effects from the heavy metal contamination of estuarine sediments, further ecotoxicological evaluations should be carried out for the estuary and the park using an integrated approach.

Influence of the Aznalcóllar mining spill on the vertical distribution of heavy metals in sediments from the Guadalquivir estuary (SW Spain).

The Natural Park of Doñana and the Guadalquivir estuary were impacted by the release of 6 million cubic meters of acid waste after the mine-tailing spill in Aznalcóllar (Andalusia, SW, Spain). Here is presented the monitoring of the accidental spill on vertical distribution of heavy metals in the estuarine sediments. The total concentration of six metals (Fe, Mn, Zn, Cd, Pb, Cu), their chemical speciation and the organic carbon concentration were analyzed in sediment vertical profiles. The results obtained determine background levels similar to previously reported in the area. The analysis catalogues the impact of the accident on the estuary as acute and mainly associated with high concentrations of Zn and Cd. The recent enrichment in Zn and Cd and their geochemical association with the more mobile fractions of the sediment determine an environmental risk associated with the acute impact and detected in some of the areas of the estuary.

Evaluation of heavy metal sediment toxicity in littoral ecosystems using juveniles of the fish Sparus aurata.

The toxicity of sediments from two littoral ecosystems of the Gulf of Cadiz was tested using juveniles of the fish Sparus aurata (seabream). Concentrations of total carbon and nitrogen, organic carbon, 14 heavy metals (Fe, Mn, Cu, Zn, Pb, Cd, Ag, Hg, As, Sn, V, Ni, Co, Cr), and the surfactant linear alkyl benzenesulfonate (LAS) in the sediments were measured. Chemical analysis was performed in the stations to determine the degree and nature of contamination. Four different endpoints were selected in the toxicity test: survival, superficial alteration, hematocrit analysis, and histological damage. After 14 days, survival, superficial alteration, and hematocrit analysis did not reveal effects of the different sediments tested. The histological and cellular damage revealed a more sensitive response to measured chemicals in sediments and they were found to be a powerful tool to evaluate sediment toxicity effects. Semiquantitative evaluation of the histological damage demonstrated correlation with sediment concentrations of some of the heavy metals (Cr, Cd, Pb, Ag, Cu) and the surfactant (LAS). Data derived from chemical concentrations and toxicity tests were assembled by multivariate statistical techniques (principal components analysis) to identify the ranges of chemical concentrations associated with an adverse effect. The results obtained, as suggested by site-specific sediment quality values, were the following: Cr>/=90.2; Cd>/=1.24; Pb>/=52.5; Ag>/=0.68; Cu>/=71.2; LAS>/=8.7 mg kg-1 of dry sediment. These results are mainly in concordance with studies performed in other areas of the world and therefore support wide application of the method.