Procambarus clarkii as a bioindicator of heavy metal pollution sources in the lower Ebro River and Delta

2D-DIGE as a proteomic biomarker discovery tool in environmental studies with Procambarus clarkii

A 2D-DIGE/MS approach was used to assess protein abundance differences in the red swamp crayfish Procambarus clarkii from polluted aquatic ecosystems of Doñana National Park and surrounding areas with different pollution loads. Procambarus clarkii accumulated metals in the digestive glands and gills reflecting sediment concentrations. We first stated that, probably related to elements accumulation, pollution increased oxidative damage in P. clarkii tissues, as shown by the thiol oxidation status of proteins and MDA levels. In these animals, the altered redox status might be responsible for the deregulated abundance of proteins involved in cellular responses to oxidative stress including protein folding, mitochondrial imbalance and inflammatory processes. Interestingly, polluted P. clarkii crayfish also displayed a metabolic shift to enhanced aerobic glycolysis, most likely aimed at generating ATP and reduction equivalents in an oxidative stress situation that alters mitochondrial integrity. The deregulated proteins define the physiological processes affected by pollutants in DNP and its surrounding areas and may help us to unravel the molecular mechanisms underlying the toxicity of environmental pollutants. In addition, these proteins might be used as exposure biomarkers in environmental risk assessment. The results obtained might be extrapolated to many other locations all over the world and have the added value of providing information about the molecular responses of this environmentally and economically interesting animal.

SIGNIFICANCE

Metal content in digestive gland and gills of P. clarkii crayfish reflects their contents in sediments at sites of Doñana National Park and its surroundings. Accumulation of essential and toxic transition metals is paralleled by clear signs of oxidative stress to lipids and proteins and by significant deregulation of many proteins involved in protein folding, mitochondrial respiratory imbalance and inflammatory response. These results indicate that P. clarkii is an excellent bioindicator to be used in aquatic ecosystems quality monitoring. Additionally, results evidence that the anthropogenic activities carried out around Doñana National Park represent an extremely serious threat to this unique Biosphere Reserve and pose a risk to the environment and their inhabitants health. The identified deregulated proteins provide information about the metabolic pathways and/or physiological processes affected by pollutant-elicited oxidative stress, may also be useful as biomarkers of environmental pollution and have the added value of providing information about the molecular responses of this environmentally and economically interesting animal.

Distribution of arsenic and other metals in crayfish tissues (Procambarus clarkii) under different production practices

Louisiana is one of the world's largest producer of crayfish. Arsenic (As) and other metals (Cd, Cu, Pb and Zn) concentrations were determined in crayfish tissues, plant and soil samples collected from Louisiana paddy rice fields, where crayfish/rice rotation farming is a common practice. The samples were collected from November 2013 to April 2014 from three different crayfish farming systems. Concentration of As in rice grain, rice straw, and native vegetation ranged between 0.33 and 0.41, 3.14-4.93, and 3.26-5.89mgkg^-1, respectively. The highest As levels in the crayfish external and internal body parts were found in gill (4.04±1.70mgkg^-1), followed by hepatopancreas (3.42±1.57mgkg^-1), exoskeleton (1.52±0.85mgkg^-1), and muscle (1.50±0.69mgkg^-1). Positive correlations between As levels in the crayfish muscle and the plant tissue on which they feed were found in all farming systems (r=0.405-0.438). The biomagnification factor (BMF) of As in different tissues varied between 0.29 and 1.08, having gill and hepatopancreas were the highest As accumulation while the lowest biomagnification was observed in crayfish muscle tissues which is a food source for human. The As levels along with other metals in crayfish muscle tissue were in acceptable levels for human consumption under all crayfish/rice rotation practices. Further studies are needed in determining the percentage of organic and inorganic arsenic in crayfish tissue.

Nutrients, emerging pollutants and pesticides in a tropical urban reservoir: Spatial distributions and risk assessment

Reservoirs located in urban areas suffer specific pressures related to human activities. Their monitoring, management, and protection requirements differ from reservoirs situated in non-urbanized areas. The objectives of this study were: (a) to determine the concentrations of select pesticides and emerging pollutants (EPs) present in an urban reservoir; (b) to describe their possible spatial distributions; and (c) to quantify the risks for aquatic life and safeguard drinking water supplies. For this purpose, the Guarapiranga reservoir was studied as an example of a multi-stressed urban reservoir in a tropical region. A total of 31 organic compounds (including pesticides, illicit drugs, pharmaceuticals, and endocrine disruptors) were analyzed twice over a period of one year, together with classical indicators of water quality. The physical and chemical data were treated using principal component analysis (PCA) to identify possible temporal or spatial patterns. Risk assessment was performed for biota and drinking water use, comparing maximum environmental concentrations (MECs) with the predicted no-effect concentrations (PNECs) or drinking water quality criteria (DWC), respectively. The results demonstrated the presence of pesticides and EPs, as well as pollution by high levels of nutrients and Chlorophyll a (Chl. a), during the study period. The nutrients and Trophic State Index (TSI) showed gradients in the reservoir and regional distributions, while the pesticides and EPs only clearly showed this pattern in the dry season. The concentrations and distributions of the pesticides and EPs therefore showed seasonality. These findings suggested that the two groups of pollutants (EPs+pesticides and nutrients) possessed different sources and behavior and were not always correlated in the reservoir studied. In the studied period, no risk was observed in raw water for drinking water use, but carbendazim, imidacloprid, and BPA showed risks for the biota in the reservoir.

Heavy metals bioaccumulation in selected tissues of red swamp crayfish: An easy tool for monitoring environmental contamination levels

In this paper we explored the heavy metal bioaccumulation (Cd, Cu, Pb and Zn) in Procambarus clarkii, a crayfish recently suggested as a potential bioindicator for metals pollution in freshwater systems. The present study is focused on crayfishes populations caught in a heavily polluted industrial and in a reference sites (Central Italy), though the results are generalized with a thorough analysis of literature metadata. In agreement with the literature, the hepatopancreas (Hep, detoxification tissues) of the red swamp crayfish showed a higher concentration of heavy metals in comparison to the abdominal muscle (AbM, not detoxification tissues) in the sites under scrutiny. Hep/AbM concentration ratio was dependent on the specific metal investigated and on its sediment contamination level. Specifically we found that Hep/AbM ratio decreases as follows: Cd (11.7)>Cu (5.5)>Pb (3.6)>Zn (1.0) and Pb (4.34)>Cd (3.66)>Zn (1.69)>Cu (0.87) for the industrial and reference sites, respectively. The analysis of our bioaccumulation data as well as of literature metadata allowed to elaborate a specific contamination index (Toxic Contamination Index, TCI), dependent only on the bioaccumulation data of hepatopancreas and abdominal muscle. In the industrial site, TCI expressed values much higher than the unit for Cd and Cu, confirming that these metals were the main contaminants; in contrast for lower levels of heavy metals, as those observed in the reference site for Cu, Zn and Pb, the index provided values below unit. TCI is proposed as a useful and easy tool to assess the toxicity level of contaminated sites by heavy metals in the environmental management.

Freshwater Crayfish: A Potential Benthic-Zone Indicator of Nanosilver and Ionic Silver Pollution

Nowadays, silver nanoparticles (AgNPs) are utilized in numerous applications, raising justified concerns about their release into the environment. This study demonstrates the potential to use freshwater crayfish as a benthic-zone indicator of nanosilver and ionic silver pollution. Crayfish were acclimated to 20 L aquaria filled with Hudson River water (HRW) and exposed for 14 days to widely used Creighton AgNPs and Ag(+) at doses of up to 360 μg L(-1) to surpass regulated water concentrations. The uptake and distribution of Ag in over 650 exoskeletons, gills, hepatopancreas and muscles samples were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES) in conjunction with two complementary U.S. EPA-endorsed methods: the external calibration and the standard additions. Reflecting the environmental plasticity of the two investigated species, Orconectes virilis accumulated in a dose-dependent manner more Ag than Procambarus clarkii (on average 31% more Ag). Both species showed DNA damage and severe histological changes in the presence of Ag. However, Ag(+) generally led to higher Ag accumulations (28%) and was more toxic. By the harvest day, about 14 ± 9% of the 360 μg L(-1) of AgNP exposure in the HRW oxidized to Ag(+) and may have contributed to the observed toxicities and bioaccumulations. The hepatopancreas (1.5-17.4 μg of Ag g(-1) of tissue) was identified as the best tissue-indicator of AgNP pollution, while the gills (4.5-22.0 μg g(-1)) and hepatopancreas (2.5-16.7 μg g(-1)) complementarily monitored the presence of Ag(+).

How toxic is the depleted uranium to crayfish Procambarus clarkii compared with cadmium?

Due to a lack of information on the assessment of uranium's (U) toxicity, our work aimed to compare the effects of U on the crayfish Procambarus clarkii with those of the well documented metal: cadmium (Cd). Accumulation and impacts at different levels of biological organization were assessed after acute (40 µM Cd or U; 4-10 days) and chronic (0.1 µM Cd or U; 30-60 days) exposures. The survival rates demonstrated the high tolerance of this species toward both metals and showed that Cd had a greater effect on the sustainability of crayfish. The concentration levels of Cd and U accumulated in gills and hepatopancreas were compared between both conditions. Distinctions in the adsorption capacities and the mobility of the contaminants were suspected. Differences in the detoxification mechanisms of both metals using transmission electron microscopy equiped with an energy dispersive X-ray were also pointed out. In contrast, comparison between the histological structures of contaminated hepatopancreas showed similar symptoms. Principal component analyses revealed different impacts of each metal on the oxidative balance and mitochondria using enzymatic activities and gene expression levels as endpoints. The observation that U seemed to generate more oxidative stress than Cd in our conditions of exposure is discussed.

Metal bioavailability in freshwater sediment samples and their influence on ecological status of river basins

The general aim of this work has been to check the ecological impact of metals on the Ebro river basin. In order to evaluate this, metal behavior considering water, sediment as well as metal bioaccumulation in fish has been studied. Total concentrations of metals, as well as the potentially bioavailable fraction of metals in sediment has also been analyzed by the application of the sequential extraction method (BCR method). In order to evaluate the influence of metal pollution on the river ecological status, according to the Water Framework Directive (WFD), diverse biological indices such as macroinvertebrates (IBMWP), diatoms (IPS) and macrophytes (IVAM), have been considered from an integrated point of view. Considering both water and sediment, metals which contributed in higher extend to the reduction of biological quality have been demonstrated to be Pb and Zn, as they presented a negative influence on macroinvertebrates, diatoms and macrophytes communities. As and Cr that seemed to have a significant influence on macroinvertebrates and diatoms too, while Ni negatively influenced only diatom communities. This study also demonstrated that monitoring programs only based on total metal determination in water are inefficient, as metals present even at undetectable concentrations in water are strongly accumulated in fish. Moreover, the high concentrations of Hg found in sediments indicated that this river basin may present pollution problems regarded to this metal, as demonstrated by the high Hg levels found in fish.

Trace element concentrations in red swamp crayfish (Procambarus clarkii) and surface sediments in Lake Preola and Gorghi Tondi natural reserve, SW Sicily

Concentrations of trace elements (Cd, Pb, As, V, Cr, Ni, Cu and Zn) were determined in superficial sediments and in muscle and hepatopancreas tissues of the red swamp crayfish Procambarus clarkii from Lake Preola and Gorghi Tondi Natural Reserve (SW Sicily). In particular, hepatopancreas showed a decidedly higher content of all analysed trace elements with respect to muscles (two- to threefold higher for Cd, Cu, As, Zn and V; four- to fivefold higher for Pb and Cr and seven times higher for Ni). However, no statistically reliable differential accumulation pattern emerged with regard to length and weight for trace elements (except for Cd for which significant positive correlations with length were recorded). Trace element concentrations found in crayfish tissues were in the range considered harmful to human health (except for Cd and Cr). Moreover, the As and Pb concentrations, either in sediment or crayfish tissues, are clearly related to intense agricultural activities, with extensive use of fertilizers and pesticides, that significantly affect the levels of these toxic metals in the study area.

Pre-exposure to Cadmium or Zinc Alters the Heart Rate Response of the Crayfish Procambarus clarkii Towards Copper

Exposure to sub-lethal concentrations of a pollutant induces, in some organisms, an acclimation process which increases their resistance to other substances (cross-acclimation). Understanding this phenomenon is important as a basis for a better comprehension of the effects of pollutants in ecosystems. In this paper we investigated whether the exposure to Cd or Zn is able to modify the heart rate response of the crayfish Procambarus clarkii to acute Cu stress. A first set of experiments provided the basis to understand heart rate changes induced by varying Cd or Zn concentrations. In a second set of experiments crayfish were acclimated for 96 h to control water, Cd or Zn enriched water, and then exposed to a 10 mg L(-1) Cu solution, known to induce bradycardia in this species. Bradycardia was suppressed in specimens previously exposed to Cd or Zn but not in those exposed to clean water, providing a clear evidence of a cross-acclimation in the heart rate response of P. clarkii.

Metals in Mediterranean aquatic species

Metals such as arsenic (As), cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), vanadium (V), have been determined in species of Mediterranean marine organisms collected from areas supposed to be at background contamination levels. The Inductively Coupled Plasma Mass Spectrometry (ICP-MS) approach was adopted for the determination of all the metals. Arsenic, Cd and Pb determined in the 42 samples, do not exceed the pertinent maximum level except a sample of hake. In wild fish, the concentration range for Cr, Ni, V and Cu was, respectively: 0.07-0.09, 87.6-124, 0.022-0.075 and 0.79-1.74 μg/g fresh weight (fw). The farmed fish samples show concentration levels below the wild fish ones, except for Cr which range at the same levels. Cadmium and Pb show a high sample number under the quantification limit. The elements do not bio-magnify among the species considered and appear to show low variations in relation to organisms' position in the food chain and at sampling sites.

Modelling terrestrial and marine foraging habitats in breeding Audouin's gulls Larus audouinii: timing matters

Although the breeding ecology of Audouin's gull has been widely studied, its spatial distribution patterns have received little attention. We assessed the foraging movements of 36 GPS-tracked adult Audouin's gulls breeding at the Ebro Delta (NW Mediterranean), coinciding with the incubation period (May 2011). This also coincided with a trawling moratorium northwards from the colony. We modelled the distribution of the gulls by combining these tracking data with environmental variables (including fishing activities from Vessel Monitoring System, VMS), using Maxent. The modelling range included both marine and terrestrial areas. Models were produced separately for every 2h time interval across the day, and for 2 fishing activity scenarios (workdays vs. weekends), allowing to assess the spatio-temporal distribution patterns of the gulls and the degree of association with fisheries. During workdays, gull distribution at sea fully matched with fishing activities, both trawling (daylight) and purse-seining (nightime). Gulls tended to avoid the area under trawling moratorium, confirming the high influence of fisheries on the distribution patterns of this species. On weekends, gulls made lesser use of the sea and tended to increase the use of rice fields. Overall, Audouin's gull activity was more intense during dailight hours, although birds also showed nocturnal activity, on both workdays and weekends. Nocturnal patterns at sea were more disperse during the latter, probably because these gulls are able to capture small pelagic fish at night in natural conditions, but tend to congregate around purse-seiners (which would enhance their foraging efficiency) in workdays. These results provide important insight for the management of this species. This is of particular relevance under the current scenario of European fisheries policies, since new regulations are aimed at eliminating discards, and this would likely influence Audouin's gull populations.

Macrobenthic assemblages, sediment characteristics and heavy metal concentrations in soft-bottom Ebre Delta bays (NW Mediterranean)

The spatial distribution of soft-bottom macrofaunal assemblages and their relationship with sediment characteristics were examined in two semi-enclosed shallow-water bays (Alfacs Bay and Fangar Bay) in the Ebre Delta (Catalonia, NW Mediterranean) during 2006 and 2011. Three assemblages were identified: group 1, present in sediments that contain a high percentage of silt-clay, small median particle size and high organic matter content and located at the most external areas of both bays and in the central basin of Alfacs Bay; group 2, present in the shallow northern platform in Alfacs Bay and in both platforms in Fangar Bay, the locations which feature highly variable sediment characteristics; and group 3, present in the shallow areas of both bays, which are characterised by low silt-clay and organic matter content. In Alfacs Bay, the differentiation of these assemblages has persisted since 1987, independently of the increase in organic matter content and heavy metal concentrations and of the shift in macrofaunal composition that have occurred over the past 20 years, most likely the result of increased agricultural activity.

Profiling the physiological and molecular response to sulfonamidic drug in Procambarus clarkii

Sulfamethoxazole (SMZ) is one of the most widely employed sulfonamides. Because of the widespread use of SMZ, a considerable amount is indeed expected to be introduced into the environment. The cytotoxicity of SMZ relies mainly on arylhydroxylamine metabolites (S-NOH) of SMZ and it is associated with the production of reactive oxygen species (ROS). There is limited information about the toxic potential of SMZ at the cellular and molecular levels, especially in aquatic and/or non-target organisms. In the present study, the red swamp crayfish (Procambarus clarkii), being tolerant to extreme environmental conditions and resistant to disease, was used as a model organism to profile the molecular and physiological response to SMZ. Haemolymphatic-immunological parameters such as glucose serum levels and total haemocyte counts were altered; moreover, a significant increase in Hsp70 plasma levels was detected for the first time. Variations at the transcriptional level of proinflammatory genes (cyclooxygenase-1, COX 1, and cyclooxygenase-2, COX 2), antioxidant enzymes (glutathione-S-transferase, GST and manganese superoxide dismutase MnSOD), stress response and Fenton reaction inhibitor genes (heat-shock protein 70 HSP70, metallothionein, MT and ferritin, FT) were evaluated, and alterations in the canonical gene expression patterns emerged. Considering these results, specific mechanisms involved in maintaining physiological homeostasis and adaptation in response to perturbations are suggested.

Massive accumulation of highly polluted sedimentary deposits by river damming

Uncontrolled dumping of anthropogenic waste in rivers regulated by dams has created contaminated deposits in reservoirs that have remained unidentified for decades. The Flix Reservoir is located in the Ebro River, the second largest river flowing into the NW Mediterranean, has been affected by residue dumping from a chlor-alkali electrochemical plant for decades. High-resolution seismic profiles, bathymetric data, surficial sediment samples and sediment cores were obtained in the Flix Reservoir to study the characteristics of the deposit accumulated by this dumping. These data were used to reconstruct the waste deposit history. Since the construction of the Flix Dam in 1948, more than 3.6×10(5) t of industrial waste has accumulated in the reservoir generating a delta-like deposit formed by three sediment lobes of fine-grained material highly contaminated by Hg, Cd, Zn and Cr (max: 640, 26, 420 and 750 mg kg(-1), respectively). This contamination was associated with the Hg that was used for the cathode in the electrochemical plant from 1949 and with the production of phosphorite derivatives from 1973. After the construction of two large dams only a few kilometres upstream during the 1960s, the solids discharged from the industrial complex became the main sediment source to the Flix Reservoir. The deposit has remained in the reservoir forming a delta that obstructs about 50% of the river water section. Its stability only depended on the flow retention by the Flix Dam. At present, this contaminated waste deposit is being removed from the water reservoir as it is a cause of concern for the environment and for human health downriver.

The environmental quality of Doñana surrounding areas affects the immune transcriptional profile of inhabitant crayfish Procambarus clarkii

This study aimed to identify differentially expressed genes in Procambarus clarkii crayfish collected from locations of different environmental qualities in the Doñana National Park surrounding areas. The pollution sustained by the crayfish was confirmed by their hepatopancreatic metal concentration. We generated forward and reverse libraries by suppression subtractive hybridization (SSH) to analyze the transcriptional profiles of crayfish from moderately and highly polluted zones in comparison with the control site within the Doñana Biological Reserve. Forty-three differentially expressed genes were detected, and most of them were identified as genes involved in a variety of biological functions, particularly in the innate immune response. To verify the SSH results and assess interindividual variability nine transcripts (ALP, AST, BTF3, CHIT, CTS, ferritin, HC, HC2, and SPINK4) were selected for absolute quantification by real-time qRT-PCR. The qRT-PCR data revealed substantial differences in the absolute amounts of the nine transcripts and confirmed their up- or down-regulation in the polluted sites. Additionally, a positive and significant linear correlation was found between the hepatopancreatic copper concentration and the levels of the transcripts encoding hemocyanins. Finally, the transcriptomic study was complemented with a detailed analysis of SNP profiles of the selected transcripts that revealed point mutations that might underlie adaptive response to environmental stress in P. clarkii. Overall, this work provides novel insights into the molecular pathways that could mediate the response to environmental pollutants in P. clarkii emphasizing the central role of the immune function and thus, should clearly benefit further immunotoxicological research in this organism.

Mitochondrial gene expression, antioxidant responses, and histopathology after cadmium exposure

The present study investigates cadmium effects on the transcription of mitochondrial genes of Procambarus clarkii after acute (0.05, 0.5, and 5 mg Cd/L; 4-10 days) and chronic exposures (10 μg Cd/L; 30-60 days). Transcriptional responses of cox1, atp6, and 12S using quantitative real-time RT-PCR were assessed in gills and hepatopancreas. Additionally, the expression levels of genes involved in detoxification and/or oxidative stress responses [mt, sod(Mn)] and enzymatic activities of antioxidants (SOD, CAT, GPX, and GST) were analyzed. The histopathological effects in hepatopancreas of crayfish were evaluated by light microscopy. Relationships between endpoints at different levels of biological organization and Cd bioaccumulation were also examined. Cd induced high levels of bioaccumulation, which was followed by mitochondrial dysfunction and histological alterations in both experiments. Moreover, perturbations in the defence mechanisms against oxidative stress tended to increase with time. Results also showed that molecular responses can vary depending on the intensity and duration of the chemical stress applied to the organisms and that the study of mt gene expression levels seemed to be the best tool to assess Cd intoxication.

Temporal Changes in Concentrations of Some Trace Elements in Muscle Tissue of Crayfish, Astacus leptodactylus (Eschscholtz, 1823), from Keban Dam Lake

Crayfish (Astacus leptodactylus Eschscholtz, 1823) is the native crayfish species in Turkey. It was exported regularly to Western Europe. In this study, bioaccumulation and temporal trends of some trace elements (arsenic: As, cadmium: Cd, copper: Cu, mercury: Hg, lead: Pb, and zinc: Zn) in edible abdomen muscle of crayfish from Keban Dam Lake (Elazığ, Turkey) were investigated for the 2006–2012 period. Sequence of metal concentration levels was Zn > Cu > Hg > Pb > Cd > As in muscle tissues. The highest concentration of Zn (21.69 mg kg⁻¹) was detected in 2006, while the lowest (4.35 mg kg⁻¹) in 2009. In general, it was found that the concentrations of trace elements investigated were lower than the maximum permissible limits of the food regulations of the Ministry of Food, Agriculture, and Livestock (MFAL), the Turkish Food Codex and Commission Regulation (EC). If the crayfish selected for the study are recognized as bioindicators of environmental pollution, then it is possible to conclude that the changes in studied trace elements concentrations in the Keban Dam Lake are being steady.

Accumulation of heavy metals in crayfish and fish from selected Czech reservoirs

To evaluate the accumulation of aluminium, cadmium, chromium, copper, lead, mercury, nickel, and zinc in crayfish and fish organ tissues, specimens from three drinking water reservoirs (Boskovice, Landštejn, and Nová Říše) and one contaminated site (Darkovské moře) in the Czech Republic were examined. Crayfish hepatopancreas was confirmed to be the primary accumulating site for the majority of metals (Cu > Zn > Ni > Cd > Cr), while Hg and Cr were concentrated in abdominal muscle, and Al and Pb were concentrated in gill. Metals found in Nová Říše specimens included Cu > Zn > Ni and those found in Boskovice included Zn > Hg > Cr. Cd concentrations were observed only in Landštejn specimens, while contaminated Darkovské moře specimens showed the highest levels of accumulation (Cu > Al > Zn > Pb). The majority of evaluated metals were found in higher concentrations in crayfish: Cu > Al > Zn > Ni > Cr > Cd > Pb, with Hg being the only metal accumulating higher in fish. Due to accumulation similarities of Al in crayfish and fish gill, differences of Hg in muscle, and features noted for the remaining metals in examined tissues, biomonitoring should incorporate both crayfish and fish to produce more relevant water quality surveys.

Ecotoxicological assessment of the impact of nitrate (NO(3)(¯)) on the European endangered white-clawed crayfish Austropotamobius italicus (Faxon)

Field studies and laboratory experiments were conducted to assess the impact of elevated nitrate (NO(3)(¯)) concentrations on the European endangered white-clawed crayfish Austropotamobius italicus (Faxon) in the Henares River Basin (Central Spain), within an area that is vulnerable to nitrate pollution. Two sampling surveys were carried out in the summer of 2009 and 2011 to collect freshwater crayfish at eight sampling sites along this vulnerable area. The invasive read-swamp crayfish Procambarus clarkii (Girard) was the only collected crayfish species. Nitrate toxicity experiments however showed that A. italicus is one of the most tolerant species to nitrate toxicity. Although the food consumption was the most sensitive endpoint to nitrate toxicity (followed by the escape response and mortality), the no-observed-effect concentration (NOEC) for this endpoint after 14 days of exposure to nitrate was as high as 100mg NO(3)(¯)N/l, with some crayfish being still alive after fourteen days of exposure to a nominal nitrate concentration of 800mg NO(3)(-)N/l. Besides, a safe concentration of nitrate for A. italicus, along with its respective 95% confidence limits, were estimated to be 68.5 (22.4-187) mg (NO(3)(¯)N/l. Overall we conclude that elevated nitrate concentrations would not be responsible for the absence of white-clawed crayfish in the Henares River Basin. Other environmental factors, particularly the presence of P. clarkii and its fungal pathogen, would be major causes.

Integrated study of metal behavior in Mediterranean stream ecosystems: a case-study

The objective of the present work was to assess the ecosystem status of Francolí river (Catalonia, Spain), a Mediterranean stream basin with contrasting human influences. An integrated approach was designed by combining physicochemical, biological and ecotoxicological analyses. The content of metals (As, Cd, Cr, Co, Cu, Hg, Ni, Pb, and Zn) was analyzed in samples of water, benthic sediments and aquatic macroinvertebrates. In addition, the potentially bioavailable fraction of metals in water and sediments was determined by using diffusive gradient in thin-films (DGTs) and sequential extraction of sediments (BCR), respectively. The biological quality was evaluated through aquatic macroinvertebrate communities, while the ecotoxicological status was assessed by Microtox(®) with Vibrio fischeri. Finally, an analysis of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) was performed to evaluate the sediment toxicity associated to metal content. According to the results, DGTs and BCR are suitable methodologies to predict the potential bioavailable fraction of metals in freshwater systems. Moreover, ecotoxicity evaluation by means of V. fischeri, in combination with the chemical characterization and the biological quality assessment, should be complementarily used to get a better diagnose of freshwater systems.

Anthropogenic input of heavy metals in two Audouin's gull breeding colonies

Anthropogenic activities have become an important source of heavy metals to the marine environments. Biological sentinels like seabirds' chicks have been widely used to monitorize the levels of some heavy metals. Due to its mainly marine foraging habits, Audouin's gull fits well for this purpose. Mercury and lead levels were measured in mantle feathers of Audouin's gull chicks from two colonies in NE Iberian Peninsula: the Ebro Delta and the Llobregat Delta. Both are anthropized areas subject to differential pollutant inputs. Lead levels were significantly higher in the Llobregat Delta probably due to the use of leaded fuel in the nearby Barcelona airport. On the other side, mercury concentrations were higher in the Ebro Delta, in relation with the disposal of the toxic sediments at the Flix site carried down by the Ebro River. These mercury levels in the Ebro chicks reached values that have been described as toxic.

Heavy metal content in oysters (Crassostrea gigas) cultured in the Ebro Delta in Catalonia, Spain

The aim of this study was to determine heavy metal content (As, Cd, Cu, Hg, Cd, Pb, and Zn) in oysters transplanted in Ebro Delta bays (Alfacs and Fangar) where oysters are traditionally cultured for human consumption. Metal body burdens were monitored weekly during the period of maximal agriculture activity from May to June in 2008 and 2009. Results indicate that regardless of the high levels of metals reported in biota living in Ebro River, metal levels in oysters from both bays were similar to those found in unpolluted areas and far below the maximum limits of tolerance recommended by the European Commission. Nevertheless, metal accumulation patterns in oysters differentiate two sources of pollution: one coming from agriculture activities within the Ebro's delta for As, Cd, Cu, and Zn and other coming from Ebro River probably related to industrial activities upstream (Hg, Pb) or to lead shot pellets form hunting activities (Pb). Reported results, thus, are in concern with previous studies and indicate that metallic pollutants do not affect oysters cultures in Ebro Delta associated bays.

Differences in the accumulation and distribution profile of heavy metals and metalloid between male and female crayfish (Astacus leptodactylus)

Concentrations of selected heavy metals and a metalloid were measured by ICP-MS in crayfish (Astacus leptodactylus) collected from Lake Hirfanli, Turkey. Aluminum (Al), chromium ((52)Cr, (53)Cr), copper ((63)Cu, (65)Cu), manganese (Mn), nickel (Ni) and arsenic (As) were measured in the exoskeleton, gills, hepatopancreas and abdominal muscle tissues of 60 crayfish of both genders. With the exception of Al, differences were determined between male and female cohorts for the accumulation trends of the above-mentioned elements in the four tissues. It was also noted that the accumulation rates of Ni and As were significantly lower in gill tissue of females compared to males and no significant difference was observed for Cu isotopes in female crayfish. Cluster Analysis (CA) recovered similar results for both genders, with links between accumulations of Ni and As being notable. Accumulation models were described separately for male and female crayfish using regression analysis, and are presented for models where R(2) > 0.85.

Are pesticide residues associated to rice production affecting oyster production in Delta del Ebro, NE Spain?

Pesticide usage in Delta del Ebro (NE Spain) during the rice growing season has been associated with oyster episodes of mortality that occur early in summer. However, there are no studies that have directly evaluated pesticide levels and effects in oysters (Crassotrea gigas) cultured in Ebro's Bays. In this study pesticide levels in water, metal body burdens and up to 12 different biochemical markers were monitored in gills and digestive glands of oysters transplanted from May to June in 2008 and 2009. Biochemical responses evidenced clear differences in oysters from 2008 and 2009. Oysters transplanted in 2009 showed their antioxidant defenses unaffected from May to June and consequently increased levels of tissue damage measured as lipid peroxidation and DNA strand breaks and of mortality rates. Conversely oysters transplanted in 2008 increase their antioxidant defenses from May to June, had low levels of lipid peroxidation and DNA damage and low mortality rates. Some pesticides in water such as bentazone and propanil together with high temperatures and salinity levels were related with tissue damage in oyster transplanted in 2008 but the observed large differences between years indicate that abiotic factors alone could not explain the high mortalities observed in 2009. An analysis of recent reported studies pointed out in the direction that in addition to abiotic factors the use of oysters sensitive to diseases may explain the observed responses.

Are the toxic sediments deposited at Flix reservoir affecting the Ebro river biota? Purple heron eggs and nestlings as indicators

The Flix reservoir, in the low course of the Ebro River, contains thousands of tons of polluted sediments, accumulated from the activities of a chemical factory. An ongoing project is working toward removing these pollutants. Piscivore birds like the purple heron (Ardea purpurea) may be useful bioindicators, so eggs and nestling feathers were sampled during the 2006-2008 breeding seasons at three localities: a reference site situated upstream and two potentially affected by the toxic muds; one at the focal area and one at a distal area, the Ebro Delta. The samples were analyzed for isotopic signatures of ¹⁵N and ¹³C and concentrations of heavy metals and selenium. Baseline nitrogen signatures were higher in riverine sites than in the delta. Nitrogen together with carbon signatures adequately discriminated riverine and deltaic ecosystems. Mercury levels are highly influenced by the polluted sediments at Flix and pose potential risks for the birds, as they are among the highest ever recorded in heron species. Selenium and copper concentrations probably derive from other sources. Except for mercury, heavy metals and selenium levels were below toxic levels. Purple heron eggs and nestling feathers have demonstrated their usefulness as bioindicators for pollution in the river biota; feathers in particular show pollutant impacts on a strict local basis. A long series of study years is necessary in dynamic ecosystems such as this, so continued monitoring of the heron population at Flix is advisable to trace the effects of the toxic muds, particularly during their removal, because of the high levels of mercury detected.

Are antioxidant and transcriptional responses useful for discriminating between chemo- and radiotoxicity of uranium in the crayfish Procambarus clarkii?

The main objectives of this study were to evaluate uranium (U) toxicity in the crayfish Procambarus clarkii at a low dose of exposure and to discriminate between the chemotoxicity and radiotoxicity of U. We conducted two sets of experiments using either 30 μg L(-1) of depleted uranium (DU) or (233)U, which differ from each other only in their specific activity (DU=1.7×10(4)Bqg(-1), (233)U=3.57×10(8)Bqg(-1)). The endpoints were oxidative stress responses and mitochondrial functioning in the gills and hepatopancreas, which were measured in terms of enzyme activities and gene expression levels. U accumulation levels were measured in different organs (gills, hepatopancreas, stomach, intestine, green gland, muscles, and carapace), and internal dose rates in the hepatopancreas were compared after DU and (233)U exposures. Significant U accumulation occurred in the organs of P. clarkii, and mitochondrial damage and antioxidant responses were detected. Despite the huge difference (21,000×) in the specific activities of DU and (233)U, few significant differences in biological responses were detected in P. clarkii exposed to these two pollutants. This finding indicates that the radiotoxicity was low compared to the chemotoxicity under our exposure conditions. Finally, genes expression levels were more sensitive markers of U toxicity than enzyme activities.

Metal bioaccumulation in the Mediterranean barbel (Barbus meridionalis) in a Mediterranean river receiving effluents from urban and industrial wastewater treatment plants

Although sewage treatment plants (STPs) play a crucial role in maintaining the water quality and flow of Mediterranean rivers, particularly during drought periods, few studies have addressed their impact on aquatic fauna. Here we analyzed the role of STPs as a source of metals in the Ripoll River, a heavily urbanized and industrialized watercourse with a long history of anthropogenic disturbance. For this purpose, we measured iron, mercury, cadmium, zinc, lead, nickel and copper accumulation in the liver and muscle of the Mediterranean barbel, Barbus meridionalis and also the concentrations of these metals in the river water. Industrial and urban sewage treatment plants are source of metals in Ripoll River but the former mainly increases Zn and Ni values. Significant differences in metal bioaccumulation between reference and polluted sites were detected. Nevertheless, there was only a significant positive relationship between bioaccumulation of Cu and Hg, and their concentration in water. In addition, the lead concentration in fish was not clearly associated with the presence of STPs. On the basis of morphometric parameters, the hepato-somatic index was the only one denoting significant differences between polluted and references sites. Given that fish are key elements in food webs, recreational fishing is practice in this area and that river water is used for agricultural purposes, we recommend long-term studies to analyze the impact of metal pollution in this river.

Mercury bioaccumulation and biomagnification in Ozark stream ecosystems

Crayfish (Orconectes spp.), Asian clam (Corbicula fluminea), northern hog sucker (hog sucker; Hypentelium nigricans), and smallmouth bass (smallmouth; Micropterus dolomieu) from streams in southeastern Missouri (USA) were analyzed for total mercury (HgT) and for stable isotopes of carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S) to discern Hg transfer pathways. HgT concentrations were generally lowest in crayfish (0.005-0.112 μg/g dw) and highest in smallmouth (0.093-4.041 μg/g dw), as was δ¹⁵N. HgT was also lower and δ¹⁵N was higher in all biota from a stream draining a more heavily populated historical lead-zinc mining area than from similar sites with mostly undeveloped forested watersheds. δ¹³C in biota was lowest at spring-influenced sites, reflecting CO₂ inputs and temperature influences, and δ³⁴S increased from south to north in all taxa. However, HgT was not strongly correlated with either δ¹³C or δ³⁴S in biota. Trophic position (TP) computed from crayfish δ¹⁵N was lower in hog suckers (mean=2.8) than in smallmouth (mean=3.2), but not at all sites. HgT, δ¹³C, δ³⁴S, and TP in hog suckers increased with total length (length) at some sites, indicating site-specific ontogenetic diet shifts. Changes with length were less evident in smallmouth. Length-adjusted HgT site means in both species were strongly correlated with HgT in crayfish (r²=0.97, P<0.01), but not with HgT in Corbicula (r²=0.02, P>0.05). ANCOVA and regression models incorporating only TP and, for hog suckers, length, accurately and precisely predicted HgT concentrations in both fish species from all locations. Although low compared to many areas of the USA, HgT (and therefore methylmercury) concentrations in smallmouth and hog suckers are sufficiently high to represent a threat to human health and wildlife. Our data indicate that in Ozark streams, Hg concentrations in crayfish are at least partly determined by their diet, with concentrations in hog suckers, smallmouth, and possibly other higher-level consumers largely determined by concentrations in crayfish and other primary and secondary consumers, fish growth rates, and TP.

Methylmercury levels and bioaccumulation in the aquatic food web of a highly mercury-contaminated reservoir

The low Ebro River basin (NE Spain) represents a particular case of chronic and long-term mercury pollution due to the presence of an industrial waste (up to 436 μg/g of Hg) coming from a chlor-alkali plant Albeit high total mercury (THg) levels have been previously described in several aquatic species from the surveyed area, methylmercury (MeHg) values in fish individuals have never been reported. Accordingly, in order to investigate bioaccumulation patterns at different levels of the aquatic food web of such polluted area, crayfish and various fish species, were analysed for THg and MeHg content. At the hot spot, THg mean values of crayfish muscle tissue and hepatopancreas were 10 and 15 times, respectively, greater than the local background level. Higher mean THg concentrations were detected in piscivorous (THg=0.848 ± 0.476 μg/g wet weight (ww); MeHg=0.672 ± 0.364 μg/g ww) than in non-piscivorous fish (THg=0.305 ± 0.163 μg/g ww; MeHg=0.278 ± 0.239 μg/g ww). Although these results indicated that THg in fish increased significantly with increasing trophic position, the percentage of the methylated form of Hg was not strongly influenced by differences in relative trophic position. This is an important finding, since the fraction of THg as MeHg in the top fish predator was unexpectedly lower than for other species of the aquatic food chain. Moreover, mean THg concentrations in piscivorous fish exceed the maximum level recommended for human consumption. From our findings, it is clear that for this specific polluted system, speciation becomes almost mandatory when risk assessment is based on MeHg, since single measurements of THg are inadequate and could lead to an over- or under-estimation of contamination levels.

Effects of uranium uptake on transcriptional responses, histological structures and survival rate of the crayfish Procambarus clarkii

This work aims to investigate the accumulation levels and effects (transcriptional responses, histopathology and survival rate) associated with a wide range of dissolved uranium (U) concentrations (0, 0.03, 0.6, 4 and 8 mg/L of U) on adult male crayfish Procambarus clarkii during 4 (T4) and 10 (T10) days of exposure. The follow-up of the crayfish mortality showed that P. clarkii was highly resistant to U. Increasing waterborne U concentrations led to increasing bioaccumulation in key crayfish organs and increasing histological damages. U distribution in tissues was also evaluated using transmission electron microscopy and showed the presence of a detoxified form of U in the gill's epithelium in the shape of flakes. Expression levels of mitochondrial genes (cox1, atp6 and 12S gene) and genes involved in oxidative stress (sod(Mn) and mt) were examined together with the housekeeping gene 18S. atp6 and mt genes of P. clarkii were cloned and sequenced before analysis. Significant correlations were observed between U bioaccumulation and the down-regulation of both cox1 and sod(Mn) genes. This work provides a first U toxicogenomic and histopathological pattern of P. clarkii, identify U biomarkers and associate gene expression endpoints to accumulation levels. It also provides new insights into the mechanisms involved in U stress.

Omic approaches in environmental issues

Biomonitoring requires the application of batteries of different biomarkers, as environmental contaminants induce multiple responses in organisms that are not necessarily correlated. Omic technologies were proposed as an alternative to conventional biomarkers since these techniques quantitatively monitor many biological molecules in a high-throughput manner and thus provide a general appraisal of biological responses altered by exposure to contaminants. As the studies using omic technologies increase, it is becoming clear that any single omic approach may not be sufficient to characterize the complexity of ecosystems. This work aims to provide a preliminary working scheme for the use of combined transcriptomic and proteomic methodologies in environmental biomonitoring. There are difficulties in working with nonmodel organisms as bioindicators when combining several omic approaches. As a whole, our results with heterologous microarrays in M. spretus and suppressive subtractive hybridization (SSH) in P. clarkii indicated that animals sustaining a heavy pollution burden exhibited an enhanced immune response and/or cell apoptosis. The proteomic studies, although preliminary, provide a holistic insight regarding the manner by which pollution shifts protein intensity in two-dimensional gel electrophoresis (2-DE), completing the transcriptomic approach. In our study, the sediment element concentration was in agreement with the intensity of protein expression changes in C. maenas crabs. In conclusion, omics are useful technologies in addressing environmental issues and the determination of contamination threats.