In situ tests for water quality assessment: a case study in Pampean rivers

Wildfire effects on two freshwater producers: Combining in-situ and laboratory bioassays

Mediterranean forests are highly susceptible to wildfires, which can cause several impacts not only within burnt areas but also on downstream aquatic ecosystems. The ashes' washout from burnt areas by surface runoff can be a diffuse source of toxic substances, such as metals, when reaching the nearby aquatic systems, and can be noxious to aquatic organisms. The present work aimed at assessing the ecotoxicological effects of post-fire contamination on two aquatic producers (the microalgae Raphidocelis subcapitata and the macrophyte Lemna minor) through in-situ bioassays, validating the obtained results with the outcomes of laboratory bioassays with surface water collected simultaneously. Four distinct sites were selected in a basin partially burnt (Ceira river basin; Coimbra district, Portugal) for bioassay deployment: one site upstream the burnt area in the Ceira river (RUS); three sites located under the influence of the burnt area, one immediately downstream of the burnt area in the Ceira river (RDS) and the other two in tributary streams within the burnt area (BS₁ and BS₂). The in-situ bioassays lasted for 13 days and began following the first post-fire major rain events. Results showed that the microalgae growth rate was able to distinguish the three sites within and downstream of the burnt area (BS₁, BS₂, RDS) from the site upstream (RUS). By contrast, the macrophytes growth rate only allowed to differentiate between the sites within the burnt area (BS₁ and BS₂) and those up- and downstream of the burnt area (RUS and RDS). The in-situ results for both species were corroborated with the results of the laboratory experiments, supporting the use of laboratory surrogates for a screening assessment of wildfire impacts in aquatic ecosystems. Direct causal relationships between the observed ecotoxicological effects on R. subcapitata and L. minor and the physical-chemical parameters of the water samples were difficult to establish, although the results suggest (i) a role of differential major and trace metal load in explaining species growth variation; (ii) interaction between metals and/or between metals and other field parameters are likely to modulate the biological responses to the challenges deriving from wildfire runoff.

Ecological impact and recovery of a Mediterranean river after receiving the effluent from a textile dyeing industry

The textile industry is one of the largest sectors globally, representing up to 20% of industrial water pollution. However, there is limited insight into how fluvial ecosystems respond and recover from this impact. From summer 2012 to spring 2013, we examined water quality and ecological status upstream and 1.5km downstream the input of a textile industry wastewater treatment plant (WWTP) in Ripoll River, NE Spain. The ecological status was determined via diversity measures and 10 biotic indices based on diatoms, macrophytes, macroinvertebrates and fish. Our results showed that the WWTP severely deteriorated water quality and biological communities at the discharge site, but that they improved at 1.5km downstream. Severity also varied across taxa and seasons, being fish the most affected taxa and spring the season with the best ecological status. The strong correlation amongst water quality variables and many biotic indices across taxa indicated that this is a chronic pollution event affecting multiple trophic levels. Thus, this study suggests that there is an urgent need to invest in wastewater treatment in this industry to preserve the ecological integrity of Ripoll River and especially its fish fauna. Likewise, it illustrates the diagnostic power of biotic indices based on diatoms, macroinvertebrates and fish, as driven by the European Water Framework Directive.

Acute toxicity of organophosphate fenitrothion on biomarkers in prawn Palaemonetes argentinus (Crustacea: Palaemonidae)

The effect of the organophosphate fenitrothion (FS) on the non-target freshwater prawn Palaemonetes argentinus was studied. Initially, the 96-h lethal concentration (LC50) of FS was determined in adult prawns. Inhibition of cholinesterase (ChE) in the muscle and hemolymph was assessed. Then, in the hepatopancreas, the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST) were analyzed. Lipid peroxidation (LPO) was also determined in the hepatopancreas. The 96-h LC50 value was 1.12 μg/L. Hemolymph ChE activity showed a significant decrease in exposed prawns to FS compared to the control group, while no significant differences in the muscle were observed between groups (p < 0.05). FS caused a significant increase in the activity of antioxidant enzymes SOD, CAT, and GST compared to the control group (p < 0.02). By contrast, LPO levels were not affected by the pesticide (p < 0.05). These results indicate that P. argentinus is very sensitive to organophosphorus which alter biochemical parameters that are related to antioxidant status. Thus, these parameters could be used as biomarkers for assessing water pollution.

Assessment of river water quality using an integrated physicochemical, biological and ecotoxicological approach

In order to maintain and improve the water quality in European rivers, the Water Framework Directive (WFD) requires an integrated approach for assessing water quality in a river basin. Although the WFD aims at a holistic understanding of ecosystem functioning, it does not explicitly establish cause-effect relationships between stressors and changes in aquatic communities. To overcome this limitation, the present study combines the typical WFD physicochemical and biological approaches with an ecotoxicological approach. The main goal was to assess river water quality through an integrated manner, while identifying potential risk situations for aquatic communities in the Cértima river basin (Portugal). To achieve this goal, surface water samples and macroinvertebrate specimens were collected under contrasting hydrological conditions (autumn and spring seasons) at three river sites exposed to distinct pollution levels defined according to the WFD (low, moderate and highly polluted). Physicochemical water quality status was defined according to the Portuguese classification for multipurpose surface waters, whereas biological water quality was assessed in accordance with the South Invertebrate Portuguese Index. Ecotoxicological assays included four standard species, a bacterial species (Vibrio fischeri), a unicellular algae (Pseudokirchneriella subcapitata), a macrophyte (Lemna minor) and a crustacean (Daphnia magna), which were exposed to different river water concentrations. The study sites represented a clear and pronounced gradient of pollution, from the unpolluted reference site to the sites under moderate to high anthropogenic pressure. In the latter sites, clear signs of organic pollution were found, such as low dissolved oxygen concentrations, high nutrient loads and prevalence of highly tolerant macroinvertebrate species. Despite the evident signs of pollution, no clear evidence of toxicity was observed in test species, suggesting that ecotoxicological assays using standard laboratory species and methodologies might not be suitable for assessing the effects of organic pollution. Nevertheless, the integrated methodology presented in this study provided important additional information on the Cértima's water quality status. Its wider use could contribute to a more comprehensive assessment of the effects of anthropogenic pollution on the status and functioning of aquatic ecosystems under the WFD and, thereby, improve the scientific foundations for the sustainable future management of surface water resources.

Biomonitoring toxicity of natural sediments using juvenile Hyalella curvispina (Amphipoda) as test species: evaluation of early effect endpoints

The utility of early effect endpoints as biomarkers of ecotoxicity of natural sediments in water-sediment static system was investigated. The particular goal was to evaluate the ecotoxicity of the sediment samples from La Choza stream, located in upper basin of the Reconquista river, the second most polluted river of Argentina. Native juveniles Hyalella curvispina were used as test organisms evaluating survival, growth, oxidative stress parameters (SOD; CAT, TBARS) and the electron transport system (ETS) activity as early toxic effect. This study used methodologies and techniques that allow the assessment of sediment pollution with a native species as test organism and provided data to discuss the viability of sublethal endpoints as tools for freshwater sediment assessment. In spring and in summer two ten-day series of whole-sediment assays were conducted simultaneously: (a) standard assays and (b) biomarkers assays. A control sediment was ran simultaneously in which no--effect on survival was measured. In summer there was a significant increase in length and biomass in both exposed and control groups. In spring an inhibitory effect on growth and an increase in oxidative damage with a concomitant rise in antioxidant defenses, was observed in animals exposed to La Choza sediment. ETS measurement indicated a significant depression of metabolic activity of amphipods exposed to contaminated sediments. The measured biomarkers represent the first record for juvenile H. curvispina exposed to polluted natural sediments under standardized laboratory conditions. The used bioanalytical tools demonstrated higher sensitivity and a more accurate assessment of the effects than those obtained by the standard tests of survival and growth. We propose their adoption in biomonitoring of freshwater sediment toxicity.

Acute toxicity of cypermethrin to the non target organism Hyalella curvispina

The acute toxicity of cypermethrin to the amphipod Hyalella curvispina was evaluated by means of a toxicity test under laboratory conditions. Cypermethrin is one of the most widely used insecticides in Argentina. H. curvispina is a widely distributed and commonly abundant component of the invertebrate assemblages in shallow waters of southern South America. The experiments were repeated three times. The mean 48-h LC(50) value for H. curvispina was estimated at 0.066μg/l. H. curvispina represents a good model for exotoxicological risk assessment.

Age differential response of Hyalella curvispina to a cadmium pulse: influence of sediment particle size

In Argentina periurban streams frequently receive agricultural, livestock and industrial discharges. Heavy metals have been found in the water column and sediments of numerous water bodies of the pampean region, at levels above the limits established for aquatic life protection. This study aimed to evaluate the effect of a contaminant pulse of cadmium discharged into a water-sediment system of different particle sizes, by means of laboratory tests using juveniles and adults of Hyalella curvispina, a native amphipod. We found that the substrate particle size was a determining factor in the toxicity of cadmium and that the adults of H. curvispina were more sensitive than juveniles. We also observed a temporal difference between the two ages for the same type of sediment. Given the nature of the sediments of regional water bodies, it is expected that a discharge of cadmium, even at concentrations as low as those tested here, will affect the survival of native amphipods.

Bioavailability, ecotoxicity, and geological characteristics of trace lead in sediments from two sites on Negro River, Uruguay, South America

Bioassays of two sites along the Rio Negro in Uruguay indicate ecotoxicity, which could be attributable to trace concentrations of lead in river sediments. Monthly samples at two sites at Baygorria and Bonete locations were analyzed for both particle size and lead. Lead was determined by atomic spectrometry in river water and sediment and particle size by sieving and sedimentation. Data showed that Baygorria's sediments have greater percentage of clay than Bonete's (20.4 and 5.8%, respectively). Lead was measurable in Baygorria's sediments, meanwhile in Bonete's, it was always below the detection limit. In water samples, lead was below detection limit at both sites. Bioassays using sub-lethal growth and survival test with Hyalella curvispina amphipod, screening with bioluminescent bacteria Photobacterium leiognathi, and acute toxicity bioassay with Pimephales promelas fish indicated toxicity at Baygorria, with much less effect at Bonete. Even though no lethal effects could be demonstrated, higher sub-lethal toxicity was found in samples from Baygorria site, showing a possible concentration of the contaminant in the clay fraction.

An in situ test to explore the responses of Scenedesmus acutus and Lepocinclis acus as indicators of the changes in water quality in lowland streams

This bioassay was designed with the aim of exploring the responses of two wild planktonic microalgae exposed in situ (72 h) as indicators of the changes in water quality. Monocultures of both strains within dialysis membrane bags were placed at two sites in a small lowland stream. Site 1 is located at a suburban area with low horticultural activity and Site 2 is impacted by toxic industrial discharges and urban land use. There was a decrease in population growth of both species at Site 2 compared with Site 1. The comparison of the algae exposed in situ with the normal specimens cultured at the laboratory indicated a significant increase in the cellular volume for both species at both sites. Abnormal shape was recorded at both sites, the percentage being significantly greater for Scenedesmus acutus at Site 2. Significant changes in pyrenoids size were observed in S. acutus and in the percentage of fragmented nuclei in Lepocinclis acus. Also in the latter abnormal paramylon grains were observed. These responses were accentuated at Site 2. This bioassay was sensitive, short term, low cost, and therefore is a suitable tool to contribute with the monitoring and ecological risk assessment of lowland streams.

Taxonomic and nontaxonomic responses to ecological changes in an urban lowland stream through the use of Chironomidae (Diptera) larvae

Biotic descriptors--both taxonomic (diversity indices, species richness, and indicator species) and nontaxonomic (biomass, oxygen consumption/production, and anatomical deformities)--are useful tools for measuring a stream's ecological condition. Nontaxonomic parameters detect critical effects not reflected taxonomically. We analyzed changes in Chironomidae populations as taxonomic parameters and mentum deformities as a nontaxonomic parameter for evaluating a South-American-plains stream (Argentina). We performed samplings seasonally (March, June, September, and December; 2005) and physical and chemical measurements at three sampling sites of the stream (DC1 at river source, through DC3 downstream). The specimens collected in sediment and vegetation were analyzed to investigate mouth deformities in Chironomidae larvae. We identified a total of 9 taxa from Chironomidae and Orthocladiinae subfamilies. Shannon's diversity index for Chironomidae decreased from 1.6 bits ind⁻¹ (DC1) to 0.3 bits ind⁻¹ (DC3). The total density of the Chironomidae exhibited a great increase in abundance at site DC3, especially that of Chironomus calligraphus. Chironomidae taxonomic composition also changed among the three sites despite their spatial proximity: C. calligraphus, Goeldichironomus holoprasinus, Parachironomus longistilus, and Polypedilum were present at all three; Corynoneura and Paratanytarsu at DC1 only; Cricotopus at DC1 and DC3; Apedilum elachistus notably at DC2 and DC3; and Parametriocnemus only at DC2. C. calligraphus individuals from DC1 showed no mentum deformities; only 2 from DC2 exhibited mouth-structure alterations; while specimens from DC3 presented the most abnormalities, especially during autumn and late winter. Type-II deformities (supernumerary teeth and gaps) were the most common. Anatomical deformities are sublethal effects representing an early alert to chemically caused environmental degradation. Mentum deformities in benthic-Chironomidae larvae constitute an effective biological-surveillance tool for detecting adverse conditions in sediments and evaluating sediment-quality-criteria compliance. Taxonomic (community composition) and nontaxonomic (condition of larval mouth parts) descriptors, used together, can indicate a stream's ecological state.

Age-related differential sensitivity to cadmium in Hyalella curvispina (Amphipoda) and implications in ecotoxicity studies

The standardization of toxicity tests requires the selection of the most suitable test species and their developmental stages, as well as the selection of the appropriate assay matrix and the evaluation of the sensitivity of the test species to the reference toxicants. International protocols recommend the use of the amphipod Hyalella azteca from the Northern Hemisphere for sediment toxicity tests. We selected the widely distributed amphipod Hyalella curvispina, representative of pleustonic, epiphitic and zoobenthic assemblages in austral South America, as test species to be used in regional studies. Our goals were to evaluate the sensitivity of three developmental stages of H. curvispina to cadmium as a reference toxicant and to select the most suitable age and exposure time for aquatic ecotoxicity assessment. The three ages were highly susceptible to cadmium, with sensitivities: neonates > adults > juveniles. Our results validate the use of the native H. curvispina as a standard species for ecotoxicological assessment studies.

Effects of discharges from the textile industry on the biotic integrity of benthic assemblages

We explored the effects of a textile industry effluent on water quality, habitat quality and structural and functional responses of benthic communities in a lowland stream. Two sampling sites were selected: site 1 was located 300 m upstream of the outflow from the textile factory and site 2 was 500 m downstream from the discharge point. Samples of water, microbenthos, invertebrates and aquatic plants were taken seasonally. The effluent from the textile industry modified the structure of the microbenthic assemblages downstream, increased the density of organisms and the biomass of primary producers, but diminished the species richness. The oxygen consumption of the microbenthic community was 3 x higher downstream of the effluent and abnormal frustules of diatoms were noticed. The richness and abundance of invertebrate taxa were lower at the impacted site. The invertebrate modes of existence and the functional feeding groups were also significantly affected. This study is an important baseline for assessment of lowland streams with high water residence time and a notable development of hydrophytes. It will also provide a baseline for the monitoring and restoration, or remediation, programs using the metrics of biotic integrity, particularly in South American countries where such metrics are rarely employed.

In situ-based effects measures: determining the ecological relevance of measured responses

The aim of this review is to examine how the choice of test species and study design employed in the use of in situ approaches in ecological risk assessment can maximize the ecological relevance of data. We provide a framework to define and assess ecological relevance that permits study designs to remain focused on the ecological question being addressed. This framework makes explicit the linkages between effects at lower levels of biological organization and higher-order ecological effects at the population, community, and ecosystem levels. The usefulness of this framework is illustrated by reference to specific examples from aquatic ecotoxicology. The use of models as both interpretive and predictive tools is discussed, with suggestions of appropriate methods for different protection goals.

Linking in situ bioassays and population dynamics of macroinvertebrates to assess agricultural contamination in streams of the Argentine pampa

The two local crustacean species Hyalella curvispina and Macrobrachium borelli were chosen for assessment of agricultural contamination in two streams (Horqueta and Maguire) in the Argentine pampa. In parallel with in situ bioassays of both species, the population dynamics and the organismic drift of H. curvispina were investigated throughout the main period of insecticide application, from December 2001 to March 2002. In Maguire none of the current-use insecticides (chlorpyrifos, alpha-cypermethrin, and endosulfan) in question were detected throughout the sampling period. During 1-week intervals with no contamination by insecticides the survival rate of H. curvispina varied between 77 +/- 6% (+/- SE, n = 4) and 85 +/- 3%. In Horqueta during a week with a peak insecticide contamination of 64 microg/kg chlorpyrifos in the suspended particles, a mortality of 100% was observed in the in situ bioassays for both species, H. curvispina and M. borelli. At the same time, in Maguire H. curvispina showed reduced survival rates of 23 +/- 5% and 25 +/- 18% at the two sites, while the survival rate of M. borelli was 60 +/- 11% upstream and 93 +/- 5% downstream, below a wetland. During the period with 100% mortality of H. curvispina in Horqueta, the population density of this species decreased correspondingly, from 106 +/- 26 to 0 individuals/m(2). We conclude that in situ bioassays can be successfully linked to in-stream population dynamics for the same species and that this link is very useful for interpreting causal exposure-effect relationships.