Body composition assessment with ultrasound muscle measurement: optimization through the use of semi-automated tools in colorectal cancer.

Colorectal cancer (CRC) is a disease with a high prevalence and major impact on global health. Body composition (BC) data are of great importance in the assessment of nutritional status. Ultrasound (US) is an emerging, accessible and non-invasive technique that could be an alternative when it is not feasible to perform computed tomography (CT). The aim of this study is to evaluate the correlation between CT, as a reference technique, and US of the rectus femoris (RF) as a "proof of concept," in a cohort of patients with CRC and assess the optimisation of results obtained by US when performed by our new semi-automated tool. A single-centre cross-sectional study including 174 patients diagnosed with CRC and undergoing surgery was carried out at the Vall d'Hebron Hospital. We found a strong correlation between CT and US of the RF area (r = 0.67; p < 0.005). The latter, is able to discriminate patients with worse prognosis in terms of length of hospital stay and discharge destination (AUC-ROC = 0.64, p 0.015). These results improve when they are carried out with the automatic tool (area AUC-ROC = 0.73, p 0.023), especially when normalised by height and eliminating patients who associate overflow. According to our results, the US could be considered as a valuable alternative for the quantitative assessment of muscle mass when CT is not feasible. These measurements are improved when measuring software is applied, such as "Bat" software.

Mid-trimester uterine artery Doppler for aspirin discontinuation in pregnancies at high risk for preterm pre-eclampsia: Post-hoc analysis of StopPRE trial.

OBJECTIVE: To assess whether aspirin treatment can be discontinued in pregnancies with normal uterine artery pulsatility index (≤90th percentile) at 24-28 weeks. DESIGN: Post-hoc analysis of a clinical trial. SETTING: Nine maternity hospitals in Spain. POPULATION OR SAMPLE: Pregnant individuals at high risk of pre-eclampsia at 11-13 weeks and normal uterine artery Doppler at 24-28 weeks. METHODS: All participants received treatment with daily aspirin at a dose of 150 mg. Participants were randomly assigned, in a 1:1 ratio, either to continue aspirin treatment until 36 weeks (control group) or to discontinue aspirin treatment (intervention group), between September 2019 and September 2021. In this secondary analysis, women with a UtAPI >90th percentile at 24-28 weeks were excluded. The non-inferiority margin was set at a difference of 1.9% for the incidence of preterm pre-eclampsia. MAIN OUTCOME MEASURES: Incidence of preterm pre-eclampsia. RESULTS: Of the 1611 eligible women, 139 were excluded for UtAPI >90th percentile or if UtAPI was not available. Finally, 804 were included in this post-hoc analysis. Preterm pre-eclampsia occurred in three of 409 (0.7%) women in the aspirin discontinuation group and five of 395 (1.3%) women in the continuation group (-0.53; 95% CI -1.91 to 0.85), indicating non-inferiority of aspirin discontinuation. CONCLUSIONS: Discontinuing aspirin treatment at 24-28 weeks in women with a UtAPI ≤90th percentile was non-inferior to continuing aspirin treatment until 36 weeks for preventing preterm pre-eclampsia.

Clinical effectiveness of routine first-trimester combined screening for pre-eclampsia in Spain with the addition of placental growth factor.

INTRODUCTION: Pre-eclampsia affects 2%-8% of pregnancies and is one of the leading causes of maternal and perinatal morbidity and mortality. First-trimester screening using an algorithm that combines maternal characteristics, mean arterial blood pressure, uterine artery pulsatility index and biomarkers (pregnancy-associated plasma protein-A and placental growth factor) is the method that achieves a greater diagnostic accuracy. It has been shown that daily salicylic acid administration before 16 weeks in women at a high risk for pre-eclampsia can reduce the incidence of preterm pre-eclampsia. However, no previous studies have evaluated the impact of routine first-trimester combined screening for pre-eclampsia with placental growth factor after being implemented in the clinical practice. MATERIAL AND METHODS: This was a multicenter cohort study conducted in eight different maternities across Spain. Participants in the reference group were prospectively recruited between October 2015 and September 2017. Participants in the study group were retrospectively recruited between March 2019 and May 2021. Pre-eclampsia risk was calculated between 11+0 and 13+6 weeks using the Gaussian algorithm combining maternal characteristics, mean arterial pressure, uterine arteries pulsatility index, pregnancy-associated plasma protein-A and placental growth factor. Patients with a risk greater than 1/170 were prescribed daily salicylic acid 150 mg until 36 weeks. Patients in the reference group did not receive salicylic acid during gestation. RESULTS: A significant reduction was observed in preterm pre-eclampsia (OR 0.47; 95% CI: 0.30-0.73), early-onset (<34 weeks) pre-eclampsia (OR 0.35; 95% CI: 0.16-0.77), preterm small for gestational age newborn (OR 0.57; 95% CI: 0.40-0.82), spontaneous preterm birth (OR 0.72; 95% CI: 0.57-0.90), and admission to intensive care unit (OR 0.55; 95% CI: 0.37-0.81). A greater treatment adherence resulted in a significant reduction in adverse outcomes. CONCLUSIONS: Routine first-trimester screening for pre-eclampsia with placental growth factor leads to a reduction in preterm pre-eclampsia and other pregnancy complications. Aspirin treatment compliance has a great impact on the effectiveness of this screening program.

Aspirin Discontinuation at 24 to 28 Weeks' Gestation in Pregnancies at High Risk of Preterm Preeclampsia: A Randomized Clinical Trial.

Importance: Aspirin reduces the incidence of preterm preeclampsia by 62% in pregnant individuals at high risk of preeclampsia. However, aspirin might be associated with an increased risk of peripartum bleeding, which could be mitigated by discontinuing aspirin before term (37 weeks of gestation) and by an accurate selection of individuals at higher risk of preeclampsia in the first trimester of pregnancy. Objective: To determine whether aspirin discontinuation in pregnant individuals with normal soluble fms-like tyrosine kinase-1 to placental growth factor (sFlt-1:PlGF) ratio between 24 and 28 weeks of gestation was noninferior to aspirin continuation to prevent preterm preeclampsia. Design, Setting, and Participants: Multicenter, open-label, randomized, phase 3, noninferiority trial conducted in 9 maternity hospitals across Spain. Pregnant individuals (n = 968) at high risk of preeclampsia during the first-trimester screening and an sFlt-1:PlGF ratio of 38 or less at 24 to 28 weeks of gestation were recruited between August 20, 2019, and September 15, 2021; of those, 936 were analyzed (intervention: n = 473; control: n = 463). Follow-up was until delivery for all participants. Interventions: Enrolled patients were randomly assigned in a 1:1 ratio to aspirin discontinuation (intervention group) or aspirin continuation until 36 weeks of gestation (control group). Main Outcomes and Measures: Noninferiority was met if the higher 95% CI for the difference in preterm preeclampsia incidences between groups was less than 1.9%. Results: Among the 936 participants, the mean (SD) age was 32.4 (5.8) years; 3.4% were Black and 93% were White. The incidence of preterm preeclampsia was 1.48% (7/473) in the intervention group and 1.73% (8/463) in the control group (absolute difference, -0.25% [95% CI, -1.86% to 1.36%]), indicating noninferiority. Conclusions and Relevance: Aspirin discontinuation at 24 to 28 weeks of gestation was noninferior to aspirin continuation for preventing preterm preeclampsia in pregnant individuals at high risk of preeclampsia and a normal sFlt-1:PlGF ratio. Trial Registration: ClinicalTrials.gov Identifier: NCT03741179 and ClinicalTrialsRegister.eu Identifier: 2018-000811-26.

Shared risk factors for COVID-19 and preeclampsia in the first trimester: An observational study.

INTRODUCTION: The association between preeclampsia and coronavirus disease 2019 (COVID-19) is under study. Previous publications have hypothesized the existence of shared risk factors for both conditions or a deficient trophoblastic invasion as possible explanations for this association. The primary aim of this study was to examine baseline risk factors measured in the first-trimester combined screening for preeclampsia in pregnant women with COVID-19 compared with the general population. A secondary aim of this study was to compare risk factors among patients with mild and severe COVID-19. MATERIAL AND METHODS: This was an observational retrospective study conducted at Vall d'Hebron Hospital Campus (Catalonia, Spain). Study patients were 231 pregnant women undergoing the first-trimester screening for preeclampsia and positive for severe acute respiratory syndrome coronavirus 2 between February 2020 and September 2021. The reference cohort were 13 033 women of the general population from six centers across Catalonia from May 2019 to June 2021. Based on the need for hospitalization, patients were classified in two groups: mild and severe COVID-19. First-trimester screening for preeclampsia included maternal history, mean arterial blood pressure, mean uterine artery pulsatility index (UtAPI), placental growth factor (PlGF), and pregnancy-associated plasma protein-A (PAPP-A). RESULTS: The proportion of cases at high risk for preeclampsia was significantly higher among the COVID-19 group compared with the general population (19.0% and 13.2%, respectively; p = 0.012). When analyzing risk factors for preeclampsia individually, women with COVID-19 had higher median body mass index (25.2 vs 24.5, p = 0.041), higher UtAPI multiple of the median (MoM) (1.08 vs 1.00, p < 0.001), higher incidence of chronic hypertension (2.8% vs 0.9%, p = 0.015), and there were fewer smokers (5.7% vs 11.6%, p = 0.007). The MoMs of PlGF and PAPP-A did not differ significantly between both groups (0.96 vs 0.97, p = 0.760 and 1.00 vs 1.01, p = 0.432; respectively). CONCLUSIONS: In patients with COVID-19, there was a higher proportion of women at high risk for preeclampsia at the first-trimester screening than in the general population, mainly because of maternal risk factors, rather than placental signs of a deficient trophoblastic invasion.

Implementation of routine first-trimester combined screening for preeclampsia based on the Gaussian algorithm: A clinical effectiveness study.

OBJECTIVE: To evaluate the clinical effectiveness of the routine first-trimester screening for preeclampsia (PE) after being implemented in six Catalan maternities. METHODS: Participants in the reference group were recruited prospectively between October 2015 and September 2017. Participants in the study group were recruited retrospectively between November 2018 and May 2019, after implementing the screening program. PE risk was assessed between 11 + 0 and 13 + 6 weeks of gestation using the Gaussian algorithm combining maternal characteristics, mean arterial blood pressure, uterine artery pulsatility index, and maternal serum pregnancy-associated plasma protein-A. Women with a risk ≥1/137 were prescribed daily salicylic acid (150 mg) until 36 weeks of gestation. RESULTS: Preterm PE occurred in 30 of 2641 participants (1.14%) in the reference group, as compared with 18 of 2848 participants (0.63%) in the study group (OR: 0.55; 95% CI, 0.31-0.99; P = 0.045). In the reference group, 37 participants (1.40%) were admitted to ICU, as compared with 23 participants (0.81%) in the study group (OR: 0.57; 95% CI, 0.34-0.96; P = 0.035). CONCLUSION: The routine first-trimester PE screening can be implemented in a public healthcare setting, leading to a significant reduction in the incidence of preterm PE and of maternal ICU admission.

Effects of the interaction between nutrient concentration and DIN:SRP ratio on geosmin production by freshwater biofilms.

The global increase of cyanobacterial blooms occurrence has been associated with the presence of compounds that generate earthy and musty odor in freshwater systems, among which geosmin stands out. The lack of information on the factors associated to geosmin production by benthic organisms has driven the development of this study, whose main goal is to determine the effects of nutrient concentration and DIN:SRP ratio on geosmin formation and release. The experiment was performed in 18 microcosms under controlled conditions for 21 days, using a natural biofilm suspension from Ter river (NE, Spain) to promote biofilm settlement. Six treatments were set crossing three DIN:SRP ratios (A = 4:1, B = 16:1 and C = 64:1) with two nutrient concentrations (Low and High). After 7 days of experiment, geosmin was detected in biofilm, being higher under high nutrient concentration and low DIN:SRP ratio conditions. In this treatment, geosmin in biofilm reached its maximum concentration at day 16 (3.8 ± 0.9 ng/mg), decreasing at the end of the experiment (21d) due to cyanobacteria detachment and geosmin release into the water (136 ± 6 ng/L). Overall, this experimental study showed that high nutrient concentration and low DIN:SRP ratio favored the Oscillatoria genus development within biofilm communities, generating the optimal conditions for geosmin production. The interaction between these two factors was demonstrated to be a potential driver of benthic geosmin production and release, and should be monitored and controlled in rivers exploited for drinking water purposes.

Water Flow and Light Availability Influence on Intracellular Geosmin Production in River Biofilms.

Hydro-morphological alterations in water bodies caused by climate change and human activities affects the ecosystem functioning and generate important water quality problems. Some of these alterations can generate an increase in cyanobacterial blooms, which are associated with the appearance of bad taste and odorous compounds such as geosmin. The factors that trigger their production are still unclear, and this inability to predict geosmin episodes provokes economic problems for water supply companies. This study aims to evaluate the effects of water flow and light availability on biofilm development and intracellular geosmin formation. A mesocosm experiment was performed between February-April, 2019. The mesocosms were a set of 10 outdoor 3 m long flumes, with a continuous water supply from the Ter river (Catalonia, NE Spain). Two light intensities were established: natural light and light reduced to 80%, combined with five gradual water flows from 0.09 to 1.10 L/s. Water samples were taken to analyze nutrients, and biofilm samples, to analyze geosmin concentration, chlorophyll a and the community. Geosmin in biofilm was detected in those treatments in which Oscillatoria sp. appeared. The concentration of intracellular geosmin was higher at lower water flows (0.09 and 0.18 L/s), and the highest (2.12 mg/g) was found in the flume with the lowest water flow (0.09 L/s) and irradiation (20%). This flume was the one that presented a greater concentration of Oscillatoria sp. (21% of the community). It stands out that, when geosmin in biofilm was found, the dissolved inorganic nitrogen and soluble reactive phosphorus ratio decreased, from an average of 417:1 to 14:1. This was mainly due to an increase in inorganic phosphorus concentration generated by a change in the nutrient uptake capacity of the community's biofilm. The results obtained in this study indicated the potential implications for stream ecosystem management to control geosmin appearance. Likewise, they could be used as an early warning system, establishing that in times of drought, which lead to a general decrease in river water flow, the situation could be optimal for the appearance and development of geosmin producing cyanobacteria in low-flow areas near the river banks.

Pharmaceuticals and pesticides in reclaimed water: Efficiency assessment of a microfiltration-reverse osmosis (MF-RO) pilot plant.

Water reuse is becoming a common practice in several areas in the world, particularly in those impacted by water scarcity driven by climate change and/or by rising human demand. Since conventional wastewater treatment plants (WWTPs) are not able to efficiently remove many organic contaminants and pathogens, more advanced water treatment processes should be applied to WWTP effluents for water reclamation purposes. In this work, a pilot plant based on microfiltration (MF) followed by reverse osmosis (RO) filtration was applied to the effluents of an urban WWTP. Both the WWTP and the pilot plant were investigated with regards to the removal of a group of relevant contaminants widely spread in the environment: 28 pharmaceuticals and 20 pesticides. The combined treatment by the MF-RO system was able to quantitatively remove the target micropollutants present in the WWTP effluents to values either in the low ng/L range or below limits of quantification. Monitoring of water quality of reclaimed water and water reclamation sources is equally necessary to design the most adequate treatment procedures aimed to water reuse for different needs.

Assessment of multi-chemical pollution in aquatic ecosystems using toxic units: compound prioritization, mixture characterization and relationships with biological descriptors.

Chemical pollution is typically characterized by exposure to multiple rather than to single or a limited number of compounds. Parent compounds, transformation products and other non-targeted compounds yield mixtures whose composition can only be partially identified by monitoring, while a substantial proportion remains unknown. In this context, risk assessment based on the application of additive ecotoxicity models, such as concentration addition (CA), is rendered somewhat misleading. Here, we show that ecotoxicity risk information can be better understood upon consideration of the probabilistic distribution of risk among the different compounds. Toxic units of the compounds identified in a sample fit a lognormal probability distribution. The parameters characterizing this distribution (mean and standard deviation) provide information which can be tentatively interpreted as a measure of the toxic load and its apportionment among the constituents in the mixture (here interpreted as mixture complexity). Furthermore, they provide information for compound prioritization tailored to each site and enable prediction of some of the functional and structural biological variables associated with the receiving ecosystem. The proposed approach was tested in the Llobregat River basin (NE Spain) using exposure and toxicity data (algae and Daphnia) corresponding to 29 pharmaceuticals and 22 pesticides, and 5 structural and functional biological descriptors related to benthic macroinvertebrates (diversity, biomass) and biofilm metrics (diatom quality, chlorophyll-a content and photosynthetic capacity). Aggregated toxic units based on Daphnia and algae bioassays provided a good indication of the pollution pattern of the Llobregat River basin. Relative contribution of pesticides and pharmaceuticals to total toxic load was variable and highly site dependent, the latter group tending to increase its contribution in urban areas. Contaminated sites' toxic load was typically dominated by fewer compounds as compared to cleaner sites where more compounds contribute.

Hydrological variation modulates pharmaceutical levels and biofilm responses in a Mediterranean river.

The Llobregat is a Mediterranean river that is severely impacted by anthropogenic pressures. It is characterized by high flow variability which modulates its chemical and biological status. The present work evaluates the effects of flow changes on the concentration of pharmaceutically active compounds (PhACs) and their relationship to cellular parameters of river biofilms. To this end, at two selected sampling sites at the lower course of the Llobregat river, surface water samples were collected twice a week over two hydrologically different periods exhibiting low and high river flows. Higher levels of PhACs were detected at the downstream sampling site. Irrespective of the flow regime, analgesics, anti-inflammatories and lipid regulators were the most abundant substances at both sampling sites with total concentrations of up to 1,000 ng/L and 550 ng/L at the upstream and downstream sites, respectively. Antibiotics (fluoroquinolones) and psychiatric treatment drugs were also detected at high levels in the second campaign achieving concentrations of up to 500 ng/L. The principal component analysis (PCA) performed with the PhACs concentrations of the two campaigns revealed differences in the various therapeutic groups depending on sampling site and period. After a flash flood event during the second sampling period, dilution of PhACs occurred, but their average concentrations measured before the flood were restored within two weeks. For the majority of compounds, PhAC concentrations displayed an inverse relationship with river discharge The effects of water containing different concentrations of PhACs on biofilm communities were evaluated and related to flow regime variations. Translocation of biofilm communities from a less to a more polluted site of the river demonstrated an increase in bacteria mortality in the translocated biofilms. After the flood, extracellular peptidase activity and chlorophyll-a concentration were significantly reduced, and biofilm growth rate was significantly lower.

Establishing potential links between the presence of alkylphenolic compounds and the benthic community in a European river basin.

INTRODUCTION: Concentrations of alkylphenolic compounds (APCs) in water and sediments were related to the composition and functional descriptors of the benthic community (biofilm and macroinvertebrates). MATERIALS AND METHODS: Samples were collected in four sampling campaigns at seven sampling points in the lower Llobregat catchment area (NE Spain). Water and sediment samples underwent chemical target analysis for nine APCs, which are known to disrupt the endocrine system. RESULTS AND DISCUSSIONS: APCs were the main stressors on the diatom community but not on the macroinvertebrate community. CONCLUSIONS: Benthic invertebrates were mostly affected by the general physicochemical water characteristics (where conductivity was a surrogate). Nonylphenol only had an influence on the diatom community in water but not in the remaining compartments, probably because of the low concentrations observed in the environment.

Triclosan persistence through wastewater treatment plants and its potential toxic effects on river biofilms.

Triclosan is a commonly used bactericide that survives several degradation steps in WWTP (wastewater treatment plants) and potentially reaches fluvial ecosystems. In Mediterranean areas, where water scarcity results in low dilution capacity, the potential environmental risk of triclosan is high. A set of experimental channels was used to examine the short-term effects of triclosan (from 0.05 to 500µgL⁻¹) on biofilm algae and bacteria. Environmentally relevant concentrations of triclosan caused an increase of bacterial mortality with a no effect concentration (NEC) of 0.21µgL⁻¹. Dead bacteria accounted for up to 85% of the total bacterial population at the highest concentration tested. The toxicity of triclosan was higher for bacteria than algae. Photosynthetic efficiency was inhibited with increasing triclosan concentrations (NEC=0.42µgL⁻¹), and non-photochemical quenching mechanisms decreased. Diatom cell viability was also affected with increasing concentrations of triclosan. Algal toxicity may be a result of indirect effects on the biofilm toxicity, but the clear and progressive reduction observed in all the algal-related endpoints suggest the existence of direct effects of the bactericide. The toxicity detected on the co-occurring non-target components of the biofilm community, the capacity of triclosan to survive through WWTP processes and the low dilution capacity that characterizes Mediterranean systems extend the relevance of triclosan toxicity beyond bacteria in aquatic habitats.

Fluvial biofilms: A pertinent tool to assess beta-blockers toxicity.

Among increasingly used pharmaceutical products, beta-blockers have been commonly reported at low concentrations in rivers and littoral waters of Europe and North America. Little is known about the toxicity of these chemicals in freshwater ecosystems while their presence may lead to chronic pollution. Hence, in this study the acute toxicity of 3 beta-blockers: metoprolol, propranolol and atenolol on fluvial biofilms was assessed by using several biomarkers. Some were indicative of potential alterations in biofilm algae (photosynthetic efficiency), and others in biofilm bacteria (peptidase activity, bacterial mortality). Propranolol was the most toxic beta-blocker, mostly affecting the algal photosynthetic process. The exposure to 531microg/L of propranolol caused 85% of inhibition of photosynthesis after 24h. Metoprolol was particularly toxic for bacteria. Though estimated No-Effect Concentrations (NEC) were similar to environmental concentrations, higher concentrations of the toxic (503microg/L metoprolol) caused an increase of 50% in bacterial mortality. Atenolol was the least toxic of the three tested beta-blockers. Effects superior to 50% were only observed at very high concentration (707mg/L). Higher toxicity of metoprolol and propranolol might be due to better absorption within biofilms of these two chemicals. Since beta-blockers are mainly found in mixtures in rivers, their differential toxicity could have potential relevant consequences on the interactions between algae and bacteria within river biofilms.

Bridging levels of pharmaceuticals in river water with biological community structure in the Llobregat River basin (northeast Spain).

A wide range of human pharmaceuticals are present at low concentrations in freshwater systems, particularly in sections of polluted river. These compounds show high biological activity, often associated with a high stability. These characteristics imply a potential impact of these substances on aquatic biota even when present at low environmental concentrations. Low flow conditions in Mediterranean rivers, most of which flow through densely populated areas and are subjected to intensive water use, increase the environmental risk of these emergent compounds. Here, we studied whether pharmaceuticals in river water affect the local benthic community structure (diatoms and invertebrates). For this purpose, we analyzed the occurrence of pharmaceuticals along the Llobregat River and examined the benthic community structure (diatoms and invertebrates) of this system. Some pharmaceutical products in the Llobregat River registered concentrations greater than those cited in the literature. Multivariate analyses revealed a potential causal association between the concentrations of some anti-inflammatories and beta-blockers and the abundance and biomass of several benthic invertebrates (Chironomus spp. and Tubifex tubifex). Further interpretation in terms of cause-and-effect relationships is discussed; however, it must be always taken with caution because other pollutants also may have significant contributions. Combined with further community experiments in the laboratory, our approach could be a desirable way to proceed in future risk management decisions.

Effects of low concentrations of the phenylurea herbicide diuron on biofilm algae and bacteria.

A system of recirculating channels was used in this study to examine the long-term effects (29d) of environmentally realistic concentrations of the herbicide diuron (from 0.07 to 7 microg L(-1)) on biofilm communities. The autotrophic activity of biofilms was affected by this herbicide, as reflected by a marked decrease in the photosynthetic efficiency. Diuron exposure also increased chlorophyll-a content and reduced the biovolume of diatom taxa at low concentrations. The effects on bacteria were also remarkable. Bacterial abundance was reduced after a week of exposure to the herbicide at a range of concentrations. Effects were on the number of live bacteria and on the increase in the leucine-aminopeptidase activity. It is suggested that inputs of herbicides to the river ecosystem at low concentrations may cause a chain of effects in the biofilm, which include inhibitory effects on algae but also indirect effects on the relationships between biofilm components.

Monitoring the effect of chemicals on biological communities. The biofilm as an interface.

Biofilms can be regarded as early warning systems for detection of the effects of toxicants on aquatic systems, because they have been successfully used for detection of other environmental stressors (e.g. pH, salinity, organic pollution). A variety of methods is used for detection of the effects of toxicants by use of biofilms. The methods range from structurally-based to functionally-based, and from in vitro-based to systemic approaches. Physiological approaches may be appropriate for detection of acute effects. Among these methods, photosynthesis is more related to the effect of toxicants affecting algal communities, directly or indirectly, and extracellular enzyme activity is less specific. Selecting one or the other may depend on the suspected direct effect of the toxicant. Integrated studies have revealed the relevance of toxicants to top-down or bottom-up regulation of the biofilm community. Persistent or chronic effects should affect other biofilm indicators, for example growth or biomass-related factors (e.g. chlorophyll), or community composition. Among these, community composition might better reflect the effects of the toxicant(s), because this may cause a shift from a sensitive to a progressively tolerant community. Community composition-based approaches do not usually adequately reflect cause-effect relationships and require complementary analysis of properties affected in the short-term, for example physiological properties. The current array of methods available must be wisely combined to disentangle the effects of chemicals on biofilms, and whether these effects are transient or persistent, to successfully translate the chemical action of toxicants into the effect they might have on the river ecosystem.