Benthic Community Indices Research Articles

Distribution characteristics of microorganisms in sediments of Dagu River and their biological indicator function for evaluating eco-environmental quality of rural river

The microorganisms in sediments play a crucial role in biogeochemical cycle processes, and numerous studies have shown that microbial community is closely related to environmental factors. However, the usability of sediment microorganisms to evaluate the eco-environment quality of rural rivers has not been adequately explored. This study investigated the distribution characteristics and response of sediment microorganisms to environmental parameters and benthic organisms. Based on the environmental parameters and benthic community indices, the 12 stations were divided into high-polluted group A, moderate-polluted group B and low-polluted group C. Station DG01 and DG02 in group A had the highest level of As and Ni pollution and nutrient concentration, and DG09 in group A had the lowest benthic diversity. Correspondingly, group A had the lowest abundance of Proteobacteria, which has a higher requirement for the environment than Planctomycetes. Group B had the highest sulfide level (97.45 mg/kg), and bacteria (Thiobacillus, Sulfurisoma and Sulfuritalea) with genes involved in sulfur cycling were more enriched in this group. Group C had the lowest level of total nitrogen (243.36 mg/kg), and Rhodanobacteraceae in Xanthomonadales might be a key bioindicator for low nitrogen. In addition, Chlorophyta was found to be more susceptible to heavy metals, and moreover co-occurrence networks showed that microeukaryotes were more sensitive to heavy metal pollution compared to benthic animals and prokaryotes. Therefore, this study suggested that benthic microorganisms especially microeukaryotes could be used as good indicators for evaluating the eco-environmental quality of rural rivers.

Benthic Macroinvertebrates and Zooplankton Communities as Ecological Indicators in Urban Wetlands of Argentina

Urban aquatic ecosystems are important sources of fresh water for multiple uses, but often receive a point or diffuse anthropic contamination. Benthic and zooplankton invertebrates are sensitive to water quality, being good indicators of ecosystem health. In this study, the composition and structure of benthic and zooplankton communities and environmental variables were analyzed seasonally in six urban wetlands of Santa Fe City (Argentina). We present the effect of water quality on both communities as bioindicators of ecological conditions, using different community attributes, functional feeding groups, and biotic indices. For the benthic community, the Macroinvertebrate Index for Pampean Rivers (IMRP) and the Benthic Community Index (BCI) were selected. For the zooplankton community, abundance of rotifers/abundance of total zooplankters, microcrustaceans/total zooplankters, cladocerans/total zooplankters, and macrozooplankton/microzooplankton ratios were applied. A functional feeding groups (FFGs) classification, adapted from the literature, is proposed for zooplankters. The urban wetlands showed a gradient from the most to the least disturbed sites. Some benthic and zooplankton species were identified as excellent bioindicators of pollution, and the FFGs and biotic indices revealed the ecological condition of each urban wetland. The present study contributes to the enhancement of management practices in urban landscapes aiming to maintain ecosystem services in sustainable cities.

Campsurus truncatus Ulmer, 1920 (Polymitarcyidae): an Ephemeroptera in eutrophic waters

Abstract: Aim The order Ephemeroptera, together with Trichoptera and Plecoptera, has been considered as sensitive in environmental quality assessment. However, the species Campsurus truncatus Ulmer 1920 (Polymitarcyidae) has been sampled in anthropically altered sites. In this paper, data on the occurrence of that species in the water quality monitoring network of the Environmental Agency of São Paulo State (CETESB) were gathered to review its position in the environmental gradient and in the quality assessment of rivers and reservoirs. Methods For this, a compilation of the occurrences and densities of Campsurus obtained in rivers and reservoirs of São Paulo state between 2001 and 2018, with grab samplers, was carried. Environmental factors, the Trophic State Index (TSI) and the Benthic Community Index (BCI) were related to the species densities to define its environmental requirements. Results The sublittoral zone of reservoirs was the most common habitat to C. truncatus, occurring more frequently at mesotrophic sites with fair ecological quality. Higher mean densities were recorded at eutrophic sites with good ecological quality conditions. The statistical analysis did not show linear correlation between C. truncatus densities and any of the analyzed environmental variable such as grain size, organic matter content, DO and light penetration, although there was a tendency for higher species densities occur in muddy, dark sediments and with intermediate levels of organic matter. As described in literature the presence of aquatic plants can actually benefit that population once the highest densities were observed in sites with many macrophytes, as Salto Grande reservoir, but it may be confusing the relationship between population density and environmental factors. Conclusions The high occurrence and densities of C. truncatus obtained in eutrophic environments suggest that the species should not be considered as a sensitive taxon in qualitative indexes, such as the BCI for rivers and the sublittoral region of reservoirs. Moreover, its exclusion from the richness of sensitive groups had low impact on the diagnoses already performed at the CETESB monitoring network.

Benthic macroinvertebrates as bioindicators of water quality in Billings Reservoir fishing sites (SP, Brazil)

Abastract: Aim The Billings Reservoir is the largest reservoir in the metropolitan region of São Paulo and has multiple uses, including artisanal fishing. Its surroundings present intense occupation, resulting in various environmental impacts. Although the water is degraded, affecting the composition and quality of the fish, this reservoir supports artisanal fishermen who survive through this activity. This study aimed to analyze the water quality in the main sites of artisanal fishing activity, with an emphasis on the benthic community as a bioindicator. Methods Three sampling sites were selected, in which water and zoobenthos samples were collected monthly from April 2012 to March 2013. Water analyses consisted of the determination of pH, temperature, conductivity, turbidity, total dissolved solids, dissolved oxygen, total nitrogen, total phosphorus, and trophic state as well as a principal components analysis. The zoobenthos analysis consisted of determining the relative abundance and total density of taxa, the Shannon-Weaver diversity index, taxa richness, uniformity, Simpson’s dominance index, and the benthic community index and conducting a canonical correspondence analysis. The non-parametric Kruskal-Wallis test followed by the Student-Newman-Keuls test were used to investigate the existence of significant differences in the abiotic and biotic variables among the sites. Results The studied sites showed a high degree of eutrophication, with nitrogen and phosphorus totals levels above the limits defined by current Brazilian legislation. Taquacetuba (P1) showed the best environmental conditions for the development of fishing activity, with the presence of sensitive organisms (Polymitarcyidae) and higher levels of dissolved oxygen. Alvarenga (P2) had the worst water quality, with a predominance of tolerant organisms (Oligochaeta) and lower levels of dissolved oxygen. Conclusion In conclusion, the benthic community in association with abiotic metrics proved to be a useful tool as a bioindicator of environmental conditions, indicating that fishing activity at Alvarenga is not recommended due to the degradation of water quality.

Comparing two biological indexes using benthic macroinvertebrates: positive and negative aspects of water quality assessment

Abstract: Aim The aim of the present study, was to apply two biological indexes based on benthic macroinvertebrates (BMWP and ICB RES-P) using as model the Itupararanga Reservoir to know what the advantages and disadvantages of the application of each index in that environment. Methods The methodology consisted on three stages: 1) macroinvertebrates sampling and determination of limnological variables in situ, and sorting of the organisms in laboratory, 2) taxonomic identification of organisms and 3) determination of the saprobic degree for the collection sites and effectiveness of the application of the BMWP (Biological Monitoring Working Party score system) index and the Benthic Community Index created by CETESB (Environmental Sanitary Company of State of São Paulo) for deep regions (ICB RES-P index). Results The study was performed over two periods (spring/summer and autumn/winter), and 8,841 organisms were sampled and divided in 17 families. The Chaoboridae (genus Chaoborus), Chironomidae (subfamilies Chironominae and Tanypodinae) and Tubificidae families had the most abundant taxa. The saprobic degree of the Itupararanga reservoir region resulted in the general classification of the reservoir as β-α mesasaprobic (βms- αms), considered critical due to its organic charge content. The BMWP index was adapted to the sample points and the scores subsequently obtained ranked the reservoir as category V, representing very poor water quality. The ICB RES-P index classified the sample points in the spring/summer period as having regular water quality, and the autumn/winter period as having good water quality. Conclusions From previous findings, it can be concluded that further study and refinement of the components of both indexes are required in order to effectively assess the quality of water in reservoirs.

Evaluation of suitability and comparability of stream assessment indices using macroinvertebrate data sets from the Northern Lakes and Forests Ecoregion

Researchers and managers within the Upper Midwest currently use a variety of sampling methodologies and biological indices to assess ecological condition of stream systems. With multiple entities collecting bioassessment data it is important that we determine the comparability of data and the indices derived from these data for effective assessment of natural systems. In this study we assessed the similarity of data collected by different agencies and we focused on data from one watershed to examine the outputs of different indices for stream assessment, and the temporal variation of index score within sites. We compared duplicate macroinvertebrate community data collected by the Little River Band of Ottawa Indians and the Michigan Department of Environmental Quality for overall community composition and index scores derived from these data. Duplicate samples were similar in composition index scores. Taxonomic resolution was addressed and indicated that genus level resolution gives a more favorable score when using indices. We also evaluated the utility of currently available macroinvertebrate indices of biotic integrity to assess data from the Big Manistee River watershed. The indices evaluated were the Hilsenhoff biotic index, the benthic community index for the Northern Lakes and Forests (NLFBCI), the Great Lakes Environmental Assessment Survey (GLEAS) procedure 51 for macroinvertebrates and a biological condition gradient model for the Upper Midwest. Outputs from the indices were moderately correlated (Spearman rank order correlation, r=0.35–0.698) though they indicated different assessments of overall site integrity. Compared with larger scale regional indices, locally calibrated indices generally classified sites as having better biological condition. Replicate samples collected within sites indicated the GLEAS had higher levels of variability (0–265%CV) within sites than the other indices (<10%CV). Data from long-term (10 year) monitoring stations were used to evaluate seasonal and long-term index performance. There were differences in index score classifications from spring and fall samples indicating that standardization of sampling time is necessary for comparative analysis. Temporal trends over 10 years reveal natural variation and set the baseline for evaluating the influence of anthropogenic effects. Overall, results indicate that choice of index can alter assessment of site condition. For bioassessment in the Big Manistee River watershed the NLFBCI performs well and accurately reflects site condition.

Effects of Trout Farm Effluent on Water Quality and the Macrobenthic Invertebrate Community of the Zayandeh‐Roud River, Iran

AbstractTo investigate the environmental impact of fish farm discharge on the Zayandeh‐Roud River in Iran, three trout farms (Dimeh, Hojat Abad, and Takab) with three different production capacities were studied by examining water physicochemical criteria and the macrobenthic invertebrate community. Six sampling sites were assigned to each farm: the inflow and outflow of the farm, the outfall into the river, 50 m upstream from the outfall (control), 50–100 m downstream from the outfall, and 1 km downstream from the outfall. Water and benthos samples were collected once during autumn, winter, and spring. Benthic samples were collected by using a quantitative technique (3 replicates/site). Results showed a significant (P &lt; 0.05) increase in 5‐d biochemical oxygen demand, chemical oxygen demand, and total suspended solids and a decline in dissolved oxygen concentration and pH in the outflow. However, concentrations of measured variables at each farm were generally within acceptable limits. Total taxonomic richness, abundance of Ephemeroptera, Plecoptera, and Trichoptera (EPT), and richness of EPT taxa were considerably lower at outflow stations than at inflow stations, especially for the farm with a higher production rate. In contrast to physicochemical results, the benthic community indices were significantly different between upstream and downstream samples. Sensitive taxa declined at downstream sites in comparison with upstream sites, while abundance of tolerant taxa (e.g., Chironomidae and Oligochaeta) increased at downstream sites. Although species richness and diversity improved farther downstream, the recovery was not complete within our study range. However, effluent effects were greatest during periods of low river flow. Thus, to reduce environmental impacts of aquaculture, production rates should be based on the lowest anticipated flow rate of rivers.

The New Bedford Harbor Superfund site long-term monitoring program (1993–2009)

New Bedford Harbor (NBH), located in southeastern Massachusetts, was designated as a marine Superfund site in 1983 due to sediment contamination by polychlorinated biphenyls (PCBs). Based on risks to human health and the environment, the first two phases of the site cleanup involved dredging PCB-contaminated sediments from the harbor. Therefore, a long-term monitoring program (LTM) was developed to measure spatial and temporal chemical and biological changes in sediment, water, and biota to assess the effects and effectiveness of the remedial activities. A systematic, probabilistic sampling design was used to select sediment sampling stations. This unbiased design allowed the three segments of the harbor to be compared spatially and temporally to quantify changes resulting from dredging the contaminated sediments. Sediment was collected at each station, and chemical (e.g., PCBs and metals), physical (e.g., grain size), and biological (e.g., benthic community) measurements were conducted on all samples. This paper describes the overall NBH-LTM approach and the results from the five rounds of sample collections. There is a decreasing spatial gradient in sediment PCB concentrations from the northern boundary (upper harbor) to the southern boundary (outer harbor) of the site. Along this same transect, there is an increase in biological condition (e.g., benthic community diversity). Temporally, the contaminant and biological gradients have been maintained since the 1993 baseline collection; however, since the onset of full-scale remediation, PCB concentrations have decreased throughout the site, and one of the benthic community indices has shown significant improvement in the lower and outer harbor areas.

Integrated assessment of trace pollutants associated with the Korean coastal environment: Exampled from the sediment TIE and triad approaches

Here we present our triad approach followed by major findings based on sediment pollution studies that determined the chemical concentration, biological effect, and community structure associated with trace pollutants in the Korean coastal environment. Since the late-1990s, over several hundred sites along the Korean coast have been surveyed including sediment (including pore-water), water, and biological samples and analyzed for instrumental quantification, in vitro and in vivo bioassays, and benthic community indices. The instrumental data of persistent heavy metals and organic pollutants in Korean sediments generally suggest that concentrations of target pollutants are relatively low to moderate but their distribution is widespread across the coasts. The compositional pattern and spatial distribution suggests that their sources are independent of each other. However, there are local zones with extremely high concentrations of certain pollutants indicating point sources. In order to search for the relationship between chemical concentrations and biological responses, some selected data (n=123) were further analyzed in terms of mass balance analysis (sediment-TIE towards TEQ approach). Most of the dioxin-like activities were observed in the fractions containing dioxins, furans, and certain polycyclic aromatic hydrocarbons (PAHs) and about half of the samples showed significant estrogenic activities in the fractions of PAHs and alkylphenols. Direct relationship(s) between chemical and ecotoxicological data could not be fully addressed between component(s). However, a positive relationship between them became apparent in some cases, indicating a general good agreement between chemical stresses and biological responses. Overall, we found that a sediment triad approach for an integrated assessment of trace pollutants in the coastal environment was extremely useful. It would be much more powerful when all the components are fully and simultaneously analyzed and interpreted.

A comparison of the sensitivity of stream benthic community indices to effects associated with mines, pulp and paper mills, and urbanization.

This study examined the relative sensitivities of seven commonly used indices of stream benthic community composition and three multivariate indices to effects associated with mines, pulp and paper mills, and urbanization. The indices included total abundance, number of taxa, diversity (H'), evenness, Hilsenhoff's biotic index (HBI), the BioMAP water quality index (WQI), the percent model affinity (PMA), and the first three ordination axes from a correspondence analysis. The second objective of the study was to determine the degree of redundancy among these indices. Six data sets (two from each of the three types of development) were used to address the objectives. In each data set, replicate benthic samples were collected from reference areas as well as one or more downstream areas exposed to a point-source or non-point-source discharge. The PMA approach and the ordination axes indicated significant differences between the reference and downstream communities for all six data sets (p < 0.05). With the exception of H', each of the other metrics revealed significant effects associated with one or two, but not all three, types of development. For example, the HBI and WQI indicated significant effects associated with pulp and paper mills and urbanization, but not mining. In all studies, effect sizes (i.e., the standardized difference between means for the reference and exposed areas expressed in units of standard deviations [SDs]) exceeded 2 SDs. However, effect sizes for the PMA and the first or second ordination axis scores were generally larger than effect sizes for the other metrics, indicating that these indices were often the most sensitive indicators of development. In addition, a high degree of redundancy was found among the various metrics, perhaps because the effects were large (i.e., >2 SDs). The greater sensitivity of the ordination axes and the PMA approach emphasizes their value as indices of benthic community composition. As a result, we recommend that any suite of indices used for assessing benthic communities should include these types of multivariate metrics.

A Benthic Community Index for streams in the Northern Lakes and Forests Ecoregion

Abstract Encompassing the northern glaciated section of the Midwest United States, the Northern Lakes and Forests Ecoregion is characterized by mixed conifer and deciduous forests and wetlands. Sites were randomly selected in the ecoregion using the Environmental Protection Agency’s Environmental Monitoring and Assessment Program designed to develop an index of biotic integrity for wadeable streams. Macroinvertebrates were sampled during the fall of 1998 and 1999 using a multi-habitat, composite-sample method. Two hundred forty-six invertebrate taxa in 97 families were collected from 94 sites. Ten of 42 candidate metrics satisfied metric selection criteria, including six structural metrics (number of Ephemeroptera taxa, number of Diptera taxa, richness, Shannon–Wiener diversity, percent Trichoptera abundance, and percent Crustacea and Mollusca abundance), two functional metrics (number of Filterer taxa and number of Scraper taxa), and two conditional metrics (number of Ephemeroptera, Trichoptera, and Plecoptera taxa and Hilsenhoff Biotic Index). These metrics were used to develop a Benthic Community Index to assess the biological integrity of wadeable streams in the ecoregion. Index values ranged from 10 to 50, and scores from impaired sites were significantly different than non-impaired sites (P

Effects of two classification strategies on a Benthic Community Index for streams in the Northern Lakes and Forests Ecoregion

Ninety-four sites were used to analyze the effects of two different classification strategies on the Benthic Community Index (BCI). The first, a priori classification, reflected the wetland status of the streams; the second, a posteriori classification, used a bio-environmental analysis to select classification variables. Both classifications were examined by measuring classification strength and testing differences in metric values with respect to group membership. The a priori (wetland) classification strength (83.3%) was greater than the a posteriori (bio-environmental) classification strength (76.8%). Both classifications found one metric that had significant differences between groups. The original index was modified to reflect the wetland classification by re-calibrating the scoring criteria for percent Crustacea and Mollusca. A proposed refinement to the original Benthic Community Index is suggested. This study shows the importance of using hypothesis-driven classifications, as well as exploratory statistical analysis, to evaluate alternative ways to reveal environmental variability in biological assessment tools.

Chemical contamination, toxicity, and benthic community indices in sediments of the lower Miami River and adjoining portions of Biscayne Bay, Florida

A large-scale survey of sediment quality in Biscayne Bay, Florida, was conducted in 1995–1996 to characterize the relative degree, geographic patterns, and spatial extent of degraded sediment quality. Chemical analyses and multiple toxicity tests were performed on 226 surficial sediment samples collected over an area of 484 km2 in greater Biscayne Bay, including saltwater reaches of several tributaries. Benthic samples were collected and analyzed at one-third of the locations. One or more chemical concentrations exceeded effects range median (ERM) values in 35 samples, representing an area of 5.4 km2 (1.1% of the survey area). Highly toxic conditions in amphipod survival tests occurred in 24 of the samples, representing 62 km2 (13% of the area). Highly significant results were more frequently observed in three sub-lethal tests: sea urchin fertilization (affecting 47% of the area), sea urchin embryological development (84% of the area), and microbial bioluminescence (51% of the area). The highest levels of chemical contamination (range in mean ERM quotients of 0.2 to 2.0, average 0.76) were observed in samples from the lower Miami River. The high degree of contamination in the river contrasted sharply with conditions in the bay, where chemical concentrations generally were much lower (range in mean ERM quotients of 0.005 to 0.21, average 0.04). Amphipod survival tests showed a very high degree of correspondence with a gradient in chemical contamination in the river and adjoining reaches of the bay. Correlation analyses, scatter plots, and principal component analyses indicated that both amphipod survival in the laboratory tests and the abundance and diversity of the benthos decreased sharply with increasing concentrations of mixtures of organic compounds and trace metals in the sediments. The triad of analyses provided a strong weight of evidence of pollution-induced degradation of sediment quality in the riverine locations.

Strategies for evaluating indicators based on guidelines from the Environmental Protection Agency’s Office of Research and Development

The Environmental Protection Agency’s Office of Research and Development (ORD) has prepared technical guidelines to evaluate the suitability of ecological indicators for monitoring programs. The guidelines were adopted by ORD to provide a consistent framework for indicator review, comparison and selection, and to provide direction for research on indicator development. The guidelines were organized within four evaluation phases: (1) conceptual relevance; (2) feasibility of implementation; (3) response variability; (4) interpretation and utility. Three example indicators were analyzed to illustrate the use of the guidelines in an evaluation. The examples included a direct chemical measurement (dissolved oxygen concentration), an estuarine benthic community index, and a stream fish community index of biotic integrity. Comparison of the three examples revealed differences in approach, style and types of information used to address each guideline. The Evaluation Guidelines were intended to be flexible within a consistent framework and the various strategies used in the examples demonstrate that the process can be useful for a wide variety of indicators and program objectives. Published by Elsevier Science Ltd.

Factors Influencing Changes in the Nearshore Benthic Community on the Canadian Side of Lake Ontario

The nearshore benthic communities on the Canadian side of Lake Ontario were surveyed in 1991 at depths of 5 and 20 m, and compared to data obtained in 1981 at the same depths and locations. The comparison was made to determine if the nearshore community reflected known reductions in nutrient concentrations over the 10-year period. The study also was designed to determine the extent to which natural environmental factors such as depth, substrate, fetch, and the likelihood of upwelling alter responses of benthic communities to improvements in water quality. In general, both 5 and 20-m communities reflected the reductions in nutrient concentrations and were indicative of the improved conditions. In 1981 at 5 m, worms were the most dominant group, accounting for 79% of the total fauna. Chironomidae (9%), Gastropoda (4%), Amphipoda (3%), and Sphaeriidae (2%) were subdominant. In 1991 at 5 m, the dominance of worms in the total fauna was reduced to about 15%, while chironomids increased to 34%, amphipods to 27%, gastropods to 18%, and sphaeriid clams to 4%. Similar to 5 m, the fauna at 20 m in 1981 were dominated by worms (65%), while chironomids (10%), amphipods (15%), and sphaeriids (8%) were less dominant. In 1991 at 20 m, the fauna remained dominated by worms but their proportion of the total numbers declined to 48%. At the same time, the proportion of chironomids increased to 20%, amphipods decreased to 7%, gastropods increased to 3%, and sphaeriids increased to 21%. With this data set, a variety of indices of benthic community composition were calculated based on lowest-practical-level identifications. Relationships between changes in these indices and habitat features were explored. Upwelling and substrate type modified the response of the benthic community at 20 m, and are thus important factors to consider in future designs examining whole lake changes in benthic community composition. In contrast, changes in benthic community indices over time at 5 m were unrelated to the type of substrate, fetch or upwelling. As a result, future surveys of 5-m benthos require data from only one substrate type and do not require stratification of study designs by fetch or upwelling. Zebra mussels were found along the western shoreline of Lake Ontario in this 1991 survey in low abundances (averaged 730 indiv/m 2), as well as sporadically along the northern shore. At these low abundances, zebra mussels had no significant effects on changes in benthic community composition.

Indices of benthic community tolerance in contaminated Great Lakes sediments: Relations with sediment contaminant concentrations, sediment toxicity, and the sediment quality triad

We evaluated the toxic-units model developed by Wildhaber and Schmitt (1996) as a predictor of indices of mean tolerance to pollution (i.e., Lenat, 1993; Hilsenhoff, 1987) and other benthic community indices from Great Lakes sediments containing complex mixtures of environmental contaminants (e.g., polychlorinated biphenyls – PCBs, polycyclic aromatic hydrocarbons – PAHs, pesticides, chlorinated dioxins, and metals). Sediment toxic units were defined as the ratio of the estimated pore-water concentration of a contaminant to its chronic toxicity as estimated by U.S. Environmental Protection Agency Ambient Water Quality Criteria (AWQC) or other applicable standard. The total hazard of a sediment to aquatic life was assessed by summing toxic units for all contaminants quantified. Among the benthic community metrics evaluated, total toxic units were most closely correlated with Lenat's (1993) and Hilsenhoff's (1987) indices of community tolerance (TL and TH, respectively); toxic units accounted for 42% TL and 53% TH of variability in community tolerance as measured by Ponar grabs. In contrast, taxonomic richness and Shannon-Wiener diversity were not correlated (P > 0.05) with toxic units. Substitution of order- or family-level identifications for lowest possible (mostly genus- or species-) level identifications in the calculation of TL and TH indices weakened the relationships with toxic units. Tolerance values based on order- and family-level identifications of benthos for artificial substrate samples were more strongly correlated with toxic units than tolerance values for benthos from Ponar grabs. The ability of the toxic-units model to predict the other two components (i.e., laboratory-measured sediment toxicity and benthic community composition) of the Sediment Quality Triad (SQT) may obviate the need for the SQT in some situations.