Ellipse Test Research Articles

Can functional units of periphytic protozoan communities be used to evaluate the effects of harmful algal blooms on ecological quality in marine ecosystems?

Based on biological traits, the ecological quality status under the pressure of two harmful algal bloom (HAB) species was evaluated using functional units (FUs) of periphytic protozoan communities. Five treatments with different concentrations of Alexandrium tamarense and Gymnodinium catenatum, i.e., 100, 102, 103, 104, and 105 cells ml-1, were used. A total of 20 FUs were identified from 25 test protozoan species. Among these FUs, vagile algivores with large sizes showed a decreasing trend (i.e., in diversity and abundance) with increasing concentrations of algae, while vagile bacterivores and non-selectives with small sizes dominated at concentrations of 104 cells ml-1 of both algal species. Ellipse tests on pair-wise functional distinctness indices revealed a significant departure of test protozoan communities from an expected functional distinctness breadth when algal concentrations exceeded 104 cells ml-1. Based on these findings, it was concluded that FUs of periphytic protozoa may be a useful tool for evaluating the effects of HABs on ecological quality status in marine ecosystems.

An approach to discriminating water quality status based on trophic-functional diversity of periphytic protozoan communities in marine ecosystems

To determine the sensitivity of trophic-functional diversity of periphytic protozoa to environmental change, a 1-year baseline survey was carried out using glass microscope slides as artificial substrates at four sampling sites along a pollution gradient in coastal waters of the Yellow Sea, northern China. Eight trophic-functional groups were identified from 144 observed species based on feeding type and food resource. Results showed that: (1) bacterivores increased, while algivores and non-selectives decreased in abundance with increasing levels of pollution; (2) the trophic-functional pattern of the biofilm-dwelling protozoan communities showed a significant variation among the four sites; and (3) the ellipse test based on paired trophic-functional distinctness indices (Δ φ+ and Λφ+) indicated a significant departure from an expected trophic-functional pattern in polluted areas. Based on these findings, it is suggested that trophic-functional distinctness of periphytic protozoa may be a feasible bioindicator of marine water quality.

Chromatic Discrimination Towards the Confusion Points

Abstract In this paper chromatic discrimination thresholds of normal colour-observers are analysed. Measurements were obtained with the Cambridge Colour Test, in different reference points. The results show differences in terms of the reference chromaticities. Reference points within the gamut of a CRT display were found where thresholds of normal colour observers measured towards the confusion points exceeded the normative upper threshold limit of normal colour observers. The discrimination thresholds estimated towards the confusion lines based on Trivector measurements exceeded the thresholds estimated by the Ellipse tests. Our results indicate that in case of determination of discrimination ellipses, measurements towards the confusion points are recommended.

The Effect of the Field of Adaptation on Chromatic Discrimination Ellipses

In this paper results of chromatic discrimination measurements obtained in two lighting scenarios are compared. Chromatic discrimination thresholds were measured in relation with systematically manipulated chromaticities seen under different visual angles. In both cases the Ellipse module of the Cambridge Colour Test (CCT) was obtained binocularly by normal colour-observers. Discrimination ellipses fitted to the measured thresholds were compared in terms of the adapting chromaticity and the visual angle of the adapting stimulus. Our findings show that changes in the reference chromaticity of the CCT have stronger effect on the elongation of the chromatic discrimination ellipses compared to the effect of the adapting chromaticity obtained in a light booth.Further comparison of discrimination thresholds estimated towards the confusion directions and the corresponding radii of the Ellipse test results suggests that the reliability of the Ellipse test results depends on the relation between the measurement directions and the confusion directions.

An approach to assessing ecological quality status due to microalgae bloom using biofilm-dwelling protozoa based on biological trait analysis

Functional diversity/distinctness measure based trait has been proved to be a robust indicator to summarize the description of community structures and to assess water quality in different types of aquatic environment. In this study, for identifying the shielding effect of microalgae against protozoan grazing, a nine-day survey was conducted by exposing protozoan communities to a series of concentration gradients (100 (control), 104, 105, 106 and 107 cells ml−1) of two microalgae, respectively. Our results showed clear resistance of two test microalgae against protozoan grazing in five treatments. The functional distinctness measures commonly represented a decreasing trend along the gradient of concentrations of both microalgae. Ellipse tests based on the paired functional distinctness indices revealed that community functioning represented an uptrend departure from the expected pattern with the concentrations of both microalgae increase. Therefore, we suggest that the functional distinctness measures might be a reliable approach to detect the ecological effect of microalgae against protozoan grazing.

Variability of chromatic visual sensitivity: discrimination according to daily shifts

ABSTRACT This study aimed to verify the daily variation in the chromatic visual sensitivity of healthy subjects. The study included 35 male adults, aged between 20 and 40 years old (M = 24.97; SD = 4.9). The evaluation of color perception was made through the Cambridge Colour Test, using the Trivector and Ellipse tests. The Pittsburgh Sleep Quality Index, the Sleep Diary, and the Karolinska Sleepiness Scale were used to assess possible influences of circadian rhythmicity. Significant differences were found for the protan confusion axes at 8 am (Z = 2.9; p = 0.012) and at 8 pm (Z = 2.8; p = 0.01), and deutan at 8 am (Z = 2.6; p = 0.028) and at 8 pm (Z = 3.5; p = 0.001), and for the A1 ellipses areas at 8 am (Z = 2.5; p = 0.037) and at 8 pm (Z = 2.4; p = 0.018), and A3 at 8 am (Z = 2.1; p = 0.039) and at 8 pm (Z = 3.6; p = 0.001). Thus, chromatic sensitivity can be characterized by an inverted U-shaped curve, with peak sensitivity in the morning and evening, and attenuation in the afternoon.

Vertical variability in taxonomic breadth of biofilm-dwelling ciliates in marine bioassessment surveys

To determine the effects of water depths on taxonomic breadth of biofilm-dwelling ciliates in marine ecosystems, (1-month) baseline survey was conducted in coastal waters of the Yellow Sea, northern China. Utilizing glass slides as artificial substrates, samples were collected at four depths of 1, 2, 3.5 and 5 m after a 14-day exposure period. Taxonomic patterns and taxonomic distinctness measures showed a significant difference among four water depths. Ellipse tests on the pairs of average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+) demonstrated a vertical variability in taxonomic structure of the ciliate communities from 1 m to 5 m, with high levels at 1 and 2 m compared to those at the other two depths. These results suggest that water depth may significantly shape the taxonomic breadth of biofilm-dwelling ciliates, and that an optimal sampling strategy should be determined before monitoring surveys in marine ecosystems.

Insights into identifying the effect of harmful algae on ecological quality status using periphytic ciliates in marine ecosystems

Abstract Our study focused on ciliates grazing potential against harmful algal blooms, because ciliates are considered as voracious feeders of toxic phytoplankton and major herbivores in marine food webs. Ciliates are major contributors to control the flux of harmful algal blooms by lessen the magnitude of their biomass from top to bottom by high consumption on these blooms. Keeping an eye on harmful algal blooms as common pollutant of marine ecosystem the community-based method was used to test the potential effects of two harmful algal species Alexandrium tamarense and Gymnodinum catenatum on the community patterns of the ciliates. For this purpose, the 14-day (mature) samples of ciliate communities were collected using glass slides as an artificial substratum at a depth of 1 m in coastal waters of the Yellow Sea, northern China. A series of algal cell concentrations of both species was prepared as 100 (control), following 102, 103, 104 and 105 cell ml−1, respectively. The study results indicated that both algal species showed strong effects on the community patterns of the ciliates at high concentration. Species abundance, relative species number and taxonomic distinctness indices of ciliate communities generally increased by increasing the concentration whereas, sharply decreased at the concentration level of (105 cells ml−1) for both algal species. Canonical analysis of principal coordinates demonstrated the variations in community structures of the ciliates driven by the concentrations of both algal species. Ellipse test showed an increased pattern in species departure from an expected breadth of species contour with increasing the algal cell concentrations. Based on our findings, it is suggested that extended studies on community-based bioassay is a valuable tool to strengthen the information about the effects of microalgae on the ciliate community structures.

Body-size spectra of biofilm-dwelling ciliates at different layers in water column of coastal ecosystems

It is increasingly recognized that the body-size spectrum of biofilm-dwelling ciliates is an informative bioindicator of environmental change in marine ecosystems. In order to reveal the effects of water depth on the body-size spectrum of biofilm-dwelling ciliates during the colonization process, a 1-month baseline survey was carried out in coastal waters of the Yellow Sea, northern China. Using glass slides as artificial substrates, a total of 240 microscopy slides were collected from four depths, i.e., 1, 2, 3.5 and 5 m, after colonization periods of 3, 7, 10, 14, 21 and 28 days. A total of 92 ciliate species were collected. Based on its equivalent spherical diameter (ESD), each species was allocated to one of eight body-size ranks (S1–S8): S1 (13–17μm), S2 (20–26μm), S3 (30–34μm), S4 (35–49μm), S5 (54–63μm), S6 (66–93μm), S7 (120–161μm) and S8 (162–247μm). The body-size spectrum showed a clear temporal variability in both frequency of occurrence and probability density during the colonization process at the four depths: S1 was dominant in immature samples whereas mature samples were dominated by S3. Multidimensional scaling ordinations (MDS) and bootstrap average analyses revealed a clear shift in body-size spectra from surface to deeper water layers during the colonization process. Ellipse tests demonstrated that the samples showed different patterns of departure from the expected body-size spectrum at each depth during the colonization period. These findings suggest that water depth may significantly shape the body-size spectra of biofilm-dwelling ciliates, and that there may be an optimal water depth when using this feature for monitoring marine ecosystems.

An approach to determining homogeneity in taxonomic breadth of periphytic ciliate communities in colonization surveys for bioassessment

Abstract Taxonomic distinctness is powerful tool to test the departure of a community from an expected pattern of taxonomic structure in response to environmental change. To determine the homogeneity in taxonomic breadth of periphytic ciliates, a 1-month baseline colonization survey was conducted in Jiaozhou Bay, near Qingdao, northern China, using glass slides as artificial substrates. A total of 240 slides were collected at depths of 1, 2, 3.5 and 5 m after colonization periods of 3, 7, 10, 14, 21 and 28 days. The taxonomic composition and structure of the periphytic ciliate communities differed among the four water depths. The temporal variations in all four taxonomic diversity/distinctness measures had different patterns of variability at each depth. Ellipse test on the pairs of average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+) demonstrated a spatial variability in homogeneity in taxonomic structure of the ciliate communities from 1 m to 5 m, with high levels at 1 and 2 m compared to those at the other two depths. These results suggest that taxonomic distinctness is a useful indicator to identify the homogeneity in taxonomic breadth of periphytic ciliate communities during the colonization process in marine ecosystems.

An approach to identifying homogeneity in community functioning of periphytic ciliates in colonization surveys for marine bioassessment

Functional diversity/distinctness, as important biodiversity parameters of a community, have proved to be a feasible tool to summarize ecosystem functions and community structures both ecological research and monitoring program. For determining the homogeneity in community functioning of periphytic ciliates during colonization process, a 1-month baseline survey was conducted at four depths of 1, 2, 3.5 and 5 m in coastal waters of the Yellow Sea, northern China. The colonization dynamics in functional trait distribution of periphytic ciliates generally showed different temporal variations during colonization period at four depths. The functional diversity (Δχ), functional distinctness (Δ*χ), average functional distinctness (Δχ+) and variation in functional distinctness (Λχ+) indices generally represented different models within colonization process at four depths. Ellipse test on the paired functional distinctness measures (Δχ+ -Λχ+) revealed that the mature samples (14–28 days) were inside the expected patterns of community functioning at only one water depth (1 m), although the 14-day communities were fallen into the contours of 10 sub-list size at the other two water layers (2 and 3.5 m). These findings suggest that the functional distinctness measures might be a useful indicator to determine the optimal sampling strategy with high homogeneity of community functioning in colonization surveys for marine bioassessment.

Use of functional distinctness of periphytic ciliates for monitoring water quality in coastal ecosystems

As trait-based ecological parameters, functional diversity/distinctness measures are robust parameters for biodiversity research by reducing “signal to noisy” ratios due to functional redundancy in a community, and have an advantage for bioassessment due to a statistical framework for testing departure from expectation by combining ecosystem functions and community structure. The effectiveness of four functional diversity/distinctness measurements for water quality assessment was based on a study of additional ciliate datasets for biological evaluation of coastal waters along the Yellow Sea in northern China. A fuzzy-coding trait system was used as a trait pool, which comprised six characters of feeding types, movement features, body size/form/flexibility, and sociability. Results showed that (1) the functional diversity (Δχ) significantly related to the spatial variation in water transparency; (2) the average functional diversity index (Δχ+) and variation in functional distinctness (Λχ+) represented a significant correlation with the changes in pH and nutrients, especially ammonium nitrogen, and soluble active phosphate; and (3) ellipse test for the paired indices (Δχ+ and Λχ+) revealed a clear departure from an expected functional trait pattern. According to our findings, it is recommended that the functional diversity/distinctness measures may be served as a robust bioindicator of water quality status in marine ecosystems.

Colour discrimination thresholds in type 1 Bipolar Disorder: a pilot study

Although some studies have reported perceptual changes in psychosis, no definitive conclusions have been drawn about visual disturbances that are related to bipolar disorder (BPD). The purpose of the present study was to evaluate colour vision in BPD patients. Data were recorded from 24 participants: healthy control group (n = 12) and type 1 BPD group (n = 12). The participants were 20–45 years old and they were free from neurological disorders and identifiable ocular disease and had normal or corrected-to-normal visual acuity. Colour discrimination was evaluated using the Lanthony D-15d, Trivector and Ellipse tests, using a psychophysical forced-choice method. The relationship of visual measures to mood state and cognitive function was also investigated. The results showed that BPD patients had higher colour discrimination thresholds in the D15d (p < 0.001), Trivector (p < 0.001) and Ellipse (p < 0.01) tests compared with healthy controls. Linear regression analysis showed that mood state was related to colour discrimination. BPD individuals were not impaired in cognitive tasks. The present study provided new evidence of potential links between type 1 BPD and visual processing impairments. This research suggests a new direction for studies and the need for research in this field of study.

A new method for evaluating defense of microalgae against protozoan grazing

Body-size spectrum has proved to be a highly informative indicator to summarize the functional structure of a community at taxon-free resolution. In this study, an approach based on body-size spectrum of protozoan communities was used to detect the defense of microalgae against protozoan grazing. The biofilm-dwelling protozoan communities were used as a test predator system, and two algal species, Chlorella sp. and Nannochloropsis oceanica, were employed as test microalgae. A nine-day bioassay test was carried out by exposing biofilm-dwelling protozoan communities to a gradient of concentrations 100 (control), 104, 105, 106, and 107 cell ml−1 of both microalgae, respectively. Results showed that both algal species represented strong defense effects on the test predator system at different levels of concentration. The body-size distinctness of the protozoan assemblages showed a sharp decrease at high concentration level more than 106 cell ml−1 in both algal treatments. Based on the paired body-size distinctness indices of the protozoa, ellipse tests demonstrated that the body-size spectrum showed an increasing trend of departure from the expected pattern with increasing concentrations of both test algae. Thus, it is suggested that the body-size spectrum of protozoa may be used as a useful indicator to identify the defense of microalgae against protozoan grazing.

Trends and Shifts in Time Series of Rainfall and Runoff in the Gambia River Watershed

For several decades, climate change and climate variability issues and their impacts on the hydrological regime of rivers have constituted a major topic for hydroclimatological sciences research and water resources planning policies. Understanding of these issues needs enough long time series of rainfall and runoff data covering a large period, and a comprehensive diagnosis of the existing trends and shifts in these time series of data. This can be done by applying robust statistical tests to relevant rainfall and runoff time annual series. The aim of this paper is to highlight the effect of climate change in the Gambia River Basin and its impacts on the availability of the water resources of this basin. To reach this objective, we have selected runoff time series of the Gambia River Basin at Mako, Kedougou Diaguéri streamgauges and rainfall time series at Koulountou’s rain gauge. Statistical tests for shift detection presented in the Khronostat software, such as Pettit, Hubert and Buishand ellipse tests are first used, Mann Kendall test for annual trend are then applied to check whether trends exist or not in these times series. When the null hypothesis of no trend is rejected, the non parametric Sen’s test is then applied to validate the Mann Kendall trend test and to estimate the magnitude of the trend and its direction. Tests for homogeneity show an increasing shift for rainfall time series of Koulountou raingauge and for runoff time series of Mako and Diaguéri and a decreasing shift for Kedougou streamgauge. According to the Mann Kendall trend test, there is an upward trend for Koulountou rainfall time series, and Mako and Diaguéri runoff time series, and a downward trend for Kedougou annual runoff time series. The Buishand ellipse and the Hubert test indicate generally the same year of the beginning of the shift. Interesting perspectives for decision makers in evaluation and precise management of water resources and water projects in the Gambia River basin are offered as well.

Trends in extreme precipitation indices derived from a daily rainfall database for the South of Portugal

AbstractThe rainfall regime of the South of Portugal is Mediterranean with Atlantic influence. Long‐term series of reliable precipitation records are essential for land and water resources management, climate‐change monitoring, modelling of erosion and run‐off, among other applications for ecosystem and hydrological impact modelling. This study provides a qualitative classification of 106 daily rainfall series from stations located in the South of Portugal and evaluates temporal patterns in extreme precipitation by calculating a number of indicators at stations with homogeneous data within the 1955/1999 period. The methodology includes both absolute and relative approaches and a new homogeneity testing procedure, besides the application of other statistical tests. The proposed technique is an extension of the Ellipse test that takes into account the contemporaneous relationship between several candidate series from the same climatic area (SUR + Ellipse test). The results indicate that this technique is a valuable tool for the detection of non‐climatic irregularities in climate time series if the station network is dense enough. The existence of trends and other temporal patterns in extreme precipitation indices was investigated and uncertainty about rainfall patterns evolution was assessed. Three indices describing wet events and another three indicators characterizing dry conditions were analysed through regression models and smoothing techniques. The simple aridity intensity index (AII) reflects increases in the magnitude of dryness. Especially pronounced trends are found over most of southern Portugal in the 1955/1999 period, highlighting the fact that large areas are threatened by drought and desertification. The trend signals of the wetness indices are not significant at the majority of stations, but there is evidence of increasing short‐term precipitation intensity over the region during the last three decades of the twentieth century. Finally, the results also indicate that extreme precipitation variability and climate uncertainty are greater in recent times. Copyright © 2008 Royal Meteorological Society

A multicommuted flow system for the determination of copper, chromium, iron and lead in lubricating oils with detection by flame AAS

In this work, a flow analysis procedure for the determination of copper, chromium, iron and lead in lubricating oils using flame AAS as detection technique is described. The flow manifold was designed to implement the multicommutation approach and it comprised three 3-way solenoid valves controlled by a personal computer. The flow system presented allowed to process the oil samples to determine wear metals without any prior preparation. Aiming to assess accuracy the results were compared with those obtained by manual procedure using flame AAS. Applying the joint-confidence ellipse test, no significant difference at the 95% confidence level was observed. Other profitable features such as a sample throughput of 50 determinations per hour; relative standard deviations ( n = 5) below 2% for Cu, and below 8% for Cr, Fe and Pb; and linear responses in the range 0–40 ppm (w/w) (Cu, Fe) and 0–15 ppm (w/w) (Cr, Pb) were also achieved.