IMPACT OF NIGHT-FLOAT ROTATION ON SLEEP,MOOD, AND ALERTNESS: THE RESIDENT'S PERCEPTION

Night-float rotations were designed to alleviate the workload of residents on night call and thereby improve patient safety. However, the impact of the night float on residents is yet to be surveyed. We assessed the impact of the night-float rotation on pediatric residents using an anonymous questionnaire that covered topics, based on recall, about sleep, mood, alertness, adjustment, and others. The study was conducted in a major tertiary pediatric teaching hospital in the United States. Participants were pediatric residents who had completed one or two night-float rotations and were in active training at our teaching hospital at the time of the study. Fifty-two of 60 eligible residents (87%) responded. Sleep duration during the night-float rotation was shorter than during day-shift work in 24 residents (46%), longer in 20 (38%), and unchanged in eight (15%). A higher proportion of residents took longer to fall asleep, had more difficulty falling asleep, had more sleep interruptions, and felt less rested upon awakening. Twenty-four residents (46%) felt that their bodies never adjusted to the night shift. Also, 22 residents (43%) felt moody or depressed in contrast to seven (14%) who felt depressed during the daytime rotation (p=0.0001). Twenty-one residents (41%) felt they were slower in their thinking during the night float than daytime rotations. The results suggest that disturbances of sleep and mood and decreased alertness, typical of night shift, are present in the night-float rotation. Residency programs should monitor closely the impact of the night-float rotation on resident well being and patient safety. The impact of night-shift work should be considered in the design of night-float schedules, and teaching should be provided for residents to learn coping strategies for night-shift work.     

CONSEQUENCES OF SHIFTWORKING ON SLEEP DURATION,SLEEPINESS, AND SLEEP ATTACKS

Rotating shift and permanent night work arrangements are known to compromise sleep. This study examined the effects of work schedule on sleep duration, excessive sleepiness, sleep attacks, driving, and domestic/professional accidents. A representative sample of the general population of the state of New York—3,345 individuals ≥18 yrs of age—was interviewed by telephone regarding their sleep and psychiatric and organic disorders. Multivariate models were applied to derive odds ratios (OR) after adjustment for age, sex, physical illness, mental disorders, obstructive sleep apnea, and sleep duration. On average (±SE), workers slept 6.7?±?1.5?h, but 40% slept <6.5?h/main sleep episode. Short-sleep duration (<6?h) was strongly associated with fixed night (OR: 1.7) and day-evening-night shiftwork arrangement (OR: 1.9). Some 20% of the workers manifested excessive sleepiness in situations requiring high attention, and it was associated with the fixed night (OR: 3.3) and day-evening-night work arrangements (OR: 1.5). Overall, 5% of the workers reported sleep attacks; however, they occurred three-times more frequently in the fixed night (15.3%) than other work arrangements (OR: 3.2). Driving accidents during the previous 12 months were reported by 3.6% of the workers and were associated with fixed night (OR: 3.9) and day-evening-night (OR: 2.1) work schedules. The findings of this study indicate that working outside the regular daytime hours was strongly associated with shorter sleep duration, sleepiness, and driving accident risk. Night work is the most disrupting, as it is associated with insufficient sleep during the designated rest span and excessive sleepiness and sleep attacks during the span of activity, with an associated consequence being increased driving accident risk. (Author correspondence: mohayon@stanford.edu)     

ROLE OF SCHOOL SCHEDULE,AGE, AND PARENTAL SOCIOECONOMIC STATUS ON SLEEP DURATION AND SLEEPINESS OF PARISIAN CHILDREN

The aim of the study was to assess the duration and quality of sleep of prepubertal (Tanner Scale level 1) physically and mentally healthy children as a function of school schedule (4 versus 4.5 days per week), age and grade (median age of 9.5 years for 4th grade versus median age of 10.5 years for 5th grade), school district (wealthy versus nonwealthy) in Paris, France, and parental socioeconomic status (high, medium, or low). We studied 51 girl and 44 boy volunteer pupils with written parental consent. The study lasted 2 weeks during the month of March. During the first study week, the children attended school 4.5 days, and during the second week, they attended school only 4 days without difference in the length of the school day. A sleep log was used to ascertain time of lights off for sleep and lights on at awakening, nighttime sleep duration, and self-rated sleep quality. A visual analog scale (VAS) was also used by pupils to self-rate the level of perceived sleepiness at four specific times of the school day. Conventional statistical methods (e.g., t and χ²tests) were used to examine differences in mean values. Sleep duration, self-rated sleepiness, and subjective sleep quality were comparable (P >. 05) by gender, school schedule, school district, and parental socioeconomic status. Overall, the sleep of this sample of Parisian children around 10 years of age was rather stable in its duration and timing, suggesting flexibility to adjust to the different school schedules. (Chronobiology International, 18 (6), 1005–1017, 2001)     

SLEEP AND CIRCADIAN PHASE CHARACTERISTICS OF ADOLESCENT AND YOUNG ADULT MALES IN A NATURALISTIC SUMMERTIME CONDITION

Our aim was to compare the circadian phase characteristics of healthy adolescent and young adult males in a naturalistic summertime condition. A total of 19 adolescents (mean age 15.7 years) and 18 young adults (mean age 24.5 years) with no sleep problems took part in this study. Two-night polysomnographic (PSG) sleep recordings and 24h secretion patterns of urinary 6-sulfatoxymelatonin were monitored in all 37 subjects. Sleep-wake patterns were initially assessed at home using a standard sleep diary. Circadian assessment included the measure of dim light melatonin offset (DLMOff) and the morningness-eveningness (M/E) questionnaire. As expected, compared to young adults, adolescents habitually spent more nocturnal time in bed and spent more time (and percentage) in delta sleep. No difference was found between adolescents and young adults on multiple sleep latency test (MSLT) sleep onset latencies, M/E, melatonin secretion measures (24h total, nighttime, daytime, and night ratio), and DLMOff. For the subjects as a whole, correlational analyses revealed a significant association between the DLMOff and M/E and between both these phase markers and habitual bedtimes, habitual rising times, and melatonin secretion measures (daytime levels and the night ratio). No association was found between phase markers and daytime sleepiness or sleep consolidation parameters such as sleep efficiency or number of microarousals. These results together indicate that adolescents and young adults investigated during summertime showed similar circadian phase characteristics, and that, in these age groups, an evening phase preference is associated with a delayed melatonin secretion pattern and delayed habitual sleep patterns without a decrease in sleep consolidation or vigilance. (Chronobiology International, 17(4), 489–501, 2000)     

AMBER LENSES TO BLOCK BLUE LIGHT AND IMPROVE SLEEP: A RANDOMIZED TRIAL

All light is not equal: blue wavelengths are the most potent portion of the visible electromagnetic spectrum for circadian regulation. Therefore, blocking blue light could create a form of physiologic darkness. Because the timing and quantity of light and darkness both affect sleep, evening use of amber lenses to block blue light might affect sleep quality. Mood is also affected by light and sleep; therefore, mood might be affected by blue light blockade. In this study, 20 adult volunteers were randomized to wear either blue-blocking (amber) or yellow-tinted (blocking ultraviolet only) safety glasses for 3?h prior to sleep. Participants completed sleep diaries during a one-week baseline assessment and two weeks' use of glasses. Outcome measures were subjective: change in overall sleep quality and positive/negative affect. Results demonstrated that sleep quality at study outset was poorer in the amber lens than the control group. Two- by three-way ANOVA revealed significant (p?<?.001) interaction between quality of sleep over the three weeks and experimental condition. At the end of the study, the amber lens group experienced significant (p?<?.001) improvement in sleep quality relative to the control group and positive affect (p?=?.005). Mood also improved significantly relative to controls. A replication with more detailed data on the subjects' circadian baseline and objective outcome measures is warranted. (Author correspondence: jphelps@samhealth.org)     

CHRONOTYPE,SLEEP LOSS,AND DIURNAL PATTERN OF SALIVARY CORTISOL IN A SIMULATED DAYLONG DRIVING

The study focused on chronotype-related differences in subjective load assessment, sleepiness, and salivary cortisol pattern in subjects performing daylong simulated driving. Individual differences in work stress appraisal and psychobiological cost of prolonged load seem to be of importance in view of expanding compressed working time schedules. Twenty-one healthy, male volunteers (mean?±?SD: 27.9?±?4.9 yrs) were required to stay in semiconstant routine conditions. They performed four sessions (each lasting ～2.5?h) of simulated driving, i.e., completed chosen tasks from computer driving games. Saliva samples were collected after each driving session, i.e., at 10:00–11:00, 14:00–15:00, 18:00–19:00, and 22:00–23:00?h as well as 10–30?min after waking (between 05:00 and 06:00?h) and at bedtime (after 00:00?h). Two subgroups of subjects were distinguished on the basis of the Chronotype Questionnaire: morning (M)- and evening (E)-oriented types. Subjective data on sleep need, sleeping time preferences, sleeping problems, and the details of the preceding night were investigated by questionnaire. Subjective measures of task load (NASA Task Load Index [NASA-TLX]), activation (Thayer's Activation-Deactivation Adjective Check List [AD ACL]), and sleepiness (Karolinska Sleepiness Scale [KSS]) were applied at times of saliva samples collection. M- and E-oriented types differed significantly as to their ideal sleep length (6 h 54 min?±?44 versus 8 h 13 min?±?50 min), preferred sleep timing (midpoint at 03:19 versus 04:26), and sleep index, i.e., ‘real-to-ideal’ sleep ratio, before the experimental day (0.88 versus 0.67). Sleep deficit proved to be integrated with eveningness. M and E types exhibited similar diurnal profiles of energy, tiredness, tension, and calmness assessed by AD ACL, but E types estimated higher their workload (NASA-TLX) and sleepiness (KSS). M types exhibited a trend of higher mean cortisol levels than E types (F?=?4.192, p?<?.056) and distinct diurnal variation (F?=?2.950, p?<?.019), whereas E types showed a flattened diurnal curve. Cortisol values did not correlate with subjective assessments of workload, arousal, or sleepiness at any time-of-day. Diurnal cortisol pattern parameters (i.e., morning level, mean level, and range of diurnal changes) showed significant positive correlations with sleep length before the experiment (r?=?.48, .54, and .53, respectively) and with sleep index (r?=?.63, .64, and .56, respectively). The conclusions of this study are: (i) E-oriented types showed lower salivary cortisol levels and a flattened diurnal curve in comparison with M types; (ii) sleep loss was associated with lower morning cortisol and mean diurnal level, whereas higher cortisol levels were observed in rested individuals. In the context of stress theory, it may be hypothesized that rested subjects perceived the driving task as a challenge, whereas those with reduced sleep were not challenged, but bored/exhausted with the experimental situation. (Author correspondence: mmoginsk@cyf-kr.edu.pl)     

TEMPERATURE PROFILES,AND THE EFFECT OF SLEEP ON THEM,IN RELATION TO MORNINGNESS-EVENINGNESS IN HEALTHY FEMALE SUBJECTS

There were 15 healthy female subjects, differing in their position on the “morningness-eveningness” scale, studied for 7 consecutive days, first while living a sedentary lifestyle and sleeping between midnight and 08:00 and then while undergoing a “constant routine.” Rectal temperature was measured at regular intervals throughout this time, and the results were subjected to cosinor analysis both before and after “purification” for the effects of physical activity. Results showed that there was a phase difference in the circadian rhythm of core temperature that was associated with the morningness score, with calculations that “morning types” would be phased earlier than “evening types” by up to about 3h. This difference in phase (which was also statistically significant when the group was divided by a median split into a “morning group” and an “evening group”) could not be attributed to effects of waking activity and existed in spite of the subjects keeping the same sleep-wake schedule. Moreover, it persisted when the subjects' data had been purified and when the data were obtained from the constant routine. That is, there was an endogenous component to this difference in phase of the core temperature. The morning group also showed a greater fall of core temperature during sleep; this was assessed in two ways, the main one being a comparison of constant routine and nychthemeral data sets after correction for any effects of activity. Even though the morning group was sleeping at a later phase of their circadian temperature rhythm than was the evening group, neither group showed a fall of temperature due to sleep that varied with time elapsed since the temperature acrophase. It is concluded that another factor that differs between morning and evening types is responsible for this difference. (Chronobiology International, 18(2), 227–247, 2001)     

SLEEP IMPAIRMENTS IN HEALTHY SENIORS: ROLES OF STRESS,CORTISOL, AND INTERLEUKIN-1 BETA

Study Objectives: Increased stress responsivity and a longer-lasting glucocorticoid increase are common findings in aging studies. Increased cortisol levels at the circadian nadir also accompany aging. We used 24h free urine cortisol to assess these age changes in healthy seniors. We hypothesized that free cortisol levels would explain individual differences in age-related sleep impairments. Design: The study compared sleep, cortisol, and sleep-cortisol correlations under baseline and “stress” conditions in men and women. Setting: Subjects were studied in the General Clinical Research Center under baseline conditions and a mildly stressful procedure (24h indwelling intravenous catheter placement). Participants: Eighty-eight healthy, nonobese subjects (60 women and 28 men) from a large study of successful aging participated in the study. Mean ages were 70.6 (±6.2) and 72.3 (±5.7) years for women and men, respectively. Measurements: The 24h urines were collected for cortisol assay (radioimmunoassay [RIA]); blood was sampled at three diurnal time points for assay (enzyme-linked immunosorbent assay [ELISA]) of interleukin-1 (IL-1) beta; sleep architecture and sleep electroencephalograms (EEGs) were analyzed (after an adaptation and screening night) on baseline and stress nights via polysomnography and EEG power spectral analysis. Results: Healthy older women and men with higher levels of free cortisol (24h urine level) under a mild stress condition had impaired sleep (lower sleep efficiency; fewer minutes of stages 2, 3, and 4 sleep; more EEG beta activity during non–rapid eye movement sleep [NREM] sleep). Similar results were obtained when stress reactivity measures were used (cortisol and sleep values adjusted for baseline values), but not when baseline values alone were used. Gender differences were apparent: Men had higher levels of free urine cortisol in both baseline and mild stress conditions. Cortisol and sleep correlated most strongly in men; cortisol stress response levels explained 36% of the variance in NREM sleep stress responses. In women, but not men, higher cortisol was also associated with earlier time of arising and less REM sleep. Higher cortisol response to stress was associated with increased circulating levels of IL-1β, explaining 24% of the variance in a subset of women. Conclusion: These results indicate that free cortisol (as indexed by 24h urine values) can index responses to mild stress in healthy senior adults, revealing functional correlations (impaired sleep, earlier times of arising, more EEG beta activity during sleep, more IL-1β) and gender differences. (Chronobiology International, 17(3), 391–404, 2000)     

CICLOGRAMA: A TOOL FOR DETECTION OF RHYTHMICITIES IN SLEEP/WAKE CYCLES

The Fourier spectral analysis of binary time series (or rectangular signals) causes methodological problems, due to the fact that it is based on sinusoidal functions. We propose a new tool for the detection of periodicities in binary time series, focusing on sleep/wake cycles. This methodology is based on a weighted histogram of cycle durations. In this paper, we compare our methodology with the Fourier spectral analysis on the basis of simulated and real binary data sets of various lengths. We also provide an approach to statistical validation of the periodicities determined with our methodology. Furthermore, we analyze the discriminating power of both methods in terms of standard deviation. Our results indicate that the Ciclograma is much more powerful than Fourier analysis when applied on this type of time series.     

A、B环羟基和吡啶的溶剂效应对甾体皂甙元19-甲基化学位移的影响

我们在对十多个A、B环上有羟基取代的甾体皂甙元~1H NMR谱研究时发现,△~5-系列的甾体皂甙元1β-OH对19-Me的吡啶溶剂位移为0.30ppm,5β-系列的甾体皂甙元其1β、5β、6β-OH对19-Me的吡啶溶剂位移大约各自为0.15ppm,与不具有1β、5β或6β-OH的甙元相比较,其19-Me的化学位移(吡啶为溶剂)随1β、5β和6β-OH取代数目的增加而向低场位移约0.3、0.6和0.9ppm,并具有可加和性。     

银屑病皮损中IL—10及IL—12 p35、p40 mRNA表达的研究

探讨IL－10和IL－12在银屑病发病机理中的可能作用,为应用基因治疗银悄病提供理论基础。采用逆转录聚合酶链反应（RT－PCR）技术检测了12例银屑病患者及6例正常皮肤组织中IL－10和IL－12p35、p40mRNA的表达情况。研究结果表明：（1）与正常皮肤组织相比银屑病皮损中IL－10mRNA明显降低（P＜0.01）。（2）IL－12p35 mRNA在银屑病皮损和正常皮肤组织中均呈阳性表达,IL－12p40 mRNA只在银屑病皮损中呈阳性表达,而在正常皮肤中为阴性。推测IL－12在银屑病的发生和发展中可能起重要,而IL-10可能在银屑病消退中起一定作用。     

扑虱灵对稻飞虱及其捕食性天敌种群的影响

扑虱灵对稻飞虱的防治效果,及对捕食性天敌的毒性,进行了田间试验,并与叶蝉散,杀虫双的使用结果作比较．试验结果表明,扑虱灵对稻飞虱的防治效果达93％,与叶蝉散,杀虫双相比较。防治效果提高了2．39～32．85％．对黑肩绿盲蝽和蜘蛛种群具有不同程度的选择性,维护较低的稻飞虱与天敌的比值,有利于天敌作用的发挥,维持对稻飞虱较长的残效期,基本上可以控制稻田后期飞虱的增长．     

大气CO_2浓度升高对植物的直接影响——国外十余年来模拟实验研究之主要手段及基本结论

本文针对国外近十几年来在ＣＯ２浓度升高对植物的直接影响方面所开展的生理生态学研究方法、动态、基本结论、存在问题等内容做了简要的介绍。大气ＣＯ２浓度在过去２００年内已增加了８０μｍｏｌ·ｍｏｌ－１,生长在高ＣＯ２环境下的植物,其生理生态、形态及化学成分等方面将会发生相应的变化。表现在光合作用速率出现不同程度的提高;呼吸作用受抑制;气孔密度减少,水分利用效率增加;生物量及产量增加;一些关键蛋白质及酶、非结构性碳水化合物含量增加;组织中的氮、硫等元素含量降低;根系及花的发育也随ＣＯ２浓度的升高而提前等。不同光合途径（Ｃ３、Ｃ４及ＣＡＭ）及不同植被类型（自然植被、栽培植被）的植物随ＣＯ２浓度发生的上述指标的变化在长期反应与短期反应方面具有很大的差异。另外,实验控制条件如温度、光照、水分、养分甚至实验装置（如花盆）的大小对预测结果也有很大的影响。     

洞庭湖区三个湖泊水生植物多样性的比较研究

比较研究了洞庭湖区华容县东湖、益阳市大通湖和岳阳市郊南湖水生植物多样性的现状,讨论了30年来3个湖泊水生植物多样性丧失的情况及与其所受人为干扰的关系,探讨了野菱、密齿苦草和菹草对人为干扰的适应机制、大通湖和南湖水生植物多样性及其退化水生态系统恢复的途径。主要结论如下：（1）199－2000年东湖、大通湖与南湖各分布有水生植物61种、56种和32种,其分别隶属于29科43属、26科39属和20科27属;各有水生植物群丛8个、6个和4个;水生植被覆盖率分别为26．17％、10．60％和9．99％。（2）30年来三个湖泊分别有3种、9种和13种水生植物消失,2个、5个和5个水生植物群丛类型消失。（3）水生植物多样性的现状是：东湖＞大通湖＞南湖,多样性下降的程度与其所受干扰强度成正相关。     

THE RELATIVE IMPORTANCE OF INBREEDING AND MATERNAL SEX IN DETERMINING PROGENY FITNESS IN SIDALCEA OREGANA SSP. SPICATA,A GYNODIOECIOUS PLANT

Gynodioecious plant populations contain both hermaphrodite and female individuals. For females to be maintained they must compensate for their loss of reproductive fitness through pollen. Females may achieve compensation by producing more and/or higher quality seeds than hermaphrodites. In this study, I investigated the independent and interactive effects of maternal sexual identity and inbreeding level on fitness of the progeny of hermaphrodites and females of Sidalcea oregana ssp.spicata. Seeds produced by selling hermaphrodites and by outcrossing or sib-crossing hermaphrodites and females, were planted in the field and greenhouse. Maternal-sex effects were substantial at the juvenile stages of the life cycle; seeds of females germinated in higher proportions and produced seedlings that grew significantly faster. Inbreeding effects were manifested primarily at the adult stage of the life cycle. Outcrossed plants were significantly larger and produced more flowers per plant than sib-crossed and selfed plants growing in the greenhouse. Progeny of hermaphrodites and females appeared to respond similarly to sib-matings. The maternal-sex effects observed in Sidalcea may have been related to cytoplasmically inherited factors and could be a driving force in the maintenance of females. Inbreeding depression could play a role in determining the fitness of both sex morphs, if females experience biparental inbreeding in the field. Frequent inbreeding of hermaphrodites may not be necessary to explain the maintenance of gynodioecy in this species.     

氨氮对鱼类毒性的影响因子及气呼吸型鱼类耐氨策略

氨氮广泛存在于养殖水体中,在氨氮过高的养殖环境下可能会导致鱼类的大量死亡。从生态、环境及养殖效益角度来看,研究氨氮对鱼类的毒性以及鱼类应对环境或体内高氨浓度的策略均具有重要意义。某些鱼类具有其特殊的策略来降低氨毒性,使得这些种类能适应极高的环境或体内氨浓度。这些耐氨策略主要为(1)合成谷氨酰胺、(2)合成尿素排出、(3)增强机体排泄、(4)Rh蛋白促进氨解毒、(5)降低周围环境pH、(6)NH_3挥发和体表碱化、(7)降低体内氨生成、(8)特定氨基酸代谢生成丙氨酸、(9)组织高氨耐受性。鱼类的氨耐受策略较多而且是可变的,主要受特定种类的生活习性和栖息环境影响。文章综述了氨氮对鱼类的毒性机理以及鱼类的应对策略,为相关的研究提供基础资料。     

DIFFERING SELECTION ON PLANT PHYSIOLOGICAL TRAITS IN RESPONSE TO ENVIRONMENTAL WATER AVAILABILITY: A TEST OF ADAPTIVE HYPOTHESES

I used phenotypic selection analysis to test the prediction from functional and comparative studies of plants that smaller leaves and more efficient water use are adaptive in drier environments. I measured selection gradients on leaf size and instantaneous water-use efficiency (a measure of carbon gain per unit water loss) in experimental populations of Cakile edentula var. lacustris placed into wet and dry environments in the field. Linear and nonlinear selection differed significantly between the two environments as predicted. Water-use efficiency was selected to be higher, and leaf area was selected toward a small intermediate optimum, in the dry environment. There was also significant positive correlational selection on water-use efficiency and leaf size, suggesting that the optimum leaf size in the dry environment is greater for plants with higher water-use efficiency. In contrast, neither leaf size nor water-use efficiency were selected in the wet environment, though larger leaves resulted in greater vegetative biomass. Path analysis of the linear selection gradients found that water-use efficiency affected plant fitness primarily because it increased vegetative biomass, as suggested by the hypotheses about the function of physiological traits. These results were not only consistent with the functional hypotheses but also with the observed genetic differentiation in water-use efficiency and leaf size between wet and dry site populations.     

THE USE OF TOXICITY TESTING IN EFFLUENT REGULATION AND CONTROL: A NEW DIMENSION TO ASSESSMENT AND MANAGEMENT OF WATER QUALITY IN SOUTH AFRICA

Summary

Efficient management tools are continually required to cope with increasing demands placed on the quality and quantity of aquatic resources. Recent developments in environmental monitoring indicate the importance of incorporating biological indicators in assessment programmes. Aquatic toxicology has consequently become an important monitoring and regulatory science. Applications of aquatic toxicity testing include: deriving water quality criteria; toxicological evaluations of whole effluents and receiving waters; and the estimation of ecological risk. Toxicity testing can potentially play a significant role in improving water quality in years to come, especially through its application in effluent regulation. Currently however, few environmental laboratories in South Africa have the required expertise and facilities to carry out a representative range of toxicity tests. Training and funding are required to build the capacity for the necessary developmental research, before toxicity testing can routinely be implemented.

The significant problems we face cannot be solved at the same level of thinking we were at when we created them. Albert Einstein.     

THE EFFECT OF SEASON ON A BIOTIC WATER QUALITY INDEX: A CASE STUDY OF THE YELLOW JACKET AND MAZOWE RIVERS,ZIMBABWE.

Summary

The effect of season on the South African Scoring System (SASS) biotic index for rapid assessment of water quality using benthic macroinvertebrates was investigated using the Yellow Jacket and Mazowe Rivers in Zimbabwe as a case study. Several impacts in the area degraded water quality. These were habitat destruction, acid mine drainage and organic pollution. SASS score at all sites changed with season. At and downstream from polluted sites, water quality determined using SASS was best at the end of the rainy season and it deteriorated steadily into the dry season. SASS scores from sites upstream of pollution appeared to improve towards the end of the rainy season. Average Score Per Taxon indices did not have a significant pattern of seasonal variation. SASS was designed to monitor water quality in South African rivers, so when implementing any monitoring programme, selection of sampling season and the interpretation of results in areas with similar climate patterns should take seasonal effects into account, It must be appreciated that water quality at impacted sites is a dynamic variable related both to the activities of polluters and to season.