Characterisation of spatial variability in water quality in the Great Barrier Reef catchments using multivariate statistical analysis.

Water quality monitoring is important to assess changes in inland and coastal water quality. The focus of this study was to improve understanding of the spatial component of spatial-temporal water quality dynamics, particularly the spatial variability in water quality and the association between this spatial variability and catchment characteristics. A dataset of nine water quality constituents collected from 32 monitoring sites over a 11-year period (2006-2016), across the Great Barrier Reef catchments (Queensland, Australia), were evaluated by multivariate techniques. Two clusters were identified, which were strongly associated with catchment characteristics. A two-step Principal Component Analysis/Factor Analysis revealed four groupings of constituents with similar spatial pattern and allowed the key catchment characteristics affecting water quality to be determined. These findings provide a more nuanced view of spatial variations in water quality compared with previous understanding and an improved basis for water quality management to protect nearshore marine ecosystem.

Cost minimisation using clinic-based treatment for common hand conditions--a prospective economic analysis.

INTRODUCTION: The purpose of this study was to compare the cost of treatment of Dupuytren's disease, ganglia and trigger digits in the out-patient department with the operating theatre. PATIENTS AND METHODS: All patients seen in a new patient hand clinic with a diagnosis of Dupuytren's disease, trigger digit or ganglion of the wrist or hand requiring treatment were prospectively identified over a 6-month period. The numbers undergoing a procedure in the out-patient clinic or theatre were recorded. Costings of theatre time and out-patient time, as well as national tariff income, were obtained from the hospital management. RESULTS: Over the 6-month period, 80, 26, and 52 patients were treated with regard to Dupuytren's disease, ganglia and trigger digits, respectively. Of these, 37, 23, and 44 were treated by an out-patient procedure, and 43, 3 and 8 underwent a formal operation. The total cost of the out-patient procedures was calculated at pound 1560 over 6 months. To perform these as formal operations would have cost pound 64,896. The cost savings were, therefore, pound 63,336, or pound 126,672 per annum. CONCLUSIONS: Out-patient interventions for Dupuytren's disease, ganglia and trigger digits result in significant cost savings over formal surgical treatment.

Differential diagnosis of adnexal masses: risk of malignancy index, ultrasonography, magnetic resonance imaging, and radioimmunoscintigraphy.

A risk of malignancy index (RMI), based on menopausal status, ultrasound (US) findings, and serum CA125, has previously been described and validated in the primary evaluation of women with adnexal masses and is widely used in selective referral of women from local cancer units to specialized cancer centers. Additional imaging modalities could be useful for further characterization of adnexal masses in this group of women. A prospective cohort study was conducted of 196 women with an adnexal mass referred to a teaching hospital for diagnosis and management. Follow-up data was obtained for 180 women; 119 women had benign and 61 women malignant adnexal masses. The sensitivity and specificity of specialist US, magnetic resonance imaging (MRI), radioimmunoscintigraphy (RS), and the RMI were determined. We identified a subgroup of women with RMI values of 25-1000 where the value of further specialist imaging was evaluated. Sensitivity and specificity for specialist US were 100% and 57%, for MRI 92% and 86%, and for RS 76% and 87%, respectively. Analysis of 123 patients managed sequentially, using RMI cutoff values of > or =25 and <1000 and then US and MRI provided a sensitivity of 94% and a specificity of 90%. Using this RMI cutoff followed by specialist US and MRI, as opposed to the traditional RMI cutoff value of 250, can increase the proportion of patients with cancer appropriately referred in to a cancer center, with no change in the proportion of patients with benign disease being managed in a local unit.

Embryology of the adrenal glands and its relevance to diagnostic imaging.

An understanding of the embryology of the adrenal glands is necessary to appreciate the location of adrenal ectopic, or rest, tissue which can occur anywhere along the course of gonadal descent. This tissue usually has no clinical significance, but may become hyperplastic in patients with primary or secondary adrenal pathology. In congenital adrenal hyperplasia, hyperplastic rest tissue may present as a soft-tissue mass, particularly in the gonads and retroperitoneum, and may be mistaken for tumour. The adrenal in the neonate is proportionately much larger than in the adult; in renal ectopy or agenesis the ipsilateral adrenal is normally sited and may be mistaken for a kidney because of its size. This review article illustrates the embryology of the adrenal with particular emphasis on the relevance of embryology to pathology.

The role of magnetic resonance imaging and ultrasound in patients with adnexal masses.

AIMS: To evaluate the accuracy of ultrasonography (US) and magnetic resonance imaging (MRI) in characterizing adnexal masses, and to determine which patients may benefit from MRI. METHODS: We prospectively studied 72 women (mean age 53 years, range 19 to 86 years) with clinically suspected adnexal masses. A single experienced sonographer performed transabdominal and transvaginal greyscale spectral and colour Doppler examinations. MRI was carried out on a 1.5T system using T1, T2 and fat-suppressed T1-weighted sequences before and after intravenous injection of gadolinium. The adnexal masses were categorized as benign or malignant without knowledge of clinical details, according to the imaging features which were compared with the surgical and pathological findings. RESULTS: For characterizing lesions as malignant, the sensitivity, specificity and accuracy of MRI were 96.6%, 83.7% and 88.9%, respectively, and of US were 100%, 39.5% and 63.9%, respectively. MRI was more specific (p<0.05) than US. Both MRI and US correctly diagnosed 17 (24%) cases with benign and 28 (39%) cases with malignant masses. MRI correctly diagnosed 19 (26%) cases with benign lesion(s), which on US were thought to be malignant. The age, menopausal status and CA-125 levels in these women made benign disease likely, but US features were suggestive of malignancy (large masses and solid-cystic lesions with nodules). CONCLUSION: MRI is more specific and accurate than US and Doppler assessment for characterizing adnexal masses. Women who clinically have a relatively low risk of malignancy but who have complex sonographic features may benefit from MRI.

Foramen ovale recordings: a presurgical investigation in epilepsy.

The aim of our study was to determine when foramen ovale recordings add useful information to scalp EEG recordings and magnetic resonance imaging (MRI) with hippocampal measurements. We evaluated the outcome of 79 patients with non-lesional partial epilepsy with presumed temporal seizure onset. Ictal foramen ovale recordings were performed in 16 patients with normal MRI ('MRI-negative group') and 41 patients with lateralizing MRI but non-lateralizing scalp EEG ('discordant group'). 22 patients with concordant MRI and scalp EEG were not investigated with foramen ovale recordings ('concordant group'). The seizure-free rate was higher in concordant than discordant patients despite additional investigation with foramen ovale electrodes (71 and 55% seizure free, respectively). No useful localizing information was added with foramen ovale recordings in MRI-negative patients.

Contrast medium extravasation injury: guidelines for prevention and management.

Extravasation of contrast material is a well-recognized complication of contrast-enhanced imaging studies. The management of this complication is contentious; therefore, the Contrast Media Safety Committee of The European Society of Urogenital Radiology decided to review the literature and issue guidelines. A comprehensive literature search was carried out. The resulting report was discussed at the 8th European Symposium on Urogenital Radiology in Genoa, Italy. Automated power injection may result in extravasation of large volumes and may or can lead to severe tissue damage. Infants, young children and unconscious and debilitated patients are particularly at risk of extravasation during contrast media injection. Fortunately, most extravasations result in minimal swelling or erythema, with no long-term sequelae; however, severe skin necrosis and ulceration may occur. Large volumes of high osmolar contrast media are known to induce significant tissue damage. Compartment syndrome may be seen associated with extravasation of large volumes. Conservative management is often adequate, but in serious cases the advice of a plastic surgeon is recommended. Based on the review simple guidelines for prophylaxis and management of contrast medium extravasation injuries are proposed.

Spleen size: how well do linear ultrasound measurements correlate with three-dimensional CT volume assessments?

Ultrasound measurement of splenic length is standard practice, but it is not known how well this represents the true size of the spleen. Previous studies, using a combination of measurements from in vivo and resected spleens, were subject to error because of changes in splenic size. The aim of this study was to correlate the dimensions of the spleen measured by ultrasound with the splenic volume measured by helical CT. Ultrasound examination was performed on 50 adult patients at the time of their attendance for abdominal CT. Linear dimensions of the spleen were measured with the patient first in the supine and then in the right lateral decubitus (RLD) position. The splenic volume was calculated from a three-dimensional reconstruction of the CT images. There was good correlation, using Spearman's rank correlation, between ultrasound measurements and CT volumes with correlation coefficients exceeding 0.7 for all parameters except one. The linear measurement that correlated most closely with CT volume was the spleen width measured on a longitudinal section with the patient in the RLD position (correlation coefficient (r)=0.89, p<0.001). There was also good correlation between splenic length measured in the RLD position and CT volume (r=0.86, p<0.001). We conclude that a good correlation exists between in vivo ultrasound assessment of splenic size and true splenic volume. The most accurate single measurement is spleen width measured on a longitudinal section with the patient in the RLD position. However, measurement of splenic length, which is the most commonly used in clinical practice, also correlates well with splenic volume, particularly when performed with the patient in the RLD position.

Testicular microlithiasis: is it a benign condition with malignant potential?

OBJECTIVE: To review the findings of testicular ultrasonography (US) in patients referred for testicular symptoms including pain, swelling and infertility, and to determine the prevalence of testicular microlithiasis (TM) and ist relevance to the development of testicular cancer. METHODS: Records of 3,026 patients referred for testicular US between 1994 and 1999 were evaluated. The indications for testicular US diagnosis, management and relevant histological details were obtained from medical records. Patients with TM had an annual sonographic follow-up unless they had testicular cancer, in which case follow-up repeat US with clinical reviews was more frequent. RESULTS: TM was found in 54 patients (1.77%; median age 34 years, range 12-83 years). The median follow-up was 36 months (range 12-18 months). Sixteen of these patients had testicular malignancy (30%). The remaining 38 patients had hydrocele and epididymal cysts (14), varicocele (7), epididymitis (2) and small testes (8), with 14 patients having no other pathology. One patient with a small testis developed a seminoma while under surveillance. Another patient with metastatic embryonal-cell carcinoma at initial diagnosis was found to have a seminoma 4 years following chemotherapy. The relative risk of testicular tumours in the presence of TM was 13.2 (confidence interval 8.3-21.5). CONCLUSION: TM can no longer be regarded simply as a benign condition because of its association with testicular malignancy. In our series, 2 patients (5.2%) developed interval testicular cancers during follow-up US. There is no convincing evidence to suggest that TM might be premalignant. In rare instances of radiologically indeterminate cases, biopsy of the testis may be necessary.

Prevention of generalized reactions to contrast media: a consensus report and guidelines.

The aim of this study was to document, using consensus methodology, current practice for prevention of generalized reactions to contrast media, to identify areas where there is disagreement or confusion and to draw up guidelines for reducing the risk of generalized contrast media reactions based on the survey and a review of the literature. A document with 165 questions was mailed to 202 members of the European Society of Urogenital Radiology. The questions covered risk factors and prophylactic measures for generalized contrast media reactions. Sixty-eight members (34%) responded. The majority indicated that a history of moderate and severe reaction(s) to contrast media and asthma are important risk factors. The survey also indicated that patients with risk factors should receive non-ionic contrast media. In patients at high risk of reaction, if the examination is deemed absolutely necessary, a resuscitation team should be available at the time of the procedure. The majority (91%) used corticosteroid prophylaxis given at least 11 h before contrast medium to patients at increased risk of reaction. The frequency of the dosage varied from one to three times. Fifty-five percent also use antihistamine Hl, mainly administered orally and once. Antihistamine H2 and ephedrine are rarely used. All essential drugs are available on the emergency resuscitation trolley. Patients with risk factors are observed up to 30 min by 48% and up to 60 min by 43% of the responders. Prophylactic measures are not taken before extravascular use of contrast media. Prophylactic drugs are given to patients with a history of moderate or severe generalized reaction to contrast media. In patients with asthma, opinion is divided with only half of the responders giving prophylactic drugs. Aspirin, beta-blockers, interleukin-2 and non-steroid anti-inflammatory drugs are not considered risk factors and therefore are not stopped before injection of contrast media. The survey showed some variability in rating of risk factors for generalized contrast medium reactions, and marked variability in the prophylactic measures used. There remain major areas of uncertainty, and there is insufficient data in the literature to guide practice. Some simple guidelines for prophylaxis of generalized contrast medium reactions are proposed.

Contribution of dihydrocodeine and dihydromorphine to analgesia following dihydrocodeine administration in man: a PK-PD modelling analysis.

AIMS: It is not clear whether the analgesic effect following dihydrocodeine (DHC) administration is due to either DHC itself or its metabolite, dihydromorphine (DHM). We examined the relative contribution of DHC and DHM to analgesia following DHC administration in a group of healthy volunteers using a PK-PD link modelling approach. METHODS: A single oral dose of DHC (90 mg) was administered to 10 healthy volunteers in a randomised, double-blind, placebo-controlled study. A computerized cold pressor test (CPT) was used to measure analgesia. On each study day, the volunteers performed the CPT before study medication and at 1.25, 2.75, 4.25 and 5.75 h postdose. Blood samples were taken at 0.25 h (predose) and then at half hourly intervals for 5.75 h postdose. PK-PD link modelling was used to describe the relationships between DHC, DHM and analgesic effect. RESULTS: Mean pain AUCs following DHC administration were significantly different to those following placebo administration (P = 0.001). Mean pain AUC changes were 91 score x s(-1) for DHC and -17 score x s(-1) for placebo (95% CI = +/- 36.5 for both treatments). The assumption of a simple linear relationship between DHC concentration and effect provided a significantly better fit than the model containing DHM as the active moiety (AIC = 4.431 vs 4.668, respectively). The more complex models did not improve the likelihood of model fits significantly. CONCLUSIONS: The findings suggest that the analgesic effect following DHC ingestion is mainly attributed to the parent drug rather than its DHM metabolite. It can thus be inferred that polymorphic differences in DHC metabolism to DHM have little or no effect on the analgesic affect.

The OMENS trial: opportunistic evaluation of musculo-skeletal physician care among orthopaedic outpatients unlikely to require surgery.

STUDY OBJECTIVE: For orthopaedic outpatients judged as unlikely to require surgery, how does the cost-effectiveness of treatment from a musculo-skeletal medicine physician compare with that of a conventional orthopaedic surgeon-led service? DESIGN: Partially randomised, pragmatic trial comparing management from a single musculo-skeletal medicine physician with orthopaedic surgeon-led management, with the timing and nature of treatments at the discretion of individual clinicians. Main outcomes were: change in patient reported health (SF-36 and EuroQol), and marginal health service costs. SETTING: Outpatient department of an Edinburgh orthopaedic hospital. SUBJECTS: One thousand three hundred and twenty six people; aged over 18, referred to and later attending the outpatient department with a 'non-surgical' musculo-skeletal condition, who provided baseline information. Eight hundred and twenty nine were randomly allocated to management by either the musculo-skeletal medicine physician (medical group) or a conventional orthopaedic surgeon-led service (surgical group); 497 were assigned to the treatment groups according to their general practitioner's preference. RESULTS: There are aspects of the study design concerning statistical power, potential selection bias and generalisability, which mean that any results must be treated with caution. Although there was no statistically significant difference in health gain between the randomly allocated groups (with similar findings in the non-randomised medical and surgical groups), the patient groups were heterogeneous and the confidence intervals did not rule out clinically important differences. The medical group received more outpatient treatment, 20% vs. 10% (difference 95% CI 5% to 15%) with a higher rate of physiotherapy referral, 45% vs. 30% (15%, 9% to 22%). The surgical group received more inpatient surgical care 6% vs. 17% (-11%, -15% to -7%). Mean healthcare costs in the medical group were 179 Pounds per patient compared with 287 Pounds in the surgical group (-108 Pounds, -25 Pounds to -191 Pounds). CONCLUSIONS: Interpretation should take into account the practical difficulties and circumstances of the study. Although no differences in health gain were found between these two management policies for 'non-surgical' orthopaedic outpatients, the trial was less statistically powerful than planned and the confidence intervals included clinically important differences. Differences in treatment emphasis gave estimated costs savings to the Health Service of 108 Pounds per patient treated by the musculo-skeletal medicine service.

Feature and classifier fusion for 12-lead ECG classification.

Two methodologies, feature and classifier fusion, for the problem of computerized 12-lead electrocardiogram classification, are investigated. Firstly, the entire classification problem is subdivided into a number of smaller bi-dimensional ones. By employing bi-group Neural Network classifiers, independent feature vectors for each diagnostic class are examined individually and the output from each classifier are fused together to produce one single result. Secondly, two classifiers, namely the aforementioned and a decision tree, are fused together through a novel approach of a Specificity Matrix. This methodology addresses the problem of unresolved conflict during fusion of classifiers and aims to exploit the merits of each classifier and suppress their weaknesses. 290 validated 12-lead electrocardiogram recordings, comprising six diagnostic classes, were used to train, validate and test both methodologies. The framework of bi-group classifiers enhanced the overall performance by 12.0% in comparison with conventional approaches. In the second instance, the fusion of the two classifiers produced a performance level of 81.3%; superior to either classifier in isolation. This approach offers a viable solution to the unresolved problem of conflict between classifiers during fusion and can be extended readily to accommodate any number of diagnostic classes and classifiers.

How common are polycystic ovaries and the polycystic ovarian syndrome in women with Cushing's syndrome?

OBJECTIVE: Women with Cushing's syndrome (CS) may present with menstrual irregularity and symptoms/signs of hyperandrogenism, a phenotype similar to that of the polycystic ovarian syndrome (PCOS); however, currently there are no data on the prevalence of either polycystic ovaries (PCO) and/or PCOS in patients with CS. The aim of this study was to investigate their presence among women of reproductive age presenting with CS by analysing clinical, endocrinological and ultrasonographic features. DESIGN: Prospective study of all women within the reproductive age (range 18-40 years) who presented with CS between August 1994 and January 2000. SUBJECTS AND METHODS: Thirteen women (median age 32 years, range 18-39 years) with CS were evaluated. The diagnosis of CS was based on the presence of appropriate clinical features and an elevated serum midnight cortisol with failure to suppress 0900 hours serum cortisol to less than 50 nmol/l following a formal low-dose dexamethasone suppression test (LDDST). All women had their clinical features relevant to possible hyperandrogenism, menstrual disorder and infertility recorded, and circulating gonadotrophins, oestradiol, androgens and SHBG levels measured; ovarian ultrasonography was performed during their initial assessment. Relevant MR/CT imaging of the pituitary and/or adrenal glands was performed. RESULTS: Eleven women had ACTH-dependent CS [nine Cushing's disease (CD), one ectopic ACTH syndrome due to a bronchial carcinoid, one periodic CS of unknown origin); two patients had ACTH-independent CS (adrenal adenomas). All women with CS had at least one symptom/sign of hyperandrogenism (13 hirsutism, seven acne, five male-pattern alopecia). Nine women (70%) had menstrual disturbances (four oligomenorrhoea, four amenorrhoea, one polymenorrhoea) while four women (30%) had a normal menstrual pattern. Serum oestradiol levels for the group as a whole were similar to those observed in the early follicular phase of normally menstruating women; however, seven women had low oestradiol, LH and FSH levels suggestive of hypogonadotrophic hypogonadism. Serum androgen levels (testosterone, androstendione and DHEAS), even in the presence of symptoms/signs of hyperandrogenism, were within the normal reference range but SHBG levels were uniformly decreased even in women with normal menstrual cycles. There was a negative correlation between urinary free cortisol, but not mean serum cortisol, and serum oestradiol, testosterone and SHBG levels (r = - 0.8, r = - 0.86 and r = - 0.66, P<0.02, P<0.01 and P<0.05, respectively), but not LH or FSH levels. Despite the fact that seven of these 13 patients lacked normal gonadotrophin stimulation, ovarian volumes of both ovaries were relatively preserved: right 7.3 ml, range 2.8-12.8 ml, and left 5.3 ml, range 2.3-13 ml. Women who were defined as oestrogen sufficient (E2 > 140 pmol/l) had higher serum androstenedione, and lower urinary free cortisol levels, than women who were oestrogen deficient (E2 < 140 pmol/l). Six of the 13 women (46%) had ovarian morphology suggestive of PCO, four of six oestrogen sufficient women and two of seven oestrogen deficient women. The results did not differ according to the underlying cause of CS. CONCLUSIONS: PCO and PCOS are common in women with Cushing's syndrome; women with Cushing's syndrome and only moderately elevated cortisol secretion maintain gonadotrophin stimulation to the ovary with normal oestradiol levels, in contrast to women with Cushing's syndrome and higher cortisol secretion who develop hypogonadotrophic hypogonadism. However, even in the latter group, high ovarian volumes were maintained and some had ovarian morphology suggestive of PCO.

Rapid MRI assessment of renal space-occupying lesions.

The aim of this study was to determine whether rapidly acquired MRI sequences, taking less than 5 min imaging time, can accurately characterise renal masses. All patients found to have a renal space-occupying lesion on CT or asked to participate in a prospective study using rapidly acquired MRI. The MRI technique was performed on a GE Signa (General Electric, Milwaukee, Wis.) 1.5 T magnet using breath-hold coronal and axial T1 GRASS (fast spoiled gradient-recalled acquisition into steady state, FSPGR30/90) and axial T2 fast spin-echo sequences. The results were analysed by two radiologists unaware of the CT or ultrasound findings. The CT/US was independently viewed by a third radiologist. Lesions were characterised as simple cysts, indeterminate or solid. The MR and CT/US results were correlated and the sensitivity and specificity of MR for the characterisation of simple cysts and solid renal masses calculated. A total of 144 lesions (68 patients; 29 women 39 men, age range 32-78 years, average age 60 years) were studied: 111 simple cysts; 3 hyperdense cysts; 26 renal cell carcinomas; and 4 indeterminate lesions on CT/US. There was agreement between the CT/US and MRI in 82% of cases. All renal cell carcinomas were correctly characterised on MRI. Of simple cysts, 79% were correctly identified using this technique. Breath-hold MRI performed in less than 5 min can accurately characterise the majority of renal masses. It is 100% sensitive in the characterisation of renal carcinoma, and it correctly identified approximately 80% of simple cysts. If used at the time a renal mass is detected on MRI, it would reduce the need for further investigation of the majority of incidentally detected lesions which are simple cysts.

Quantitative magnetic resonance imaging in consecutive patients evaluated for surgical treatment of temporal lobe epilepsy.

We present the results of quantitative Magnetic Resonance Imaging (MRI) in 55 consecutively referred patients with clinical evidence of temporal lobe epilepsy (TLE). The Cavalieri method was used in combination with point counting to provide unbiased estimates of the volume of the left and right hippocampus, amygdala, temporal lobe, lateral ventricles and cerebral hemisphere, and pixel by pixel maps of the T2 relaxation time were computed for both central and anterior sections of the hippocampus. The 99th centiles of hippocampal volume, hippocampal volume asymmetry and T2 relaxation times in 20 control subjects provided limits which identified the presence of MTS. The results of the quantitative MRI were compared with the results of conventional diagnostic MRI, foramen ovale (FO) recording and the WADA test. Thirty-one patients were found to have unilateral MTS (17 left and 14 right) and 7 bilateral MTS. No evidence of MTS was detected in 16 patients. Of the 31 patients diagnosed with unilateral MTS on the basis of hippocampal volume and T2 measurement, 74% and 77% would respectively have received the same diagnosis on the basis of hippocampal volume and T2 measurements alone. In comparison to FO recording, quantitative MRI has a sensitivity of 55% and a specificity of 86%, while conventional diagnostic MRI has a sensitivity of 42% and a specificity of 80% for detection of MTS. Unilateral abnormalities were detected by FO recording in 30% cent of patients who appeared normal on quantitative MRI. WADA test results were available for 40 patients. The findings were consistent with quantitative MRI showing reduced memory function ipsilateral to unilateral MTS in 18 patients, but reduced memory function contralateral to unilateral MTS in two patients, and reduced memory function without MR abnormality in seven patients. WADA testing revealed unilateral memory impairments where MRI found bilateral pathology in 4 patients and in 4 patients in whom quantitative MRI detected unilateral MTS there was no evidence of reduced memory during WADA testing of the corresponding cerebral hemisphere. In the patients with unilateral right MTS a highly significant negative correlation (p = 0.0003) was observed between age of onset and the volume of the contralateral temporal lobe. Quantitative MR imaging of the hippocampus (i.e. volume and T2 measurement) is preferable to conventional radiological reporting for providing objective evidence of the presence of MTS on which to base the referral of patients for surgery, and since it has associated morbidity FO recording is now only being used in selected patients. Furthermore, stereology provides a convenient method for estimating the volume of other brain structures, which is relevant to obtaining a better understanding of the effects of laterality and age of onset of TLE.

Novel techniques for field assessment of copper toxicity on fouling assemblages.

Laboratory toxicity tests generally expose organisms to a constant concentration of a toxicant in a uniform environment. The two techniques outlined in this paper assess the impact of a model toxicant, copper, on marine fouling assemblages in the field. These techniques allow natural assemblages to develop under a regime of toxicant dosing. The experiments were conducted using both techniques over time frames ranging from 2 weeks to 6 months. Short term experiments using the techniques assess the effects of toxicant exposure on recruitment. The longer term experiments enabled detection of certain indirect impacts of pollution. These include effects due to competition for space and variations in the susceptibility of organisms with age. Over the course of the experiments, a range of responses to copper was observed for different taxa. Both techniques have the potential to be used for testing the impact of other toxicants. Approaches such as those described are necessary in order to understand how communities react to toxicants in real world situations.