Phytoplankton community responses in a shallow lake following lanthanum-bentonite application

The release of phosphorus (P) from bed sediments to the overlying water can delay the recovery of lakes for decades following reductions in catchment contributions, preventing water quality targets being met within timeframes set out by environmental legislation (e.g. EU Water Framework Directive: WFD). Therefore supplementary solutions for restoring lakes have been explored, including the capping of sediment P sources using a lanthanum (La)-modified bentonite clay to reduce internal P loading and enhance the recovery process. Here we present results from Loch Flemington where the first long-term field trial documenting responses of phytoplankton community structure and abundance, and the UK WFD phytoplankton metric to a La-bentonite application was performed. A Before-After-Control-Impact (BACI) analysis was used to distinguish natural variability from treatment effect and confirmed significant reductions in the magnitude of summer cyanobacterial blooms in Loch Flemington, relative to the control site, following La-bentonite application. However this initial cyanobacterial response was not sustained beyond two years after application, which implied that the reduction in internal P loading was short-lived; several possible explanations for this are discussed. One reason is that this ecological quality indicator is sensitive to inter-annual variability in weather patterns, particularly summer rainfall and water temperature. Over the monitoring period, the phytoplankton community structure of Loch Flemington became less dominated by cyanobacteria and more functionally diverse. This resulted in continual improvements in the phytoplankton compositional and abundance metrics, which were not observed at the control site, and may suggest an ecological response to the sustained reduction in filterable reactive phosphorus (FRP) concentration following La-bentonite application. Overall, phytoplankton classification indicated that the lake moved from poor to moderate ecological status but did not reach the proxy water quality target (i.e. WFD Good Ecological Status) within four years of the application. As for many other shallow lakes, the effective control of internal P loading in Loch Flemington will require further implementation of both in-lake and catchment-based measures. Our work emphasizes the need for appropriate experimental design and long-term monitoring programmes, to ascertain the efficacy of intervention measures in delivering environmental improvements at the field scale.

Inhibition of methanogenesis by human bile

The factors that regulate methanogenesis in humans have not been established. The presence of bile acid, which is lost into the colon from the small intestine, may be an important regulatory factor of methanogenesis. To examine this possibility, the effect of human bile on methane production by faecal cultures, and the in vivo effect of biliary diversion on breath methane excretion in a methanogenic choledochostomy patient, were investigated. Faecal suspensions (0.1%) from five methanogenic humans were incubated anaerobically with bile (0.3-30%) from three choledochostomy patients, and headspace methane measured by gas chromatography. All biles inhibited headspace methane. Inhibition of methanogenesis was dose dependent, plateaued at 10-30% bile concentration, and was abolished by 0.6% cholestyramine. The maximum inhibition by bile, median (range), was 38 (0.9-56)% of control methane values. Reversal of the bile fistula in the fourth choledochostomy patient converted that subject from methanogenic to 'non-methanogenic' status, It is concluded that inhibition of methanogens in the caecum by bile acid could significantly reduce the number of methanogens in the colon. This and the effect of transit time could explain much of the known epidemiology of 'non-methanogenesis', which has been related to obesity, (comparatively) fast colonic transit in healthy persons, and to small intestinal Crohn's disease.

Congenital genitourinary anomalies. Is there a predilection for multiple primary malignant neoplasms?

A case of simultaneous uterine and renal cell carcinoma in an elderly woman who had a septate vagina, double cervix, uterus didelphys, and a single kidney secondary to contralateral renal agenesis is reported. She was treated for a period of 8 months, first with pelvic irradiation followed by total abdominal hysterectomy and bilateral salpingo-oophorectomy and subsequently with heminephrectomy. Her renal function was normal postoperatively. The patient died of congestive heart failure in June 1990 after being free of carcinoma for approximately 18 years. The authors believe that this is the only case of its kind currently reported in the literature. Four of her family members died of either gastric (n = 3) or lung (n = 1) cancer, and one sister is alive with colon cancer. Only 19 proven cases of this constellation of congenital anomalies have been reported in the literature, and none have been associated with genitourinary (GU) carcinomas. There is a 50% to 70% incidence rate of genital tract anomalies in female patients with unilateral renal agenesis, secondary to the intimate association of the mesonephric and müllerian ducts. It has been suggested that the GU tract is prone to multiple primary malignant neoplasms, and there are families genetically predisposed to the development of large bowel and GU carcinomas. No conclusions can be drawn concerning the development of carcinoma in patients with congenital GU anomalies because of the small number of patients and the lack of follow-up in the literature.