Polychlorinated biphenyls and organochlorine pesticides in EELS (Anguilla anguilla L.) from Welsh rivers

Organochlorine concentrations in the muscle tissues of eels at 41 freshwater sites across Wales were surveyed in 1993. Positive but weak relationships were detected between eel age or length and the concentration of some organochlorines. Isomers of HCH were below detection at most sites. Dieldrin was widespread at 10-100 microg kt(-1) wet weight, despite its ban in sheep dip in 1989. Total DDT residue concentrations averaged 73 microg kg(-1). Total PCB burdens expressed as Arochlor 1260, were > 50 microg kg(-1) at 76% of sites and > 100 microg kg(-1) at 46% of sites. The range of concentrations was comparable with other UK data. Rural sites had relatively low levels of PCBs, highest contamination occurring in the lower reaches of industrialised catchments. The inferences for environmental effects are discussed.     

Diversion of water flow from a floodplain wetland stream: an analysis of geomorphological setting and hydrological and ecological consequences

Diversion of water has been ongoing in the Mkuze Wetland for several decades. Two canals form the focus of this study; the Mpempe-Demazane Canal and the Tshanetshe Canal. The former involved an ambitious excavation over a distance of 13.5 km in the lower part of the wetland, while the latter was a minor excavation over a distance of approximately 100 m in the upper part of the wetland. Although ambitious and costly, the Mpempe-Demazane Canal resulted in little downward or headward erosion, and there was minor diversion of flow. However, the minor excavation of the Tshanetshe Canal resulted in erosion downstream of the excavation (the Tshanetshe Stream), downward and lateral erosion of the excavated section, and headward erosion that has propagated almost 4 km upstream along the Mkuze River. Most of the flow of the Mkuze River has been captured by the Tshanetshe Canal and Stream. The impact of canalisation on floodplain wetlands is thus more dependent on the location than the scale of activity. The avulsion of the Mkuze River into the Tshanetshe Canal and Stream is due to a large difference in elevation between the Mkuze River and floodplain into which it was diverted, and the fact that in this region the river typically has high discharges. This avulsion may have been inevitable as a result of natural processes of sedimentation. In contrast, the difference in elevation between the Mkuze River and the basin into which it was diverted via the Mpempe Canal was small as is discharge of the Mkuze River in this part of the wetland. Thus, the diversion was unsuccessful. The presence of hippos that create hydraulically efficient pathways that are oriented parallel to the regional hydraulic slope, may accelerate avulsion in large African wetlands. Overall, it is argued that the environmental consequences of excavation need to be viewed against the background that wetlands are dynamic features within the landscape.     

Cat ownership and Proximity to Significant Ecological Areas Influence Attitudes Towards Cat Impacts and Management Practices

Environmental Management - Cat ownership is increasing globally, representing a growing threat to urban wildlife. Although some cities have policies and strategies for managing owned cats, the...