Understanding the structure and functioning of polar pelagic ecosystems to predict the impacts of change.

The determinants of the structure, functioning and resilience of pelagic ecosystems across most of the polar regions are not well known. Improved understanding is essential for assessing the value of biodiversity and predicting the effects of change (including in biodiversity) on these ecosystems and the services they maintain. Here we focus on the trophic interactions that underpin ecosystem structure, developing comparative analyses of how polar pelagic food webs vary in relation to the environment. We highlight that there is not a singular, generic Arctic or Antarctic pelagic food web, and, although there are characteristic pathways of energy flow dominated by a small number of species, alternative routes are important for maintaining energy transfer and resilience. These more complex routes cannot, however, provide the same rate of energy flow to highest trophic-level species. Food-web structure may be similar in different regions, but the individual species that dominate mid-trophic levels vary across polar regions. The characteristics (traits) of these species are also different and these differences influence a range of food-web processes. Low functional redundancy at key trophic levels makes these ecosystems particularly sensitive to change. To develop models for projecting responses of polar ecosystems to future environmental change, we propose a conceptual framework that links the life histories of pelagic species and the structure of polar food webs.

Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centred food web.

The Scotia Sea ecosystem is a major component of the circumpolar Southern Ocean system, where productivity and predator demand for prey are high. The eastward-flowing Antarctic Circumpolar Current (ACC) and waters from the Weddell-Scotia Confluence dominate the physics of the Scotia Sea, leading to a strong advective flow, intense eddy activity and mixing. There is also strong seasonality, manifest by the changing irradiance and sea ice cover, which leads to shorter summers in the south. Summer phytoplankton blooms, which at times can cover an area of more than 0.5 million km2, probably result from the mixing of micronutrients into surface waters through the flow of the ACC over the Scotia Arc. This production is consumed by a range of species including Antarctic krill, which are the major prey item of large seabird and marine mammal populations. The flow of the ACC is steered north by the Scotia Arc, pushing polar water to lower latitudes, carrying with it krill during spring and summer, which subsidize food webs around South Georgia and the northern Scotia Arc. There is also marked interannual variability in winter sea ice distribution and sea surface temperatures that is linked to southern hemisphere-scale climate processes such as the El Niño-Southern Oscillation. This variation affects regional primary and secondary production and influences biogeochemical cycles. It also affects krill population dynamics and dispersal, which in turn impacts higher trophic level predator foraging, breeding performance and population dynamics. The ecosystem has also been highly perturbed as a result of harvesting over the last two centuries and significant ecological changes have also occurred in response to rapid regional warming during the second half of the twentieth century. This combination of historical perturbation and rapid regional change highlights that the Scotia Sea ecosystem is likely to show significant change over the next two to three decades, which may result in major ecological shifts.

Clinical trial of mebendazole, a broad-spectrum anthelminthic.

Eighty-five children aged 5-14 years who were infested with worms were treated with mebendazole 100 mg twice daily for three days. The percentage cure rates were ascaris 100%, trichuris 94%, hookworm 82%, and hymenolepis 39%. The drug was well tolerated and with its broad activity should be very useful in treating those with multiple infestations.

Survey of intestinal pathogens from immigrant children.

Four thousand immigrant schoolchildren were screened by using a concentration method on a single faecal specimen for intestinal helminths; 1,468 (37%) were positive. Carriage rates were highest (51%) in children from the West Indies, in whom trichuris (75% of carriers) and ascaris (40% of carriers) predominated; carriage of two or more species was common (36% of carriers). Carriage of worms was low in children from Kenya (16%) and Uganda (7%). Children from South-east Asia, predominantly from India and Pakistan, had carriage rates between 30 and 40%; girls and boys from Pakistan differed significantly in their carriage patterns of hook-worm (commoner in boys) and hymenolepis and ascaris (commoner in girls).Five salmonellas were found, two of which were Salmonella typhi, and five Shigella sonnei were isolated. No isolates were made of Vibrio cholerae (classical or El Tor biotypes) from 590 South-east Asian children.

Prevalence of symptomless urinary tract disease in Birmingham schoolchildren. I. Pyuria and bacteriuria.

In a pilot project 2,122 schoolchildren were screened for symptomless urinary tract disease by the examination of midstream urine specimens. These were tested for albumin, blood, and glucose with Labstix commercial strips, together with microscopy for abnormal cellular excretion.One case of renal glycosuria was found but none of previously undiagnosed diabetes mellitus. Out of 1,096 boys, 11 (1%) had pyuria-a leucocyte count greater than 10/cu.mm.-but only four showed abnormal counts on retesting. None had urinary tract infection.Out of 1,026 girls, 96 (9.3%) had pyuria initially but 35 were normal on retesting. Of the remaining 61 girls, 59 attended the outpatients department for further investigation, and in 30 vulvitis appeared to be the sole cause. Ten were proved to have significant bacteriuria and six of them showed radiological abnormalities.It is suggested that careful long-term studies are needed to study the economics and the implications of screening on a national scale.