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.

Estimates of absorption of radiofrequency radiation by the embryo and fetus during pregnancy.

This paper reports that the specific absorption rate induced in the embryo or fetus can exceed that recommended for the general public when the mother is exposed to radiofrequency radiation at the occupational limits. This result applies to two-tiered radiofrequency radiation standards where a factor of 5 differentiates occupational and nonoccupational exposure limits. Using simple axisymmetric geometries for the pregnant worker, and assuming plane wave exposures, a finite element method provides estimates of prenatal exposure. Various layered shapes are used to model skin, fat, uterus, blood, embryonic, and fetal tissues. Applying current exposure limits given by IRPA, ANSI, and SAA, the results indicate that overexposures to the embryo or fetus can occur from early pregnancy at 80-100 MHz, and in late pregnancy across the range 300-1500 MHz.

Implanted medical devices in workers exposed to radio-frequency radiation.

This paper discusses the management of radio-frequency radiation workers who have implanted medical devices which may be adversely affected by such radiation fields. The implants include orthopedic devices, cardiac pacemakers, and cochlear implants, but exclude dental work. The effect of radio-frequency radiation on the devices may be to increase heat load and/or produce signal interference. The mechanics of interaction are outlined and protocols for managing cases are described. The implications for safety standards are discussed.