High PCB levels were recorded in porpoises and common dolphins from European coasts.
AbstractConcentrations of polychlorinated biphenyls (PCBs) in blubber of female common dolphins and harbour porpoises from the Atlantic coast of Europe were frequently above the threshold at which effects on reproduction could be expected, in 40% and 47% of cases respectively. This rose to 74% for porpoises from the southern North Sea. PCB concentrations were also high in southern North Sea fish. The average pregnancy rate recorded in porpoises (42%) in the study area was lower than in the western Atlantic but that in common dolphins (25%) was similar to that of the western Atlantic population. Porpoises that died from disease or parasitic infection had higher concentrations of persistent organic pollutants (POPs) than animals dying from other causes. Few of the common dolphins sampled had died from disease or parasitic infection. POP profiles in common dolphin blubber were related to individual feeding history while those in porpoises were more strongly related to condition.
As top predators, marine mammals can provide information on the accumulation of anthropogenic toxins which present the greatest risk to consumers. We assessed the impacts of persistent organic pollutants (POPs) on two cetacean species that feed on commercially important fi sh species in the eastern North Atlantic; the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena). In order to evaluate the possible long-term effects of POPs on the continued viability of these populations, we investigated their effects on reproductive activity in females, using ovarian scars as an index of reproductive activity. In harbour porpoises, high POP burdens tended to be associated with lower ovarian scar number, possibly indicating that high contaminant levels were inhibiting ovulation, or some females may go through a number of infertile ovulations prior to a successful pregnancy, birth, and survival of their fi rst offspring during early lactation. In contrast, initial results identifi ed that the common dolphins with contaminant burdens above a threshold level for adverse health effects in marine mammals (17 μg g -1 total PCBs lipid) were resting mature females, with high numbers of ovarian scars. This suggests that (a) due to high contaminant burdens, females may be unable to reproduce, thus continue ovulating, or (b) females are not reproducing for some other reason, either physical or social, and started accumulating higher levels of contaminants. Additional analyses were carried out on a control group of ''healthy'' D. delphis, i.e. stranded animals diagnosed as bycatch and were assessed for evidence of any infectious or non infectious disease that would inhibit reproduction. Results suggested that high contaminant burdens, above the threshold level, were not inhibiting ovulation, conception or implantation in female D. delphis, though the impact on the foetal survival rate (in both species) requires further examination. Investigations into accumulation and persistence of ovarian scars and use as an index of reproductive activity were also undertaken within this study.
The Higgs mechanism is an essential but elusive component of the Standard Model of particle physics. Without it Yang-Mills gauge theories would have been little more than a warm-up exercise in the attempt to quantize gravity rather than serving as the basis for the Standard Model. This article focuses on two problems related to the Higgs mechanism clearly posed in Earman's recent papers (Earman 2003, 2004a, 2004b): what is the gauge-invariant content of the Higgs mechanism, and what does it mean to break a local gauge symmetry?
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