"Foraminiferal and larger invertebrate faunas inhabiting the northern and central coastal zone of the Argentine shelf are impoverished. Plankton is sparsely developed near the shore in these same areas. Spectrographic analysis of shells from the impoverished areas reveals lead, in addition to other trace elements. It is absent in the southern area, where the faunas are normal. The evidence seems to indicate that impoverishment may be due to traces of lead, probably brought into these areas by streams arising in the Andes."