SAO PAULO — More than 100 dolphins have died in the Brazilian Amazon rainforest in the past week as the region grapples with a severe drought, and many more could die soon if water temperatures remain high, experts say. The Mamiraua Institute, a research group of Brazil’s Ministry of Science, Technology and Innovation, said two more dead dolphins were found Monday in the region around Tefe Lake, which is key for mammals and fish in the area.