A few years ago some of the sea otter populations off of the Alaskan coast started to decline rapidly

The reading and the lecture are both about the decline in sea otter populations. While the reading’s author states that pollution is a cause of their populations declining, the lecturer suggests that the greatest factor is predation. The lecturer casts doubts on the main points made in the reading by providing three reasons. First of all, according to the reading, higher levels of pollutants in water samples support the pollution theory. However, the lecturer disputes this by explaining that if sea otters had been killed by pollutants in water, their remains would appear on shores, which indicates predators ate the sea otters. Secondly, the reading states that populations of other small sea animals have been hurt by pollution. Nevertheless, the lecturer refutes this argument. He argues that because the whale population decreased, nearby orcas had to eat otters instead. Finally, the reading claims that pollutant concentration can explain the uneven pattern of diminishing sea otter populations. On the other hand, the lecturer believes that this uneven population decline corresponds with the prevalence of orcas in different areas. He thinks that the otter population declines more in places with orcas, and less in those inaccessible to orcas. In conclusion, although the reading and the lecture both concern hypotheses about diminishing sea otter populations, the three main points made in the reading are effectively challenged by the lecturer.