The reading claims that the cause of the sea otter declining which lives along the Alaska coast, is the environmental pollution and provides three reasons of support.

The reading claims that the cause of the sea otter declining which lives along the Alaska coast, is the environmental pollution and provides three reasons of support. However, the professor states that investigation revealed that the sea otter attacks by predators and it is the most cause for declining. She refutes each of the author's reasons. First, the article avers that there were known sources of pollution along the Alaska coast, such as oil rigs and other resources of industerial chemical pollution. In contrast, the speaker opposes this point by saying that the pollution theory is weak because there was no dead otters. In fact, if the infection by pollution was the cause, this would start to kill the otters so there was problem in the hypothesis. Second, the passage posits that other sea mammals such as seals and sea lions along the Alaskan coast were also declining, indication that whatever had endangered the otters was affecting other sea mammals as well. On the other hand, the lecturer counters this point by stating that ocra, a large whale, hunts a large prey but the large prey disappeared because of human activities so the ocra changed their diet. Actually, ocra started to hunt otters instead. Third, the article asserts that at some locations the otter populations declined greatly, while at others they remained stable and this approved the pollution theory. Conversely, the professor casts doubt on this point by explaining that the uneven pattren is caused by predators theory because the ocra hunted the otters which lived deeply so ocra access easily to otters. However, because otters were large in shallow and ocra couldn't go there, so other locations had not declined.