TOEFL integrated writing The sea otter

The article introduces the topic of the hypothesis of why sea otters decline. The writer says that the main reason is related to environmental and ecosystem pollution. The lecturer diagrees. He says that the typical effect is the predators.
First, the author mentions environmental pollution. It states that along the Alskan coast, there are lots of oil rigs, which could threaten the otter’s lives. On top of that, many chemicals sprinkled in the ocean are also dangerous to their health. The professor believes there are flaws in the author’s position. He contends that there is a lack of dead otters on Alaska beaches. Therefore, it might be eaten by predators and then there are no traces on it.
According to the writer, according to the decline of seal mammals which lived with otters, it could be shown by environmental pollution. The speaker, on the other hand, points out orcas and whales. The whale, which is the orcas main prey, was caught by the people. Thus, orcas found another alternative prey to eat such as otters and seals. As a result, the resemblance with otters mammals declined simultaneously.
Also, the reading passage notes that ocean current resulted with the unstable otters population. The professor refutes this argument. He says that the uneven concentrated population of otters depended on the orcas population. Some areas that are shallow and roky are hard to approach orcas.
As you can see, the author and the lecture hold very different views on the hypothesis of the declination of otters.