The reading and the lecture are both about the decline of the sea otter population along North America's West Coast. The author of the article feels that the sea otter decline is caused by environmental pollution. The lecturer disputes the claim made in the article. His position is that the otter decline is caused by predation.
According to the reading, there were known causes of pollution along the Alaskan coast like oil rigs. The article also mentions that an increased concentration of chemicals was found in water samples taken in the area. It further mentions that this could affect the otter's immune system which may result in its death. This specific claim is challenged by the lecturer. He claims that if the pollution was the likely cause then there should be plenty of dead sea otters crashing on the surface of surrounding beaches. He also mentions that sea otters were seldom found on the beaches.
Secondly, the author reasons that, the other sea animals have also been on the decline. In the article, it is said that pollution affects the entire ecosystem of animals instead of a single species. It also mentions that orcs were the only predators living in the region of sea otters and they generally hunt larger prey. The lecturer, however, asserts that the orc food supply may have been affected by the killing of whales by humans. He further goes on to say, since the orcs did not have any other food source they started preying on sea otters for survival.
Finally, the author posits that the population of otters varied widely from region to region. The author contends that the non-uniform concentration of pollutants due to ocean currents and other environmental factors may have been the cause for the variation of sea otter population. In contrast, the lecturer's stance is that the uneven population could be explained by the uneven predatory species population. He further notes that the shallow rocky region had a stable otter population which could not be accessed by the predators.