Hi everyone, I hope someone out there could help me with this. I don’t have so much time to get ready for my exam so I really would like to know if this is at least a good answer.
Sea otters are a small mammal that lives in the waters along North America’s west coast from California to Alaska. A few years ago some of the sea otter populations off of the Alaskan coast started to decline rapidly and raised several concerns because of their important role in the coastal ecosystem. Experts began investigating and came up with two possible explanations. One explanation was environmental pollution and the second was attacks by predators.
At first it seemed as if the pollution was the most likely cause for the population decline. One reason pollution was more likely was because of the known pollution sources along the Alaskan coast such as oil rigs. Also water samples taken in the area showed increased levels of chemicals that could decrease the otters’ immune systems and indirectly result in their deaths.
Another thing that pointed to pollution as the culprit was the decline of other sea mammals such as seals in the same areas. This indicated that whatever was affecting the otters was also affecting the other sea mammals. Environmental pollution usually affects an entire ecosystem instead of just one species. Only predators that occurred in a large area, such as orcas (a large predatory whale), could cause the same effect, but they usually hunt larger prey.
Finally, scientists believed the pollution hypothesis would also explain the uneven pattern of otter decline. In some Alaskan locations the otter population declined greatly while other populations remained stable. Some experts suggested this could be explained by ocean currents, or other environmental factor, might have created uneven concentrations of pollutants along the coast.
Ongoing investigations have shown that predation is the most likely cause of the sea otter decline after all.
First, there is a lack of dead sea otters washing up on Alaskan beaches which is not what you would expect from infections caused by pollution killing them off. However, the fact that dead otters are seldom found supports the predator hypothesis. If a predator kills an otter, then it is eaten right away and can’t wash up on shore.
Second, orcas prefer to hunt whales, but whales have essentially disappeared in that area from human hunters. Since the whales are not as available, orcas have had to change their diet to what is available. Since it is only smaller sea animals available, the orcas have probably started hunting those more and created the decline in all of the species mentioned in the passage.
Finally, predation is a more likely reason for the uneven pattern of otter decline. Otters in locations that are more accessible to orcas are more likely to be hunted. This is supported by the stable populations of otters in shallow rocky locations where orcas can’t access.
The lecturer position in this issue is clearly opposite to the author one, while in the reading passage it can be read that pollution is the most influential variable in the decline of sea otters population, the lecture use the impact of predation as the guilty one.
To start with something, even when the things that the author mention like oil rings affecting immune systems are really important and probably true, it will take a lot more time to see their impact, and, on the other hand, the fact that there are no death bodies of sea otters in shore is one of the most substantial information to this case because it´s a proof that predators are eating them. If polution was the problem, it would not be a pretty view at the beach.
Following this idea is that there is an uneven pattern of this populations declines, the author exposes that this is due to the different concentrations of pollutants and how they move through ocean currents, altough, the lecturer makes a strong point saying that what´s happening is that whales are the one specie that decline in the zone because hunters, and being this huge krill eating machine the predilect food for orcas, they have to change their diet in order to survive. And then, it is proved that the populations of sea otters in rocky locations where orcas can´t reach are healthy as always. So, it is not too crazy to think that for an animal that is used to eat a whale, just one little sea otter might not be enough.