TOEFL Integrated Writing Practice Test 056Sea Otters

The sea otter, a small marine mammal, inhabits the waters along the western coast of North America, from California to Alaska. When certain sea otter populations near Alaska began to decline rapidly a few years ago, it raised significant concern because sea otters play a key role in maintaining the coastal ecosystem. Researchers began investigating the cause of the decline and quickly identified two possible explanations: environmental pollution or predator attacks. At first, pollution was considered the more likely cause.

One reason pollution seemed to be the more probable explanation was the presence of known pollution sources along the Alaskan coastline, such as oil rigs and other industrial operations releasing harmful chemicals. Water tests in the area showed elevated levels of pollutants that could weaken the otters’ immune systems, making them more vulnerable to fatal infections, which could lead to their deaths indirectly.

Another point supporting the pollution theory was the decline of other marine mammals, such as seals and sea lions, in the same region. This suggested that whatever was threatening the otters was also impacting other species. Pollution usually harms entire ecosystems rather than targeting one species, making it a likely culprit. Although large predators like orcas could have a similar widespread effect, orcas generally hunt larger animals, such as other types of whales, rather than sea otters.

Finally, the pollution hypothesis could account for the uneven nature of the otter population decline: in some parts of Alaska, otter numbers dropped significantly, while in other areas, the populations remained stable. Some researchers proposed that ocean currents or other environmental conditions might have caused pollutants to concentrate unevenly along the coast, resulting in varied impacts on the otters.