Which of the following statements best summarize factors leading to the collapse of the kelp forest ecosystem in Alaska? Group of answer choices
A All of the above.
B Killer whales began hunting otters, creating a trophic cascade in this system.
C Killer whales began eating kelp after their typical food sources were hunted to near extinction.
D Increased sea temperatures led to an outbreak of disease in the kelp population.
E Killer whales began hunting otters, weakening the trophic cascade in this system.
The correct answer and explanation is:
The correct answer is B: Killer whales began hunting otters, creating a trophic cascade in this system.
The collapse of the kelp forest ecosystem in Alaska is largely attributed to changes in the predator-prey dynamics that disrupted the food chain. This is best understood through the concept of a trophic cascade, where changes at one trophic level (such as the removal of a key predator) lead to cascading effects throughout the ecosystem.
Killer whales, which typically prey on larger marine mammals like seals and sea lions, began targeting sea otters in the 1990s. This shift in predation pressure on otters was linked to a decline in the population of the orcas’ usual prey species. As otters are a key predator of sea urchins, their decline allowed sea urchin populations to increase dramatically. Sea urchins are herbivores that feed on kelp, so the overabundance of urchins resulted in extensive grazing of kelp forests. As a result, the once-thriving kelp forests began to disappear, causing a collapse in the ecosystem that depended on this critical habitat.
The trophic cascade started with killer whales preying on otters, leading to the growth of sea urchin populations, which in turn devastated the kelp forests. The collapse of the kelp forest ecosystem had broad effects on marine biodiversity, as many species depend on kelp for shelter and food. This situation highlights how a shift in the behavior of apex predators can have far-reaching consequences throughout an ecosystem, even impacting organisms at lower trophic levels.
The other options do not accurately capture the primary drivers of the collapse. For example, killer whales eating kelp (Option C) is not supported by evidence, and increased sea temperatures (Option D) while a concern for marine ecosystems, were not the main factor in the collapse of the kelp forests in this case.