Here are the key reasons why the effect of biomagnification is so great in killer whales:
1. High trophic level: Killer whales occupy a high trophic level, meaning they are several steps removed from the primary producers at the base of the food chain. As they consume prey that have already accumulated contaminants, they ingest the accumulated toxins from various trophic levels below.
2. Long lifespan: Killer whales have an exceptionally long lifespan, with some individuals living for over 90 years. Over their extended lifetime, they accumulate a higher burden of contaminants that are not effectively eliminated from their bodies.
3. High metabolic rate: Killer whales have high metabolic rates to sustain their large body size and energetic activities, such as hunting and long-distance migrations. This high metabolism leads to a greater uptake and retention of contaminants.
4. Accumulation of persistent organic pollutants (POPs): Killer whales, like many other marine mammals, accumulate persistent organic pollutants (POPs) in their blubber and tissues. POPs are chemicals that are resistant to degradation and can bioaccumulate in the food chain. Killer whales ingest these contaminants through their diet and retain them in their bodies for extended periods.
5. Blubber storage: Killer whales have a thick layer of blubber, which acts as an energy reserve and insulation. Unfortunately, contaminants like POPs tend to accumulate in fat tissues, including blubber. As killer whales rely on their blubber for survival and accumulate substantial fat deposits over their lifetime, they store increasing amounts of contaminants.
The combination of these factors results in the significant biomagnification of contaminants in killer whales, making them vulnerable to the adverse health effects of toxic substances.