Okay the question is:
Why would there be differences in the pesticide levels found in different species? Atlantic Puffin (feeds on small fish) and its pesticide levels are lower compared to Double-crested Cormorant (fees on larger fish) and Leach's Storm-Petrel (feeds on small organisms near the surface of the water), why would this be?
To understand why there might be differences in pesticide levels among different species, we need to consider their feeding behavior and ecological roles. Pesticides are chemicals used to kill or control pests, but they can also have unintended effects on non-target species when they enter the environment.
1. Feeding behavior: Different species have different diets, which can influence their exposure to pesticides. In the example you mentioned, the Atlantic Puffin feeds on small fish. Pesticides tend to bioaccumulate, meaning they can become more concentrated as they move up the food chain. Since small fish are lower in the food chain, they have had less time to accumulate high levels of pesticides compared to larger fish that might have been exposed to these chemicals over a longer period. So, the Atlantic Puffin, feeding on lower trophic levels, will have lower pesticide levels.
2. Ecological roles: Each species occupies a specific niche in the ecosystem, and this can affect their exposure to pesticides. For instance, the Double-crested Cormorant feeds on larger fish, which may have accumulated higher levels of pesticides in their tissues. Additionally, cormorants are known to dive and forage underwater, which increases their chances of coming into contact with contaminated sediments or waters that may contain pesticides. As a result, Double-crested Cormorants might have higher pesticide levels compared to a species like the Atlantic Puffin.
3. Environment and prey availability: The differences in pesticide levels could also be influenced by the availability of prey species. In the case of Leach's Storm-Petrel, which feeds on small organisms near the water's surface, the prey might have lower exposure to pesticides compared to larger fish species that reside in deeper parts of the water column. This could explain the lower pesticide levels in Leach's Storm-Petrels.
It's important to note that these explanations are not definitive and may vary depending on the specific circumstances and geographical location. Studying the foraging behavior, trophic levels, and habitat preferences of different species can provide insights into why pesticide levels differ among them.