例： The whole food chain is affected by the overuse of chemicals in agriculture.
整个食物链因农业中过度使用化学品而受到影响。
例： Droppings from seabirds could be introducing radioactive isotopes into the food chain.
海鸟粪可能会把放射性同位素引入食物链。
例： animals further up the food chain.
食物链上游的动物。