Final answer:
Overfishing tuna can lead to a trophic cascade, affecting various species differently, causing unpredictable changes in the food web, and potentially leading to its collapse.
Step-by-step explanation:
When humans overfish a species like tuna, the resulting depletion can lead to serious consequences within the marine ecosystem. If tuna, which are typically apex predators, are removed from the system, it can cause a trophic cascade. This cascade occurs because the absence of a top predator can lead to an increase in the populations of prey species. However, the effect on the entire food web is complex and not always predictable.
For instance, if tuna predation on herring decreases due to overfishing, the herring population might initially increase. But as the herring consume more plankton, the plankton population could potentially decrease. Conversely, if cod feed on herring, their population might decrease due to the increased competition for prey. Over time, the food web could lose balance and collapse, which can have dire ecological and economic consequences. Diverse species including plankton, herring, and even cod, would experience shifts in their populations, not invariably in the direction suggested by simple predator-prey relationships.
The domino effect caused by overfishing higher trophic levels is an example of the complex interplay within ecosystems. The eventual outcome could be the deterioration of an entire aquatic system as a viable food source.