A boom of one particular species is not necessarily indicative of a healthy ecosystem. We don't welcome algal blooms as signs of life bouncing back; rather, the

A boom of one particular species is not necessarily indicative of a healthy ecosystem. We don't welcome algal blooms as signs of life bouncing back; rather, they are brutally disruptive to ecosystems. They leave mass death in their wake. Without a closer study of which species you're observing (they might be human-borne invasive species after all), it's not really easy to say if what you're seeing is healthy at all. And the timescales are important. This year or this decade might be a boom and 20 years from now they've managed to deplete their environment of resources and crash.