Power
You may have a B.S., a master's in ecology, and even the right to call yourself "Dr. Siren the Limnologist," but if it's traditional power you're looking for, you may want to consider becoming an aircraft mechanic (think about it), a parole officer, or even (if you have the stomach for it) the President of the United States.
The "power" you have as a limnologist (cue bubbling water background music) may not be what the average person may think of as typically powerful, but the recommendations you make to whomever needs them—the university you work for, the government (such as the EPA), and even the small research firm you work for—can change the lives of the animals and people who live among the waters you've been studying.
Keeping living things safe has a power of its own; and making sure water is available and safe is right there, too.