Salary
Average Salary: $75,530
Expected Lifetime Earnings: $3,153,000
The average salary for a limnologist who works for the federal government is about $80,000-$85,000 a year; on the state level, you can expect about $65,000 (though it depends on what state, of course); and on the local level, on average, it pays a bit more than the state-employed limnologists at $70,000 (source).
If you work your way up to consulting or managing, you'll find yourself earning about $80,000, and if you decide to go to work for private research and development services, you can expect around $70,000 (source).
The important thing here is that you're doing what you love to do and it fits in with your interests and personality, as well as your other wants and needs in your life (a family, a social life, dry socks at least twice a week, etc.).