A lake in distress will have some visible and measured attributes that prove it is out of balance and may include the following warning signs:
1.) The water has converted from a clear to a turbid state. This could be due to algae, sediments, or other suspended solids in the water column.
2.) The aquatic vegetation is too thick, creates a surface canopy, and is converting to a monoculture of either invasive, exotic species or a dominant culture of only one or a few species. The lower the biodiversity of the lake, the less likely it is to respond to disturbances with a fast recovery.
3.) The usual biota (i.e., loons, mergansers, fish) are not present in usual quantities. Many lake taxa require high water quality conditions such as ample dissolved oxygen, moderate lake nutrients, and low pollutants.
4.) The lake experiences widespread fish kills. This is a sign of a very unhealthy ecosystem that is likely high in pollutants and low in dissolved oxygen.
5.) The algae in the lake has converted from green algae to a dominance of blue-green algae that may be toxic. This phenomenon may result from stagnation of waters that are low in dissolved oxygen and high in water temperatures.