Lakes and Light
Lake ecosystems are incredibly heterogeneous and dynamic! Sunlight is a key driver of activity within lake ecosystems, serving as a catalyst for everything from photosynthesis to heat transfer and stratification, to visual predation and light cues for migration.
Typical lakes have three distinct HORIZONTAL ZONES that each provide unique habitat characteristics:
Littoral Zone: Shallow water habitat, defined by where sunlight can reach all the way to the sediment, allowing for the growth of rooted plants.
Limnetic Zone: Open water habitat, where the water is too deep for sunlight to reach the sediment.
Benthic Zone: Habitat associated with the bottom of the lake, on or in surface layers of sediment, home to many invertebrates, such as insect larvae and small crustaceans.
IMAGE: WOW. 2004. Water on the Web - Monitoring Minnesota Lakes on the Internet and Training Water Science Technicians for the Future - A National On-line Curriculum using Advanced Technologies and Real-Time Data.(www.waterontheweb.org).
Lakes also have distinct VERTICAL ZONES, defined by the ability of light to penetrate:
Euphotic Zone: Vertical portion of the water column that receives greater than 1% of the surface light, in which photosynthesis readily occurs.
Aphotic Zone: Vertical portion of the water column that receives less than 1% of surface light (including areas of complete darkness), where photosynthesis is unable to occur.
The amount of sunlight penetrating the water column is highly variable over time, related to water clarity (or lack thereof), suspended sediment, humic/organic substances, turbidity from algae, and seasonal snow cover.
Additional Resources
Lake Ecology Primer – Water on the Web | University of Minnesota