Lakes (Oligotrophic and Eutrophic) By: Chloe’ Vorseth

Location Lakes are usually located close to the rivers and streams of the world in low parts of the landscape. There are many lakes around the world in many different areas. Examples: Caspian Sea, the Great Lakes, Russian Lakes, Australian Lakes, South American Lakes, and African Lakes.

Precipitation The precipitation in lake biomes vary depending on what area of the world a certain lake is in (basically every part of the world). Some lakes in the world have a lot of precipitation in the summer, spring, winter and fall months in the form of snow, ice, and rain. Lakes can cause lake effect snow on regions surrounding the lakes. Some lakes around the world are in drier areas, and provide a water source and precipitation for the surrounding area.

Temperature Temperatures around the lake regions can remain fairly constant or may change drastically according to season, but usually the temperatures do not cause the entire lake to freeze over in the winters, or the entire like to evaporate in the summers. Temperatures in lakes themselves vary at different depths: -Top (Epilimnion) Layer: Warmest layer, with most photosynthesis and life. -Middle (Metalimnion) Layer: A mixture of warm and cooler water that contains less life, but still has life. -Bottom (Hypolimnion) Layer: Coldest layer, with the smallest amount of life and little/no photosynthesis in the deepest lakes.

Amount of Light The amount of light in a lake ecosystem can vary depending on what region of the world the lake is in, the climate around the lake, and what season the area is in. At different depths of the lake, different amounts of lights are experienced. Near the top, there is much light available for photosynthesis and life, but as the lake gets deeper less light shines through the water. Oligotrophic Lakes are more like the one to the right, with deeper depths, less life on the lake floor, and clearer waters to allow for deep light penetration. Eutrophic Lakes are shallower, without a bottom layer of lifelessness. They have more plant life because underwater plants get more sun, but less light penetration because of cloudy algae infested waters.

Salinity Some lakes can have high salinity if they are around soil and ground matter that contains salt in an inland location. Through erosion, lakes can take this salt from the ground or can receive it from the rivers that run through them. Lakes are generally fresh water basins with little salinity. For example, Great Salt Lake in Utah (above) has a salinity of 200,000 milligrams per liter, while Lake Superior (right) contains only about 75.

Nutrient Level There are two kinds of lakes with different levels of nutrient content. 1. Oligotrophic lakes contain a very low amount of nutrient input. They have pockets of organism populations scattered around that live with high oxygen levels. 2. Eutrophic lakes contain very high amounts of nutrient input. They have a wide diversity of life because the variety of nutrients in the water make plant life very abundant. Organisms that can withstand lower oxygen levels flourish in these kinds of lakes. Most lakes start out as oligotrophic and slowly turn into Eutrophic with human, plant, and animal interaction.

Common Lake Plants Water hyacinth Great Salvinia Water lilly Duckweed Coontail Bladderworth Cattail Bulrush Algae

Endangered Lake Plants Dwarf Lake Iris Fasset’s Locoweed Lakeside Daisy

Common Lake Animals Ducks, geese, and swan. Zoo Plankton Fish (Sturgeons, Salmon, and many more). Turtles and frogs. Mollusks/Clams/Snails

Endangered Lake Animals Bear Lake Sculpin Chinese River Dolphin Great Lake Freshwater Snail Lake Salmon

Influence of Humankind on Lakes Damming- we dam rivers and streams in order to create energy using the water flow, to control lake levels, and to make lakes. This effects systems downstream and can disrupt migratory fish patterns. Channelizing- we manipulate lakes to go the way we want them to. This can effect where water floods. Dumping and Littering- we dump and litter things into lakes that can be very harmful and pollute the water for the entire lake ecosystem. Recreation- we use lakes for boating, fishing, swimming, etc. This can effect the habitats and movement of many species in lakes. Invasive Species- humans have accidentally introduced some species into lakes that disrupt the ecosystem by adding more competition among the species.

Sources http://aoc.rain.org/facts/types_of_habitat/lakes1.html http://www.thewildclassroom.com/biomes/lake.html http://www.ourlake.org/html/temperature.html http://www.mlswa.org/lkclassif1.htm http://www.epa.gov/bioiweb1/aquatic/classify.html http://www.waterontheweb.org/under/lakeecology/09 _nutrients.html http://www.earthsendangered.com/search.asp http://www.biosurvey.ou.edu/posters/EdGuidePDFs/P rairieRivers_edguide_riverhealth.pdf