Freshwater Ecosystems
Freshwater ecosystems are bodies of water naturally existing on the Earth's surface with less than 1000 mg dissolved salt per liter of water. There are many types of freshwater ecosystems on earth. Rivers, lakes, swamps, bogs, underground lakes, and frozen water such as icebergs and snow are all sources of freshwater. In this section, we'll look at the abiotic factors of a lake and a bog.
Abiotic Factors of Lakes
Lakes are large bodies of water on the surface of the earth. Most lakes are freshwater, although there are some examples of lakes with high salinity, like the Caspian Sea in Europe. The important abiotic factors in lakes are the low salinity, temperature, sunlight, and soil composition. Temperature varies in the lake depending on depth and season. The topmost layer is the warmest, supporting a host of life such as fish, amphibians, and birds. As we descend deeper into the lake, the temperature drops. Even in the summer, lake temperatures at the bottom can be as cold as 39 degrees Fahrenheit. The deeper you descend, the less sunlight (another abiotic factor) the water receives. A shallower lake will have more diversity of plant and animal life, because the sunlight penetrates more of the water layers. The soil of lakes depends on the location, but most have a bottom made of clay, silt and gravel.
Vermilion Lakes in Canada have a wide range of temperatures from -8F in the winter to 78F in the summer
 |
Abiotic Factors of Bogs
Bogs are a type of wetland rich in moss and have very acidic water and soil. These unique ecosystems can be home to cranberry farms, and often host other berries, like blueberries or huckleberries. The moist, flooded, acidic soil helps cultivate these types of berries. Bogs receive the majority, if not all, of their water from local precipitation, not runoff from other bodies of water like rivers or streams. As a result, there is high acidity in bogs, an important abiotic factor for this ecosystem. The lack of nutrients which runoff would provide and the constant flooding of the soil contributes to the high acidity. These abiotic factors create a challenging location for plants and animals to survive without specific adaptations.
The temperature varies greatly depending on the location of the bog. Bogs in Northern Siberia have average temperatures below freezing, while bogs in the Northern United States, like Pennsylvania, have warmer average temperatures, up to 78 degrees Fahrenheit in the summer.
Due to the lack of nutrients, most plants in the bog grow close to the ground and do not compete for sunlight. Trees dot the edges of the bog, leaving plenty of room for direct sunlight on the water during the day.
A wet sphagnum bog has nutrient poor soil which supports only certain types of species
 |
Abiotic Factors of Oceans
The most important abiotic factor in the ocean is its incredibly high salinity of 35,000 mg dissolved salt per liter of water. Animals living in the ocean all have special adaptations that allow them to survive in high salt concentrations. Oceans make up about 70% of the surface of the Earth. Thus, the abiotic factors can be quite different depending on which ocean we are considering. Ocean temperatures range from quite warm, around 80 degrees Fahrenheit in tropical waters near the surface, to freezing temperatures (below 32 degrees Fahrenheit) in the deep ocean and near the poles of the Arctic and Antarctic Oceans.
Abiotic factors like high sunlight and warm temperatures promote growth of coral reefs near the shore
 |
Sunlight is plentiful near the shore and shallow waters, but the water below 1000 meters, called the midnight zone, gets no sunlight at all. Here, some organisms use chemicals from the ocean floor to produce food instead of using sunlight like their counterparts in shallow waters.
The midnight zone in the ocean has no sunlight at all, supporting only species with adaptations for the dark
 |
Sand, one of the main components of the ocean floor, is made of silicon rocks that have been crushed and eroded for millions of years by the sea. Some areas of the ocean are bordered by sharp, rocky cliffs, and others have long, soft beaches that drift inland.
The shore of Castle Cape in Alaska has primarily rocky soil
 |
Lesson Summary
Summary of abiotic factors in freshwater and salt water
 |
Abiotic factors are non-living factors in an ecosystem. Freshwater is any body of water on the Earth's surface with low salinity, 1000 mg or less of dissolved salt per liter of water. These bodies of water include lakes, bogs, swamps, underground water and rivers. The temperatures in lakes vary with depth and location on Earth. Water is warmer near the surface. Sunlight decreases as depth increases and soils usually consist of silt, clay and gravel. In bogs, the soil is very acidic, nutrient poor, and flooded year round. Oceans are large bodies of water on the surface of the Earth with high salinity, 35,000 mg of salt per liter of water . The temperature can be warm in shallow waters but decreases drastically with depth, as well as location on the Earth, with the Arctic and Antarctic oceans being very cold. Sunlight also decreases with depth and is completely absent in the midnight zone. Soil is made of mostly sand and rock.
