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Abiotic Factors in Freshwater vs. Ocean Biomes

Instructor: Amanda Robb

Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.

This lesson is on the abiotic factors in oceans and in freshwater. In this lesson we'll learn what abiotic factors are, and how they look in two freshwater ecosystems. We'll also compare them to abiotic factors in the ocean.

What Is an Abiotic Factor?

Usually, people can be divided into two camps when it comes to a summer vacation near the water. Some people love lakes, with their peaceful waters, calm docks, and the prospect of floating on a raft surrounded by trees and wildlife. Other folks opt for the beach: salt, sand, rough waters, and abundant sunshine.

These two options for a summer oasis have a lot in common, but there are some key differences: salt water versus freshwater, mud versus sand, and differences in temperature and sunlight. These differences are known in science as abiotic factors or the non-living factors in an ecosystem. The abiotic factors we will look at for freshwater and oceans include salinity, temperature, sunlight, and soil composition. By the end of this lesson, you'll be able to make a scientifically based decision for your next vacation.

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
Vermilion Lake

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
sphagnum bog

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