Nutrients are chemical substances found in every living thing on Earth. They are necessary to the lives of people, plants, animals, and all other organisms. Nutrients help break down food to give organisms energy. They are used in every process of an organism’s body. Some of the processes are growth (building cells), repair (healing a wound), and maintaining life (breathing).
Plants and other autotrophs absorb nutrients from soil and water. Autotrophs are organisms that can make their own food. The most important nutrients they need are carbon, hydrogen, and oxygen. Other nutrients needed by plants are nitrogen, phosphorous, potassium, calcium, magnesium, and sulfur.
From these basic nutrients, plants and other autotrophs synthesize, or create, their own nutrients, such as sugars. The human body can also synthesize some nutrients, such as amino acids. However, most organisms need nutrients created by autotrophs. People and animals get most of their nutrients from food.
Essential nutrients are nutrients that the human body is unable to synthesize. They must be obtained from food or water. Essential nutrients include carbohydrates, proteins, fats, vitamins, and minerals.
Carbohydrates, proteins, and fats are all part of a group of essential nutrients called macronutrients. “Macro-” means large, and these are the nutrients humans need in the largest amounts. Foods that are high in macronutrients include potatoes, which are high in carbohydrates; nuts, which are high in proteins; and avocados, which are high in fats.
Each macronutrient supplies a specific amount of energy. We know how much energy is in a kind of food by how many calories it has. A calorie is a unit of energy. Think of calories like gallons of fuel in a tank: If your car can go 20 kilometers by using one gallon of fuel and you are taking a 40-kilometer trip, you know that you need two gallons of fuel. Calories are fuel in the human body.
Vitamins and minerals are part of a group of essential nutrients called micronutrients. “Micro-” means small; humans need micronutrients in small amounts. Vitamins have names like vitamin A, vitamin C, and vitamin D. Vitamins contain the element carbon, which means they are organic compounds. Minerals, such as calcium and iron, come from the earth or environment. Minerals do not contain carbon, meaning they are inorganic compounds.
Nutrients in the Environment
Nutrients accumulate, or build up, in the environment. Nutrient-rich soil or water contains large amounts of nitrogen, carbon, phosphorus, sulfur, and potassium. These nutrients can come from natural sources, like plant and animal remains. As plants and animals die, they decompose. Decomposition releases nutrients into the environment.
Human activity also adds nutrients to soil and water. Many factories use nutrients to help preserve their products. Nutrients are either released as gas into the atmosphere, or as liquid. Either way, the nutrients enter the water cycle.
Sewage and wastewater are also full of nutrients such as carbon. Wastewater is often used on golf courses, where it enters local creeks as runoff. Treated wastewater is sometimes released directly into the environment.
Fertilizers, used in agriculture, are rich in carbon, nitrogen, and phosphorus. Farmers use fertilizers on crops such as grains, fruits, and vegetables. Phosphorus-based fertilizers are also used on golf courses, parks, and even neighborhood lawns.
Fertilizer not absorbed by plants accumulates in the soil. Nutrients from fertilizer can also leech into groundwater or runoff. Nutrient-rich runoff flows into creeks, rivers, and bays. Ponds, lakes, and even the ocean can absorb huge amounts of nutrients, especially nitrogen and phosphorus.
Balance of Nutrients
Nutrients such as carbon, oxygen, and nitrogen make all life possible. Nutrient-poor areas cannot support much biodiversity. Bogs, for instance, are nutrient-poor wetlands found in cool climates. The soil of bogs is much more acidic than fertile, or nutrient-rich, soil. Few species of plants can grow in the nutrient-poor soil of bogs. With fewer species of plants available, the ecosystem is unable to support a large variety of other organisms, such as animals and fungi.
The introduction of nutrients into an environment can make the ecosystem healthy and fertile. Upwelling is the natural process of cold, nutrient-rich water being pushed to the upper layers of the ocean. Upwelling brings a huge supply of nutrients to fish, seaweeds, and marine mammals. Economic activity also depends on upwelling. The fisheries off the western coast of South America, for instance, depend on the annual upwelling of the Pacific Ocean to bring nutrients to fish and shellfish stocks.
Excess Nutrients
Although life depends on nutrients, too many nutrients can have a negative impact on an ecosystem. Algal blooms, for instance, are caused by excess nutrients. They can actually prevent the natural nutrient flow in an aquatic ecosystem.
Algal blooms form as excess nutrients, from natural and manmade sources, accumulate in a body of water. When the conditions are just right, algae, bacteria, and other microbes bloom, or multiply quickly. The rapid reproduction uses almost all the nutrients in the water. The bloom forms a thin mat near the surface of the water, preventing light from reaching below.
The organisms in many algal blooms are not eaten by other organisms, so they are not part of the food web. An algal bloom uses up important nutrients—including oxygen—without contributing to the aquatic environment. Some algal blooms even contain toxic microbes. This type of algal bloom is called a harmful algal bloom (HAB). Without light and oxygen, plants die quickly. An algal bloom uses up nutrients and prevents the development of plants that fish and other living things depend on for survival.
Algal blooms can die off as quickly as they form. The dead algae and other microbes sink to the bottom of the body of water. Sunlight and nutrients can once again enter the ecosystem. However, bacteria that help decay the algal bloom now absorb most of these nutrients. It can take weeks or even months for an ecosystem to recover from an algal bloom.
Algal blooms can reduce nutrients in an area to such a degree that the area is known as a dead zone. This means that few organisms can survive in the environment. Dead zones do not have enough nutrients to support a food web.
Excess Nutrients in the Chesapeake Bay
Dead zones are a frequent problem for the Chesapeake Bay, a huge estuary on the East Coast of the United States. This region is home to 13.6 million people. Its watershed includes the large urban areas of Washington, D.C., and Baltimore and Annapolis, Maryland.
The western corridor of the Chesapeake Bay is highly industrialized. The eastern corridor is home to many farming communities. Runoff from factories, homes, and farms has polluted the bay with excess nutrients.
The size and duration of dead zones in the Chesapeake Bay vary. They depend on the season and the weather. During heavy rains, more nutrients are washed into the bay. During the spring and summer, farms fertilize their crops, leading to more nutrient runoff. About one-third of the excess nutrients in the Chesapeake Bay is the result of air pollution. Burning fossil fuels releases carbon and nitrogen into the air. Eventually, these nutrients return to the soil and water through the water cycle.
People and businesses can control the nutrients they release. At home, people can help by using phosphorus-free fertilizer and preventing lawn waste from washing into the gutter. Native plants help filter water and stop debris from washing into a watershed. Making sure septic systems don’t have leaks, safely disposing of household chemicals (like paint and batteries), and minimizing activities that erode soil also help prevent algal blooms.
Factories and farms can help control the amount of nutrients released into the environment by following safety standards and reducing runoff.
Photograph by Timothy Olmstead, MyShot
Blue-Green Algae
Blue-green algae is not blue-green, or even algae. The organism, also known as pond scum and cyanobacteria, is a bacterium that can be blue, green, reddish-purple, or brown.
CHNOPS
The most common elements on Earth are also the most important nutrients for plants. These nutrients are often grouped together by the acronym CHNOPS (shnahps). The letters stand for the elements chemical abbreviations: C (carbon), H (hydrogen), N (nitrogen), O (oxygen), P (phosphorus), and S (sulfur).
to soak up.
to gather or collect.
chemical compound that reacts with a base to form a salt. Acids can corrode some natural materials. Acids have pH levels lower than 7.
the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).
(singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.
the rapid increase of algae in an aquatic environment.
nutrient containing carbon, hydrogen, oxygen, and nitrogen that is critical for all life.
yearly.
a freshwater or marine ecosystem.
organism that can produce its own food and nutrients from chemicals in the atmosphere, usually through photosynthesis or chemosynthesis.
(singular: bacterium) single-celled organisms found in every ecosystem on Earth.
body of water partially surrounded by land, usually with a wide mouth to a larger body of water.
type of aquatic bacteria (not algae) that can photosynthesize light to create energy. Also called cyanobacteria and (in freshwater habitats) pond scum.
wetland of soft ground made mostly of decaying plant matter.
chemical element with the symbol Ca.
unit of energy from food, equal to the amount of heat required to raise the temperature of one kilogram of water by one degree Celsius.
type of sugar that is an important nutrient for most organisms.
chemical element with the symbol C, which forms the basis of all known life.
large, shallow estuary of the Susquehanna and other rivers that flow through the U.S. states of Maryland, Virginia, West Virginia, Delaware, Pennsylvania, and New York and the capital of Washington, D.C., before emptying in the Atlantic Ocean.
acronym for the most common nutrients on Earth: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
hallway, or connecting passage of land.
flowing body of water that is smaller than a river.
type of aquatic bacteria that can photosynthesize light to create energy. Also called blue-green algae (even though it is not algae) and (in freshwater habitats) pond scum.
remains of something broken or destroyed; waste, or garbage.
to rot or decompose.
to decay or break down.
length of time.
Atlantic coast of the United States.
having to do with money.
capacity to do work.
substance an organism needs for life but is unable to synthesize.
extra or surplus.
one or more buildings used for the manufacture of a product.
person who cultivates land and raises crops.
material found in organisms that is colorless and odorless and may be solid or liquid at room temperature.
able to produce crops or sustain agriculture.
nutrient-rich chemical substance (natural or manmade) applied to soil to encourage plant growth.
to catch or harvest fish.
industry or occupation of harvesting fish, either in the wild or through aquaculture.
material, usually of plant or animal origin, that living organisms use to obtain nutrients.
coal, oil, or natural gas. Fossil fuels formed from the remains of ancient plants and animals.
often.
edible part of a plant that grows from a flower.
material that provides power or energy.
state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion.
rapid growth of algae, bacteria, or other plankton that can threaten an aquatic environment by reducing the amount of oxygen in the water, blocking sunlight, or releasing toxic chemicals.
chemical element with the symbol H, whose most common isotope consists of a single electron and a single proton.
having to do with factories or mechanical production.
composed of material that is not living, and never was, such as rock.
area of grass mowed, watered, and maintained by people.
carnivorous or bloodsucking worm.
state of matter with no fixed shape and molecules that remain loosely bound with each other.
large.
nutrient needed by people in large quantities.
chemical element with the symbol Mg.
an animal that lives most of its life in the ocean but breathes air and gives birth to live young, such as whales and seals.
small.
tiny organism, usually a bacterium.
nutrient needed by people in small quantities.
nutrient needed to help cells, organs, and tissues to function.
indigenous, or from a specific geographic region.
required or needed.
in a bad, unpleasant, or unpopular way.
chemical element with the symbol N, whose gas form is 78% of the Earth's atmosphere.
composed of living or once-living material.
chemical element with the symbol O, whose gas form is 21% of the Earth's atmosphere.
chemical element with the symbol P.
type of aquatic bacteria that can photosynthesize light to create energy. Also called cyanobacteria and blue-green algae (even though it is not an algae).
chemical element with the symbol K.
to keep something from happening.
one of many complex compounds, made of chains of amino acids, that make up the majority of all cellular structures and are necessary for biological processes.
materials left from a dead or absent organism.
marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.
individual sewage treatment system, usually for a single residence or place of business.
liquid and solid waste material from homes and businesses.
any aquatic organism that has a shell or exoskeleton.
top layer of the Earth's surface where plants can grow.
exact or precise.
to supply.
type of chemical compound that is sweet-tasting and in some form essential to life.
chemical element with the symbol S.
to create or manufacture.
poisonous.
sewage or contaminated water that has been treated to remove physical, chemical, and biological pollutants.
process in which cold, nutrient-rich water from the bottom of an ocean basin or lake is brought to the surface due to atmospheric effects such as the Coriolis force or wind.
to change.
plant that is grown or harvested for food.
chemical substance that is necessary for health.
chemical substance necessary for healthy eyesight and skin. Also called retinol.
chemical substance important for health. Also called ascorbic acid.
chemical substance necessary for healthy bone and tooth development. Also called calciferol.
water that has been used for washing, flushing, or industry.
state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.
