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.

nutrient
Fruits are full of healthy nutrients.

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).

absorb
Verb

to soak up.

accumulate
Verb

to gather or collect.

acid
Noun

chemical compound that reacts with a base to form a salt. Acids can corrode some natural materials. Acids have pH levels lower than 7.

Noun

the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

Noun

harmful chemicals in the atmosphere.

algae
Plural Noun

(singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.

algal bloom
Noun

the rapid increase of algae in an aquatic environment.

amino acid
Noun

nutrient containing carbon, hydrogen, oxygen, and nitrogen that is critical for all life.

annual
Adjective

yearly.

aquatic ecosystem
Noun

a freshwater or marine ecosystem.

Noun

layers of gases surrounding a planet or other celestial body.

Noun

organism that can produce its own food and nutrients from chemicals in the atmosphere, usually through photosynthesis or chemosynthesis.

Plural Noun

(singular: bacterium) single-celled organisms found in every ecosystem on Earth.

Noun

body of water partially surrounded by land, usually with a wide mouth to a larger body of water.

Noun

all the different kinds of living organisms within a given area.

blue-green algae
Noun

type of aquatic bacteria (not algae) that can photosynthesize light to create energy. Also called cyanobacteria and (in freshwater habitats) pond scum.

bog
Noun

wetland of soft ground made mostly of decaying plant matter.

calcium
Noun

chemical element with the symbol Ca.

calorie
Noun

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.

carbohydrate
Noun

type of sugar that is an important nutrient for most organisms.

carbon
Noun

chemical element with the symbol C, which forms the basis of all known life.

Chesapeake Bay
Noun

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.

CHNOPS
Noun

acronym for the most common nutrients on Earth: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.

Noun

all weather conditions for a given location over a period of time.

corridor
Noun

hallway, or connecting passage of land.

creek
Noun

flowing body of water that is smaller than a river.

Noun

agricultural produce.

cyanobacteria
Noun

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.

Noun

area of low oxygen in a body of water.

debris
Noun

remains of something broken or destroyed; waste, or garbage.

decay
Verb

to rot or decompose.

decompose
Verb

to decay or break down.

duration
Noun

length of time.

East Coast
Noun

Atlantic coast of the United States.

economic
Adjective

having to do with money.

Noun

community and interactions of living and nonliving things in an area.

energy
Noun

capacity to do work.

essential nutrient
Noun

substance an organism needs for life but is unable to synthesize.

Noun

mouth of a river where the river's current meets the sea's tide.

excess
Noun

extra or surplus.

factory
Noun

one or more buildings used for the manufacture of a product.

farmer
Noun

person who cultivates land and raises crops.

fat
Noun

material found in organisms that is colorless and odorless and may be solid or liquid at room temperature.

fertile
Adjective

able to produce crops or sustain agriculture.

fertilizer
Noun

nutrient-rich chemical substance (natural or manmade) applied to soil to encourage plant growth.

fish
Verb

to catch or harvest fish.

fishery
Noun

industry or occupation of harvesting fish, either in the wild or through aquaculture.

Noun

material, usually of plant or animal origin, that living organisms use to obtain nutrients.

Noun

all related food chains in an ecosystem. Also called a food cycle.

fossil fuel
Noun

coal, oil, or natural gas. Fossil fuels formed from the remains of ancient plants and animals.

frequent
Adjective

often.

fruit
Noun

edible part of a plant that grows from a flower.

fuel
Noun

material that provides power or energy.

gas
Noun

state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion.

Noun

harvested seed of such grasses as wheat, oats, and rice.

Noun

water found in an aquifer.

harmful algal bloom (HAB)
Noun

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.

hydrogen
Noun

chemical element with the symbol H, whose most common isotope consists of a single electron and a single proton.

industrial
Adjective

having to do with factories or mechanical production.

inorganic
Adjective

composed of material that is not living, and never was, such as rock.

lawn
Noun

area of grass mowed, watered, and maintained by people.

leech
Noun

carnivorous or bloodsucking worm.

liquid
Noun

state of matter with no fixed shape and molecules that remain loosely bound with each other.

macro-
Prefix

large.

macronutrient
Noun

nutrient needed by people in large quantities.

magnesium
Noun

chemical element with the symbol Mg.

marine mammal
Noun

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.

micro-
Prefix

small.

microbe
Noun

tiny organism, usually a bacterium.

micronutrient
Noun

nutrient needed by people in small quantities.

mineral
Noun

nutrient needed to help cells, organs, and tissues to function.

native
Adjective

indigenous, or from a specific geographic region.

necessary
Adjective

required or needed.

negatively
Adverb

in a bad, unpleasant, or unpopular way.

nitrogen
Noun

chemical element with the symbol N, whose gas form is 78% of the Earth's atmosphere.

Noun

substance an organism needs for energy, growth, and life.

organic
Adjective

composed of living or once-living material.

oxygen
Noun

chemical element with the symbol O, whose gas form is 21% of the Earth's atmosphere.

phosphorus
Noun

chemical element with the symbol P.

pond scum
Noun

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).

potassium
Noun

chemical element with the symbol K.

prevent
Verb

to keep something from happening.

protein
Noun

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.

remains
Noun

materials left from a dead or absent organism.

Noun

overflow of fluid from a farm or industrial factory.

Noun

period of the year distinguished by special climatic conditions.

seaweed
Noun

marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.

septic system
Noun

individual sewage treatment system, usually for a single residence or place of business.

sewage
Noun

liquid and solid waste material from homes and businesses.

shellfish
Noun

any aquatic organism that has a shell or exoskeleton.

soil
Noun

top layer of the Earth's surface where plants can grow.

specific
Adjective

exact or precise.

stock
Verb

to supply.

sugar
Noun

type of chemical compound that is sweet-tasting and in some form essential to life.

sulfur
Noun

chemical element with the symbol S.

synthesize
Verb

to create or manufacture.

toxic
Adjective

poisonous.

treated wastewater
Noun

sewage or contaminated water that has been treated to remove physical, chemical, and biological pollutants.

Noun

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.

Noun

developed, densely populated area where most inhabitants have nonagricultural jobs.

vary
Verb

to change.

vegetable
Noun

plant that is grown or harvested for food.

vitamin
Noun

chemical substance that is necessary for health.

vitamin A
Noun

chemical substance necessary for healthy eyesight and skin. Also called retinol.

vitamin C
Noun

chemical substance important for health. Also called ascorbic acid.

vitamin D
Noun

chemical substance necessary for healthy bone and tooth development. Also called calciferol.

wastewater
Noun

water that has been used for washing, flushing, or industry.

Noun

movement of water between atmosphere, land, and ocean.

Noun

entire river system or an area drained by a river and its tributaries.

Noun

state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.

Noun

area of land covered by shallow water or saturated by water.