• 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.

    Fruits are full of healthy nutrients.

    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).

    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.

  • Term Part of Speech Definition Encyclopedic Entry
    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.

    agriculture Noun

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

    Encyclopedic Entry: agriculture
    air pollution Noun

    harmful chemicals in the atmosphere.

    Encyclopedic Entry: air pollution
    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


    aquatic ecosystem Noun

    a freshwater or marine ecosystem.

    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    autotroph Noun

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

    Encyclopedic Entry: autotroph
    bacteria Plural Noun

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

    bay Noun

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

    Encyclopedic Entry: bay
    biodiversity Noun

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

    Encyclopedic Entry: biodiversity
    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.

    climate Noun

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

    Encyclopedic Entry: climate
    corridor Noun

    hallway, or connecting passage of land.

    creek Noun

    flowing body of water that is smaller than a river.

    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    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.

    dead zone Noun

    area of low oxygen in a body of water.

    Encyclopedic Entry: dead zone
    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.

    ecosystem Noun

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

    Encyclopedic Entry: ecosystem
    energy Noun

    capacity to do work.

    essential nutrient Noun

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

    estuary Noun

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

    Encyclopedic Entry: estuary
    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.

    food Noun

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

    Encyclopedic Entry: food
    food web Noun

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

    Encyclopedic Entry: food web
    fossil fuel Noun

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

    frequent Adjective


    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.

    grain Noun

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

    Encyclopedic Entry: grain
    groundwater Noun

    water found in an aquifer.

    Encyclopedic Entry: groundwater
    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


    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


    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.

    nutrient Noun

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

    Encyclopedic Entry: nutrient
    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.

    runoff Noun

    overflow of fluid from a farm or industrial factory.

    Encyclopedic Entry: runoff
    season Noun

    period of the year distinguished by special climatic conditions.

    Encyclopedic Entry: season
    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


    treated wastewater Noun

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

    upwelling 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.

    Encyclopedic Entry: upwelling
    urban area Noun

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

    Encyclopedic Entry: urban area
    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.

    water cycle Noun

    movement of water between atmosphere, land, and ocean.

    Encyclopedic Entry: water cycle
    watershed Noun

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

    Encyclopedic Entry: watershed
    weather Noun

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

    Encyclopedic Entry: weather
    wetland Noun

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

    Encyclopedic Entry: wetland