Nutrients in Water
WHAT ARE NUTRIENTS?
Nutrients, specifically nitrogen and phosphorus, are chemicals that are essential for plant growth. We add nutrients when we fertilize our gardens and fields, and in the same way, adding nutrients to water fertilizes water-dwelling plants. Nutrients usually occur at very low concentrations relative to plant demands. Nutrient levels change throughout the year as growing plants take up the nutrients and dying plants release them back into the water.
WHY CARE ABOUT NUTRIENTS
When waterways become over fertilized with nitrogen or phosphorus, heavy plant growth can occur. Excessive plant growth can decrease the aesthetic value of the water because of the smelly decomposing mats of vegetation, and it can create algal blooms which can be toxic. Also, when bacteria decompose dead plant material they use up dissolved oxygen which is important for the survival of macroinvertebrates and other aquatic organisms. If a waterbody doesn't have enough of a nutrient to sustain plant growth, then the nutrient in short supply is called the limiting nutrient.
Two main groups of nitrogen exist, organic and inorganic. Organic nitrogen includes all of the nitrogen that is part of living animals, animal wastes and the remains of living things. Organic forms of nitrogen must be broken down into inorganic forms in order to be used by plants. Examples of inorganic nitrogen are N2, N03, NH3, N02. Nitrate (N03) is the most common form of inorganic nitrogen found in waterways. Plants can directly use this form of nitrogen to build proteins.
WHY CARE ABOUT NITROGEN?
When waterways become over fertilized with nitrogen, heavy plant growth can occur. Excessive plant growth can decrease the aesthetic value of the water because of the smelly decomposing mats of vegetation. Also, when bacteria decompose dead plant material they use up dissolved oxygen which is important for the survival of macroinvertebrates and other aquatic organisms.
Nitrates are odorless, colorless, and tasteless so it is important to test feed and drinking water to determine levels of nitrate. High concentrations of nitrate in drinking water can cause methemoglobinemia (also known as blue baby syndrome). Concentrations greater than 10 parts per million can be harmful to young babies, and should be avoided by nursing mothers. Concentrations of nitrate over 100 parts per million are toxic to livestock Find out more about nitrate.
Utah Nutrient Standards
- Maximum concentration of Nitrate in drinking water: 10 mg/L
- Greater than 4 mg/L in surface water indicates pollution
NATURAL FACTORS INFLUENCING NITROGEN
- Runoff- In Utah concentrations are usually highest in the springtime when runoff from melting snow carries nutrients from lawns, farms and other areas into the water. Many people in Utah get their culinary water from groundwater from cities or private wells. Groundwater has naturally higher concentrations of nitrate.
- Plant uptake- during the spring and summer months plants grow causing concentrations of nitrates to be low during this time. In the winter and fall, when plants stop growing and die, much of the nitrogen is released into the water again, increasing the nitrogen concentration.
HUMAN FACTORS INFLUENCING NITROGEN
- Fertilizers- Because plants require nitrogen, farmers often add nitrogen in the form of fertilizers, sometimes the nitrate leaches into groundwater systems. Fertilizers can also be washed into surface waters and increase productivity, causing eutrophication.
- Livestock manure- Fecal matter contains nitrogen, so when livestock manure washes into surface water (among other pollutant problems), the excess nitrogen can cause eutrophication.
- Malfunctioning septic systems- Similar to livestock manure, when a septic system leaches into the ground the bacteria and nutrients can get into ground water systems and surface water systems.
- Discharge from sewage facilities acid precipitation- Acid precipitation can cause acidification in a water body. Acidification, like eutrophication can lead to a decreased diversity of aquatic species.
Resources to limit human influences: Protect Your Water
Phosphorus is very important to plants. It is found in two forms, organic and inorganic, and moves very slowly through the environment. Plants use an inorganic phosphorus called orthophosphate, and it is usually scarce in water because it attaches to sediments in the water.
WHY CARE ABOUT PHOSPHORUS?
Phosphorus is often the nutrient that limits plant growth in a waterbody, so adding a little can easily cause excess plant growth. When these plants die, algal blooms often occur and these can sometimes be toxic. Also as they die they use up oxygen which effects fish and macroinvertebrates.
Utah Phosphorus Standards
- Concentrations of 0.05 mg/L or above in a stream or river indicates pollution
- Concentrations of 0.025 mg/L or above in a lake indicates pollution
NATURAL FACTORS INFLUENCING PHOSPHORUS
Runoff- During spring runoff or when flows are high, more sediment is collected in the streams and rivers. Phosphorus attaches to sediment, so this may cause the water to have a higher concentration of phosphorus as well.
HUMAN FACTORS INFLUENCING PHOSPHORUS
- Building activities- Urban construction that removes plants along the edge of a stream or other water body inhibits plant’s ability to filter out sediments in surface runoff. The stream banks themselves may become unstable and erode into the stream.
- Damage to riparian vegetation- When the riparian zone is damaged or destroyed, phosphorus is not used by the plants, instead it washes directly into the waterbody.
- Runoff from fertilizers- Fertilizers that run off lawns, golf courses, and agricultural fields during snow melt, rainstorms, or heavy irrigating can wash excess nutrients into rivers and streams.
- Poorly functioning septic tanks- When a septic tank malfunctions it can release phosphorus into groundwater.
- Resources to limit human influences: Protect Your Water
Utah Water Watch- Learn how volunteers across the state are measuring nutrients.
Stream Side Science- Explore different lesson plans involving nutrients and see how they apply to the core curriculums for grades k-12.