What are nutrients?
Nutrients are any essential element that living organisms needs to live, grow, and reproduce. Many nutrients are found naturally in our surrounding environment in small amounts. However, when excessive amounts of nutrients are introduced to the environment, they can be harmful to plants, animals, and water quality. Nitrogen and particularly phosphorus are two commonly found nutrients that can affect water quality.
Phosphorus is a naturally occurring nutrient found in water, soil, and air. It helps stimulate plant growth and is essential for animal and plant life. Phosphorus exists in water in a number of different forms. For example, soluble reactive phosphorus, also called orthophosphate, is the form that is quickly taken up by growing algal populations. Total phosphorus includes both the soluble phosphorus and the phosphorus that is bound to plant and animal fragments or that is bound to other ions such as calcium and iron.
Phosphorus is the primary limiting nutrient for plants and algae in temperate lake systems — like Lake Whatcom . That is, the growth rates of plants are limited, or regulated, by the naturally occurring amounts of phosphorus that is available in the environment. When an excessive amount of phosphorus is introduced, some plant species, such as algae, experience explosive growth. Overgrowth of algae clouds water and blocks sunlight form other plants and aquatic life, killing them or limiting their growth. When algae die, they sink to the bottom of the lake and begin to decompose. Bacteria feed on this decomposing algae and consume oxygen in the water. This process can deplet oxygen levels in the lake to a level tha is too low to support other plant and animal life. In addition, dead algae creates more nutrient to fertilize even mor algal growth, accelerating the depletion of oxygen in the lake.
Nitrogen is also a nutrient of concern for the Lake Whatcom watershed. Like phosphorus, it occurs naturally in small amounts, contributes to plant and animal growth, and excessive nitrogen can also harm water quality.
Nitrogen can exist in lakes in several forms. Lake water quality analysis usually includes total nitrogen, total Kjeldahl nitrogen, nitrate-nitrogen, nitrite-nitrogen, or ammonia-nitrogen. Total nitrogen is the total nitrogen in a sample. Total Kjeldahl nitrogen is the fraction of total nitrogen that is not available for plant or algal growth. Nitrate-nitrogen, nitrite-nitrogen, and ammonia-nitrogen are inorganic forms of nitrogen and can support the growth of aquatic plants and algae.
Although phosphorus and nitrogen are naturally occurring, other sources inlcude exposed soil from construction and landscaping, lawn and garden fertilizers, animal waste, failing septic tanks, automobile exhaust and car washing, and phosphorus-based soaps, detergents, and chemicals.
Sediments and Exposed Soils
Nutrients are immobile and need to be attached to something in order to be transported into Lake Whatcom . Nutrients often become attached to sediments , and sediments are easily transported by stormwater .
Soils naturally contain nutrients such as phosphorus and nitrogen. When soils become exposed, they are very susceptible to erosion and can easily be washed into streams and lakes during storm events. Large areas of cleared land and construction sites not equipped with proper best management practices contribute a significant amount of nutrient-containing sediments into Lake Whatcom .
When fertilizers, pesticides, and herbicides are over-applied, the nutrients they contain that are not taken up by the plants or lawn can be washed into stormdrains, which lead to our streams or the lake during rain events.
Animal waste contains nutrients, and if not properly disposed of, nutrient-rich feces can be washed into our waterways.
Failing sewer and septic systems can also leak nutrient-rich sewage into streams, ground water, and ultimately Lake Whatcom .
When leaves and grass clippings decompose, they release phosphorus and nitrogen into the environment. When excessive grass clippings and leaves make their way into gutters, streets, ditches, and storm drains, they can be carried into our waterways, and ultimately Lake Whatcom.
How can we prevent nutrient loading into Lake Whatcom ?
Addressing the sources of nutrients before they reach Lake Whatcom is one of the most effective way to reduce their impact to water quality. As water quality degrades, it is much harder and much more expensive to reverse the negative impacts or improve water quality. Prevention is key. Here are some resources available on reducing nutrient loading into Lake Whatcom.
- A Lake-Friendly Gardening kit is available with tips and alternatives to reduce fertilizer and pesticide use, as well as erosion control tips.
- Native vegetation can aid in preventing erosion, and often requires no fertilizers or pesticides. The Native Plan for Lanscaping in Bellingham, Washington booklet is available from the City of Bellingham's Planning Division as well as on-line.
- Pet waste education, programs, and Mutt Mitt stations are available to prevent nutrient-rich pet wast from entering into streams and Lake Whatcom.
- Erosion control standards exist in the City of Bellingham and Whatcom County to prevent sediments from entering the lake from construction sites. The Lake Whatcom homebuilding series provides regulatory guidance to those who are building their new homes.
- Street sweeping is provided to remove leaves and other pollutants from the streets before they are washed into storm drains.
- Stormwater retrofit projects continue in the watershed to help treat stormwater carrying nutrients before it enters the Lake Whatcom.
- On-site sewage systems should be inspected and serviced on a regular schedule. The County Health and Human Services Department provides education and services for on-site sewage systems.