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Reducing Nutrient Inputs to Coastal Ecosystems

What are nutrients and from where do they come?

Nutrients are both man-made and naturally occuring.

Naturally occurring nutrients
Hydrogen (H), Oxygen (O), and carbon (C) are the three non-mineral nutrients found in air and water. Plants use a process called photosynthesis, a process where plants use energy form the sun to change carbon dioxide (CO2) and water (H2O) into starches and sugars (a plant’s food).  Photosynthesis means “making things with light.” Since these nutrients are in the air and water, people have little control over how much a plant can use.

There are 13 mineral nutrients found in a combination of soils; sand, silt, clay and organic matter. These nutrients are categorized into macronutrients (large amounts) and micronutrients (small amounts).

Macronutrients are divided into two groups, primary and secondary.  Primary nutrients are potassium (K), phosphorus (P), and nitrogen (N). Secondary nutrients are calcium (Ca), sulfur (S) and magnesium (Mg). These critical nutrients are usually deficient in soils because plants use large amounts for growth and survival. This is why farmers, gardeners and households use fertilizers to enrich soil chemistry.

Micronutrients, essential for plant growth, include boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn).

Soil pH, a measure of the acidity or alkalinity of soil, is the property that affects the availability of nutrients. High levels of pH means lower levels of micronutrient and low levels of pH means high levels of macronutrients. If soils are acidic, then additional Calcium and Magnesium are added if lime is put into the treated soil. So human behavior now becomes a major factor in controlling the amounts of macronutrients and micronutrients in any given environment.

The human challenge is to seek the optimal balances.

Man-made sources of nutrients include wastewater treatment plants, urban and agricultural run-off, and nutrients deposited from the air (atmospheric deposition). Carbon dioxide from the air is one of the most critical man-made nutrients and is at the forefront of the global climate change environmental issue. Nutrients, especially nitrogen and phosphorus, from agricultural run-off are also at the forefront of causes of hypoxic zones.  Wastewater is sometimes mixed with storm water and can therefore contain a wide variety of toxins and other compounds.  Wastewater is also treated with a number of chemical processes which adds even more to the challenges of proper balances of chemicals in our environment. 

  • Hypoxic Zone/Dead Zone-This simply means what it says…..a zone where nothing lives because of low or no oxygen levels … a more detailed explanation of hypoxia in the Gulf of Mexico can be found at toxics.usgs.gov/definitions/hypoxia.html. This environmental phenomenon occurs mostly in the Texas-Louisiana area where the vast Mississippi River, carrying multitudes of nutrients from the farming heartland of America, into the Gulf of Mexico. Recently, smaller pockets of hypoxia have occurred at the mouth of the Brazos River as it enters the Gulf of Mexico in Texas and other isolated spots around the Gulf. Efforts are underway to expand the number of water quality monitoring sites around the Gulf of Mexico. This will require greater participation by both workers and volunteers from the public.
  • Biologic Index-Biological indices are used to develop the necessary information to restore and maintain the chemical, physical and biological integrity of our nation’s waters. Biological indices are mandated by the Clean Water Act and a variety of federal and state agencies strive to obtain required scientific knowledge to make best management decisions. These indices will be made available to the public in understandable formats. For a better understanding of biological indices go to www.epa.gov/waterscience/biocriteria/modules/index101-01-intro.pdf.
  • Trends- A trend is the general direction in which something tends to move. With regards to nutrient reduction, trends in nutrient types and amounts are strong indicators of things going right and things going wrong and indicate a sense of when changes are occurring. Scientific data collection in the Gulf of Mexico region will allow for several kinds of trends to be analyzed by experts and made available to the public in understandable formats. For a better understanding of scientific trends go to www.trends.com .