Control of Coastal Ecosystems: or Denitrification Demystified

Introduction:

People need a balanced diet with enough calories and vitamins to reach their full potential. The same is generally true of plants. If you reduce plants down to their essential elements the ratio will be about sixteen nitrogen atoms to one potassium atom to 106 carbon atoms. This is why farmers add fertilizers to their crops. There is usually enough phosphorous (its chemical symbol is P) in the soil for the available nitrogen (N). If the farmer adds nitrogen-containing fertilizer the plants grow better; they were limited by the amount of N available. However, in some ecosystems there may be plenty of N and not enough P for optimal plant growth; that is, they are P limited.

Along the Cooper River in South Carolina the streamside vegetation is P limited in its freshwater upper reaches, and as the river debouches into the salt water estuary they become N limited. This gradient from freshwater to saltwater is a good natural laboratory to study how the physical environment shapes plant communities.

P.V. Sundareshwar's work on the Cooper River community found that the soil dwelling bacteria play an important role in determining plant community structure. In a similar vein a recent article in Science1 describes the new appreciation we have of the role gut bacteria play in the ecology of the human body. We know enough to appreciate the plant community for providing us food, oxygen, and fiber. Now it seems the lowly bacteria also play an important role in deciding who and what lives where.

We spoke with Dr. Sudareshwar about his work on the dynamics of the plant community along the Cooper River.

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