The growth of aquatic plants is usually limited by nutrients of one kind or another. We conduct nutrient limitation bioassays to identify which of the macronutrients (nutrients needed by plants in large quantities) is scarcest and therefore limits aquatic plant growth. Experience showed that the best approach was to use a "nutrient deletion" design, in which one of the three macronutrients (nitrogen, phosphorus or silicate) was not added, to detect limitation by one or more nutrients. The hypothesis tested in these bioassay experiments is that plant growth (changes in plant biomass measured as chlorophyll a) is highest when the limiting nutrient(s) are added. Results of nutrient limitation bioassays performed in four local stormwater ponds are presented below:

Results of nutrient limitation bioassay for pond at Clear Run Apartments (Pond E on map below). This pattern shows Nitrogen and Phosphorus co-limitation.

Results of nutrient limitation bioassay for pond at UNCW campus (Pond G on map below). This pattern shows Nitrogen and Phosphorus co-limitation.

Results of nutrient limitation bioassay for pond at McCrary Park (labeled "McCrary" on map below). This pattern shows Nitrogen and Phosphorus co-limitation.

Results of nutrient limitation bioassay for pond at McMillan Oaks apartments (Pond H on map below). Pattern suggests Nitrogen and Phosphorus co-limitation with a tendency toward Phosphorus limitation.

Map of ponds sampled:

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