Nutrients and Algal Growth

Algal production is correlated to the levels of nitrogen (N) and phosphorus (P) in the water column. Phosphorus is the primary concern in most freshwater systems because it limits algal growth. However, if phosphorus availability is high, nitrogen may also be a concern.

1. Phosphorus A. Select the answer that most clearly describes the total phosphorus concentrations of your water resource:

> 0.5 mg/l
0.03 - 0.5 mg/l
<= 0.03 mg/l No problem at this level. Return to the Water Resource page

B. Select the answer that most clearly describes the orthophosphate concentrations of your water resource:

> 0.08 - 0.1 mg/l
0.05 - 0.08 mg/l
< 0.05 mg/l No problem at this level. Return to the Water Resource page

2. N:P Ratio
Above a 10:1 (N:P) ratio in the water column, the freshwater system will likely experience an algal bloom, the severity of which will be in relation to excess phosphorus available; below that ratio, nitrogen is the limiting nutrient in the system and the bloom will be related to excess nitrogen (Schindler, 1978).

? Information on Phosphorus
? Information on Nitrate
? Information on Algal blooms

NCSU Water Quality Group

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