Tom,
In Oceeneering, The Redfield Ratio of 16:1 is a constant for N:P in phytoplankton the world wide. This ratio varies with macroalgae and approaches 100:1 in some species. Because I was selling ediable seaweed, I had it analyzed for mineral content by a regional agriculture lab. Gracilaria Parvispora, Red Ogo has a N:P ratio of 30:1;
https://www.wardlab.com/services/plant-analysis/P-2. Routine Plant Tissue Testing
$27.50 USD
This is a great entry point for plant testing! Send us a sample, following directions for your individual crop. We’ll test your sample for nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, zinc, iron, manganese, copper, boron and molybdenum. You’ll receive a complete report of your results, allowing you to adjust management techniques accordingly.
W-5. Household Complete Mineral Test
We offer a package that includes the cost of this test, plus a convenient testing kit that includes shipping labels and packaging.
Bicarbonate, Calcium, Carbonate, Chloride, Fluoride, Iron, Magnesium, Nitrate, Potassium, Sodium, Sulfate, Total Hardness (Lime), Total Alkalinity, Electrical Conductivity, pH, Est. Total Dissolved Solids
$30.00 USD
(sample analysis only)