Macro algae biomass calculation?

[feh]

Is there a way to calculate how much of a biomass you would need maintain with chaeto or other macro algaes based on trends from test results with nitrates and phosphates? Curious.

 

[Randy Holmes-Farley]

Roughly. I've not seen the data for chaeto, but other macroalgae are likely not too far off on a dry weight basis.

I discuss it here:

Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php

from it:

For example, Caulerpa racemosa collected off Hawaii contains about 0.08 % phosphorus by dry weight and 5.6% nitrogen. Harvesting 10 grams (dry weight) of this macroalgae from an aquarium would be the equivalent of removing 24 mg of phosphate from the water column. That amount is the equivalent of reducing the phosphate concentration from 0.2 ppm to 0.1 ppm in a 67-gallon aquarium. All of the other species tested gave similar results (plus or minus a factor of two). Interestingly, using the same paper's nitrogen data, this would also be equivalent to reducing the nitrate content by 2.5 grams, or 10 ppm in that same 67-gallon aquarium.

 

[norskfisk]

Yes, actually, not how much you need to maintain, but how much you need to grow and harvest to get rid of a certain amount of nitrate or phosphate. For example if you have X mg nitrate per liter and you know how much water there is then you know how much nitrate there is in total in the system and by multiplying that with a constant you find the mass of nitrogen in this nitrate. A gram of cheato has a know mass of nitrogen (roughly) per gram of total biomass. So if you can google up those two numbers (I have done it before, it may be some wading through cryptic biology literature) then the calculations are easy. Also there are at least 3 ways to measure biomass: Wet weight, dry weight, and ash free dry weight.

You must also take into account that some of the algae biomass is "harvested" by your skimmer, so the actual weight you need to harvest is a little lower than the calculated one.

 

[feh]

Roughly. I've not seen the data for chaeto, but other macroalgae are likely not too far off on a dry weight basis.

I discuss it here:

Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php

from it:

For example, Caulerpa racemosa collected off Hawaii contains about 0.08 % phosphorus by dry weight and 5.6% nitrogen. Harvesting 10 grams (dry weight) of this macroalgae from an aquarium would be the equivalent of removing 24 mg of phosphate from the water column. That amount is the equivalent of reducing the phosphate concentration from 0.2 ppm to 0.1 ppm in a 67-gallon aquarium. All of the other species tested gave similar results (plus or minus a factor of two). Interestingly, using the same paper's nitrogen data, this would also be equivalent to reducing the nitrate content by 2.5 grams, or 10 ppm in that same 67-gallon aquarium.

Thanks.

 

[Randy Holmes-Farley]

:thumbsup:

Happy Reefing.