N:P RATIOS IN ESTIMATING NUTRIENT LIMITATION IN AQUATIC SYSTEMS

[Garf]

http://www.cost869.alterra.nl/FS/FS_NPratio.pdf

[Garf]

A few illustrations as to why it's necessary to control N:P

http://i1269.photobucket.com/albums/jj597/Garf1971/5738b048d313c77de5995fee424c1e15.jpg (http://http://i1269.photobucket.com/albums/jj597/Garf1971/5738b048d313c77de5995fee424c1e15.jpg)
http://i1269.photobucket.com/albums/jj597/Garf1971/2d00f3d3046037ad2ba996162a7f891e.jpg (http://http://i1269.photobucket.com/albums/jj597/Garf1971/2d00f3d3046037ad2ba996162a7f891e.jpg)

[Ace25]

The last part of this paragraph is interesting. I wonder how that translates to GFO effectiveness, since GFO is Fe.


Rationale

Aquatic eutrophication results from excessive amounts of nutrients available for primary producers,
such as planktonic algae, macroalgae and macrophytes. To successfully mitigate eutrophication, one
should be able to identify which nutrient(s) is/are responsible for enhanced primary production so
that management actions can be focused on nutrients having the highest impact.

Ecological stoichiometry is a discipline that seeks to understand the balance of multiple chemical
elements in ecological interactions. As to freshwaters (lakes, rivers, reservoirs), it has traditionally
been assumed that P is the nutrient present in lowest amount in relation to the requirements of phytoplankton.
Therefore, when the flux of P entering a body of water is cut down, the biomass of algae is assumed to be reduced.
In marine systems, N has been identified as the growth limiting nutrient, whereas in estuaries P may be limiting in the
fresh-water part and N in the marine part [1]. Nitrogen limitation in marine systems has been attributed to (i) stronger
N removal in coastal waters e.g. by denitrification, (ii) lower amount of N-fixing cyanobacteria ('blue-green algae') and (iii) to
higher rates of microbial SO4 reduction that makes Fe unable to sequester P.

[Garf]

Ace - never looked into GFO till now;

http://www.reefkeeping.com/issues/2004-11/rhf/index.php

Its almost "experimental" and rather scary if you ask me.

[Garf]

Looks like cyano makes use of IRON limitation, and turns it into a competitive advantage. May be useful info for struggling scrubber screens which also get cyano outbreaks. Apparently the addition of iron does not increase cyano production, but this cyano appearance could be used as a "low Iron" indicator for screens;
http://web.bio.utk.edu/wilhelm/Wilhelm%20lab%20papers/Wilhelm%20et%20al%201996.pdf

[Garf]

Already posted this on Floyds LED UAS thread

http://www.mendeley.com/research/effects-morphology-water-flow-photosynthesis-marine-macroalgae/

Looks like NP ratio of algae can be manipulated by flow speed. More flow = more phos uptake Less flow = more nitrate uptake

This suggests a simple method to keep the NP ratio high enough to prevent cyano outbreaks etc. on the downside, it also suggest 3d growth will reduce phosphate uptake relative to nitrate due to relative reduced flow, therefor bigger screens may be required to control NP ratios completely.


The plasticity of morphologies and the interaction of these morphotypes with, flow may represent a trade-off between maximizing NP and reducing the susceptibility of the thallus to mechanical damage and/or dislodgement by hydrodynamic forces.

[Garf]

How about using the colour of your screen to assess the amount of nitrogen your screen is removing ?

http://www.botany.uwc.ac.za/pssa/articles/students/no58-randersson.htm

http://i1269.photobucket.com/albums/jj597/Garf1971/6260f8dee6127764f3fc04748cf4716c.jpg (http://http://i1269.photobucket.com/albums/jj597/Garf1971/6260f8dee6127764f3fc04748cf4716c.jpg)

Lithe lighter colours obviously means chlorosis, and a limiting factor.

[SantaMonica]

Looks like NP ratio of algae

NP is not nitrate phosphate; it is net photosynthesis. The abstract does not say anything about nitrate vs. phosphate vs. flow rate.

As for the color of growth vs nutrients, we learned that back in 2008 :)

[Ace25]

Yup, SM is right, NP is not the NP you are hoping it was. ;)


The relationship between surface area/volume ratio (SA/V) and rates of biomass-specific net photosynthesis (NP) across functional-form groups was examined to test the hypothesis that NP is related positively to SAN. The rate of NP increased with increasing SAN across functional groups.

[Garf]

Damn it - so increasing the flow reduces the net photosynthesis, that's not what we're told at all. Back to google then.

[SantaMonica]

Actually the abstract said that net photosynthesis increases up to a point, but decreases if flow increases further. This is common in flow studies.

[rleahaines]

An experiement to see what actually happens should be fairly easy to do with a waterfall scrubber or even a UAS.

run the scrubber with high flow for a while and then compare it to low flow

Athough I wonder if we could even get to a high flow state that actually decreases photosynthesis and algae growth at all in a scrubber set up.

From a practical standpoint, I could see that dwell time of water over a scrubber may have something to do with gas exchange and therefore growth, but I suspect that the actual growth would be more dependent on light, the kind of algae and multiple other factors once we have a certain flow rate.

[Floyd R Turbo]

There is a balance factor here as well. I have ran a scrubber with low flow (20 GPH/in) and got great growth, also good growth at even lower flow, but too low and your overall turnover rate is too low and you get algae growth in the tank. Too much flow seems to grow a little less bulky algae, it doesn't stay in the holes as well, and it grows much longer and sort of "slimier" but still green, and the very high flow rate seems to not outcompete tank algae any better than low-flow with very thick growth. This is why I upped the pump size in my units and included a inlet ball valve.