Water quality model proposal

[mkirda]

Hello, everyone.

My earlier post did not really elicit the type of responses I was hoping for.

I've been working on a coral database and have one last hurdle- How to handle water quality.
Two models presented themselves- one based strictly on test kit measurements, the other based strictly on observation. Both of these had problems.

With no third model presenting itself, I have opted to submit for comments a combination of the two- which I believe closely mimics what most reefkeepers do anyway.

Here we go:

Nutrient levels, from high to pristine.

High- Measurable PO4 (1ppm) and measurable nitrates (10ppm+). Nuisance algal growth is high.
Medium – Lower PO4 (0.2ppm), possibly some nitrates (5-9ppm). Nuisance algal growth slows. Cyano growth limited.
Low- Low PO4 (0.1ppm), very low nitrates (1-5ppm). Algae tend to do poorly. Very little, if any, cyano. Coralline algae growth takes off.
Pristine- No nitrates, No PO4. Water sparkles. Nuisance algae tend to wither away quickly. Coralline algae become a nuisance.

I really am looking for feedback on whether people think this is workable.
Wording and levels probably need further refinement.

FWIW, I decided that for other nutrients besides N/P, recommendations were superfluous- I would be basically recommending NSW levels anyway. Calcium, alkalinity, salinity, silicate, etc. will all be covered in a separate article on the website. A water chemistry primer, if you will...

Regards.
Mike Kirda

 

[Dana Riddle]

Hi Mike,

Long time, no see - missed you on the last trip to Chicago.

Just a quick comment on your model. As you're probably aware, certain nutrient mass transfer is limited when water motion is low. The boundary layers around a static object may limit diffusion rates. But I'm assuming that your model assumes water motion is sufficient and nutrients are absorbed by algae, plants and corals.

I have an interesting observation (to me, anyway).
All houses along Ali'i Drive were recently required to hook on to a recently laid sanitary sewer. Almost all 'nuisance' algae growing close to shore have disappeared and coralline algae are starting to become predominate. I suspect some of this is related to some algae growths being seasonal, but a dramatic improvement in visual appeal is obvious. I wonder if all the herbivorous fishes follow this line of thinking...

Dana

 

[mkirda]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Dana Riddle:
<strong>Hi Mike,

Long time, no see - missed you on the last trip to Chicago.

Just a quick comment on your model. As you're probably aware, certain nutrient mass transfer is limited when water motion is low. The boundary layers around a static object may limit diffusion rates. But I'm assuming that your model assumes water motion is sufficient and nutrients are absorbed by algae, plants and corals.

I have an interesting observation (to me, anyway).
All houses along Ali'i Drive were recently required to hook on to a recently laid sanitary sewer. Almost all 'nuisance' algae growing close to shore have disappeared and coralline algae are starting to become predominate. I suspect some of this is related to some algae growths being seasonal, but a dramatic improvement in visual appeal is obvious. I wonder if all the herbivorous fishes follow this line of thinking...

Dana</strong><hr></blockquote>

Dana,

Wasn't aware you had come to town- let me know next time!

The algal growth is exactly what I would expect- I wonder if anyone had measurements for N/P from before and after...

As far as the model, water motion is covered separately. I think that it is a fair assumption though.

Any other thoughts, Dana? Do you think this is workable?

Craig? Randy? Was hoping for some critical responses from you two. Should I assume that your silence indicates disapproval, apathy or tacit approval?

Regards.
Mike Kirda

 

[randy holmes-farley]

In my case, I didn't have much to add, but here are a few comments:

1. Since many people now have sand beds, and these sand beds are a good way to drive down nitrate but do nothing for phosphate, I would not make the assumption that these nutrients move together, as your categories suggest.

2. I'd quantify the "no phosphate, no nitrate" to be less than some value. It will never be none.

3. I'm not sure water clarity relates much to inorganic nutrient levels.

4. With many different descriptors for each level, a single tank might fall into several of them, maybe even all of them.

[ April 19, 2002: Message edited by: Randy Holmes-Farley ]</p>

 

[CraigBingman]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by mkirda:
<strong>Hello, everyone.

I've been working on a coral database and have one last hurdle- How to handle water quality.
Two models presented themselves- one based strictly on test kit measurements, the other based strictly on observation. Both of these had problems.

With no third model presenting itself, I have opted to submit for comments a combination of the two- which I believe closely mimics what most reefkeepers do anyway.

Here we go:

Nutrient levels, from high to pristine.

High- Measurable PO4 (1ppm) and measurable nitrates (10ppm+). Nuisance algal growth is high.
Medium - Lower PO4 (0.2ppm), possibly some nitrates (5-9ppm). Nuisance algal growth slows. Cyano growth limited.
Low- Low PO4 (0.1ppm), very low nitrates (1-5ppm). Algae tend to do poorly. Very little, if any, cyano. Coralline algae growth takes off.
Pristine- No nitrates, No PO4. Water sparkles. Nuisance algae tend to wither away quickly. Coralline algae become a nuisance.

I really am looking for feedback on whether people think this is workable.
Wording and levels probably need further refinement.

</strong><hr></blockquote>


I think you are trying to compress things too much. I would favor asking people for test values for phosphate and nitrate, (prompting them for some information on limit of detection if they find "none") and also asking them for information about algal growth in the system.

Just as a philosophical note, the "pristine" upper boundary in your scheme is an order of magnitude or so higher than ocean surface concentrations for phosphate and nitrate in reef-forming regions of the ocean.

Craig Bingman

 

[mkirda]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Randy Holmes-Farley:
<strong>In my case, I didn't have much to add, but here are a few comments:

1. Since many people now have sand beds, and these sand beds are a good way to drive down nitrate but do nothing for phosphate, I would not make the assumption that these nutrients move together, as your categories suggest.

2. I'd quantify the "no phosphate, no nitrate" to be less than some value. It will never be none.

3. I'm not sure water clarity relates much to inorganic nutrient levels.

4. With many different descriptors for each level, a single tank might fall into several of them, maybe even all of them.</strong><hr></blockquote>

Randy,

Thanks for the reply.

1) I can't think of a better way to handle it.

2) Wording change: Levels below detection limits on typical home test kits.

3) Made an assumption: Water clarity is about the only proxy for dissolved organics that is even remotely 'measureable'. If you can tell me of another way to measure DOCs, please do so. The one method I am aware of required temperatures beyond what most people could safely create in their homes.

4) I would then suggest that you choose the worst case as a characterization of your tank. {grin}

I am not yet wedded to this model.
I am, however, unable to come up with a better alternative.

Regards.
Mike Kirda

 

[mkirda]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by cbingman:
<strong>


I think you are trying to compress things too much. I would favor asking people for test values for phosphate and nitrate, (prompting them for some information on limit of detection if they find "none") and also asking them for information about algal growth in the system.

Just as a philosophical note, the "pristine" upper boundary in your scheme is an order of magnitude or so higher than ocean surface concentrations for phosphate and nitrate in reef-forming regions of the ocean.

Craig Bingman</strong><hr></blockquote>

Hi, Craig.
Thanks for the reply.

Regarding your first comment- I am certainly aware of this possibility.
Any model you make where parameter can be some number just greater than zero to 100 or so, the lines where you create the demarcations will be up to debate.

I chose roughly on the order of magnitude for nitrate, a bit less for phosphates.

I could expand the number of choices out greatly, out to five or ten different ranges, but I am not sure what exactly that would gain me, other than dilution of the differences between the ranges.

Reading your reply, you almost seem to be telling me to go forth and do a lot of testing of various tanks, then re-formulate the model based on what I find...

That could be do-able.

Your philosophical concerns are noted- The change in wording would be reflected as above in my reply to Randy.

Again, I thank you for your reply, and hope to continue this further.

Regards.
Mike Kirda

 

[Dana Riddle]

Mike,

I did indeed check a few chemical and physical parameters before the sewer ties were made.

First, some background. Kailua-Kona is a popular tourist attraction because of abundant sunshine and low rainfall. Being in the water business, we routinely monitor groundwater nutrients. Just above Kailua is the Hualalai volcano (currently listed as dormant). This volcano reaches to 4,000 feet elevation and receives abundant rainfall. This groundwater migrates to the ocean through fissures in the lava bed.

These readings were taken 9/23/99, at the beach in front of my house:
Temp = 80°F
D.O. = 7.8 mg/l
Orthophosphate (as P) = 0.16 mg/l
Nitrate (N-NO3) = 3.6 mg/l
Water Color (APHA) = 4
Water (wave) velocity (boy, is this variable) = 2.45 ft/sec.
Salinity = 32 ppt.
pH = 8.3

I suspect most of the nutrient loading was from septic tank leachate, but know from experience that some are related to minimal rainfall infiltration. I'll check these levels again. Wish I could predict a date - too many projects to take on another one!

Dana

 

[mkirda]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Dana Riddle:
<strong>These readings were taken 9/23/99, at the beach in front of my house:
Temp = 80°F
D.O. = 7.8 mg/l
Orthophosphate (as P) = 0.16 mg/l
Nitrate (N-NO3) = 3.6 mg/l
Water Color (APHA) = 4
Water (wave) velocity (boy, is this variable) = 2.45 ft/sec.
Salinity = 32 ppt.
pH = 8.3
</strong><hr></blockquote>

Dana,

How were the readings taken? Hobbyist kits or lab equipment? Someone asked me how you would measure DO and Water Color specifically...

Thanks.
Mike Kirda

 

[CraigBingman]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by mkirda:
<strong>

Dana,

How were the readings taken? Hobbyist kits or lab equipment? Someone asked me how you would measure DO and Water Color specifically...

Thanks.
Mike Kirda</strong><hr></blockquote>

Mike,

People usually measure dissolved oxygen by a titration method, or electrochemically. If you have a lot of measurements to make, the electrochemical route is the way to go.

Water color is either measured with a test kit or (preferably) a spectrophotometer. I'm amazed that Dana found 4 APHA units of water color "in the wild." That and the nutrient concentrations indicate that the area was a real cesspool before they cleaned it up.

Yuck.

Craig