[Coral-List] Fluorescent sediment tracers

[Dennis Hubbard]

Hi Emily:

While the method is not new, your field requirements do create unique
problems. The USGS did a lot of this 50 years ago to determine beach
transport with siliclastic sediments. We modified their methods to dye
carbonate sediments that we released in a variety of environments. Pretty
much any epoxy-based paint will work well. In our case, we gathered natural
sediment from sandy areas in the reef, washed it thoroughly and then
applied the paint liberally thinned with toluene. We used a small cement
mixer so we could keep the sediment moving and disaggregated as the toluene
dried. The good news was that we noted no difference in the grain size
distribution before and after, but I suspect that we did modify the bulk
density as the paint undoubtedly filled in small pores in the skeletal
matrix. The bad news is that this might not work with your environmental
and logistical constraints. In our case, toluene was readily available in
any hardware store on the island of St. Croix and we could even take the
paint with us as long as we filed the proper MCSD paperwork with thee
airlines. You didn't mention specifically where your "remote" site is and
whether surface shipping might be an option.

Depending on your specific use, the cement mixed might be optional;. We
wanted to make sure that we didn't have any grains sticking to one another
and were using rather large quantities to assume quality control. In the
end, the sediment appears to have been quite inert, so "pollution didn't
seem to be a major issue. I'm not sure how well this would pass through the
"gut" of a sponge if you are "tracing" biological throughput - we were
interested in sediment transport and reintroduced about a cup of dyed
sediment into a small depression. We came back after varied intervals and
recovered small cores  (500 ml syringes with the ends cut off) on a tight
grid. The number of dyed grains in each sample were counted manually to
determine how much dyed sediment had reached each grid square and then used
the method of moments to determine advection.

I just did a quick web search and it looks like there are a lot of
commercial dyes available for lab use (one by Lycor). Without more
information on your goals and logistical constraints, that's about the best
I can offer.

Dennis


On Thu, May 1, 2014 at 10:19 PM, Emily McGrath <emilycmcgrath at gmail.com>wrote:

> Hi all,
>
> Does anyone have experience with fluorescent dyeing sediment? I am
> interested in dyeing small quantities of sediment to be used as tracers for
> a series of experiments involving coral reef sponges. The sediment will be
> gathered from a shallow coral reef and will range in size from ~35-150µm
> and should fluoresce under UV light. The application of the dyed sediment
> will be *in situ *so non-toxic materials are preferable.
>
> Another complication is that the staining process will occur on a remote
> field site with few resources so ideally all materials will need to be
> airline approved.
>
> Any suggestions would be greatly appreciated!
>
> Cheers,
>
> Emily McGrath
> PhD Candidate
> School of Biological Sciences
> Victoria University of Wellington
> P.O Box 600
> Wellington 6140
> New Zealand
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-- 
Dennis Hubbard
Chair, Dept of Geology-Oberlin College Oberlin OH 44074
(440) 775-8346

* "When you get on the wrong train.... every stop is the wrong stop"*
 Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"