Doing Diatoms - part 2

Here you can discuss sample and specimen preparation issues.
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Phill Brown
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Re: Doing Diatoms - part 2

#31 Post by Phill Brown » Wed Apr 26, 2023 8:35 am

It's worth printing and framing your best finds.
A4 is the most cost effective and is about right for wall space.
When asked what you do for fun it saves reaching for a device.
If selling it's better to use inks that don't fade.
The great thing about Canon Chromalife is the number of genuine CLi-8 pigment black that are available at low cost.
DF works great behind glass.
Happy days.

Phill Brown
Posts: 603
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: Doing Diatoms - part 2

#32 Post by Phill Brown » Fri May 05, 2023 9:15 am

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Fossil diatoms from Monterey.
Miocene formation.
Too many frustules in the mix, many in near perfect condition.
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Made the effort to label this time from the sample.
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Made a simple inline filter,2 sections of tube with a 30 micron mesh screen.
Set in Canada balsam.
Image in DF with 40x .65 f.o.v 0.03mm.
Camera is a Lumix G3.
Scope is Watson Hilux.
It's just a hobby so I don't need it to be perfect.
I have several kilos of diatomite from Miocene formations, need to make a selection of screen sizes to isolate the larger diatoms.

Sure Squintsalot
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Re: Doing Diatoms - part 2

#33 Post by Sure Squintsalot » Wed May 17, 2023 5:21 am

A few darkfield images of some Puget Sound planktons. Nearly all of these images are extensively photoshopped: stacking, contrast enhancement, edge "sharpening", fringe removal, spot removal, etc., etc., etc. Note that despite the considerable photo manipulation, no details are ever added to the subject itself.
Asteromphalus heptactis ... I think.
Asteromphalus heptactis ... I think.
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Same A. heptactis in context of the strew it lives in. Note the extensive background removal (in PS) in the first image.
Same A. heptactis in context of the strew it lives in. Note the extensive background removal (in PS) in the first image.
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Pleurosigma gang....but looks like a standoff. The right side 'diatom' could be a "ribbon" of many individual diatoms. That's my guess.
Pleurosigma gang....but looks like a standoff. The right side 'diatom' could be a "ribbon" of many individual diatoms. That's my guess.
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Never seen one before, in books or online. Have no idea what it is.
Never seen one before, in books or online. Have no idea what it is.
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DIC (above) vs. DF (below)
DIC (above) vs. DF (below)
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Sure Squintsalot
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Joined: Mon May 16, 2022 3:44 pm

Re: Doing Diatoms - part 2

#34 Post by Sure Squintsalot » Sun Dec 17, 2023 10:37 pm

A recent scuba trip to the Red Sea meant a plankton net upgrade, including a quantitative way to measure net depth when towing.

First, a proper net requires shaping, ribs for strength, and endless scouring of the internet for images:
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Followed by a lot of frustrating sewing:
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And then some expletive laden sewing:
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Finally, rope measuring and marking. It takes a lot of rope (and a lot of weight) to get a net down to any kind of depth, otherwise you're just dragging the thing along the sea surface:
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Unfortunately, a 20kg plow-shaped weight would have put my luggage way over the airline weight limit, so, I had to improvise with some scuba weights. Even with 13kg of weight and 100 meters of rope, I could only get the net down to 18 meters.

Sure Squintsalot
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Re: Doing Diatoms - part 2

#35 Post by Sure Squintsalot » Sun Dec 17, 2023 10:52 pm

Once at sea, I had to bribe a deck hand to get me out on the water in the zodiac while everyone else was under the water.
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The trick is playing out the line while keeping tension and making sure the boat travels straight at never more than 1-2 knots. Measuring depth is some simple trig, still done the same way by the big kids on their fancy research vessels.
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After an hour, it all gets hauled back in, and immediately rinsed with formalin.
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And finally, the goods:
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It doesn't look like much, but this stuff is like gold! A quick peak and I saw tons of worms and copepods. Boy, would I be surprised later on!

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zzffnn
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Re: Doing Diatoms - part 2

#36 Post by zzffnn » Sun Dec 17, 2023 10:56 pm

Red sea is a nice place! I have some interesting seashells from that area.

Why are you aiming for a specific depth range (is 18 meters in depth not good enough for your purpose)?

I am guessing you are not allowed to bring (visible) dived specimens across the border?

Sure Squintsalot
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Re: Doing Diatoms - part 2

#37 Post by Sure Squintsalot » Sun Dec 17, 2023 11:05 pm

Funny you should mention...

Getting plankton samples across borders is certainly not an issue if you're a research institution and have miles of associated paperwork. I had to improvise:
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Each little bottle is a concentrated sample of microscopic stuff from several plankton drags at different depths and syringed samples from selected locations within different coral reef features like marine snow on cave walls, algaes within dead coral fingers....that sort of thing.

I was looking for the kind of stuff that hides at some depth during the day, away from the glare of the sun, then comes up later in the day. Frankly, I wasn't sure what I was doing, more or less just exploring, seeing what I could see. A quick look-see of some wet samples:
A fairly typical assortment of ceratium and copepods:
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MANY arrow worms. Here's its head with grasping barbs and maw. Vicious little things that prey on copepods.
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Arrow worm tail with oblique light:
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Sure Squintsalot
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Re: Doing Diatoms - part 2

#38 Post by Sure Squintsalot » Sun Dec 17, 2023 11:43 pm

Basic dark field is definitely an awesome technique for plankton and diatoms, especially with low RI media like formalin or methanol. I'm holding off on the DIC until I mount legitimate slides. These, by the way, are all stacked images from about 4-8 photos, heavily cleaned up in photoshop, though no details added unless I say as much.
A shrimp larva:
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Rhabdonella
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A sponge spicule.
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Some kind of Nassileria
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A foraminifera. These things are pretty awesome.
Screenshot 2023-12-17 163015.jpg
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Sure Squintsalot
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Re: Doing Diatoms - part 2

#39 Post by Sure Squintsalot » Wed Jan 17, 2024 7:05 am

Printed photos of diatoms do a poor job of conveying their beauty and complexity, unless you have an SEM. After wrestling with the problem of how best to show off these things, I thought it best to arrange within some sort of organic-looking large format framework:
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At 56cm wide and 100cm tall, each individual plankton is large enough to see in detail without the "fuzziness" that comes with high magnifications, which is pretty OK when printed to poster size:
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Of the 70 or so different plankton that I obtained from this one tow, performed one night last year in the Philippines, 56 made it on to this poster. About 12 of these have utterly eluded identification. Let the sleuthing continue!

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