First caught plankton creatures

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Hobbyst46
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First caught plankton creatures

#1 Post by Hobbyst46 » Mon Jul 29, 2019 6:59 pm

Hello all,
Here are first images of Nauplius, alga, diatoms and a sand grain collected with the DIY 25um plankton net. It was towed by a friend at the depth of ~3m in the Meditteranean Sea, near the shore. The large nauplius is ~1mm long. Imaged with a 6.3X0.16 Plan or 10X0.30 Neofluar, POL or DF+POL.
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Brown alga +diatoms.jpg
Brown alga +diatoms.jpg (230.84 KiB) Viewed 2866 times
Plankton+sand grain.JPG
Plankton+sand grain.JPG (112.02 KiB) Viewed 2866 times
Nauplius Stack of 6.jpg
Nauplius Stack of 6.jpg (36 KiB) Viewed 2866 times
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

Sauerkraut
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Re: First caught plankton creatures

#2 Post by Sauerkraut » Mon Jul 29, 2019 8:12 pm

Beautiful images and a nice haul too. Life takes so many forms it's a bit mind boggling.

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75RR
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Re: First caught plankton creatures

#3 Post by 75RR » Mon Jul 29, 2019 8:16 pm

A successful trial! How did you get it to remain at -3m and why did you choose that depth? Is it supposed to especially rich in plankton?
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

Hobbyst46
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Re: First caught plankton creatures

#4 Post by Hobbyst46 » Mon Jul 29, 2019 8:19 pm

Thanks folks
75RR, my friend who towed the net choose the conditions - I will have to ask him, he knows the sea...and its inhabitants. In alga-rich drops within the jar of ca. 100ml of collected seawater, there are (say) 2-3 naupli per drop. The alga are tiny, fibrous, thin, brown.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
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Re: First caught plankton creatures

#5 Post by MicroBob » Mon Jul 29, 2019 9:07 pm

Hi Doron,
nice dark field images! Did you make them with your new cardioid condenser or with your nice phase condenser?
Have I missed your post describing the plancton net? :oops:
There are very few manufacturers of these nets and even here in Germany, were we have a comparatively rich market there are not many available, and none of them for little money. So how did you make your net?

Bob

Hobbyst46
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Re: First caught plankton creatures

#6 Post by Hobbyst46 » Mon Jul 29, 2019 10:19 pm

Thanks Bob.

The images were done with the Ph3 phase contrast position of the turret condenser, which creates DF with the 4, 6.3 and 10X objectives (maybe the 16X objective as well). The cardiodid is being prepared for repainting - if successful, I will post a report.
No, I did not previously show the net, and it is not with me right now, but here is a description. It is modified from the various recipes of plankton nets for children on the www. Dimensions are provisional and nothing has been "optimized".

The fabric is a 25um Chinese nylon cheese filter cloth, purchased via Aliexpress by the square-m. It is woven, yet thin enough. A cone (frustum really) was formed by overlock machine stitching (a friend's contribution). The top and bottom hemline stitches leave space for threading a wire loop, that keeps the openings of the net round and stiff. The wire was a piece of a single-braided thick electrical coated wire (~2mm diameter of the metal or so).

The top wire loop is the anchor, via three small loops, for three strings that are tied to the towing gadget. The bottom end of the fabric cone is wrapped around a "funnel" - namely, the neck of a 2-liter disposable soda bottle, including the thread, which protrudes outside of the cloth cone. The collecting vessel is a small (~100ml capacity) wide disposable jar (cheap kid's birthday party stuff). The lid of the soda bottle and the lid of the jar are glued back-to-back to each other (with Super-7 glue). A wide hole is bored through the combined lids, to allow liquid passage from the cone to the jar. The lid is screwed onto the soda bottle thread and the jar is screwed into its lid. So jars can be easily switched.

Hopefully the scheme below is clear.
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MicroBob
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Re: First caught plankton creatures

#7 Post by MicroBob » Tue Jul 30, 2019 5:27 am

Hi Doron,
thank you for posting, this is a really neat design, better than anything available that I know of. The lid of the plastic bottle and the lid of the plastic jar are probably glued or welded together?
Aliexpress is a really cheap source for the net material. I would use 50µ mesh, and it is only 8,26€ per m² - thank you for this source!

I was recently asked whether I could buy two nets for the group members to borrow but was not too fond of the idea. My idea was to assemble a DIY instruction and perhaps prepare a net sewing meeting, but I didn't find an affordable source for the net material.
I hope you don't mind if I copy your design for this project.

Here in Germany there used to be a net available of this dimensions, with a small jar that contains ca. 30ml, connected by a bayonett mount. It was quite popular among amateur microscopists but is not available for 20 years now. I have one, but it has 90µ mesh size which is a bit more than I would prefer. This size is big enough to collect a lot of critters and small enough to carry it around on a day trip with the family to catch some plancton towards the end of the trip.

Bob

MichaelG.
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Re: First caught plankton creatures

#8 Post by MichaelG. » Tue Jul 30, 2019 6:50 am

Thanks for the net details, Doron

... nicely done :!:

MichaelG.
Too many 'projects'

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Re: First caught plankton creatures

#9 Post by Hobbyst46 » Tue Jul 30, 2019 7:54 am

MicroBob wrote:...The lid of the plastic bottle and the lid of the plastic jar are probably glued or welded together?
Yes, they are glued with Super-7. This glue is water-resistant and somewhat more flexible than epoxy, even after curing.
...I would use 50µ mesh...
some of the cloth samples I bought 2 years ago were rapidly delivered. On the whole I now prefer eBay, though, on behald of their customer service.
I hope you don't mind if I copy your design for this project.
Why, I am complimented. I hope that the dimensions are good - have seen a research article that treats it from an enginnering aspect, and derived the dimensions from the speed of water flow in and out, etc.

See my response to 75RR about dead weights.
Last edited by Hobbyst46 on Tue Jul 30, 2019 9:56 am, edited 1 time in total.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

Hobbyst46
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Re: First caught plankton creatures

#10 Post by Hobbyst46 » Tue Jul 30, 2019 9:34 am

75RR wrote:A successful trial! How did you get it to remain at -3m and why did you choose that depth? Is it supposed to especially rich in plankton?
Correction: when towed, the net mostly floated on the water surface (specific gravity of plastic< 1.04), but was manually pulled and submerged to the depth for less than a minute. In fact, we plan to add some dead weights (order of magnitude, say, 100g) to make it sink below the surface. So far we assume that the amount of plankton does not depend on the depth.
I assume that we shall know the correct weight within 1-2 weeks.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
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Re: First caught plankton creatures

#11 Post by MicroBob » Tue Jul 30, 2019 3:16 pm

Here is alink to one of the few companies that make plancton nets: https://www.pokorny-netze.at/planktonnetze,106
Their version with the cock at the end to release the catch is only practical when you have at least on assistant with you. I much prefer nets with a beaker at the end, though sampling planton is much nicer in company of cause. :D

When I collect samples from the shore I do multile throws befor I empty the beaker. Here it is good to have the right size of beaker so the net flies with beaker first but doesn't land with too much force. My big net (ca. 22cm and quite long) has a 100 ml urine sample beaker and my small net a ca. 30ml special beaker with a bayonet mount.

Bob

Hobbyst46
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Re: First caught plankton creatures

#12 Post by Hobbyst46 » Tue Jul 30, 2019 4:30 pm

MicroBob wrote:Here is alink to one of the few companies that make plancton nets: https://www.pokorny-netze.at/planktonnetze,106
Their version with the cock at the end to release the catch is only practical when you have at least on assistant with you. I much prefer nets with a beaker at the end, though sampling planton is much nicer in company of cause. :D
I saw the Apstein designs in the link. Is the entrance of these nets supposed to block large creatures from swimming inside ? Nitex is a well-known name for filter cloth in biology, but probably quite expensive.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
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Re: First caught plankton creatures

#13 Post by MicroBob » Tue Jul 30, 2019 6:24 pm

Hi Doron,
a conical plancton net always has an increased water pressure inside of it and pushes some water at the front to the side. So when you draw it through 10m of water the sampled volume is not 10m x D² x Pi/4, it is less. And you don't know how much less.
The front of the nose reduced the water entry while the filter surface remains the same. This way the difference to the theoretical sample volume is reduced and the impact of the guesswork is diminished. This is only important if you want to know the number of critters per m³. With a normal net you catch more.

Bob

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Re: First caught plankton creatures

#14 Post by MicroBob » Tue Jul 30, 2019 6:31 pm

To go below the surface my nets have these weights:

Big: Wire ring at front and metal strap to fix net to beaker lid
Small: Wire ring at front, M10 nut on the back of the beaker (removable)
I think this is about what most amateur microscopists use.

This works for me - but I'm no expert. My small net had a threaded adapter to connect to a telescopic stick. I is broken of and I haven' t fixed it yet, but it is useful, especially for a small net.

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75RR
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Re: First caught plankton creatures

#15 Post by 75RR » Tue Jul 30, 2019 7:46 pm

Perhaps you can add a lip to the net (similar to fishing lures) that will make it dive. Different lips will give different depths.

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Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

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