If, while in Brooklyn, you head west, back toward Manhattan, and continue in that direction down a long hill, until you are in the narrow wedge between the Manhattan Bridge and the Brooklyn Bridge, you’ll find you are in a neighborhood called DUMBO. I offer up this fun bit of New York trivia you can impress your friends with (if your friends are the sorts to be impressed by New York trivia): the name DUMBO is one of the most complex in a long tradition in NY real estate of naming neighborhoods with acronyms. In the case of DUMBO, it’s Down Under the Manhattan Bridge Overpass.

Of course, if realtors in New York were at all concerned about geographic accuracy, they would rename the area Slightly Left or Right of the Manhattan Bridge Overpass (though that would be SLORMBO, which is not nearly as appealing) because directly under the overpass, you find a neighborhood of a different sort.

Dumbo Tidal Pool 3

Another fun bit of New York trivia is that the East River, which the Brooklyn Bridge spans, is actually not a river, at all. It is actually an interstitial tidal creek, connected at both ends to the ocean. At just about low tide, that cluster of rocks and seaweed becomes exposed, and a brilliant tidal pool forms. I’ve never been able to resist the lure of a tidal pool, the promise of discovery that comes with it, and since we’re experiencing an unusually (and frankly, quite frighteningly) warm November, last weekend I took my plankton net out with me and gathered some creatures to look at. My plankton net met an unfortunate end, though (Pro tip when using a plankton net: make sure it’s attached to you before you toss it into the water), so I focused on what I could find living in the seaweed.


As it turns out, that’s quite a bit. The East River has a reputation for being a heavily polluted, unlivable waterway, but right away I saw creatures moving around in my jars. The first of these were skeleton shrimp, which I caught climbing up the branches of the mermaid’s hair and posing as seaweed to wait for passing creatures to hunt. When they weren’t moving, this camouflage was so effective that it was nearly impossible to see them. Their back feet helps keep this illusion.

Skeleton Shrimp Back Legs Skeleton Shrimp Rear Legs

A long, many jointed body and back claws that wrap around the base of the seaweed let it hang out like a praying mantis, catching whatever floated by with its claws.

Skeleton Shrimp Claw

These skeleton shrimp were such effective hunters that within a single night, the population of free swimming amphipods in the jar dropped to nearly zero. Which also had the unfortunate side effect of making the water less hospitable to life, so I had to separate out a few interesting samples of seaweed from the jar and put the rest back into the river.

While searching through these samples, though, I found, much to my amazement, a nudibranch crawling along, also well hidden among the plants.

Considering that just a few weeks ago, I commented on this very site that I was jealous of other people who could go hunting among the kelp beds and find nudibranchs, this was very much a jackpot sort of find. The nudibranch has managed to keep an interesting sort of balance in the retooled sample container. It wanders around eating many of the protozoa in the water, keeping their population in check. The bits of seaweed meanwhile seem to keep the water oxygenated enough for everyone. Though it’s too large a creature to really benefit from a microscopic shot, I did manage to catch its gills ever so briefly in the microscope.

The luck in catching the nudibranch was doubled a few days later when it laid eggs, first at the surface of the water, and then again a few days later on the side of the jar.

Nudibranch Eggs Macro

I’m not sure if they’re fertilized or not. Knowing that nudibranchs can’t fertilize themselves, I would guess that the nudibranch either was fertilized before I caught it, or these eggs are infertile. Microscopic shots haven’t revealed much yet. This is a long video of the eggs taken a day or so after they were laid.

Nudibranch Eggs 5 Nudibranch Eggs 14 Nudibranch Eggs 8

In the closeup photos, I see what looks like cell division to me, though I am skeptical of what my eyes are showing me. I so very much want to see tiny baby nudibranchs swimming around in my tank that it is possible I’m just seeing what I want.

Clearing out the sample jar and allowing for a more sparse collection of seaweed and water has also allowed me to start taking in the numbers of free-floating plankton and other tiny creatures in the jar. Among these, a small population of naupilius larvae has surfaced.

I would guess this belongs either to a species of copepod or to barnacles, which there are many of in the water. You can see clearly the movement of the naupilius, its incredible speed and its form in multiple dimensions as it floats through the water.

Naupilius (Copepod?) 12

The speed with which it moves made catching a still shot difficult, but I managed a few closeups of it that catch that mite appearance.

They are joined by a planarian, this one so small that it barely seems to be a worm at all, floating around in the water like a cartoon ghost riding a small carpet of cilia.

In this shot, you can plainly see the movement of cilia around its body.

I’ve found planarians (another model creature in science) in virtually every water sample I’ve ever taken, and I always learn something from finding them. I had never, for example, realized that part of their ability to swim is driven by cilia, and yet here is visible proof of that.

Multiple adaptations of cilia were present in the water. The evening after I transferred the sample to its new container, I found this vorticella colony floating at the surface.

This is the second of several such colonies I’ve seen. They look to me like thought maps floating in the water. Here is one floating on what seems to be a small seed. I lit it using a side light technique to get the color of the object, and it looked so much like an apple, I couldn’t resist naming it.

They are just a few of the extraordinary variety of creatures I’ve found clinging to these small samples of grass. Last among them (for this post, anyway, if not for nature) are the diatoms. I noticed them hanging off of the seaweed, and assumed they were some kind of egg.

Diatoms 10 Diatoms 5 Diatoms 16

They are so prevalent in this water that I have also found long chains of diatoms wrapped around seaweed stalks.

I am planning to spend some time with this water in coming weeks. Of course, I hope the nudibranch eggs will hatch and give me some more veligers to look at, and some tiny nudibranchs to follow, but this post has also only scratched the surface of what I’ve found living in this water. These are the macro creatures, but the protozoa in this water swarm to a degree I’ve never seen in another sample.  I have literally hundreds of pictures taken from this sample already. If the water stays healthy, I’ll have a few weeks of posts out of it.

When I commented a few weeks ago that I wished I could live in a place where I could harvest nudibranch eggs, I committed a fallacy in which I allowed myself to assume that life was elsewhere. That I was somehow not living in a place where I could find things to look at. But, of course, life is everywhere, and while I might assume I cannot find interesting things in the city, they are here. In a tidal pool no more than four feet wide, I’ve found creatures I never thought I would find in my city.

12 Comments Add yours

  1. Manu Prakash says:

    @matt: Incredible, incredible.. I had a loud burst of laughter reading this..
    “My plankton net met an unfortunate end, though (Pro tip when using a plankton net: make sure it’s attached to you before you toss it into the water)”

    I will follow the pro tip.

    I am rushing (to buy a car); but quick note on detecting if fertilization happened would be is to look if a clearing zone appears on the eggs. This is to ensure only one sperm is allowed to enter. That clear zone will be visible just around the periphery of the eggs.


  2. Manu Prakash says:

    @Matt: starting with your comments about the naming convention; you found exactly what would live under DUMBO. Sea creatures Offcorse.

    It’s incredible how well camoflagued skeleton shrimps are. Unless one has ever seen them; you can not appreciate the hiding powers. What I did not know is how they hunt. Those hanging legs.. Oh my.


  3. Matt.Rossi says:

    @Manu, interestingly, I did see something burrowing into the nudibranch’s eggs as I was watching them. It didn’t occur to me to think of it at the time, but perhaps it was a sperm. I’m so used to thinking of fertilization from an anthropocentric viewpoint as something that happens internally that I forget many creatures don’t fertilize until after the egg has been laid. It occurs to me another way to find out will be to simply keep looking at the egg sacs until something happens.

  4. Matt.Rossi says:

    Two questions have resolved themselves. First, the naupilius has conveyed its type by obligingly turning into a copepod. Second, a look at the eggs shows a lot of movement, which makes me think many, if not all of the eggs have been fertilized.

  5. Manu Prakash says:

    @matt: that’s exciting. Try to put it on time lapse – I tried this once – see here:

    A crucial thing is photo toxicity; so you could use a couple of tape pieces to reduce light intensity. This would give a higher chance that the eggs would survive long term in the chamber. Most often; they get deprived of oxygen too.


  6. Matt.Rossi says:

    Manu, that’s a great idea. I think I have plenty of eggs at the moment to give it a go and not risk mucking up my future viewing (the nudibranch went ahead and laid some eggs this morning, too; I’ve got eggs for days). The risk of photo toxicity makes me wonder if I should be storing the eggs in a darker place.

    Incidentally, in that post you mentioned you would post on how to harvest eggs from sea urchins. Did you ever post it?

  7. Manu says:

    @matt: I never went and posted that – I will go ahead and do the same. It’s a very simple injection in the cavity. The trick also works for a number of echinoderms. I will make a list of spawning protocols and post them together.

    For sea urchins; it’s a simple injection of 0.5M KCl. Here is a nice video for the same.

    If you are already seeing natural egg deposition; I would stick to that..


  8. Manu says:

    @Matt: Photo-toxicity is only an issue when imaging with time lapse for a long time (5-10hours); needed for watching all of cell divisions. In normal storage – the biggest thing is oxygen and evaporation (which increases salinity).

    I also have another trick where I turned Foldscope upside down in “inverted microscopy” mode. I should write it as another post – but a simple description is to remove the back light module; and put your phone (recording device) screen facing down; and foldscope on top. Now when you put eggs in a petri dish (with thin bottom); and use a table lamp as illumination – you will get an image. You have to bend down to be able to see your image since the screen is covered – so some kind of glass table is useful (or you can raise your phone on a small post). Now adding water increases weight in the dish; allowing you to focus on the bottom of the dish. The advantage of this method is that your sample will never evaporate (necessary for long term time lapse imaging). You can leave it overnight – wake up in the morning and see what you find. I also use an app called “time lapse” for setting parameters for my time lapse videos.


  9. Matt.Rossi says:

    Do I also flip the Foldscope over for reverse microscopy, so the petri dish sits where the illumination unit would, or does the petri dish sit on top of the small aperture of the lens? I might give this one a try so I can catch some cell division.

  10. laksiyer says:

    Absolutely Brilliant @Matt. The only thing is change in salinity, so if you can supplement the evaporation with fresh water from the same source, you have something for months and I cant wait to see what else you have found.

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