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7 Reasons to Get Excited about Plankton!

By Heather Flanagan
April 3, 2017

There’s an amazing microscopic world in every drop of New York Harbor water.  Fancy equipment helps, but you can even spot these key players in the harbor ecosystem using DIY materials!

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An isopod collected by BOP teachers under a DIY smartphone microscope made by The River Project.

“Plankton” is a catch-all term for an extremely diverse range of species that share one trait: they live in the water column and are unable to swim against the current.  These organisms, some tiny and some not-so-tiny, are a hugely important part of New York Harbor’s food web, and include many frequent guests to our Oyster Restoration Stations.  At a Billion Oyster Project Curriculum and Community Enterprise for Restoration Science professional development this February, public school teachers from all over NYC visited The River Project (TRP), a marine science field station located above the Hudson River to learn all about these harbor residents, lead by TRP’s educators Eli Caref and Melissa Rex.  

Teachers who want to give their students a closer look at plankton should check out our new curriculum, NY Harbor Populations Investigation.  This unit starts with NY Harbor food and habitat webs, gets students hands-on designing experiments with their own small tanks of amphipods and isopods, and culminates in students reading middle school-friendly digests of real scientific studies as models to propose their own study.

1) Some plankton are invisible to the naked eye, but we can see their effects when they turn oysters’ gills green!


Crassostrea virginica with a natural dye job.  Photo via In a Half Shell.

Oysters eat a type of microscopic plankton called phytoplankton, which they filter into their bodies using their gills.  Phytoplankton get energy from the sun through photosynthesis like plants.

The term “phytoplankton” encompasses many different, unrelated species from different kingdoms, both unicellular and multicellular, and to complicate things further, different types of phytoplankton are grouped into different categories:

(And even more complicated is the fact that the categories themselves aren’t perfect- many dinoflagellates can photosynthesize, but many of them can’t and ingest other microorganisms instead, and still others can do both.)

Even though you can’t see the phytoplankton that oysters eat with the naked eye, you can sometimes see them when there are a lot of them in one place.  One species of phytoplankton, the diatom Haslea ostrearia, has long been noted for a special property- it turns oysters’ gills green when they filter the diatoms in!


Light micrograph of Haslea ostrearia from the study “Marennine, Promising Blue Pigments from a Widespread Haslea Diatom Species Complex.”

Luckily, as the oyster blog In a Half Shell, notes,”The green tint is temporary and doesn’t change the taste.”  Recent studies have found that Haslea ostrearia and other species in its genus can produce “a water-soluble blue pigment, marennine” which might “present a commercial potential for aquaculture, cosmetics, food and health industries.”

2)  19th century hobbyists created art out of microscopic phytoplankton.

New York Harbor is full of diatoms, a type of phytoplankton with cell walls made out of silica- or, as our UMCES partner Bill Dennison once put it, “glass houses.”  That glass shell is called a “frustule.”  Diatoms are organisms made up of only one cell, and they range in size from 5 to 200 micrometers.  (To put this in perspective, you could fit 2,000 of the tiniest diatoms across the width of a paperclip.)

Despite their diminutive size, Victorian hobbyists would use diatoms to create fantastically intricate patterns called diatom arrangements like the one below- a whole arrangement would fit inside the period at the end of this sentence.  Wealthy amateur naturalists would exhibit these under a microscope at parties!


Photo via Smithsonian.

There’s only one living person in the world who practices the craft of diatom arrangement anymore.  You can watch a short film about him in this Smithsonian article.

3) A seahorse’s favorite snack is a type of plankton that can change colors.

At least one of our teachers has been lucky enough to encounter a live lined sea horse in their Oyster Restoration Station- science teacher Rachelle Travis of Dr. Susan S. McKinney Secondary School of the Arts snapped the picture below:

sea horse

Photo courtesy of Rachelle Travis.

According to Melissa, a sea horse’s favorite snack is an amphipod, a tiny crustacean.  Amphipods are a type of zooplankton, a name for plankton that ingest other organisms (instead of producing their own energy through photosynthesis).  Mud crabs, a more common ORS visitor, also like to eat amphipods.


Amphipod photo courtesy of Mollie Thurman of BioBase/BioBus.

Different species of amphipods have different food preferences, including both living organisms (diatoms, tunicate larvae, and even other small crustaceans) and decaying material.  These tiny crustaceans are often visible to the naked eye and like the green gilled oyster, their color can change based on what they’ve eaten.  The green amphipod below was a special guest at the professional development!  This creature’s color likely came from eating algae.

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Amphipods, like other organisms in New York Harbor, may face some unintended consequences from the pharmaceuticals that pass through our bodies and get flushed down our toilets.  A study in 2010 showed that amphipods exposed to Prozac at levels found in urban waterways showed a “five times greater preference for light,” which makes them more susceptible to predation.  This could affect their population levels, but scientists don’t know for sure yet.  (Another, perhaps less-expected-to-be-hazardous thing in New York Harbor that can affect amphipods is the sea lettuce Ulva lactuca L.  Some research has shown that this seaweed produces substances that can interfere with sexual communication between amphipods.)

4) Some plankton get awesome names like “megalops.”

“Megalops” sounds like a dinosaur and looks like an alien, but it’s actually a larval stage for crabs!  While organisms like crabs, oysters, fish, and barnacles don’t count as plankton as adults, the larval forms of these organisms are planktonic and serve as an important food source for fish and crustaceans in New York Harbor.

5) New York Harbor plankton can be bioluminescent.

Some plankton are bioluminescent- and we’ve got some in New York Harbor!  These organisms can use chemicals in their body to generate light, using only their food as an energy source.  Bioluminescence is a useful adaptation because it confuses predators.

Among New York Harbor’s bioluminescent plankton is Leidy’s comb jelly.  While many species of plankton are microscopic, larger organisms like comb jellies and jellyfish that can’t swim against the current are also considered to be plankton.  Comb jellies, or ctenophores, look like jellyfish but can’t sting. (Although if you find one in your Oyster Restoration Station it might just look like a blob.)

YouTube video “Animales del mundo – Mnemiopsis leidyi”  from user lagunadani.

The New York Times’ “Wild in the Streets: A 24 Hour Field Guide to New York City” mentions that you can spot Leidy’s comb jelly in Jamaica Bay and Pelham Bay, and describes the experience of encountering them: “When they are abundant, the animals can make a walk along the water’s edge seem like a hike among the stars. The species lights up when disturbed, which may be when tides carry them past stones or wooden piers, or for an hour or two after the tides wash them onto sandy shorelines, as your foot brushes past.”

For a less glamorous view of comb jellies, check out this video and article from National Geographic: Watch: Pooping Comb Jellies Just Upended Gut Evolution

Read more information on ctenophores here.

6) Phytoplankton might be the reason your chicken nuggets are killing your crab cakes. 

blue crab

Blue crabs are residents of New York Harbor, but in the Chesapeake Bay they’re also an important fishery in addition to being part of the marine food web.  Maryland is famous for its crab cakes made from these Chesapeake residents.  Image via Wikimedia Commons.

Phytoplankton is a vital part of the food web, but when there is too much of it, the consequences can be deadly for marine life.  Like plants, phytoplankton consume carbon dioxide and produce oxygen, and they also need nutrients (in varying amounts depending on the species) like nitrate, phosphate, silicate, calcium, and iron.

These nutrients can become too readily available, according to NOAA, “from wastewater treatment facilities, runoff from land in urban areas during rains, and from farming.”  The same chemical agricultural fertilizers that foster extra growth in plants also encourage phytoplankton and other algae.  (“Algae” is another blanket term like “plankton” that refers to a wide range of “aquatic, plant-like organisms.”  All phytoplankton are algae, but all algae are not phytoplankton.)


Suspended matter caused by runoff in the Chesapeake Bay before and after heavy rainfall via NOAA.

Unfortunately, this triggers a phenomenon known as “algal blooms,” which lead to “dead zones,” or the condition known as “eutrophication.”  Phytoplankton growth explodes with the influx of nutrients, but so does waste from the organisms that consume it.  And when the supply runs out, the phytoplankton die and are consumed by bacteria, who use up a tremendous amount of oxygen in the process, causing “hypoxia.”  The marine life that depends on oxygen either dies or leaves, essentially becoming “biological deserts.”  The second largest dead zone in the world is in the Gulf of Mexico, the result of agricultural runoff into the Mississippi River:


Photo credit: NOAA

In July 2011, a Mother Jones piece about the Chesapeake’s annual dead zone noted that “[a]lready, fully a third of the bay—once one of the globe’s most productive fisheries—is incapable of supporting sea life” due to “massive concentrations of chicken farms right on the banks of the Chesapeake.”  In 2016, writing about that year’s projected dead zone, NOAA explained that “[e]xcessive nutrient pollution in the Chesapeake Bay threatens its commercially and recreationally important blue crab fishery through oxygen depletion.”  Meanwhile, the fertilizer runoff from the midwestern corn that feeds Maryland’s chickens (and people across the US in the form of corn syrup) “blots out 3,300 square miles of our nation’s most important fishery” in the Gulf of Mexico.

Yet another reason to eat farmed oysters instead!

(Teachers- our Nitrogen Cycle Investigation unit on the BOP Digital Platform covers this topic and more.  If you’re intrigued by the Mother Jones piece, the lesson “Nitrogen Pollution” [part 9] uses this article and maps to get students thinking about how the food system, and their participation in it, affects our waterways.)

7) You can collect and observe plankton with DIY materials- including nylons!

Melissa shows off TRP's DIY plankton net.

Melissa shows off TRP’s DIY plankton net made from nylons and a plastic bottle.

Now that you know why plankton are so amazing and important, it’s time to get out there and collect some!  To collect plankton, you can buy a plankton net like the one held by Eli (left), or you can make your own out of nylons and a small bottle like the one held by Melissa (right).  There’s a tutorial from NASA on how to make your own here.

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Here’s BOP-CCERS fellow Clarissa Lynn of Central Park II collecting plankton in the purchased plankton net:

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…and here’s Nancy Azcona of M.S. 88 trying out the DIY net:

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Once you’ve collected all of that plankton, it’s a great experience for students to set up a few different kinds of microscopes in a room and let them have the freedom to put a few drops on a slide themselves and explore what they’ve found.  And the equipment doesn’t need to be fancy!  The River Project built some DIY smartphone microscopes that let us get a closer look at an isopod (a tiny crustacean).  Check out the plans to build one yourself for $10 here!

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An isopod collected by BOP teachers under a DIY smartphone microscope made by The River Project.

The River Project also has a nice collection of resources on plankton publicly available online, including a plankton key and activity sheet for students, a guide to collecting and viewing estuarine plankton, and a great list of resources for teachers and students.  Take a look in the Google Drive folder here.

The teachers had a great time trying this activity out for themselves!  Check out the gallery below- there are more pictures from the day on Flickr and Facebook.  Interested in joining us next time?  Take a look at our upcoming professional developments on the Digital Platform Events page!  And if you can’t get enough of The River Project, we’ve got Critters at The River Project in May, and you should definitely bring your whole class in for one of their awesome field trips this spring.  We hope to see you soon!