Shedding light on the diverse plankton universe of the Northern California Current

Moritz S Schmid* and Margaret E Martinez


The northern California Current (NCC) is a dynamic, highly productive region within the broader California Current Large Marine Ecosystem (CCLME), that exhibits strong ecosystem variability on seasonal, interannual, and decadal time scales. Along the California, Oregon, and Washington coasts, wind blowing alongshore the US coast can create upwelling and downwelling events. Wind blowing Southward pushes surface water away at a 90-degree angle (through the Coriolis force, see more info here). Surface waters moving away are then replaced by the deeper water underneath. This deeper water coming to the surface has more nutrients than the surface water (because the nutrient-using phytoplankton doesn’t grow as good at depth – without sunlight), and thus this upwelled, nutrient-rich water can now sustain new phytoplankton growth, which in turn can then support more zooplankton growth, and so on. Downwelling on the other hand occurs when the alongshore wind is blowing Northward. The same Coriolis effect now pushes water into the landmass at a 90-degree angle from the Northward blowing wind. Because the water has nowhere to go, the least resistance for the water is to push downward. Thus, surface water is forced deeper, and no upwelling effect occurs. Along the CA, OR, and WA coasts, wind patterns differ, and while most of the California coast experiences Southward blowing winds year-round, and subsequent upwelling also occurring year-round, Oregon and Washington experience a mix of North-, and Southward winds in summer, and predominantly Northward winds winter. The mix of South-, and Northward wind means the coast gets some upwelling and some downwelling, also referred to as intermittent upwelling, while Northward winds in winter mean that the coast gets less new nutrients from depth during that time. Ultimately, this means that the California coast experiences continuous new nutrient input from deep water that can be used by the organisms, while along the OR and WA coasts this input is more inconsistent. Nonetheless, also OR and WA coastal waters provide a unique and productive environment for plankton and fishes that sustains the livelihood of many communities on the Pacific Northwest coast.

In May and early June 2021, we joined the National Oceanic and Atmospheric Administration’s (NOAA) Northern California Current (NCC) cruise aboard NOAAS Bell M. Shimada. NOAA’s NCC cruises occur on a regular basis and are designed to characterize the planktonic ecosystem ranging from northern California to Washington, with a focus on the Newport Hydrographic Line. Our aim was to collect zooplankton imagery for the NCC Marine Biodiversity Observation Network (MBON, see more info here and here) funded by NASA, as well as the Belmont Forum-funded project ‘World Wide Web of Plankton Image Curation’ (wPIC, see more info here and here), using the In Situ Ichthyoplankton Imaging System (ISIIS, Figs. 1-4).

The MBON project’s focus is on seascapes. Similar to different landscapes on land, the surface ocean can be classified into different categories based on environmental variables such as phytoplankton abundance and temperature. While seascapes are currently classified using data from the surface ocean (i.e., the first 10 m of the ocean) largely due to heavily relying on satellite data, we collect data using ISIIS to inform seascapes also using information from deeper waters (e.g., data on plankton and temperature down to 100 m). wPIC is aiming at very different things – it is largely a project focused on underwater imaging methods. The idea is that all around the world laboratories use different instruments for imaging aquatic animals, and these instruments also come with different methodologies of processing the images and ancillary data. wPIC’s aim is to streamline these efforts more and to better exploit synergies between different projects and instruments. wPIC includes project partners from France, Japan, Brazil, and the US.

Figure 1. Deploying ISIIS on a gray day off the Oregon Coast.
Figure 2. ISIIS is secured to the aft deck of NOAAS Bell M. Shimada as it heads out past the bar in Newport, Oregon, for the start of the Spring 2021 NCC cruise.
Figure 3. Moritz and Margaret posing with ISIIS after a successful nighttime recovery.
Figure 4. “Flying” ISIIS means observing multiple monitors, each tracking several variables, ranging from ship and ISIIS speeds, communication with the winch operator outside who hauls-in and pays-out oceanographic wire, raising and lowering the ISIIS, to making sure all cameras are recording, and looking for interesting ecological features in the live imagery coming through the fiber optic data stream.

ISIIS is a line-scan and shadowgraph imager that records the shadows of organisms swimming through the beam of light projected by a LED (Fig. 5). With this setup, a water parcel measuring 13 cm x 13 cm x 45 cm is recorded by the camera system, ultimately leading to 180 L of seawater imaged per second. Compared to other imaging systems, this is a very large volume of imaged water, which gives us the ability to look at rather rare larval fishes (Fig. 6) as well as fragile jellies and the ubiquitous crustacean zooplankton (Figs 7-8).

Figure 5. A schematic of the lower pods of ISIIS (compare with Fig. 1) housing the LED and camera setup.

Figure 6. A myctophid (lanternfish, left), and an engrauliid (anchovy, right).


A dense layer of doliolids.
A chaetognath (arrow worm).
A cydippid ctenophore.
Eutonina indicans, a leptomedusae, with gonads visible in the radial canals.


Figure 7. Key gelatinous zooplankton in the NCC includes doliolids, chaetognaths, ctenophores, and hydromedusae*.


Several euphausiids having a dance party.
Mitrocoma cellularia.

A large euphausiid dwarfs a calanoid copepod.
A lobate ctenophore showing off its auricles (red arrow).


Figure 8. Key crustaceans include euphausiids and calanoid copepods. ISIIS’s ability to image fragile jellyfish without disturbance is clearly visible in the images of Mitrocoma and its many tentacles, as well as a ctenophore with its auricles clearly visible*.

*All images except the doliolids (Crescent City line, 5/26/2021), were taken from Newport Hydrographic Line imagery (5/23/2021).

Using a sophisticated image processing pipeline (Luo et al. 2018, Schmid et al. 2021), based on artificial intelligence, we can quickly identify all plankton in the images, and also get their sizes. These ecological data can then be used in a diversity of ecological studies. As ISIIS produces vast quantities of data (ca. 75-100 million images for a 7-hr ISIIS transect) we collaborate with the National Science Foundation’s Extreme Science and Engineering Discovery Environment (XSEDE), a nationwide supercomputing cluster. Controlling the processing from Oregon State University’s (OSU) Center for Genomics and Biocomputing (CGRB), but utilizing hardware at XSEDE (Fig. 9), we are able to get through the data blazingly fast. The resulting data enables us to tackle ecological questions that wouldn’t be possible with more traditional net systems (e.g., Briseño-Avena et al. 2020, Schmid et al. 2020, Swieca et al. 2020).

Figure 9. The Plankton Ecology Lab’s image processing pipeline deployed at OSU’s CGRB and using resources on NSF XSEDE. The orange panel shows components at the CGRB, while components in the lower panel (i.e., the cloud) are deployed on NSF’s XSEDE supercomputing cluster.

At this point we want to give a big shout out to all our citizen scientists at Plankton Portal who help with making these studies possible by volunteering to classify plankton. This effort helps us to fine-tune plankton classification image libraries and models, and provides insight into how automated plankton classifications differ from human annotations (Robinson et al. 2017). We hope that you enjoyed this little glimpse into collecting the images that you get to look at. We also thank Jennifer Fisher, the Chief Scientist on NOAA’s NCC cruise on NOAAS Bell M. Shimada, as well as Bell M. Shimada’s CO Amanda Goeller, and crew, as well as all scientists who helped with manning the ISIIS winch.


Briseño-Avena C, Schmid M, Swieca K, Sponaugle S, Brodeur R, Cowen RK. 2020. Three dimensional cross-shelf zooplankton distributions off the central Oregon coast during anomalous oceanographic conditions. Progr Oceanogr 188:102436

Luo JY, Irisson J-O, Graham B, Guigand C, Sarafraz A, Mader C, Cowen RK. 2018. Automated plankton image analysis using convolutional neural networks. Limnol Oceanogr Methods 16: 814-827

Robinson KL, Luo JY, Sponaugle S, Guigand C, Cowen RK. 2017. A tale of two crowds: Public engagement in plankton classification. Frontiers Mar Sci 4:82

Swieca K, Sponaugle S, Briseño-Avena C, Schmid M, Brodeur R, Cowen RK. 2020. Changing with the tides: fine-scale larval fish prey availability and predation pressure near a tidally-modulated river plume. Mar Ecol Progr Ser 650:217-238

Schmid MS, Daprano D, Jacobson KM, Sullivan CM, Briseño-Avena C, Luo JY, Cowen RK. 2021. A Convolutional Neural Network based high-throughput image classification pipeline – code and documentation to process plankton underwater imagery using local HPC infrastructure and NSF’s XSEDE. [Software]. Zenodo.

Schmid MS, Cowen RK, Robinson KL, Luo JL, Briseño-Avena C, Sponaugle S. 2020. Prey and predator overlap at the edge of a mesoscale eddy: fine-scale, in-situ distributions to inform our understanding of oceanographic processes. Sci Rep 10:921

Upcoming cruise to collect California Current (summer) data

We are gearing up for another cruise! These data will augment our California Current (summer) dataset that you all have been diligently sorting for the last few weeks. 

Yesterday PI Bob Cowen, post-doc Moritz Schmid, and graduate students Kelsey Swieca and Margaret Martinez began cruise mobilization by moving the plankton imager (In situ Ichthyoplankton Imaging System) from the lab to the marine center’s loading dock.  It was a tight squeeze, but we made it! Today we will check all of the nuts and bolts on the imager then transport it to the ship staging area before beginning a 7 day shelter in place prior to cruise departure (a COVID precaution). 

Keep an eye out for an at-sea blog post over the next few weeks.

Plankton Portal Publication: Thank you!

“The archetypal approach of a single research group processing and analyzing large datasets in isolation is becoming increasingly infeasible — particularly given the need for the data to be promptly incorporated into ocean health assessments and marine ecosystem management. An effective, alternative approach is citizen science.” 

This was a main finding of Robinson and colleagues’ recent paper examining how citizen scientists, including those from Plankton Portal, can help researchers chip away at their ‘big data’ processing goals. The authors of this article, including many of Plankton Portal‘s Science Team members, explain that with the advent of high resolution sampling technologies, it has become essential for biological oceanographers to develop innovative ways to process their data in a timely matter. One approach to this problem is citizen science.

Excitingly, this paper also found that Plankton Portal and its sister citizen science project, Kaggle, where data scientists competed to develop computer algorithms for automated image processing, are effective tools for engaging, educating, and promoting public engagement in plankton classification.

Citizen science has proven invaluable to Plankton Portal‘s Science Team. Check out our paper and be sure to read the Acknowledgements section were we give a special thanks to our most active volunteers. Thank you for your contributions and we look forward to continuing to work with you!



Paper link:

Citation: Robinson KL, Luo JY, Sponaugle S, Guigand C, Cowen RK (2017) A tale of two crowds: public engagement in plankton classification. Front Mar Sci 4: 82. doi: 10.3389/fmars.2017.00082

Leptocephalus larvae

Some of the most beautiful and conspicuous animals we encounter in the plankton images are leptocephalus larvae. Eels, bonefish, ladyfish, and tarpon form a diverse superorder of fishes (Elopomorpha) that all begin their planktonic lives as leptocephalus larvae, which are characterized by long and laterally compressed bodies that are almost completely transparent. This type of larva is known by scientists to be relatively primitive, meaning that leptocephalus larval forms have been utilized by fishes for millions of years – probably since the Cretaceous period.

In this image, the you can see the backbone and the myomeres along the body. On the left side, the mouth of this larva is open.

Tarpon and bonefish larvae are slightly modified from the classic leptocephalus form. Unlike the eel leptocephali, tarpon and bonefish larvae are thinner vertically and have a well-developed caudal fin, which they use to swim.

Partial image of the tail region of a tarpon, bonefish, or ladyfish.

Most leptocephalus larvae (sometimes referred to as “leptos”) have a large set of teeth that protrude outward. For a long time, the diet of leptos was a complete mystery because their guts appeared to be empty. We now know that they rely on particulate matter, also known as “marine snow”, as their primary food source (Miller et al. 2013). Our in situ imaging work has revealed that leptos are quite abundant, particularly in the northern Gulf of Mexico, and have a variety of complex behaviors that may help them survive in a realm of intense predation pressure. We recently published a paper presenting evidence that the morphology of these leptos indicates that they likely serve as Batesian mimics of cestid ctenophores, which are strikingly similar in appearance (Greer et al. 2016). By resembling an animal with low nutritional value that predators avoid (the cestid ctenophore), the leptos gain protection from predators. The only perceivable morphological difference is that leptos have a head and a dark backbone with myomeres (muscle strands) that are visible when viewed through a shadowgraph imager, while cestid ctenophores lack these features. For a fish predator relying on vision in a complex ocean light environment, it may not be able to tell the difference, which could explain why predation rates on leptos are much lower than expected (Miller et al. 2015).

Cestid ctenophore

Leptocephalus larva – note the similarity in morphology to the cestid ctenophore above.

Leptos display complex behaviors that can make them difficult to identify in the images (and likely has a similar effect on predators). This one is curled up. The main cues that this is indeed a lepto are the visible myomeres, and the head and tail are meeting on the left and right sides of the body, respectively.

Leptocephalus larvae are fascinating, and we are just beginning to unlock some of the secrets of their biology and ecology through imaging. By combining the data produced from imaging them in their natural environment with other techniques to assess diets and predation pressure, we hope to learn more about these animals and what processes impact their survival during their time in the plankton. After all, some of these leptos eventually grow up to do this:



Greer AT, Woodson CB, Guigand CM, Cowen RK (2016) Larval fishes utilize Batesian mimicry as a survival strategy in the plankton. Mar Ecol Prog Ser 551:1-12

Miller MJ, Chikaraishi Y, Ogawa NO, Yamada Y, Tsukamoto K, Ohkouchi N (2013) A low trophic position of Japanese eel larvae indicates feeding on marine snow. Biol Lett 9:20120826

Miller MJ, Dubosc J, Vourey E, Tsukamoto K, Allain V (2015) Low occurrence rates of ubiquitously present leptocephalus larvae in the stomach contents of predatory fish. ICES J Mar Sci 72:1359-1369

Introducing Kelsey Swieca!

As a new member of the Plankton Portal Science Team, I would like to introduce myself. I am Kelsey Swieca, a Doctoral Student at Oregon State University under Drs. Su Sponaugle and Robert Cowen. Originally from Chicago, I moved to Oregon to attend the University of Oregon where I received my B.S. in Marine Biology. At Oregon State University I will use our first set of ISIIS images off the Oregon Coast to try and answer a few questions about larval fish interactions with prey, predators, and competitors.

Plankton distributions are typically patchy in nature forming aggregations of prey with their predators following suit. Although these prey aggregations enhance larval fish feeding, they may also promote predation and competition by decreasing spatial distances between larval fish and their predators and competitors who have all come to feed on the prey. My work aims to understand how different oceanographic conditions impact these spatial distributions and thus larval fish interactions in the highly productive and oceanographically dynamic Northern California Current.

I’m really excited to be a member of this team and look forward to classifying with you!


Kelsey Swieca on a research cruise aboard the NOAA FSV Bell M. Shimada off the Oregon Coast in June, 2016.


Dr. Robert Cowen and Kelsey Swieca in the dry lab of the NOAA FSV Bell M. Shimada, monitoring an ISIIS transect off the Oregon Coast. June, 2016.

What’s it like in a thin layer?

During the CONCORDE summer field sampling campaign, we had the good fortune of towing the ISIIS through a unique oceanographic feature called a “thin layer.” Thin layers are dense aggregations of phytoplankton or zooplankton that have a vertical dimension of less than 3 meters and have concentrations of at least 2-3 times the water column average abundance. They can span hundreds of meters to several kilometers in the horizontal dimension. This series of images shows how the plankton concentrations dramatically change from just underneath to above the thin layer. The hairlike objects are phytoplankton called diatoms, but there are also lots of zooplankton in the vicinity of the layer. Here you can see the barrel shaped doliolids, which are grazers of phytoplankton, as well as copepods and chaetognaths.

Image taken just below the thin layer

Image taken just below the thin layer

Within the thin layer

Just above the thin layer

Just above the thin layer you can see lots of marine snow particles and a chaetognath.

Further above the thin layer, the plankton concentrations are not as intense.

Further above the thin layer, the plankton concentrations are not as intense.

Keep in mind that all of these images were taken within a few meters of each other. It is amazing to see firsthand how dramatically the ocean environment can change, and how these organisms respond this variability. Is this something they normally experience? The next steps are to use the image data to quantify the changes in abundances and look at the different mechanisms that may have caused this thin layer to form.


innovative citizen sailing oceanography

Just discovered this, after reading the Tara Expedition news periodical while visiting Tara in Miami! This is a very interesting Citizen Science project inspired from the Tara Expeditions. The idea is to “recruit” the help of volunteer sailors across the world and have them collect plankton using a very simple method of sample preservation. The sample is then sent to a lab for DNA barcoding to look at the different species present in the sample. A very elegant way to do oceanography.



go visit:

Happy anniversary Plankton Portal 2.0!

Blog post by Jean-Olivier Irisson

A year ago, we announced Plankton Portal 2.0, which featured a more streamlined design, a simpler tagging interface, and most importantly, a whole new dataset. Since then, this new data from the Mediterranean Sea has spurred a lot of interest and plenty of new questions. Participants on the site were surprised by the difference in size of everyone’s favourite jellies, the Solmarisidae (Solmaris rhodoloma in California, Solmissus albescens in the Med), which are much larger! Siphonophores also seem more abundant there. And the Mediterraean data came with brand new categories of organisms to mark: nice and cute medusa ephyrae (i.e. baby jellies), elegant Pteropods and the elusive fish larvae.
In total, as of last Sunday, 368,361 organisms were marked, on 50,519 distinct images. Through time, the classifications were marked by two peaks in activity: a huge one when the new version was announced through a mailing to the Zooniverse community (thanks everyone!) and another one when we pushed for 1,000,000 classifications in total, to celebrate Jessica’s PhD defense. When we zoom in, we see activity fluctuating around 1000 and now 500 classifications per day. This is still great (but coming back to 1000 would be even better! 😉 ).


The top 11 contributors, all authors of over 5000 classifications each, are displayed below. If you made this top 11, we owe you special thanks (and probably a beer too). We hope you will stay interested and involved in this project. If you did not, you should really not be disappointed because all other volunteers still collectively account for 60% of the classifications; so you matter very much! Hopefully all of you will be happy to see some of the outcome of your work below.


Time for a bit of science! The most common classification was… nothing, empty, zero, zlich, zip… Well, you get the idea. Indeed, when we film the sea, we most often see nothing (nothing living at least). Even though we pre-selected potentially interesting frames for Plankton Portal (the ones having some kind of large object in them), about a third of your classifications did not contain any organism we were interested in. In real life, the proportion of dead detritus vs. living organisms is more around 95% vs. 5%, so our pre-filtering still avoided you a lot of blank frames! In terms of organisms, the 10 most abundant are shown in the figure below.



Doliolids, Copepods, and Radiolarian colonies dominate the rest. We immediately noticed, when we shot the images, that Doliolids were particularly abundant. Those organisms are very effective filtering machines and they may therefore have an impact on the density of smaller organisms, in particular unicellular algae. The relative abundance of Copepods and Radiolarian colonies is to be interpreted carefully: Radiolarian colonies can be large and span several frames (therefore increasing the total count) and Copepods are likely under-estimated because we mostly see the larger ones with ISIIS, and they are not the dominant ones in the Mediterranean. Still, it echoes nicely a recent Nature paper by Tristan Biard (a contributor to PlanktonPortal’s talk, under the username Collodaria), which showed that Rhizaria (a large taxonomic group to which Radiolarians belong) can be equivalent in biomass to Copepods, who were previously thought to largely dominate the plankton. These findings were also based on in situ images, because these fragile Rhizaria cannot be collected with nets.


Finally, the images in the Mediterranean were collected along transects (i.e. straight lines) perpendicular to the shore. We were interested in how organisms were distributed along a gradient between coastal and open ocean conditions. In the plots below, the coast is on the left, the open ocean on the right and the vertical direction is depth (top: surface; bottom: 100 m depth). So you basically see a “slice” of water along which ISIIS undulated. The size of the dots is proportional to the number of classifications recorded. You can immediately notice that Doliolids (first plot) are concentrated near the surface, and fish larvae (second plot) even more so! This is a surprising finding for fish larvae, which sometimes ended up in concentrations of over 10  individuals per cubic meter, a number much higher than what was previously observed elsewhere, with conventional plankton nets.
Radiolarian colonies, on the opposite, tend to be concentrated in mid water (see figure below). Within this messy picture, some structure seems to emerge. Indeed, the white lines on top of the plot are contours of the concentration of Chlorophyll A in the water (i.e. of the amount of unicellular algae). If you look carefully, you will see that those lines are moving up, towards the surface, as we travel offshore (from left to right on the plot). This is actually well known in this region. What is interesting is that the radiolarians seem so follow the same pattern, and that higher concentrations of colonies sit on top of this high Chlorophyll region. Something is definitely going on between these two!
That’s it for now — thanks again to everyone for this wonderful year of activity! We apologise for not being as active as we would like to be on Talk. To that end, we thank the active moderators who take over this important responsibility. And finally, we thank Zooniverse for the great opportunity and community they created. Now, on to next year!

Stomatopods: amazing eyes

The more I learn about stomatopods (also known as “mantis shrimps”), the more fascinated I become with these true marvels of evolution. From the image data we have processed so far from the CONCORDE fall and spring field campaigns, it is pretty clear that stomatopod larvae were quite abundant in the nearshore waters of the northern Gulf of Mexico. As you can see from the images below, they are really cool looking animals – even Hollywood took notice, as stomatopods served as the inspiration behind the alien queen in the movie “Alien.”

Stomatopod larvae imaged in the northern Gulf of Mexico on October 30, 2015

Stomatopod larvae imaged in the northern Gulf of Mexico on October 30, 2015

The first thing you notice when you see the images of the larvae are those giant stalked eyes protruding from their heads. The eyes, which appear to be well developed in the larvae, are one of the most remarkable adaptations of the adult stomatopod. Unlike mammals and cephalopods, which have a camera like eye (single lens projecting an image onto a retina), stomatopods have a highly specialized compound eye, and each eye often moves independently from the other. They also have 12 visual pigments, giving them a huge range of detectable wavelengths, from infra-red to ultraviolet – much more than other invertebrates (Land & Nilsson 2012). In comaprison, humans only have three visual pigments (red, green, and blue), and the stomatopods can even detect different types of polarized light. Have you ever heard of circular polarized light? Well, they can see that too! The males have certain parts of the body can reflect circular polarized light in both right and left hand directions. The band across each eye has 4 rows of ommatidia that can see in color, and two rows (one on each end) detect polarized light (Chiou et al. 2008).

Image source:

Image source: Also, check out the interview with Dr. Justin Marshall who has been studying mantis shrimps for almost 20 years

Another impressive thing about stomatopods is their method of capturing prey. Different species of stomatopods use one of two different attack methods: smashing and spearing. You can tell what method it uses based on the morphology of the stomatopod appendages. The smashers have clubbed appendages that they flick outwards to smash their prey, and the spearers have pointy appendages that they can use to puncture their prey. The force created by these attacks is extremely powerful for their size. In fact, the movement of the appendages is so quick that it generates a large cavitation bubble. The phenomenon of cavitation happens when something in the water moves so fast that an empty space is created that the water cannot fill quickly enough. When a boat propeller rotates at a fast rate, it generates tiny cavitation bubbles. It is quite rare for an animal as small as the stomatopod to generate enough force to cause cavitation.


Chiou T-H, Kleinlogel S, Cronin T, Caldwell R, Loeffler B, Siddiqi A, Goldizen A, Marshall J (2008) Circular polarization vision in a stomatopod crustacean. Current Biology 18:429-434

Land MF and Nilsson D-E (2012) Animal Eyes (2nd ed.) Oxford University Press

Fantastic Find Fridays: Feb 2016

Hey plankton hunters!  We are bringing you another round of Fantastic Finds from the Plankton Portal.  Citizen scientists continue to reel in new captures of some truly awesome plankton.  Here are just a few neat finds, ID’s, and novel taxa:

Pteropod mollusk


Did you ever learn about marine butterflies in grade-school?  Well good, because there is no such thing as a marine butterfly.  This elegant-looking critter is a pteropod, a type of gastropod mollusk—in other words, a slug!  These mollusks are highly adapted for life in the water-column, as you can see from the butterfly-like wings, (or “parapodia” to a malacologist).  The pteropod wings are actually a highly-modified molluskan foot, i.e. the muscular and slime-secreting mass that slugs glide on.  Evolution really did these slugs a favor, as I do not think anyone could say “ewww!” to such a beautiful animal.

Calycophoran Siphonophore


Now this is a fantastic image.  A close-up, finely-detailed capture of the head (nectosome) portion of a calycophoran siphonophore—so aptly referred to as a “rocket-ship sipho” here on the Plankton Portal.  The two siphon-like features propelling this colonial critter are very apparent in this image.  Maybe, in truth, siphon-ophore is a pretty apt name for this plankter as well.

Ctenophore: Thalassocalyce inconstans


Thalassocalyce inconstans is a predatory species of ctenophore, captured feeding in this frame.  The body of the ctenophore is contracted and engorged about the anteroposterior (vertical) axis, giving it the appearance of an inflated, heart-shaped balloon.  Within the fragile and transparent body, you can see the 8 condensed comb rows captured as an array of ragged segments crowning the aboral end.  Fine mesenterial canals also appear as contoured markings that line the engorged body. Ctenophores are tactile predators, meaning all predatory behavior is triggered by physical, non-visual stimulus.  Something in the water column bumped into this Thalasso and got it all riled up, providing ISIIS a great opportunity for this detailed capture of foraging behavior.  If we had a hydrophone for this deployment, I am fairly certain a satisfied lip-smacking would be recorded in a few seconds.

Copepods: Families Eucalanidae and Metridinidae. 


Copepods are abundant in these ISIIS data, and it is easy to forget what a broad diversity of these important crustaceans are classified on the site.  Here we have two broadly identifiable PP copepods for sample.  The image on the left shows a copepod belonging to the family Eucalinidae: it has a narrow, torpedo-shaped body and the anterior end of the head forms a pointed-triangle.  We think this critter might be a Rhincalanus spp.—if you look close you might be able to make out a small rostrum-like appendage extending forward and tucked down from the head, as well as what may be lateral spination at the end of each mid-body segment (prosome).  This guy’s cruising, antennas spread out and scanning the surroundings.  On the right, we have a copepod belonging to the family Metridinidae, perfectly poised for the ISIIS cam.  How do we guess this ID?  At the end of this copepods lengthy tail (urosome), look closely at the paired fin-like feature (ferka).   Along the outer edge, right before the separation of the individual ferka, can you make out a small, skirt-like protrusion?  If so, just tell your buddies: “hmm, check out that lengthy urosome and ferka segmentation; it must be a Metrinidae species,” and blamo—you are a crustacean taxonomist!

Anthomedusae: Leukartia spp.


At first glance, you might be thinking “is this medusae sticking its tongue out at me?” Or maybe it is sporting a ten-gallon hat?  While I couldn’t blame you for such outlandish assertions (I mean, who would write such silly things?), this odd anthomedusae is readily identified to genus by the conical appendage extending from the bell (“apical process”) and causing much confusion on the Plankton Portal.  In this image we get a great view of many internal and external features of this Leukartia sp., including a crenulated (ragged) bell margin, a tall mouth (“manubrium”) in the center of the bell, and many long tentacles projected both downwards and in front of the bell.

Larvacean and mucous house


We find a good deal of larvaceans on the site, but this capture is a real beauty.  Larvaceans are gelatinous plankton that filter-feed on detritus in the water column.  You see the critter poking its head out, like the cap on a rolled-up toothpaste tube?  That’s the larvacean, curled up in preparation to pump surrounding detritus through its elaborate mesh-like mucous house.  For a critter that takes up residency in its own secretion, this guy is pretty adorable!

Physonect Siphonophore


Now this is quite the fantastic find!  Here we are looking at a large siphonophore projecting numerous tentacles across the frame.  It is all-hands-on-deck for this colonial jelly, as it is putting on a mighty foraging display for us.  The big guy is hungry—watch out, ISIIS.

There have been way too many great images to fit in this small serving of photogenic plankton.  We look forward to serving up more fantastic finds in the future.  Keep exploring, plankton hunters!