Drifter science!!

Here is a very funny educational video from the Carthe group (University of Miami). How physical oceanographers study and track currents and why it is important.

Very useful data if you want to know where our precious plankton is going! Just watch! funny and instructive.

Video credit: Laura Bracken (CARTHE), Patrick Rynne (Waterlust) and Fiona Graham (Waterlust), Sharon Chinchilla (CARTHE) and Jennah Caster (Waterlust)

Ctenophore, a soft bodied but voracious predator

Also known as Comb jellies or sea gooseberries. The name comes from the Greek Ctena (comb) and Phora (bearer). They first appeared more 500 million years ago!

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A little Beroida

These are plankton predators which can swim with the help of a several rows of cilia. Some catch their food with long fishing tentacles laden with sticky cells (colloblast) like the #Cydippids.

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Cydippid showing its deadly tentacles

Others can engulf their meal directly like the #Lobates. They can consume anything from other ctenophores, copepods to fish larva. The weirdest of all is the #Cestida which body plan is totally flat, yet it has all the attributes the Ctenophore group!

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Lobate ctenophore ready to engulf anything in its path.

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Cestida the weirdest of all. it body is flat and shaped like a ribbon

One species (Mnemiopsis Leidyi) was accidentally introduced in the black sea via ship ballast water coming from the Atlantic Ocean. Result: local fisheries collapsed due to M. Leidyi appetite for fish larvae.

Here is an amazing Ctenophore video from our Plankton Chronicles colleagues. Shimmering waves of light, stalking their prey, ctenophores are on the move.
Plankton Chronicles Project by Christian Sardet, CNRS / Noe Sardet and Sharif Mirshak, Parafilms
See Plankton Chronicles interactive site: planktonchronicles.org

Amazing Plankton Videos

Hi all! we wanted to share this website, called Plankton Chronicles, with you. It is an amazing collection of plankton related mini videos. You’ll get to see some color videos of your favorite plankton. Who knows? it may also help you in your classification effort. Enjoy!

http://www.planktonchronicles.org/en

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The Plankton Chronicles series was created by Christian Sardet (CNRS), Sharif Mirshak and Noé Sardet (Parafilms) in the context of the Tara Oceans Expedition and the Marine Station of Villefranche sur Mer (CNRS / UPMC). The series has received financial support from CNRS (INSB / INEE), IBISA, UPMC and the Ville de Nice.

Why do the images look the way they do?

As you may know by now, the In Situ Ichthyoplankton Imaging system (ISIIS) is the instrument we used to obtain the images of plankton for Plankton Portal.  It captures images as it travels through the water column.  The idea behind this imaging system was to film a large volume of water in order to detect and image relatively rare zooplankton, like larval fish and small jellies.

So why are the images are black and white, very contrasted and almost like a line drawing? Our challenge in designing this instrument was to be able to employ macro-photography at a fast speed, obtain a large depth of field (large volume sampled), while minimizing motion blur. After researching for a few months we settled on an imaging technique that could answer our demands: Shadow imaging or focus shadowgraphy!

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a) prehistoric shadowgraphy, b) sunlight shadowgram of a martini glass, c) “focused” shadowgram of a common firecracker explosion, d) “Edgerton” shadowgram of the firing of an AK-47 assault rifle
Gary S. Settles

This technique is actually not new and was used extensively for the study of shockwaves as well as ballistic. The idea is to cast a shadow onto a sensor or film instead of trying to directly record the imaged object. Let me explain: since most plankton are small and quite transparent, imaging using a traditional camera must rely on ambient sunlight. In this scenario, you won’t see much because the organisms blend into the surrounding water. Imaging a shadow cast by ISIIS reveals their distinct shape and location. It’s like looking at the shadows at the bottom of a swimming pool created by the sun going through the water! In this case, we do not use the ambient sunlight, but create our own light beam using a blue LED light and a set of mirror and lenses. The light is collimated, meaning that the light beam travels in a tight, parallel direction like that of a laser thus ensuring that even over long distances, we can create a very good shadow. We then use a specific set of lenses aligned with the camera to capture this shadowgraph image. Since the light beam is directed toward the camera sensor, it allows for very high speed imaging and avoids motion blur when moving through the water. Lastly, we invert the images for aesthetic purposes on the site, and voila! Now you have a beautiful set of black and white images of plankton for the world to see!

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This schematic shows the optical alignment inside ISIIS. A bean of light is collimated by a large lens and the refocused after going through the water. The camera records the shadows casted by the plankton as the moves behind the ship

So for all the people who asked about why some of the ctenophores (like lobates, beroids, and cydippids) were so ‘overexposed,’ now you know. These animals are dense and not very transparent, thus casting a hard shadow onto the lens. Instead of appearing black as a typical shadow, we have inverted the image and now they appear white.

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Lobate ctenophore

How do we get the images?

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Since the 1800’s, plankton has been studied and collected using simple nets with very fine mesh. The process of analysis of these plankton ‘samples’ is tedious, labor intensive, confined to laboratory, and can only be done on relatively small areas of the ocean. By sampling in this manner, it is difficult to get a good understanding of how planktonic organisms are distributed and how they interact with each other. Yet plankton represents a very important part of a global system feeding larger animals like fish, whales and many others. The In Situ Ichthyoplankton Imaging System (ISIIS) is one of a few systems in the world capable of improving the way we study plankton to better understand their life and function in the marine environment. Instead of using an actual net to capture plankton, ISIIS captures the images of the organisms and information about their immediate surroundings. ISIIS samples continuously, resulting in a collection of digital images that record the exact location of the various plankton organisms in relation to each other and the environment in which they live. Further, the images are recorded onto a simple hard drive instead of slurry of plankton all mixed together in a sample jar with formaldehyde (yech!).

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ISIIS is an underwater imaging system developed to capture real time images of plankton that are relatively rare, small, and fragile such as fish larvae and delicate gelatinous organisms (like jelly fish). ISIIS is composed not only of a macro-camera system with its own illumination but it also is integrated into an underwater vehicle with a variety of additional sensors to measure the depth, salinity and temperature of the water, as well as such properties as dissolved oxygen, light level, and even how much chlorophyll a (measure of primary production) is present. Together, the camera and sensors provide detailed profiles and tracks of what plankton are where and what the ocean environment around them is like.

isiis schematic

The vehicle, and associated imaging system and sensors, moves up and down through the water column using side-mounted, user-controlled dive fins (like an underwater glider) while being towed behind an oceanographic ship moving at 5 knots. The vehicle frame is divided into four compartmentalized enclosures with imaging and optical equipment seamlessly integrated into ISIIS’s ventral housings and environmental sensors and electronics in the dorsal housings. ISIIS is designed to undulate in a zigzag fashion between the surface and a maximum depth of 200 meters.

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The ISIIS system utilizes imaging technology very similar to an office scanner flipped on its side. The imaged parcel of water passes between the forward portions of two streamlined pods where it is “scanned” and transformed into a continuous image. The resulting very high-resolution image is of plankton in their natural position and orientation. When a sufficient volume of water is imaged this way, quantification of concentration (individuals per unit volume) and fine scale distribution is possible. ISIIS is capable of imaging a maximum of 162 Liters (43 gallons) of water per second (when moving at 5 knots) with a pixel resolution of 70 µm (the thickness of a human hair).

The imaging data and associated oceanographic data are sent to the surface ship via a fiber optic cable and recorder onto a main computer for later viewing and analysis.

Welcome to the Plankton Portal!

Plankton species are a beautiful and fascinating group of organisms. We can’t wait to show you what we have seen of these diverse and elusive critters.  Let us start from the beginning—the five W-questions:

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What is plankton?
The word Plankton comes from the Greek word planktos meaning “wanderer” or “drifter”.  They are a group of organisms that are too small or too fragile to swim against naturally occurring currents. Plankton inhabit both freshwater and marine environments, such as lakes, ponds, and oceans.  Plankton can be broadly divided into two main groups: phytoplankton (plants) and zooplankton (animals). Phytoplankton are one of the primary producers in the ocean; like plants, they carry out photosynthesis to covert inorganic nutrients and light energy into organic material. Zooplankton, on the other hand, graze on phytoplankton or consume other zooplankton smaller than themselves. While you might think that plankton are too small to be seen by unaided eyes; that is not entirely true. Planktonic organisms have a very wide range in sizes. Many of them are microscopic in size; but others, like jellyfish, could grow up to more than one meter long.

Why do we study plankton?
Plankton are crucial to the marine ecosystem.  As a group, plankton form the basis of many marine food webs in that they are an important food source to organisms ranging from larval fish to the largest animal on earth—the blue whale. In addition, plankton play an important role in nutrient cycling in the ocean; such as carbon and nitrogen cycle.  Even humans are affected by plankton. As plankton are a food source for many marine organisms, our fishery industries depend highly upon these planktonic organisms as a source of fish productivity. Beyond being food, some plankton can also create problems to the fishing industry and even tourists visiting the shore when forming noxious blooms such as red tides.

How do we study plankton?
There are several ways to sample plankton: bottles, nets, acoustics, imaging systems, etc. Nets are the most common way of plankton sampling. Nets of different size, shape and design are used depending on the type of plankton of interest. A net is towed behind a moving vessel at the desired depth in order to collect and concentrate the planktonic organisms. When the net moves through the water column, plankton is retained in the net. One on board, the plankton ‘slurry’ is removed from the net and then (usually) preserved for later viewing and analysis under a microscope in the laboratory.

In this project, we sampled plankton by using a plankton imaging system – In Situ Ichthyoplankton Imaging System (ISIIS). ISIIS acts as a “virtual net” which captures the images of the organisms and information about their immediate surroundings. By sampling continuously, the result is a collection of digital images that record the exact location of the various planktonic organisms in relation to each other and the environment in which they live.

Where and when
The images currently shown in the Plankton Portal were taken in the Southern California Bight approximately 30 miles south of San Nicolas Island on October 15-17, 2010, on board the NOAA Ship Bell M. Shimada. But we are continuously traveling the world to bring new images and better understand how these little guys make a living in the ocean! ISIIS has also been towed in the Atlantic off of Georges Bank and Stellwagen Bank, MA, Straits of Florida, Gulf of Mexico, and recently off southern France in the Mediterranean.

This current project is to study the aggregation (patchiness) and distribution of different plankton in a small-scale front (where two different water masses meet) in the SCB. We want to know which organisms are present at the front (vs. those that may avoid it), and what they are doing there (e.g. are they prey or predators?). We need your help in identifying the organisms captured by ISIIS.