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Edu-tainment

For your edu-tainment. Let's demystify the science and learn some fun facts about bioluminescent algae.

While you’re enjoying and playing with your Mushlume UFO you may ponder the meaning of a dinoflagellate’s life. Who wouldn’t want to float around in the water all day soaking up sunshine and then magically glow every night? It’s like the ocean’s version of Burning Man! These single-cell creatures seemingly have it all figured out.  While this is true, you also have the opportunity to discover that there is much more to dinoflagellates than meets the eye. They hold valuable lessons about life on Earth. 

Below are five general concepts to get your brain cells firing:

Optics

Let’s start with a question: Why do fireflies glow yellow or green and most bioluminescent ocean dwellers including dinoflagellates glow blue?

The answer lies in light waves — light behaves differently when it moves through air versus when it moves into water.

Seawater absorbs light much more strongly than air does. The visible light spectrum is made up of a literal rainbow of colors, each of which have different wavelengths. The colors with shorter wavelengths have higher energy (higher frequency) and longer wavelength colors have lower energy. Light with a longer wavelength is absorbed more quickly in water than light with a shorter wavelength (higher frequency).

  •  Violet: 380–450 nm (688–789 THz frequency)
  •  Blue: 450–495 nm
  •  Green: 495–570 nm
  •  Yellow: 570–590 nm
  •  Orange: 590–620 nm
  •  Red: 620–750 nm (400–484 THz frequency)

As a result of its shorter wavelength, blue light penetrates farther into seawater. At the same time, seawater absorbs red, orange, and yellow wavelengths, which are longer wavelengths, thereby removing these colors in the water below a certain depth. At 40 meters, saltwater absorbs nearly all the red visible light, yet blue light is still able to penetrate beyond these depths.

Ocean light water penetration diagram

 This phenomenon is why the ocean appears blue. It is also the reason why oceanic creatures have evolved to produce their bioluminescence in the blue spectrum of light. Blue bioluminescence travels farther in seawater and is visible to most fish whereas red, orange and yellow are more easily absorbed. In fact, many fish in the deep sea have lost the ability to see red.

Conversely, an ecological adaptation of bioluminescence on land is centered around green. Most species, including those that are active during twilight, have developed photoreceptors with maximum sensitivity in the green spectrum.

So there you have it. Dinos bioluminesce blue because blue wavelengths of light travel farther in seawater where many fish have the ability to see blue light. And fireflies glow yellow or green on land because terrestrial organisms have adapted to easily see light in the green spectrum.

Bioluminescence

Bioluminescence is the production of light through a chemical reaction within a living  organism. 

The chemistry behind the glow of dinoflagellates (and many other bioluminescent creatures) involves an enzyme called luciferase, which adds oxygen to a light emitting substrate called luciferin, resulting in the production of photons of visible light. A typical dinoflagellate flash of light contains about 100 million photons and lasts a fraction of a second.

Many different types of organisms produce bioluminescence — from dinoflagellates in the sea to fireflies on land. It is thought that bioluminescence likely originated in the oceans based on the chemical structures of the light producing molecules. 

In the deep sea (aphotic zone) where there is no sunlight penetration, more than 90% of the creatures are bioluminescent. The use of light is an important tool for their communication.

Euphotic Zone and Distance light travels in water

In general, bioluminescence is used for a variety of purposes such as to attract mates, find prey, and as a defense against predators.

In contrast to the deep sea, only a small percentage of terrestrial life is bioluminescent. Examples of these organisms are fireflies, mushrooms, millipedes and click beetles.

A species of snail called luminescent limpets is the only freshwater animal that produces bioluminescence. It is likely that freshwater residents don’t need to produce light because they exist in sunlit worlds where they are able to find prey and meet mates without elaborate light shows.

Photosynthesis

We often learn or hear about photosynthesis in relation to plants. Photosynthesis is the process in which plants and trees use sunlight to make their own food.

Many dinoflagellates are also photosynthetic. They are referred to as phytoplankton. The name comes from the Greek words phyto meaning plant and planktos meaning “wanderer” or “drifter”. 

In Nature, these “plant drifters” float around in the euphotic (sunlit) zone of oceans and certain lagoons and are able to use the sun’s energy as a food source. Each dinoflagellate cell contains machinery to harvest the sun’s rays.

Photosynthesis requires sunlight, chlorophyll, water, and carbon dioxide gas (also known as CO2). Chlorophyll is a pigment that gives green plants their color (think: the leaves of plants and trees). Chlorophyll’s job is to absorb light. In Pyrocystis fusiformis, the species of dinoflagellates in your Mushlume UFO, each cell has chloroplasts that contain chlorophyll. Similar to plants, the chlorophyll in the dinoflagellate cells absorb light in order to photosynthesize. In addition to light, dinoflagellates take in water (from their aquatic surroundings) and CO2 either from the air or the dissolved CO2 in the water.

During photosynthesis, the CO2 and water molecules are used to make sugar for energy. The process of incorporating inorganic carbon (CO2) into organic carbon (glucose and other biologically useful compounds) is called carbon fixation, and is part of the biological carbon pump (a crucial component of Earth’s carbon cycle). Importantly for all the animals on Earth (that includes you), a byproduct of photosynthesis is oxygen. So in additional to regulating CO2 in the atmosphere, these tiny cells provide more than half the air we breathe. Think about it. Every second breath you take is thanks to all those phytoplankton floating around in the ocean soaking up rays.

Circadian rhythm

Circadian rhythm is a natural, internal process that regulates the sleep-wake cycle and repeats roughly every 24 hours (in many, but not all organisms). Think of this rhythm like an internal biological clock that is influenced by environmental cues like day (light) and night (dark).

P. fusiformis dinoflagellates have a circadian rhythm which controls their bioluminescence and photosynthesis on a 24-hour cycle. These dinoflagellates only photosynthesize when they sense it is day and they only produce bioluminescence when they sense it is night. The mechanisms they use to “sense” day and night is apparent by viewing the changes inside the cell during the day and night phases with a microscope. During the day (light cycle), the dinoflagellate cell disperses its chloroplasts throughout the cell to absorb light. At night (dark cycle) when there is no light to absorb, the cell moves all of the chloroplasts to the center of the cell and disperses scintillons (vacuoles that contain light emitting molecules for bioluminescence) to the periphery of the cell.

Note: It is possible to observe the cellular differences with the naked eye but a 10x microscope (at minimum) is helpful to see these internal changes between day/night.

It is important to keep the dinoflagellates on a regular schedule of light and dark as a result of their circadian rhythm. Otherwise, the natural rhythm of the cells will be out of sync and they won’t sense when to photosynthesize and when to bioluminesce. Ideally, dinoflagellates should get 12 hours of light and 12 hours of darkness every 24 hours and at the same time every day. By following this routine, the the dinos will be brightly luminescent whenever they are in their "night phase" and will be soaking up the light in their "day phase”. 

Pro tip: If you want to precisely control their light/dark schedule, use a timer and artificial light in a room where you can ensure darkness during the night phase of the dinoflagellates. **It is possible to change the circadian rhythm of the dinoflagellates by shifting their light/dark cycles. If you grow the dinos in an area that doesn’t get any sunlight, you can control the 12-hour day/12-hour night times. Note: it may take several weeks for the dinos to adapt to their new light/dark schedule. This is similar to humans when we travel to a different time zone and our bodies need to adapt to the time change.

Lastly, remember that the dinoflagellates are only bioluminescent in their night phase. By understanding their circadian rhythm and that they move their chloroplasts and scintillons around in their cell based on this day/night cycle, it is possible to understand why they don’t luminesce during their day phase even in a dark room. Because they are photosynthesizing in their day phase!

Cell division (binary fission)

P. fusiformis dinoflagellates have a complete life cycle of approximately 6-7 days. These dinoflagellates reproduce asexually via binary fission. Binary fission is the process by which a parent cell divides to produce two daughter cells. In this process the two daughter cells are genetically identical to that of the original cell.  

The advantages of asexual reproduction are that the dinoflagellates are able to keep the same genes and reproduce at a faster rate than organisms that use sexual reproduction. Additionally, sexual reproduction often requires an organism to expend energy finding a mate and in some cases use risky behaviors to attract that mate.

Other than sex, a main disadvantage to asexual reproduction is the lack of gene recombination that allows for variability of the organisms DNA which may be needed for adaptation to changing environmental conditions. Sexual reproduction allows genes best suited to the changing environment to survive through selective pressure over time. In contrast, organisms that reproduce asexually must rely on DNA mutations for their evolution.

The process of becoming two

Pyrocystis fusiformis reproduces by replicating the DNA of the parent cell and forming zoospores inside the parent’s cell walls. Each zoospore is separated into alternate ends of the single cell. The outer membrane of the parent cell begins to pinch the cell apart, until one cell becomes two. At this final stage, each daughter cell is capable of all the functions of life.