Energy: Research Project
April 17, 2021
Research Project
Topic 1: Chemosynthesis
In the world as we know it, the energy used to support organic life travels up a food chain beginning with primary autotrophic producers. These organisms use the light from the sun to generate energy and grow. This process is known as Photosynthesis.
Photosynthesis is possible by “the absorption of light by pigments in the thylakoid membranes inside bacterial and plant chloroplasts.” (Smil, 45). Surprisingly though, the actual efficiency of this process is quite poor. That said, the process is able to energize enough food for the plant to feed itself. When there is less light, however, it becomes harder for plants to metabolize the sun’s rays. There are, of course, plants that have adapted to this, but with the improper amount of sun, plants would not be able to use this process to thrive. Our world is completely penetrated by light from the sun. In most cases, there is more than enough light to aid photosynthesis, despite the inefficiency of the natural process. But what happens in a deep environment with no light?
Much of the ocean life we perceive follow the same rules as on land. Within the top layer of the ocean, millions of microorganisms called Phytoplankton grow with photosynthesis and feed a vast variety of shallow life. In this way, they can function as our primary producers. There is, of course, other marine life that can photosynthesize (some sea slugs, algae, and more). However, as we go under water, light cannot penetrate as deep.
IMAGE HERE
As explained by Smil in his book, Energy, photosynthesis is best energized by a combination of blue and red light. As you can see in the graphic above, red light penetrates the shallowest. Often, you will lose red light after the first 30 feet of water. Additionally, things like thermoclines (a sudden, steep temperature drop as water gets deeper, often due to a change in how much the water is warmed by the sun) can inhibit photosynthesis. All this is to say that by the time we reach 100-200m deep, we can lose all visible light, entering into what we know as the Bathypelagic (twilight) zone. But the ocean goes deeper, with both abyssopelagic and hadalpelagic zones. So how do ecosystems thrive here?
For the longest time, we knew very little about what occurs deep in the ocean. When we first started to explore the deep, scientists discovered a lot of scavenger type organisms that would wait for marine life to die, and sink to the bottom of the ocean as it begins to decay. This is very true, but within the most recent discoveries of the deep ocean, it was found that an entire array of species have found ways to live in these harsh, cold, and dark environments.
If one side of the coin is photosynthesis, there exists another side of the coin called Chemosynthesis.
On the bottom of the ocean (hadalpelagic zone), there is a diverse array of sea life. There are Octopuses, fish, crustaceans, and many small microbes. These microbes are obviously alive, but without anything smaller than them, they have to rely on something other than carnivorous tendencies to survive.
These ecosystems are often found built around something called a hydrothermal vent. “These systems are essentially hot springs on the seafloor, and they provide the basis for life in the deep sea independent of sunlight.” (Wilborn) These hot springs are only possible when there is a heat source powerful enough to warm the water. A common place for this to occur is at “Mid-ocean ridges […] there, tectonic plates move apart below the oceans, forming new seafloor, and magma occurs comparatively shallow.” The cold seawater flows through cracks deep into the seafloor and heats up.
This water will not only heat up to 400 degrees Celsius, but chemically react with the rocks and form a fluid full of nutrients and minerals from the earth. This eventually created a hydrothermal vent (which were only really discovered in the 1970s). Within these fluids, you will find Hydrogen Sulfide, Hydrogen, and Methane. Using these compounds, the microbes are able to metabolize the compound elements and generate energy. Then, these chemoautotrophs form thick mats on the vents where they can access the hydrothermal fluid easily. They are in turn fed on by first order carnivores and are the building blocks for deep sea bioenergy transfer.
It is worth noting that the processes are remarkably similar as well. If we look at the equation of photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 as opposed to chemosynthesis: 18H2S + 6CO2 + 3O2 → C6H12O6 you will see that the end product is the same without any O2 produced. Also, instead of just carbon dioxide and O2, we have 18 molecules of Hydrogen Sulfide and use no water.
Sources: https://www.scisnack.com/2020/04/15/the-deep-sea-is-completely-dark-how-does-life-thrive-there-without-photosynthesis/ https://www.pmel.noaa.gov/eoi/nemo/explorer/concepts/chemosynthesis.html https://www.youtube.com/watch?v=BLOUFrncG7E&ab_channel=EVNautilus Smil, Energy
Bioluminescence
Bioluminescence describes the phenomenon of living organisms creating light. It appears primarily in the deep ocean, though humans can experience the phenomenon on the surface through Dinoflagellates (algae) that will produce light when agitated in the sea. They often will glow brighter if they are exposed to a lot of sunlight during the day.
Before we understand what is actually occurring behind the scenes, it is a good idea to understand why animals will luminesce, and what different kinds exist.
As we spoke about during our exploration of Chemosynthesis, light does not penetrate all the way to the bottom of the sea. Furthermore, not every frequency of light passes through the same depth. We lose Red very quickly, while green and blue will reach much deeper parts of the water. because of this, a lot of deep sea animals have actually evolved to be red, this makes they incredibly difficult to spot in the water.
in this desolate environment, light is often used to invite specific behavior. Some animals will use light to attract mates, some use it to lure prey, and others use it to protect themselves. Protection via light is fascinating because some animals can shine so bright they can briefly blind predators, or they can use light to “counterilluminate.” This is done because, when viewed from below, it is usually easier to make out figures against a slightly lighter surface. In shallower waters, animals like sharks use “countershading” to have lighter undersides. In the deep sea, some animals can use bioluminescence to countershade/counterilluminate themselves. But how do animals actually enable these features?
The basis of all bioluminescence is Luciferin. Luciferin is a substance that can create light, but not without an enzyme to create a reaction. This enzyme is called Luciferase. The words come from the Latin “Lucifer” which means “light bringer.” Additionally, Luciferin and Luciferase are non-scientific terms. This is because a myriad of different chemicals can act as the light-triggering substances. For instance, “the luciferin coelenterazine is common in marine bioluminescence. Dinoflagellates that obtain food through photosynthesis use a luciferin that resembles chl.”
LUCIFERIN IMAGE
However, the process often requires other elements to catalyze. This can include ATP (Adenosine Triphosphate), which is how many species, including humans, transport energy.
The reason that the explanation of how bioluminescent is so broad is because there are so many different methods and uses for bioluminescence. One of the most interesting cases is the “burglar alarm” response, that led to the first footage of a giant squid.
Written by Philip Cadoux, current ITP student and Creative Technologist. Follow me on Instagram