LESSON TWO - The Needs of Living Things - OceanLink

Lesson Two – The Needs of Living Things 3 Science on the Leading Edge (S.O.L.E.)-Producers such as plants, seaweeds, and phytoplankton harness energy from the sun to make sugars.This process is called photosynthesis. Organisms that are photosynthetic use the sun’s energy toproduce simple sugars from carbon dioxide and water, releasing oxygen in the process.C0 2 + H 2 O + sunlight (energy) sugar (C 6 H 12 O 6 ) + O 2One of the major scientific discoveries of the last 100 years is the presence of complex deep-seacommunities that do not depend upon sunlight as their primary source of energy. Hot ventcommunities like the one found at the Endeavour Ridge Node, and methane seep communities like theones found at the Barkley Canyon Node are two examples of undersea ecosystems that thrive withoutsunlight. Instead, these communities get their energy from chemicals through a process calledchemosynthesis. Organisms that are chemosynthetic use chemicals as the energy source to producesugars from carbon dioxide, oxygen, and water.For example, hydrogen sulfide is abundant in the water erupting from hydrothermal vents, and is usedby microbes to produce sugars that are the base of the vent community food chain. These bacteria gettheir energy by oxidizing hydrogen sulfide to sulfur:C0 2 + O 2 + H 2 S (energy) sugar (CH 2 O) + S + H 2 OPut into words, carbon dioxide plus oxygen plus hydrogen sulfide makes organic carbon in the form ofCH 2 O, sulfur, and water. Chemosynthetic bacteria grow on and below the seafloor at hydrothermalhot vent sites, and are even found growing within other animals found at the vents, such as tubeworms.Just like hydrothermal hot vents, chemosynthetic bacteria are also the bottom of the food web in coldseep communities like the one found at the Barkley Canyon Node. Cold seeps are generally foundalong continental margins, where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepageoccurs, often in the form of a brine pool. Cold seeps are home to many species of organisms that havenot been found anywhere else on Earth. Similar to the bacteria found at the hot vent sites ofEndeavour Ridge, the bacteria that live at Barkley Canyon process sulfides and methane throughchemosynthesis. The bacteria here form thick bacterial mats, or live in close association with otherorganisms.Instead of photosynthesis, vent ecosystems derive their energy from chemicals in a process called“chemosynthesis.” Both methods involve an energy source (1), carbon dioxide (2), and water to produce sugars(3). Photosynthesis gives off oxygen gas as a byproduct, while chemosynthesis produces sulfur (4).Image courtesy Woods Hole Oceanographic Institution.Text from Ocean Explorer:oceanexplorer.noaa.gov/explorations/02fire/background/education/media/ring_candy_chemo_9_12.pdf