Dead Jellyfish Help Absorb Carbon Dioxide
May 29, 2013

Dead Jellyfish Help Oceans Absorb Carbon Dioxide

Rebekah Eliason for — Your Universe Online

Humans constantly produce carbon dioxide (CO2), both naturally and as a byproduct of industrial processes. The ocean absorbs about 25 percent of the carbon dioxide emitted by human activity. Tiny organisms called plankton live in the ocean and break down this natural greenhouse gas by converting itinto sugars and carbohydrates through photosynthesis.

In order to understand the efficiency of the ocean´s carbon dioxideprocessing capabilities, it is important to collect data on how fast carbon-carrying organisms sink to the bottom of the ocean. Previously no one believed that jellyfish were a significant factor in the carbon cycle.

Along with other sea organisms, jellyfish are part of the ocean´s natural carbon recycling process. Jellyfish eat microscopic plankton and consequently ingest broken down carbon dioxide. Dead jellyfish then sink to the bottom of the ocean taking a large amount of carbon with them. This carbon becomes trapped in the deep sea water, allowing room for more carbon dioxideto dissolve into the ocean.

Together with a handful of colleagues, Dr. Mario Lebrato, biological oceanographer at GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, studied Jellyfish and similar organisms to measure the rate at which they sank. Researchers collected dead Jellyfish and recorded how fast they fell in tanks of ocean water. They discovered that Jelly fish sink very rapidly and reach the ocean floor before major decay has occurred. A report of their research appeared recently in the journal Limnology and Oceanography.

“The sinking speed of jelly remains is much, much higher than what we expected, about 500 to 1600 meters per day,” said Lebrato. "And, what puzzles researchers working on the biological carbon pump: it is higher than that of non-calcifying phytoplankton and marine snow, the main sinking particles and organic carbon sources to the ocean interior.” The fast sinking of jellyfish thus traps carbon on the ocean floor for thousands of years, keeping it out of Earth´s atmosphere.

"Our dataset provides an initial overview and comparison for modelers and experimentalists to use in subsequent studies examining the role of jellies in carbon export and the efficiency of the biological pump,” Lebrato says. "We are continuously asked, how much organic carbon and CO2 do gelatinous plankton sink worldwide, whether their export capacities are similar to phytoplankton and marine snow. And if an increase of jellyfish in the future will enhance organic carbon export and CO2 sequestration.”

Because no one suspected that jellyfish were important in the carbon cycle, there has been very little research focused on these ubiquitous marine invertebrates.

“Until recently, few people believed that jelly organisms could play any major role in the carbon cycle, thus they have been excluded from large biogeochemical research programs. In consequence, the data available up to now are scarce and we are just starting to comprehend the fundamental properties that will allow us to better understand the role of jellyfish and pelagic tunicates in the global carbon cycle."