An international team conducted the first of its kind global survey of the ecological diversity of ocean viruses while on board a ship, Tara. They identified nearly 200,000 marine varieties that significantly exceed 15,000 known from previous ocean studies of these waters and approximately 2000 genomes available from cultivated microbial viruses. Their findings appear on April 25 in the journal cellhave implications for understanding issues ranging from evolution to climate change because they help create a new picture on our planet and how it can be influenced by interactions between organisms.
"Viruses are these small things you can not even see, but because they are present in such huge quantities, they really matter," says senior author Matthew Sullivan, a microbiologist at Ohio State University. "We have developed a distribution map that is fundamental to anyone who wants to explore how viruses manipulate the ecosystem. There were many things that surprised us about our discoveries.
Among the surprises were the presence of these nearly 200,000 marine viral species. In addition, meta-community analysis has shown that viruses are organized in five different ecological zones throughout the ocean, which is unexpected given the liquid nature of the oceans and the complexity of many of the marine regions. Also, despite the paradigm of larger organisms that species diversity is highest near the equator and the lowest near the poles, researchers have gathered a large number of samples in the Arctic compared to previous ocean life studies and are found a hotbed of biological diversity in the Arctic Ocean.
Samples were collected between 2009 and 2013 on Tara as part of Tara Oases' efforts. Launched in 2006, the Tara project aims to conduct a unique and innovative ocean science to anticipate and better anticipate impacts of climate change. In these efforts, a rotation team of scientists spends time in the ocean water sampling boat from different depths in many geographic regions. Once collected, samples for this study were filtered and sent back to about a dozen different analysis laboratories.
Researchers examined not only water samples for viruses, but also other microbes and other living things. "We've filtered samples to analyze organisms ranging from viruses to fish eggs," Sullivan says. He adds that there are documents in which some of the other microbial components of the samples are reported.
Another remarkable aspect of the project was the vast number of samples collected in the Arctic that was not part of earlier ocean life research.
This study has significant implications for understanding how oceanic micro-organisms affect the Earth's atmosphere. "Over the last 20 years we have learned that half of the oxygen we breathe comes from marine organisms," Sullivan notes. "In addition, oceans absorb half of the carbon dioxide from the atmosphere."
"Due to sophisticated chemistry, elevated levels of carbon dioxide on the surface are acidifying the oceans," Sullivan adds. "But if carbon dioxide is converted into organic carbon and biomass instead, it can become a particle and sink into deep oceans. This is a good result to help mitigate climate change caused by humans, and we know that viruses can help ease this sinking. Having a new map of where these viruses are located can help us understand this "ocean carbon" pump and, more generally, the biogeochemistry that affects the planet. "
Researchers say that a fuller picture of the prevalence and abundance of marine viruses will help them determine which viruses should focus on further research. Additionally, maps based on this study set a baseline for other collection efforts that can help answer questions about how the levels of microorganisms change over time in response to both seasonal variations, so and climate change.
"Models from previous ocean ecosystems are usually ignored microbes and rarely include viruses, but now we know they are a vital component for inclusion," Sullivan concludes.