Arctic Ocean may be invaded by microbes from tropics, affecting ecosystems: Study

Global warming may cause microscopic organisms habiting polar regions of Earth's oceans, such as Arctic, to be slowly conquered by ir counterparts from tropical regions, affecting multiple ecosystems, according to two major studies which assessed more than 35,000 samples collected from all world's oceans between 2009 and 2013.

two studies, published in journal Cell on Thursday, found that diversity of microscopic organisms habiting Earth's oceans are least at higher latitudes -- nearer to poles -- and increase in a grient towards equator. two studies analyzed diversity of se organisms in samples collected from ocean water currents to predict how se communities might apt to changing environmental conditions.

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'Study focused on Plankton'

researchers, including Chris Bowler from Institut de Biologie de l'Ecole rmale Superieure (IBENS) in France, said one of studies focused on diversity of groups of microscopic marine organisms called plankton, and or assessed activity patterns of genes among microbial communities across Earth's oceans.

"Our study focused on plankton because it's a major contributor to marine ecosystems in terms of biomass, abundance, and diversity," said Lucie Zinger of IBENS, co-senior author of plankton study. 

"All s of life have representatives in plankton -- bacteria, archaea, protists, animals and plants, as well as viruses. But large majority of this diversity is invisible to naked eye," he said.

findings of study revealed that plankton groups across planet follow a grient of diversity along latitudes -- with lowest level of ir diversity closest to poles, and diversity increasing towards equator. 

"Ocean temperature is mainly responsible for this pattern. Ocean warming due to climate change is likely to le to a 'tropicalization,' or increase, of plankton diversity in temperate and polar waters," Zinger said. 

or study assessed ocean microbial communities to see what genes y h, and which ones were actively involved in ir cellular processes, across grients of both depth and latitude.

"Looking at transcriptomes is important for determining t just which microbes are present, but what those microbes are doing with regard to activities like photosynsis and nutrient uptake," said Shinichi Sunagawa, senior author of microbe geme analysis study from ETH Zurich in Switzerland. 

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"One of our goals was to learn wher microbial communities just to environmental and temperature variations with changes in ir composition relative to each or or with changes in gene expression patterns within se communities," he said.

species of bacteria, genes present, and activities of genes varied distinctly in waters with boundaries separating m both across surface water to deep water, and across poles towards equator, study said.

"We did t expect to find biogeographic patterns for underlying mechanisms of metatranscriptomic composition variation. Specifically, we found differences in polar communities to be dominated by changes in organismal composition, while in npolar waters, differences were dominated by changes in expression of genes," Sunagawa said. 

He ded that researchers were surprised to find evidence for a nitrogen-fixing bacterium -- commonly present in soil or plant roots on land -- in deep Arctic waters.

"And what this means, toger with results of diversity study, our findings suggest that microbial communities to warmer waters have a larger gene pool, which may allow m to be quite flexible and responsive temperature changes by cold counterpart and colder waters seem to be more hardwired to m," Sunagawa explained in a telephonic press briefing where PTI was also present.

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While studies did t probe into diversity changes that may result in communities of larger organisms like fishes, y said changes in microbial composition in Arctic might le to cascing effects related to nutrition on larger eukaryotic organisms in food chain.

"In Arctic one thing that is very prominent in high latitudes like Arctic is importance of lipids and fats in diet," Bowler told PTI.

He explained that higher organisms in food web of Arctic ecosystems need to urish mselves with organisms rich in fat to build fat reserves that can help m withstand extreme cold conditions of region. 

"So if food sources that se organisms are eating or less rich in fats, n we could perhaps imagine that se large organizations will struggle to survive," Bowler said.  

Sunagawa said due to climate change cold water microbial communities may experience displacement of some species, possibly by those with better aptive capacity.  Sunagawa said in press briefing that it is critical is to continue to monitor state of oceans by certain interdisciplinary efforts, and to try and capture temporal trends in microbial community changes.

"Every drop of marine water is full of microbes, which play a central role in many processes relevant to life on Earth," he said.

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