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Sea’s health in a drop

Scientists are working to obtain the genetic sequence of phytoplankton to discover which species compose it and which of them live in every water, either pristine or polluted. These new technologies will enable the development of kits to analyze the sea’s health just with a drop of water.


Marine phytoplankton. Picture: Magda Vila, ICM-CSIC. Scientists at the Institut de Ciències del Mar (CSIC) are working on the European project DEVOTES to obtain the genetic sequence of marine plankton. The team, led by scientist Esther Garcés, is composed of Jordi Camp, Ramon Massana and Josep M. Gasol.

 

The goal is to combine traditional technologies with advanced tools of genetic sequencing in order to identify the plankton microorganisms, as Esther Garcés explains. Her group is working on a specific fraction: the one that goes from bacteria to protists seized few microns. The other fractions of plankton, such as virus, zooplankton or the benthic nematodes, are being sequenced by the other DEVOTES partners.

As Esther Garces explains, there is a group of species, called “cryptic species”, which morphologically cannot be differentiated through microscopy from others: visually they appear to be exactly the same. It happens with most part of bacteria, Archae and small protozoa and algae. Nevertheless, it has been proved that they are genetically different. This leads to the conclusion that if techniques of genetic identification were applied on microorganisms, it would be possible to identify more species than only through microscopy.

Especially valuable is to find out which species are common in pristine waters and which are common in polluted waters, in order to use them as biomarkers.

What scientists expect from this work is to discover which species compose the smallest fractions of phytoplankton, where species with a high metabolic diversity can be found. These species are highly sensitive to water changes.

Especially valuable is to find out which species are common in pristine waters and which are common in polluted waters, in order to use them as biomarkers. Why can this be useful?  As Esther Garcés explains, “because we could have a method to know in real time the quality of water. We could develop something like a kit or a DNA chip to find out, just with a drop of water, which species are present”.

This knowledge and their methodology would have attractive advantages compared to the conventional method of taking water samples; sending them to a lab and waiting for the results -that will arrive after the technicians analyze the water samples through microscopy.

Another issue is to find out whether a high diversity in one organism group such as bacteria will correspond always to a high diversity in all groups. Traditionally, scientists have always thought that high biodiversity in one fraction of phytoplankton means a general high biodiversity.  “We think that this is true”, says Garcés, “but nobody has demonstrated this until now”.