Nav: Home

A DNA analysis of ballast water detects invasive species

December 09, 2015

The German research vessel Polarstern covers thousands of kilometres between the northern and southern hemispheres in search of samples of biological material. This ship, however, has some other on board passengers: organisms that can adapt to extreme water temperatures and could potentially invade the new waters where this ice breaker takes them. Upon analysing the DNA present in this vessel's ballast water, a team of scientists showed the first molecular evidence of the persistence of DNA belonging to a tiny sea snail which is capable of tolerating adverse conditions.

Maritime transport is considered one of the most important ways that native species are moved between marine regions. The trip can be especially successful if these species latch on to the vessel's anchors or chains, or even if they travel in the ship's ballast water tanks. Each year, between 2.2 and 12 billion tons of water are transported around the oceans of the world in these ballast water tanks which also serve as a means of transport for about 7,000 species per day.

In a European report that analysed 15 samples of ballast water, live specimens of more than one thousand species were discovered in ship tanks that arrived to European ports. These taxa, however, must face very harsh conditions upon arrival: darkness, temperature changes, salinity, murky waters, turbulence and a lack of oxygen. Not all of the species will survive, and the ones that do become potential invasive species.

In order to identify which organisms are most capable of tolerating non-native waters and are thus the most invasive, a team of researchers led by the University of Oviedo (UO) analysed the environmental DNA present in the 70 m3 of ballast water in the tank -- filled with water from the North Sea -- of the scientific research vessel Polarstern. This ship travelled between Bremerhaven (Germany) and Cape Town (South Africa) between October and December of 2012.

"Seeing as this ballast water has travelled from the north to the south and has even crossed the tropics, it has thus been subjected to extreme temperature variations in addition to anoxic conditions [a total lack of oxygen]," explains Alba Ardura to SINC, the main author of the study published in the Journal of Molluscan Studies and a researcher at the University of Perpignan (France) at present.

Is this snail a potential invasive species?

While filling up the ballast water tank, the organisms that were alive upon entry into the tank in Bremenhaven could have been subjected to conditions of stress which could result in their death, thus meaning that "the number of DNA molecules would decrease over the course of the trip," points out Ardura. Nonetheless, this is not what happened to the laver spire shell, also called the mudsnail (Peringia ulvae): "The number of one of the haplotypes (variations in DNA within the same species) increased during the trip," affirms the scientist.

Animals like this invertebrate leave behind traces of their presence in the waters where they live such as dead cells that have sloughed off or fluids. In this case, the mudsnail left behind traces in the ballast water. It is possible to extract DNA from a sample of water in order to determine what species are living there. "We can thus have a wide range of information about the species which are present in the environment we are analysing without having to carry out individual sampling one by one," observes the expert.

Nonetheless, finding evidence of the mollusc does not confirm that it is alive, "but it does confirm the resistance of its DNA to adverse conditions," indicates Ardura. Up until now there has not been any evidence of the presence of this small snail outside of its natural habitat, although some studies have indeed described its ability to tolerate diverse ecological conditions.

For researchers, environmental DNA and its massive sequencing are a 'very promising' tool for rapid biodiversity analysis and the detection of potentially invasive species that are present in ships' ballast waters. Though we should also point out that "the tool has its limitations which need to be remedied in order to develop an effective and robust method for applications in this field," concludes the scientist.
-end-
References:

Ardura, Alba; Zaiko, Anastasija; Martínez, Jose L.; Samuiloviene, Aurelija; Borrell, Yaisel; García-Vázquez, Eva. 'Environmental DNA evidence of transfer of North Sea molluscs across tropical waters through ballast water' Journal of Molluscan Studies 81: 495-501 Subdivisión: Nov. 4, 2015. DOI: 10.1093/mollus/eyv022 November 2015

FECYT - Spanish Foundation for Science and Technology

Related Dna Articles:

Penn State DNA ladders: Inexpensive molecular rulers for DNA research
New license-free tools will allow researchers to estimate the size of DNA fragments for a fraction of the cost of currently available methods.
It is easier for a DNA knot...
How can long DNA filaments, which have convoluted and highly knotted structure, manage to pass through the tiny pores of biological systems?
How do metals interact with DNA?
Since a couple of decades, metal-containing drugs have been successfully used to fight against certain types of cancer.
Electrons use DNA like a wire for signaling DNA replication
A Caltech-led study has shown that the electrical wire-like behavior of DNA is involved in the molecule's replication.
Switched-on DNA
DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices.
Researchers are first to see DNA 'blink'
Northwestern University biomedical engineers have developed imaging technology that is the first to see DNA 'blink,' or fluoresce.
Finding our way around DNA
A Salk team developed a tool that maps functional areas of the genome to better understand disease.
A 'strand' of DNA as never before
In a carefully designed polymer, researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences have imprinted a sequence of a single strand of DNA.
Doubling down on DNA
The African clawed frog X. laevis genome contains two full sets of chromosomes from two extinct ancestors.
'Poring over' DNA
Church's team at Harvard's Wyss Institute for Biologically Inspired Engineering and the Harvard Medical School developed a new electronic DNA sequencing platform based on biologically engineered nanopores that could help overcome present limitations.

Related Dna Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...