Science - January 14, 2016

Uninvited guests in the polar sea

Hilde de Laat

A ship’s hold is crawling with plankton that come along for the ride. How can you keep these uninvited guests out of the northern Polar Sea without harming the local population in the process? Andrea Sneekes of Imares studied this question last summer on the SEES expedition. She will present her results at the Arctic Frontiers conference in Norway at the end of this month.

Midnight on the expedition vessel the Ortelius. Photo Andre Sneekes

Polar beers, reindeer, oil pollution... Of all the studies carried out during the Dutch polar expedition Scientific Expedition Edgeøya Svalbard (SEES), Sneekes’ work on plankton in ballast water is perhaps the least headline-grabbing. And yet her results are of vital importance, she explains. Exotic species often lack natural enemies in their new habitat, causing them to disturb the natural balance. ‘As examples just take the Japanese oyster and the American jackknife clam in the Wadden Sea.’ Some exotic species even pose a direct threat to humans. ‘Alexandrium, for instance, is a big problem in Europe because it can cause shellfish poisoning. In humans the poison can cause paralysis and can even be fatal,’ stresses Sneekes.

Andrea Sneekes takes a plankton sample in Spitsbergen. Photo Meike Scheidat
Andrea Sneekes takes a plankton sample in Spitsbergen. Photo Meike Scheidat

Shipping plays a key role in the spreading of exotic species. Empty cargo shops pump up seawater to serve as ballast. Sneekes: ‘This ballast water is full of uninvited guests: small plants and creatures that get sucked up with the water.’ Then the ship pumps out this ballast water on the other side of the world so as to load up with new containers or other cargo. Like this, seawater gets moved around the world and exotic plankton end up in natural habitats where they do not belong.


‘Governments have been working on the introduction of international legislation for some time. Such legislation would oblige shipping owners to render the plankton harmless before dumping it in the water,’ explains Sneekes. Her institute is taking care of the certification of these ‘ballast water systems.’ She sighs. ‘I hope the legislators get a move on. The spreading of exotic species must be stopped before it is too late.’

The ballast water systems that Imares is now testing use chlorine to kill the plankton. ‘We have been working on improving these systems for years. We check whether the apparatus really does kill 100 percent of the plants and animals in the ballast water. We also look into whether dumping the chlorine in the sea doesn’t harm the environment.’

There is just one problem: ‘These systems are tested in temperate regions such as the North Sea. We don’t know how the plankton from the North Pole region reacts to chlorine. Nor do we know whether dumping the treated water harms the environment in these cold regions.’ High time for research on this, then.

The marine biologists from Imares and NIOZ on the SEES expedition. Photo Andrea Sneekes
The marine biologists from Imares and NIOZ on the SEES expedition. Photo Andrea Sneekes

Lab on deck

Sneekes collected plankton on the SEES expedition from a small boat using a simple bucket and fishing net. Back on board the ship Ortelius she used a primitive microscope to see which species she had caught. ‘I had enough specimens of six species for an experiment. I exposed them to different concentrations of chlorine in order to find out which concentration would kill everything.’

That was no easy task. Sneekes had to do the work in an improvised laboratory on deck. ‘I wanted to do as many tests as possible in a short period, so I was often up in a freezing cold lab till long after midnight.’ Fortunately it was not a lonely existence, though. ‘I got to know a couple of colleagues from other branches really well,’ she reports with satisfaction.

‘We saw that the plankton in the Arctic reacted more strongly to chlorine than it did around the Netherlands.’ That was surprising because earlier tests showed that plankton in cold regions reacts less strongly than those in temperate regions. ‘The metabolism of Arctic plankton is slower, so the chlorine has less effect. But the low temperature also means the chlorine breaks down more slowly, so it can be toxic for longer. In theory these things balance each other out, but that doesn’t appear to be the case here.’ This could mean that existing ballast water systems that have been tested in temperate climates and pronounced safe are damaging to life forms in the frozen north.

Sneekes gives a radio interview in the laboratory on board the Ortelius. Photo Bart van den Heuvel
Sneekes gives a radio interview in the laboratory on board the Ortelius. Photo Bart van den Heuvel


Sneekes will be travelling to Tromsø next week to present her results at a conference (see box). ‘This orientation project could in itself be of interest to other scientists.’ But her research is not finished yet. ‘We want to repeat this experiment with other species of plankton. Only then can we issue advice about the ballast water systems and adjust the certification to the conditions in the Arctic region.’

The researcher hopes then to return to the north to do more tests. ‘The SEES expedition was my first visit to Spitsbergen, a vast area which I would love to go back to.’

She won’t forget her trip in a hurry. ‘The glacier ice cracked as we sailed through it. That was such a special sound.’ One thing is clear to Sneekes: ‘We humans must make way because the natural world is so much bigger than we are.’

Arctic Frontiers

The annual Arctic Frontiers conference, to be held this year between 24 and 29 January in the northern town of Tromsø, bridges the worlds of science, business and policy. The 29 countries that are represented discuss developments in the North Pole region from the ecological, social and economic perspectives. This year the theme of industry and environment is central.

A key issue in this context is shipping. The melting of the sea ice in the Arctic region is making new northern shipping routes available. That creates opportunities but also threats, such as the unintended spreading of exotic species of plankton through ballast water.