Sun radiation, proliferation of krill as a consequence of the impoverishment of whales’ population and, specially, the lack of iron, are some of the factors that could be controlling the phytoplankton of the sea ecosystem of the frozen continent. In the waters of the Southern Ocean, there is a low concentration of phytoplankton for the high availability of dissolved nutrients, known in the scientific world as Antarctic paradox. To study the causes that are provoking this situation, a team of scientists of the University of Granada in collaboration with researchers of the IMEDEA, the State University of New Cork, the Universidad de las Palmas de Gran Canaria and the IIQAB de Barcelona has undertaken for more than a month an expedition on board the Hespérides, which has taken them from the Bellingshausen Sea to the Weddell Sea taking chemical and biological samples of the sea ecosystem.
The campaign, carried out during last February after more than two years of wait, has been “more than fruitful” as, according to the Professor of the University of Granada and one of the researchers who supervises the project, Isabel Reche Cañabate, “most of the samples extracted were analysed on board the ship, obtaining in most times in situ results”.
The data obtained by this project will be essential in the future from the environmental viewpoint: “The phytoplankton that grows in the waters of the Antarctic Sea can act as a CO2 drain. If the researchers manage to find the reason for the limitation of this compound of the trophic chain they could induce artificially its growth and solve part of the problem of global warming”, Reche declares, after saying that “this can be one of the applications of the protect. We should consider ethical and scientific questions to put this solution into practice”.
Although the ICEPOS project team (Complex Interactions in the Pelagic Ecosystem of the Southern Ocean) has focused its explication of phytoplankton limitation on two factors: sun radiation and the proliferation of the krill, there are other hypothesis around this topic such as that “the nutrients are so deep that they hardly receive sunshine to do the photosynthesis or that the Southern Ocean does not contain the necessary amount of iron for phytoplankton to grow”, the scientist says.
In this sense, Reche refers again to the “paradox of the Antarctica”, as although in the Antarctic Ocean there is a high concentration of inorganic nutrients (in shape of nitrates and phosphates), the first step of the trophic chain still does not grow.
As regards the theories that point out the lack of iron as one of the possible causes of this situation, The researcher of Granada says that although these are the most supported by the scientific community, it has been tested that in areas like Deception Island, in which there is a high amount of iron thanks to the volcanic activity, there is also a great limitation of phytoplankton, and as regards the hypothesis that indicates the lack of sun to do the photosynthesis, the biologist clears up that although in winter this situation could happen “the sea ecosystem would recover during the austral summer, which does not happen”.
First data
Although in this first expedition they have had to carry out the experiments in the laboratory of the ship and not directly in the oceanic ecosystem, that is where they will finish the research project, the first extracted data have turned Krill into one of the main figures of the trophic chain of the Antarctica. According to Reche, the indiscriminate hunting of whales which fundamentally fed on this crustacean could have provoked the uncontrolled proliferation of this species that subsists thanks to phytoplankton. But there is a new paradox in this point that leaves the problem of phytoplankton decrease unsolved and is that “although the increase of the population of these crustaceans limits the growth of the first link of the trophic chain, their excretion products contain the nutrients phytoplankton needs to develop”. The first results solve part of the problem but they open a new one that will be analysed together with the role of sun radiation in the laboratory thanks to the samples taken throughout the 16 stations located in the frozen continent.
On the other hand, the Professor of the University describes her experience in the Antarctic continent as “gratifying” in a double sense: “Besides the challenge of contributing knowledge to understand the behaviour of the Southern Ocean, we were lucky to go out on deck, look at the horizon and feel cold air in the face, which allows us to breath the intensity of nature and reminds us how fragile we can be”.
Reference
Professor Isabel Reche Cañabate
Dpt. of Animal Biology and Ecology
Phone number. 958 246 166 / 958 248 590
E-mail. ireche@ugr.es
