Scientists Create Global Atlas On Oceanic Plankton
July 19, 2013

Scientists Create Global Atlas On Oceanic Plankton

April Flowers for - Your Universe Online

An international group of scientists has created a global atlas of oceanic plankton -- from bacteria to krill -- by recording times, places and concentrations of the organism's occurrences.

Over 70 percent of the world's surface is covered by the oceans. Compared with terrestrial ecosystems, the animals and plant species of the oceans have been researched relatively little. Because of this, the knowledge base concerning the distribution of plankton -- those organisms that are too small to swim against the ocean currents -- is fairly scarce.

Researchers at ETH Zurich and the University of East Anglia, UK, spearheaded the large-scale project that combined the resources and scientists of numerous universities to make a survey of when, where and which plankton species occur and to determine how much carbon they absorb. The team collected data on the species diversity and biomass of plankton at 500,000 locations around the world. The findings of their study, collected as a global atlas, were published under the name MAREDAT in a special edition of Earth System Science Data.

The atlas provides data on organisms ranging in size from phytoplankton and bacteria just one picometer, one billionth of a meter, to centimeter-large zooplankton such as krill and other small crustaceans. Despite the small size of the individual organisms, plankton are crucial to the world's oceans. For example, they are an important driver of global biogeochemical cycles, and they form the basis of the food chains in marine ecosystems.

Absorbing carbon dioxide (CO2) for photosynthesis, phytoplankton release oxygen into the atmosphere and carry a good portion of the absorbed carbon into the oceans depths as the phytoplankton die and sink to the bottom. With this process, phytoplankton remove CO2 from the atmosphere, contributing to the regulation of the global climate.

The marine nitrogen cycle is also controlled by plankton, which can even influence cloud formation through the sulfur cycle. Krill, and other zooplankton, are an important food source for whales, fishes and other marine species higher up in the food chain. These species are then exploited by humans.

The project was coordinated by Meike Vogt, senior scientist at the Institute of Biogeochemistry and Pollutant Dynamics at ETH Zurich. "Analyzing data from half a million survey stations was an incredibly ambitious undertaking and would have been impossible without international collaboration," says Vogt. The team of scientists performed a literature review, combing through databases, publications and even extracting data from hand-written notes. Before using the data to calculate biomass, the team put it through a careful quality control screening. Persuading the various research institutes that gather such data to participate, and standardizing the various contributions, some of which were historical, took longer than the actual calculations.

The new atlas will help us understand how planktonic organisms are organized into ecosystems by providing insight into the biodiversity of different oceanic regions. One area that is of particular interest to the scientists is determining which species occur together and whether they indicate certain habitats and biogeographical regions with similar biogeochemical functions. The team hopes that their data will shed light on the role of plankton in different oceanic regions as a driver of the planet's various biogeochemical cycles.

To facilitate the development of this knowledge, the team has made their data available to climate scientists. This will allow the climatologists a more solid foundation of data with which to validate their models. Previously, climatologists have worked with simple ocean ecosystem models that differentiate between two kinds of zooplankton and phytoplankton at most. Taking into account more plankton types will allow scientists to map the ecological diversity more accurately. In turn, this will allow for more precise predictions with regard to the role of the ocean as a carbon sink.

"Humans disrupt the ocean system in diverse ways and on various levels of the food chain," says Vogt.

She explains that the oceanic ecosystems are very complex, meaning that we still only have a vague idea about the future impact of overfishing and ocean acidification, for instance, especially if we do not know which species occur where.

Initial analysis of the MAREDAT atlas shows that there are far more organisms in the world's oceans than was previously assumed. It also seems that zooplankton have at least as much biomass across the world's oceans as phytoplankton. This is surprising, since it is usually just the other way round in the terrestrial systems, where there are more plants than animals," says Vogt.

Vogt's group is also using MAREDAT to form fundamental hypotheses about ecological diversity, and to validate their models with the new data.

"At the moment, we can generate initial rudimentary distribution maps with statistical models. These maps, however, will change greatly in the next ten years, because we have too few samples from some regions to map them accurately," says Vogt.

For instance, the South Pacific and some regions in the Southern Ocean have hardly been studied. The team of scientists plans to revise MAREDAT for the first time in 2015, aiming to collect more data in order to document changes in plankton communities over time.