IBED Biologists reveal colourful coexistence of plankton in waters
Three years ago, Maayke Stomp and Jef Huisman of IBED published the results of intriguing laboratory experiments, demonstrating that red and green plankton species can coexist by partitioning of a white light spectrum. In the years thereafter, they traveled around the world to sample lakes and seas. Their samples now confirm the laboratory findings. The new findings were recently published in the leading journal Ecology Letters, and have been selected as Editor's Choice in Science.
Plankton species occur in various colours, including red algae, green algae, and bluegreen algae. The colours of these species are determined by their pigments, which absorb sunlight for photosynthesis and growth. Green species contain pigments that absorb red light, but reflect green light. That’s why these species are green. It is the opposite for red species. They contain pigments that absorb green light, but reflect red light. Thus, red and green species use different wavebands of the solar spectrum. What happens in a mixture of red and green species? In Nature of 2004, Maayke Stomp and Jef Huisman of the Institute for Biodiversity and Ecosystem Dynamics (IBED) at the Universiteit van Amsterdam described the results of a series of laboratory competition experiments. When exposed to red light, green species became dominant. Conversely, under green light, red species became dominant. White light contains the full spectrum of colours. And indeed, under white light, the competition experiments yielded to a stable community of red and green species. They shared the spectrum.However, these results were based on lab experiments. What happens in the real world? To address this question, an international team of scientists headed by Maayke Stomp and Jef Huisman gathered data from all over the world. They visited clear blue waters of the tropical Pacific Ocean, green coastal waters of the Baltic Sea, many lakes dotting the Hungarian Puszta and Canadian Shield, and dark brown lakes in peatlands of The Netherlands. Everywhere, the plankton was sampled and underwater light spectra were measured. In addition, they developed a new mathematical model to predict the competition between red and green plankton species in different underwater light spectra.
The results of this extensive study were published in March 2007 in the international journal Ecology Letters (Volume 10, pp. 290-298). In clear ocean waters, blue and green wavelengths penetrate the deepest. Here, the competition model predicts a competitive advantage for red species. In turbid water, with high concentrations of organic matter, red wavelengths dominate. This favours green species. The model predicts stable coexistence of red and green species in waters of intermediate turbidity, including many coastal waters and a wide variety of lakes. These model predictions match the data. Clear waters are indeed dominated by red species, turbid waters are dominated by green species, and waters of intermediate turbidity are characterized by a colourful mixture of red and green species.
The study concludes that partitioning of the light spectrum among different species enables an optimal utilization of the solar energy, and supports a colourful plankton community.