New perspective on phytoplankton

Phytoplankton form the 'forest' under the sea, and are responsible for providing nearly half of the oxygen needed for life on Earth, including ourselves. However, unlike the 'co-workers' on land, this marine plant is usually very small in size, and out of sight of humans. Therefore, we are at an early stage of understanding the most fundamental aspects of biology and ecology of phytoplankton.

In a new article published in Nature, a group of international scientists, including two oceanographers of the University of Hawaii at Manoa (UHM), describe a new strategy for the development of phytoplankton in undernourished habitats in tropical and subtropical seas. The research team Benjamin Van Mooy of the Woods Ocean Academy, Cape Cod, MA directed; with the contributions of scientists Michael Rappé and David Karl of the Earth and Marine Science and Technology School (SOEST) and the new Center for Microbiology and Oceanography of the UHM (C-MORE)

Until now, scientists still claim that all cells are surrounded by membranes containing molecules called phospholipids - compounds that contain phosphorus and other basic elements such as carbon and nitrogen. These phospholipids are the basis of cell structure and function, and for that reason they are thought to be an integral part of life.
Phospholipids are one of the molecules that contain elemental phosphorus, which has low reserves in many marine ecosystems. Deep in the sea, phosphorus is very abundant, but the amount that is deposited on the surface where photosynthesis occurs is limited because of the temperature stratification and the inability to mix seawater to the depths of phosphorus. Research conducted at the ALOHA station near Hawaii in the past two decades has shown that phosphorus is rapidly declining in the stratified area of ​​the North Pacific Ocean, which may be the result of changes in the living environment. sea.

Van Mooy and colleagues discovered that phytoplankton in the sea can adapt to low phosphorus levels by altering their cell structure. Instead of synthesizing phosphorus - which requires phospholipids to be used in their membranes, these plants can use 'reserve lipids' that contain sulfur elements, found in seawater, not phosphorus. These alternative sulfolipids allow phytoplankton to continue to grow and survive under phosphorus deficiency, a special strategy for marine life.

To test the biochemical strategy mentioned above, the authors compared the reaction of phytoplankton in different sea basins with different phosphorus concentrations. In areas where phosphorus scarcity is very scarce, such as the area called Sargasso Sea in the center of the North Atlantic Ocean, phospholipids are almost non-existent. In contrast, the South Pacific region where phosphorus is available, phospholipids are also abundant. The area around Hawaii is at an average level, consistent with data from the Hawaii Sea Time Program, which shows that the amount of phosphorus remains moderate but is disappearing from the water surface at an alarming rate.

Scientists predict that phytoplankton in Hawaiian waters are likely to become more like phytoplankton in the Sargasso Sea because the supply of phosphorus is depleted. So far, the ability to synthesize replacement lipids is restricted only to phytoplankton, heterotrophic bacteria and other organisms that need other strategies for survival. This has important implications for the future structure, biodiversity and function of Hawaiian marine ecosystems, including fish production and the ability to sequester carbon dioxide.

Refer:
Benjamin AS Van Mooy, Helen F. Fredricks, Byron E. Pedler, Sonya T. Dyhrman, David M. Karl, Michal Koblíek, Michael W. Lomas, Tracy J. Mincer, Lisa R. Moore, Thierry Moutin, Michael S. Rappé & Eric A. Webb.Phytoplankton in the ocean use non-phosphorus lipids in response to phosphorus scarcity.Nature, 2009;458 (7234): 69 DOI: 10.1038 / nature07659