Ocean plants stun researchers with alternative body-building technique

You may prefer to have a house built of wood, but if there's no wood around, you can use concrete or steel.

Turns out phytoplankton have similar options available to them.

(Image: Ocean researchers deploy a Conductivity, Temperature, Depth rosette to conduct inquiries into conditions on the ocean. Credit: Lance A. Fujieki.)

In a bit of groundbreaking research, teams of researchers have found that when their favored cellular wall building blocks are unavailable, microscopic ocean plants can build their cell walls out of replacement compounds.

The teams are from Woods Hole Oceanographic Institution, University of Southern California, University of Hawai'i, the Czech Academy of Sciences, the Bermuda Institute of Ocean Sciences, University of Southern Maine, and the Centre d’Océanologie de Marseille.

Cell membranes are generally known to be built of a range of compounds, with a phosphorus-based oil compound known as phospholipid prominent among them. And it has been assumed that except in very rare exceptions, you need phospholipids to make cell membranes.

But what is a bit of phytoplankton to do in ocean areas starved of phosphorus? The Sargasso Sea is such an area, and it turns out that phytoplankton like cyanobacteria grow just fine there.

Their trick? They manufacture their cell membranes out of other compounds, notably sulfur.

It's interesting news in a world of climate change, in part because there is evidence that phosphorus may be disappearing from surface waters in parts of the world—including around Hawai'i—due to reduced mixing of nutrient-rich deep water with nutrient-deprived surface water.

Phytoplankton produce much of the world's oxygen, and need to do that near the surface, where there's sunshine to fuel the production. They do lots of other useful things, including suck carbon dioxide out of the atmposphere, and serve as a basic feature of the oceanic food web—with impacts on fisheries, among other things.

“Phosphorus is still measurable but is disappearing from the surface waters (near Hawai'i) at an alarming rate. One prediction from this initial study is that the phytoplankton in Hawaiian waters are likely to become more like those in the Sargasso Sea over time as phosphorus supplies dwindle further,” the University of Hawai'i said in a news release.

What's not clear is what effects such a change would have on all the ocean processes and species that are associated in some way with phytoplankton.

It's also not clear whether other forms of life have the same flexibility in building their cell membranes that phytoplankton have.

“To date, the ability to synthesize substitute lipids appears to be restricted to the phytoplankton; heterotrophic bacteria and other organisms must have a different strategy for survival, or none at all,” the University of Hawai'i release said.

Two Hawai'i researchers, Michael Rappé and David Karl of the School of Ocean and Earth Science and Technology and UH’s new Center for Microbial Oceanography, are co-authors of the new research, published in the March 5, 2009, issue of the journal Nature.

The paper is “Phytoplankton in the ocean use non-phosphorus lipids in response to phosphorus scarcity,” by Benjamin A. S. Van Mooy, Helen F. Fredricks, Byron E. Pedler, Sonya T. Dyhrman, Karl, Michal Koblíek, Michael W. Lomas, Tracy J. Mincer, Lisa R. Moore, Thierry Moutin, Rappé and Eric A. Webb.

The University of Hawai'i School of Ocean and Earth Science and Technology release is here.

©2009 Jan TenBruggencate