Didmyo invades Patagonian rivers

A leathery brown slime is slowly creeping across what are widely considered to be the world’s most pristine rivers. Discovered first by William Horvath, a Patagonian kayaking guide, Didymosphenia geminata, or Didmyo, is a highly invasive alga that has mucked up numerous freshwater bodies across the world.  Didmyo forms large algal mats, secreting a thick layer of muck for which the popular nickname “rock snot” was given.

Aesthetics aside, Didmyo can be ecologically devastating. By coating river surfaces, it prevents sunlight from penetrating, thus killing off other photosynthetic organisms. Thick colonies rapidly deplete both river nutrients and oxygen; in much the same was that algal blooms have devastated the Gulf Coast and led to a massive anoxic dead zone.

Didmyo has appeared in numerous northern hemisphere rivers, and its first southern hemisphere appearance was in New Zealand five years ago. Researchers at the National Fisheries Service have identified several common factors in Didmyo blooms. Didmyo apparently thrive in stable water bodies, downstream of nutrient sources such as farming operations and wastewater treatment plants. Why it spreads so rapidly, and particularly in remote, unpolluted regions of southern Chile and New Zealand, remains a mystery.

Though scientists are not necessarily optimistic, the Chilean government is now launching a huge effort to stop the spread of the algae.

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“Solar salamander” crosses symbiotic boundaries

Scientists have recently discovered the first example of a plant living symbiotically within a vertebrate, broadening our understanding of what sorts of symbioses are possible.

The spotted salamander Ambystoma maculatum is known to engage in a symbiotic relationship with the algae Oophila amblystomatis during embryonic development. Developing salamander eggs are covered in an algae-filled slime. The embryos produce nitrogen-rich waste, which the algae use for nutrition. In turn, the algae increase the amount of oxygen available to A. maculatum through photosynthesis.

This mutualistic relationship has long been understood. Recently, transmission electron microscopy, a high resolution microscopic imaging technology, has revealed O. amblystomatis cells residing within salamander embryos. Time-lapse videos of embryonic development reveal a fluorescent green flash occurring within an embryo as its nervous system forms.

There is evidence that these symbiotic algae may be maternally derived- they are the same algae that occur in female oviducts, where the embryo-encompassing jelly sacs form.

This unique symbiosis may provide insight into the early formation of eukaryotic cells. Chloroplasts, the principle photosynthetic organelle in plant cells, are thought to be the product of an ancient symbiosis between a free-living photosynthetic prokaryote and a larger proto-cell.

Credit:  Petherick, A. A solar salamander. Nature News. Nature. 30 July 2010.

ocean color may affect hurricane activity

a recently study suggests that the color of the ocean, determined largely by the concentration of phytoplankton at the surface, may affect the development of tropical cyclones. “greener” sea surfaces with higher concentrations of photosynthetic plankton absorb more sunlight, causing light to scatter at the surface. in parts of the ocean that are devoid of phytoplankton, sunlight penetrates deeper and sea surface temperatures (SSTs) tend to be lower.

phytoplankton are a diverse group of photosynthetic microorganisms that form the basis of marine food chains

what do SST differences mean for tropical storm formation? higher SSTs lead to the formation of more energetic storms, providing both thermal energy and moisture required for storm formation. a new study suggests that if the north pacific subtropical gyre (an ocean circulation cell that comprises most of the north pacific) were entirely devoid of “light scattering particles” such as phytoplankton, the number of  cyclones forming in this region may be reduced by up to 2/3.