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By: Amanda Kelley
You’ve probably heard about coral bleaching of various reefs around the world that is attributed to rising ocean temperatures. But did you know that this same phenomenon is also occurring in several species of seaweed?
Researchers at the University of New South Wales in Australia have discovered that a variety of normally harmless bacteria can cause bleaching disease in seaweeds when the seaweeds become stressed by high water temperatures.
The researchers, led by Dr. Suhelen Egan of the UNSW Centre of Marine Bio-Innovation, completed their work on the red algae species Delisea pulchra by collecting both healthy and bleached samples of the seaweed from the wild.
They then identified the bacteria that were more abundant on the diseased algae versus the healthy algae, and proceeded to test those microbes for the ability to cause bleaching.
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Under normal conditions, D. pulchra produces a chemical compound that binds to bacterial receptor sites, acting as a defense against infection. However, the researchers believe that higher temperatures stress the seaweeds in a way that prevents them from allocating resources to support this chemical defense system, leaving the bacterial receptor sites vulnerable.
In addition, rising temperatures stimulate microbial populations to propagate rapidly and seek out hosts, making the weakened algae an easy target. Interestingly enough, the bacteria found to be responsible for the disease are nearly always found on algal surfaces. However, they are only a danger to the seaweed in high densities.
“Bleaching reduces the ability of the seaweed to photosynthesize and harvest energy from the sun, and to reproduce. It also makes them more susceptible to grazing by fish and other herbivores in the ocean,” says Dr Egan.
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Algae provide a multitude of ecological services to the marine environment. Widespread loss of habitat-forming seaweeds could negatively impact the organisms that rely on them for food and protection, and in turn affect the predators that depend on those organisms for nourishment.
Us humans have stock in the fate of seaweeds as well: various extracts and compounds from algae can be found anywhere in your house from your fridge to your bathroom. Coupled with the seaweed that is harvested for human consumption, the growing international seaweed industry has a lot to lose if bleaching continues.
The pressure is on for our algal pals! Let’s hope it doesn’t get to them, they have enough to stress out about with those rising temperatures…