Algal bloom regulated by poison
Diatoms use an aldehyde toxin to protect themselves from predators, while also regulating their colony density. This is reported by researchers led by Chris Bowler from the Ecole Normale Supérieure in Paris.
Diatoms, responsible for around twenty percent of global primary production worldwide, multiply in the oceans during regularly recurring algal blooms and at these times also increasingly attract predators such as crabs. Algae communities protect themselves against these and pathogenic germs with the help of the toxic aldehyde decadienal, which is released by wounded algae. Among other things, the substance hinders the development of the crab spawn, but it also kills the algae themselves.
But this is only the case in high doses, according to Bowler and colleagues after diatom experiments with different doses of the aldehyde: Only larger amounts of the substance first boost the intracellular calcium release and then the production of the signaling substance nitrogen monoxide, which then goes hand in hand with the death of the protozoa. On the other hand, in small amounts, the aldehydes do not cause higher intracellular NO values. Instead, the diatoms incubated with low doses are later resistant to higher levels of toxin.
Apparently, the substance not only regulates the population of predators, but also that of the algal community itself, the scientists conclude.