Lake Kinneret study sheds new light on algae

Hebrew University researcher figures out how algae ‘enslavement’ threatens freshwater bodies.

By EHUD ZION WALDOKS
A Hebrew University of Jerusalem PhD student has figured out how toxic, blue-green algae out-compete other organisms, by studying their proliferation in Lake Kinneret.
The spread of the algae can deleteriously affect drinking water and even cause deaths in humans and animals, and it has become a matter of worldwide concern.
Yehonatan Bar-Yosef, a PhD student in Prof. Aaron Kaplan’s group at the Hebrew University’s Alexander Silberman Institute of Life Sciences, suggests a novel mechanism in a paper published online on Thursday in Current Biology.
A toxic cyanobacterial blue-green alga known as Aphanizomenon ovalisporum was first detected in Lake Kinneret in 1994, and its presence has been noted each summer since. However, how the toxic algae bloomed has remained a mystery.
Bar-Yosef has discovered that Aphanizomenon is known to produce the toxin cylindrospermopsin (CYN). Secretion of the CYN, Bar-Yosef found, induces phosphate-limitation responses in other microorganisms in the ecosystem, even in the presence of ample phosphate in the water. Phosphate is an essential nutrient for growth in many organisms.
By blocking other organisms from absorbing phosphate, Aphanizomenon reserves more of the mineral for itself.
The investigators have used the term “enslavement” to describe this novel interspecies interaction, mediated by CYN. This research provides an explanation for the significant rise in massive cyanobacterial bloom events worldwide during the last decade, despite attempts by water management authorities to reduce the inflow of phosphates from watersheds.
The research on the Kinneret water was carried out in conjunction with Dr. Assaf Sukenik and Dr. Ora Hadas from the Kinneret laboratory of the Israel Institute of Limnology and Oceanography.