Scripps Oceanography Research pegs ID of red tide killer

Bacteria gang up on algae, quashing red tide blooms

A cell of the dinoflagellate Lingulodinium polyedrum. Click here for more information.

Researchers at Scripps Institution of Oceanography at UC San Diego have identified a potential “red tide killer.” Red tides and related phenomena in which microscopic algae accumulate rapidly in dense concentrations have been on the rise in recent years, causing hundreds of millions of dollars in worldwide losses to fisheries and beach tourism activities. Despite their wide-ranging impacts, such phenomena, more broadly referred to as “harmful algal blooms,” remain unpredictable in not only where they appear, but how long they persist.

New research at Scripps has identified a little-understood but common marine microbe as a red tide killer, and implicates the microbe in the termination of a red tide in Southern California waters in the summer of 2005.

While not all algal outbreaks are harmful, some blooms carry toxins that have been known to threaten marine ecosystems and even kill marine mammals, fish and birds.

Using a series of new approaches, Scripps Oceanography’s Xavier Mayali investigated the inner workings of a bloom of dinoflagellates, single-celled plankton, known by the species name Lingulodinium polyedrum. The techniques revealed that so-called Roseobacter-Clade Affiliated (“RCA cluster”) bacteria—several at a time—attacked individual dinoflagellate by attaching directly to the plankton’s cells, slowing their swimming speed and eventually killing them.

Using DNA evidence, Mayali matched the identity of the RCA bacterium in records of algal blooms around the world.

A red tide bloom flourished along the coast of La Jolla, Calif., in June 2005. Click here for more information.

In fact, it turns out that RCA bacteria are present in temperate and polar waters worldwide. Mayali’s novel way of cultivating these organisms has now opened up a new world of inquiry to understand the ecological roles of these organisms. The first outcome of this achievement is the recognition of the bacterium’s potential in killing red-tide organisms.