The dinoflagellate Karenia brevis is responsible for red tide harmful algal blooms that negatively impact Gulf of Mexico coastal communities. These blooms have a long history in the Gulf of Mexico, but recent blooms persisting for 8-16 months have focused attention on understanding causes of termination. Previous research has shown marine viruses are capable of infecting and clearing phytoplankton blooms. Despite this, no K. brevis viruses have been isolated before and their potential influence on algal blooms are mostly unknown. To explore this microbial interaction, K. brevis cultures were incubated with 2021 K. brevis bloom waters that were size fractionated by passing it through either a 1-µm filter to remove protists, a 0.22-µm filter to remove protists and large bacteria, or a 0.02 µm filter to remove all biological particles. Uninoculated K. brevis culture acted as a control. Two-week incubations resulted in K. brevis lysis only when incubated with the 1-µm or 0.22-µm size fractionated bloom seawater. Flow cytometry identified two different viral sized populations only present in the lysed K. brevis incubations. Consistent with flow cytometry, metagenomic sequencing identified the presence of novel giant eukaryotic nucleocytoplasmic large dsDNA virus genomes only in the lysed cultures. Cumulatively these data indicate at least two undescribed large viruses may infect and lyse K. brevis. Natural marine viruses can thus influence K. brevis and may play a role in bloom termination.

Primary Presenter: Anne Booker, Bigelow Laboratory for Ocean Science (abooker@bigelow.org)

Authors:

Anne Booker, Bigelow Laboratory for Ocean Sciences  (abooker@bigelow.org)

Joaquín Martínez Martínez, Bigelow Laboratory for Ocean Sciences  (jmartinez@bigelow.org)

Cong Fei, New York University Abu Dhabi  (cf2290@nyu.edu)

Shady Amin, New York University Abu Dhabi  (samin@nyu.edu)

So Hyun (Sophia) Ahn, Horn Point Laboratory University of Maryland  (sahn@umces.edu)

Nayani Vidyarathna, Horn Point Laboratory University of Maryland  (nayani.vidyarathna@gmail.com)

Patricia Glibert, Horn Point Laboratory University of Maryland  (glibert@umces.edu)

Sarah Klass, Mote Marine Laboratory   (sklass@mote.org)

Cynthia Heil, Mote Marine Laboratory   (cheil@mote.org)