Mitogenome analysis of a green tide forming Ulva from California, USA confirms its identity as Ulva expansa (Ulvaceae, Chlorophyta).

An unknown species of marine sea lettuce was observed forming green tides consecutive years from 2014 to 2016 in Seaside, California. This Ulva sp. was similar in thallus size and shape to U. expansa. To confirm this identification, whole genome sequencing was performed on the bloom-forming species of Ulva and the holotype specimen of U. expansa. The complete green tide Ulva mitogenome is 64,143 bp in length, contains 65 genes, and displays high gene synteny with U. pertusa Kjellman. The mitogenome was incomplete for the holotype of U. expansa, but the analysis yielded the mitoexome, plastid, and nuclear genetic markers. These data verify that the native U. expansa is responsible for the blooms in central California.