First record of a population of Caulerpa okamurae (Bryopsidales) in the Mexican Pacific

Abstract

On the western coast of the Baja California Peninsula, 5 Caulerpa species have been recorded as part of a regional floristic checklist. However, in late 2023, the presence of Caulerpa okamurae was detected in Ojo de Liebre Lagoon, on the Pacific coast of Baja California Sur, where its abundance increased notably during 2024–2025. This macroalga adheres to oyster cultivation systems, increases cleaning costs, and threatens seagrass meadows and other habitats, with potential effects on fishery resources. Distinguishing between cryptogenic, non-native, and invasive populations is crucial in research on species introductions, as a species is considered invasive when its presence threatens biodiversity, the economy, or health. In Mexico, guidelines and a national strategy exist to prevent, detect, and control these species. This work presents the first record of a C. okamurae population on the coasts of the Mexican Pacific, based on morphological evidence from specimens collected in Ojo de Liebre Lagoon, in the absence of previous records in Mexico. Confirmation of this finding adds to the 16 introduced macroalgae already documented in the Mexican Pacific, the majority of which originate in Japan and Korea and whose spread is associated with maritime traffic and aquaculture. Given the introduction and potential establishment of C. okamurae to Ojo de Liebre Lagoon, it is essential to implement continuous and rigorous monitoring programs to precisely determine its spatiotemporal distribution.