Desiccation resistance and survivorship of Caulerpa racemosa in Galápagos

Abstract

Algae are important components of marine ecosystems as they are primary producers and support the aquatic food chain. Invasive species impact ecosystem dynamics by outcompeting native organisms for resources, destroying habitats. These impacts can ultimately lead to a decline in an area's biodiversity. Caulerpa racemosa is a cryptogenic (species with an unknown origin) alga displaying invasive characteristics around the Galápagos Marine Reserve (GMR). This alga was first reported around Isabela Island and has since been observed in abundance near Fernandina and Santa Cruz islands, raising concerns about its impact on native reefs. Fragmentation is a key mechanism of spread in Caulerpa species, and boat anchors may mechanically fragment and transport C. racemosa. While fragmentation and desiccation tolerance are well studied in C. taxifolia, they remain understudied in C. racemosa. This study investigates the desiccation resistance of C. racemosa in Tortuga Bay, Santa Cruz Island, Galápagos, to understand the capabilities of fragments to travel via entanglement with boat anchors between bays and islands. Samples were collected and desiccated for up to three days, then measured daily to assess survivorship and growth. Here we show that desiccation time significantly impacts the growth and survivorship of C. racemosa. These results indicate that as desiccation time increases, growth and survivorship decrease. While this is the first time desiccation impacts of C. racemosa has been studied in the GMR, similar studies on C. taxifolia show these trends. We observed a significant difference in survivorship and mass loss between 0 or 12 hour desiccated fragments and 24 to 72 hour fragments. Our results suggest a potential for anchor spread of C. racemosa for short boat trips around the GMR. These results inform management and environmental boating regulations around the GMR. Understanding the desiccation limit and geographic spread potential is crucial for protecting these unique marine ecosystems.