Assessing the impacts of Caulerpa racemosa on sand dwelling benthic invertebrates in the Galápagos

Abstract

The introduction of invasive marine algae has resulted in significant losses of native benthic fauna and incurred substantial costs for monitoring and management efforts. Isolated volcanic archipelagos, such as the Galápagos, are especially vulnerable to the introduction of nonnative species due to high levels of tourism, marine traffic, and ENSO events. Currently, the cryptogenic alga Caulerpa racemosa exhibits invasive behavior and rapid spread, posing a severe threat to the native ecosystems. This study examines the impact of Caulerpa racemosa on benthic invertebrate populations in the Galápagos Islands' shallow sandy habitats. Selected sampling locations included Cerro Dragon, Playa Estación, Tortuga Bay, Garrapatero, Concha Perla, and Venecia. Each site was analyzed for invertebrate diversity, richness, and abundance in areas with and without C. racemosa with the use of transects to collect sediment samples and percent cover quadrat images. Sediment samples were sieved and stored in preservatives, and the number of invertebrates identified to class were counted using microscopy. The dry weights of each sediment sample were taken to calculate diversity per gram. Kruskal-Wallis and Pairwise Wilcoxon tests was used to assess intergroup differences. Results showed no significant correlation between C. racemosa presence and invertebrate diversity, richness, or abundance. Findings suggest that the percent cover of C. racemosa was not correlated to the benthic invertebrate diversity of sampled locations as hypothesized. Inter-site differences in species richness and abundance were evident. The variability in results highlights the need for further monitoring to understand the ecological impacts of invasive algae and inform management strategies.