The Caribbean bivalve Isognomon bicolor (C. B. Adams, 1845) is currently among the main invasive species along the Brazilian coast. The present study evaluated the co-occurrence, influence, and relationship of the native macrobenthic community with I. bicolor. The study was performed on samples collected from two sandstone reefs located in Northeast Brazil. We observed that the macrobenthic community differed significantly across reefs, zones, and seasons. The higher density of I. bicolor in the lower intertidal zone (347.7 ind/m² ± 800.8) was one of the main differentiation factors of zonation. The results indicated that the evenness of the community and some gastropods had a negative effect on I. bicolor. We found a negative correlation between the co-occurrence of I. bicolor with the macroalgae Hypnea sp. and Gracilaria caudata J. Agardh 1852 and the microgastropod Eulithidium affine (C. B. Adams, 1850). This study provides data on the relationship between I. bicolor and the native community of sandstone reefs, which could be applied to monitor the expansion of I. bicolor to the Northeast region of Brazil.

In the last decade, corals from northeastern Brazil have experienced bleaching events linked to thermal anomalies, the consequences of which have been the appearance of disease outbreaks affecting different species. As a way to explain and monitoring diseases progression and other characteristics regarding the identification in the field for coral diseases, this article aimed to demonstrate the particularities that follows each diseases symptom. This study presents the results of an assessment of the presence of coral diseases on six coastal reefs in northeastern Brazil, including marine protected areas. After 300 hours of visual censuses, a total of 875 colonies were observed; of these, 114 colonies had some disease, representing 13.02% of the colonies analyzed. Five diseases/syndromes were recorded in four host coral species: white syndrome, white plague, red band, dark spots, and white band. This is the first record of white band on the Brazilian coast. The massive coral Siderastrea stellata showed colonies with all registered diseases, which arouses great concern for conservation of the Brazilian coast.