Importance of rhodoliths as habitats for benthic communities in impacted environments

This study characterized rhodolith beds and the structure and function of their invertebrate communities in three tropical beaches subjected to different environmental impacts. The highest rhodolith density and invertebrate diversity and density were found on a beach with coarser sands (interpreted as indicative of higher hydrodynamics) and the high availability of calcium carbonate in nearby locations. On the opposite, higher rhodolith mortality, lower invertebrate diversity and density were recorded in the beach with high thermotolerant coliforms concentrations and finer sands. The functional composition was similar in the less polluted beaches, despite differences in sediment composition. In these beaches, polychaetes and echinoderms dominated, being primarily biodiffusors, with slow free movement and predators. These traits appeared advantageous due to food and structural protection provided by rhodoliths while providing oxygenation and remobilization of sediment by resident biodiffusers fauna. The most polluted beach was marked by lower densities of those taxa and traits, with suspension feeders' bivalve dominance, with limited movement, associated with higher suspended material, common in organic polluted environments. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study revealed that rhodolith beds are sensitive to sediment and environmental impacts, where rhodolith density and invertebrate diversity and density are influenced by environmental factors. In cleaner beaches, polychaetes and echinoderms dominate, while suspension feeders, particularly bivalves, are dominant in more polluted beaches.