Effects of algal mats on a tropical estuarine benthic system: sediment biogeochemistry and macrofauna

Abstract

The effects of compacted algal mats grown attached to sediments on the benthic biogeochemistry and macrofauna were investigated in a tropical estuarine mudflat in northeastern Brazil. During the study, the algal mat was restricted to algal patches and two types of patches were recognized based on the physiological stage (live and decomposing algae). Quantitative analyses of sediment parameters were obtained within and outside each type of algal patch. Sediment biogeochemistry and fauna below the algal patches were significantly affected in comparison with sediment not covered by algae. Physiological stage influenced the sediment concentrations of organic matter, carbohydrates, phaeopigments, total-P, and total-N. Macrofauna declined markedly in both algal patches, with strong effects regardless of the physiological stage. The results showed that the effect of compacted algal mats on environmental parameters depends on the physiological stage of the algae, and this should be considered in analyses of benthic systems. The adverse effects observed on macrofauna highlight the importance of monitoring and managing the development of algal mats in tropical estuaries.