Biodiversity and Reproductive Status of Beach-Cast Seaweeds from Espírito Santo, Southeastern Brazil: Sustainable Use and Conservation

Abstract

The state of Espírito Santo has one of the greatest diversities of macroalgae along the Brazilian coast. Beach-cast seaweeds are a frequent phenomenon and exhibit great diversity. This study assessed stranded macroalgae’s composition and reproductive status to evaluate their potential for sustainable use by the local community. Monthly collections were carried out from March to November 2022, covering the rainy and dry seasons, on five beaches in Espírito Santo: three in the north and two in the south. At each beach, two 50 m transects were set up parallel to the coastline over the stranded algae patches, one near the wave-breaking zone during low tide and another around high tide, and three 1 × 1 m quadrants were randomly selected in each transect. All material within each quadrant was collected, resulting in six samples per beach. We identified 81 taxa, including 54 Rhodophyta, 16 Ulvophyceae and 11 Phaeophyceae. The taxon composition was relatively consistent across the studied regions, with the rainy season exhibiting the greatest species richness. Seventeen of the identified taxa had reproductive structures, although only four consistently presented these structures. Our results suggest that removing stranded macroalgae does not significantly impact their role as propagule sources.