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<p>Brazilian rocky shores occur across a wide range from wave-exposed headlands to sheltered embayments, and zonation patterns can shift even within small or enclosed areas as wave exposure, geomorphology, and local hydrodynamics modify intertidal stress gradients. We investigated how this fine-scale variability shapes polychaete assemblages on hard substrates at two rocky shore localities in eastern Rio de Janeiro, Brazil: Itaipu (22°58′S, 43°02′W), an urban site with intense recreational use, and Sacristia (22°57′S, 42°40′W), an isolated protected site. Sampling was conducted in midlittoral and upper infralittoral zones at two stations per site, between April and June 2024, totaling 24 samples. We recorded 1,293 individuals belonging to 15 families, with Syllidae, Sabellidae, and Nereididae as the most abundant. Rarefaction curves did not reach an asymptote, suggesting that total richness is higher than recorded. PERMANOVA showed that polychaete assemblage structure varied across spatial scales: assemblages differed between sites, vertical zonation was detected at Sacristia but not at Itaipu, and stations differed within Itaipu, with higher richness and diversity at the less accessible station. SIMPER indicated that these dissimilarities were largely driven by shifts in the dominant families. Canonical Correspondence Analysis indicated associations between families and environmental gradients, particularly salinity, dissolved oxygen, temperature, and algal biomass. These findings show that even neighboring rocky shores can display sharply contrasting community organization, highlighting the value of polychaetes for monitoring environmental change in coastal ecosystems.</p>

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Rocky-shore polychaetes in southeastern Brazil: diversity, zonation, and human influence

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月19日

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  • Alexia de Lima Domingues da Cruz,
  • Breno Monzato Gisbert,
  • Patrick Targino Braga Pessoa,
  • Cinthya Simone Gomes Santos

摘要

Brazilian rocky shores occur across a wide range from wave-exposed headlands to sheltered embayments, and zonation patterns can shift even within small or enclosed areas as wave exposure, geomorphology, and local hydrodynamics modify intertidal stress gradients. We investigated how this fine-scale variability shapes polychaete assemblages on hard substrates at two rocky shore localities in eastern Rio de Janeiro, Brazil: Itaipu (22°58′S, 43°02′W), an urban site with intense recreational use, and Sacristia (22°57′S, 42°40′W), an isolated protected site. Sampling was conducted in midlittoral and upper infralittoral zones at two stations per site, between April and June 2024, totaling 24 samples. We recorded 1,293 individuals belonging to 15 families, with Syllidae, Sabellidae, and Nereididae as the most abundant. Rarefaction curves did not reach an asymptote, suggesting that total richness is higher than recorded. PERMANOVA showed that polychaete assemblage structure varied across spatial scales: assemblages differed between sites, vertical zonation was detected at Sacristia but not at Itaipu, and stations differed within Itaipu, with higher richness and diversity at the less accessible station. SIMPER indicated that these dissimilarities were largely driven by shifts in the dominant families. Canonical Correspondence Analysis indicated associations between families and environmental gradients, particularly salinity, dissolved oxygen, temperature, and algal biomass. These findings show that even neighboring rocky shores can display sharply contrasting community organization, highlighting the value of polychaetes for monitoring environmental change in coastal ecosystems.