Taxonomic and functional diversity of benthic macrofauna associated with rhodolith beds in SE Brazil

Patricia Sarcinelli Stelzer; Ana Carolina A Mazzuco; Luiz Eduardo Gomes; João Martins; Sergio Netto; Angelo F Bernardino

doi:10.7717/peerj.11903

Taxonomic and functional diversity of benthic macrofauna associated with rhodolith beds in SE Brazil

PeerJ. 2021 Jul 29:9:e11903. doi: 10.7717/peerj.11903. eCollection 2021.

Authors

Patricia Sarcinelli Stelzer¹, Ana Carolina A Mazzuco¹, Luiz Eduardo Gomes¹, João Martins², Sergio Netto², Angelo F Bernardino¹

Affiliations

¹ Department of Oceanography, Universidade Federal do Espírito Santo, Vitoria, Espirito Santo, Brazil.
² Laboratório de Ciências Marinhas, Universidade do Sul de Santa Catarina, Tubarão, Santa Catarina, Brazil.

Abstract

Rhodoliths are free-living and morphologically diverse marine calcareous algae commonly distributed over the continental shelf seafloor. They increase the seabed structural complexity and are of potential value as feeding and reproductive grounds for a myriad of marine fauna. The higher structural seabed complexity within rhodolith beds may also increase benthic diversity by creating microhabitats, but this relationship has been rarely explored within rhodolith beds worldwide. Here we compared benthic macrofaunal (>500 µm) structure on rhodolith beds (nodule epifauna) and within unconsolidated sediments (sediment infauna) under high and low-density beds to test whether rhodolith bed density and nodule morphology influenced macrofaunal assemblages. We observed that macrofaunal density on nodules (2538 ± 288.7 ind·m^-2) was 15-fold higher when compared to sediments under those beds (166 ± 38.8 ind·m^-2). Rhodolith bed density was positively related to macrofaunal density, composition, and functional diversity on the rhodoliths. Low-density beds (61 ± 27.1 nodules·m^-2) with discoid-shape nodules were dominated by peracarid crustaceans whereas high-density beds (204 ± 18.7 nodules·m^-2) with spheroidal nodules were dominated by Annelid polychaetes. The sediment macrofauna was also positively influenced by the density of rhodolith nodules, which increased sediment carbonate and organic quality (protein and lipids) under high-density beds. Macrofaunal functional diversity was generally higher on rhodoliths, with low similarity (low nestedness) and high taxa turnover between macrofaunal assemblages of rhodoliths and sediments. These findings indicate that rhodolith beds provide an unique habitat for benthic macrofaunal communities, with exclusive functional and taxonomic richness that are likely not typical in the unconsolidated sediment below these beds in SE Brazil. This study highlights the importance of protecting rhodolith beds from multiple sources of anthropogenic disturbance and exploration on continental shelves.

Keywords: Benthos; Ecology; Macrofauna; Rhodolith; South Atlantic.

Grants and funding

This study was funded by Programa Ecológico de Linda Duração Habitat Costeiros do Espirito Santo PELD-HCES/CNPq/CAPES/FAPES (Nos. 441243/2016-9 and 79054684/2017) to Angelo Bernardino. Angelo Bernardino was also supported by a PQ grant No. 302700/2020-0. Patricia Stelzer and Luiz Eduardo Gomes were supported by graduate scholarships from the PELD program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.