Distribution of benthic fauna in sediment grains and prop roots of a mangrove channel in south-eastern Brazil

Abstract

We examined the benthic fauna in four areas along a mangrove tidal channel in south-eastern Brazil, between October 2008 and August 2009. The tested hypothesis is that the most abundant groups avoid competition as they occupy different types of substrata and that the longitudinal distance from the sea also affects the occurrence of benthic fauna along the channel. We also examined the prop root epibiont fauna to describe this different community. Polychaeta was the dominant group in the sediment whereas Isopoda and Tanaidacea were the dominant groups on the prop roots. We found a tendency for higher infauna species richness and diversity in the innermost channel area during the summer. Higher abundance of epibiont fauna was also found in summer with tidal movements allowing the colonization of the prop roots of the mangrove forest by some taxa. The polychaetes Ceratocephale sp. and Laeonereis acuta had indication of habitat partitioning, with the first occurring mainly in very fine sand sediment whereas the latter preferred medium sand sediment. The microcrustaceans Chelorchestia darwini and Tanaidacea sp. 1 occurred in high abundance colonizing the prop roots. Exosphaeroma sp. was found in high abundance in infauna and epibiont fauna. The tested hypothesis of spatial partitioning of the mangrove channel by the benthic fauna was confirmed with the most abundant species occupying the substrata with different grain fractions and prop roots in different stations.

Variação Em Pequena Escala Da Macrofauna Bentônica Em Uma Planície De Maré Do Estuário Do Rio Pacoti - Ceará, Brasil

“…As relações entre a distribuição dos bentos e as variáveis sedimentológicas têm sido discutidas por muitos autores (Reise, 1985;McCall & Tevesz, 1982;Ishikawa, 1989;Alongi & Christoffersen, 1992). Vários autores têm registrado que sedimentos com proporções elevadas de silte e argila, como aqueles encontrados em planícies flúvio-marinhas de ambientes estuarinos, são propícios para a vida de organismos bentônicos, visto que tais sedimentos: apresentam maiores proporções de matéria orgânica, que podem servir como principal fonte de alimento para muitas espécies; possuem alta abundância de microrganismos, dada a maior razão superfície/área de partículas finas; estão associados a ambientes de baixa hidrodinâmica, favorecendo a fixação e a locomoção dos organismos epifaunais e cavadores superficiais, e o assentamento das larvas planctônicas; e são tipicamente moles, facilitando a locomoção e os movimentos escavatórios da infauna cavadora (Reise, 1985;Silva-Camacho et al, 2016).…”

Mangrove or mudflat: Prioritising fish habitat for conservation in a turbid tropical estuary

“…Most fish in the present study were juvenile benthic invertivores -particularly favouring microcrustaceans (Marley unpublished). While microcrustaceans are abundant components of the epibiota of prop roots (Silva-Camacho et al 2017), their density and diversity in mangrove sediments are compromised by the poor digestibility of mangrove leaves and anoxic conditions (Sheridan 1997, Dittmann 2001. In contrast, macroinvertebrate abundances peak in the sediments of the lower intertidal area in front of mangroves, and this could be a critical hotspot in ecological processes of tropical estuaries (Sheaves et al 2016a).…”