Benthic macrofauna associated with decomposition of leaves in a mangrove forest in Ilhéus, State of Bahia, Brazil

Abstract

We identified and quantified the benthic macrofauna associated with decomposing leaves of Rhizophora mangle and Laguncularia racemosa, to observe the differences in the abundance and composition of macrofauna between these mangrove species, and to examine whether the abundance and composition of organisms changed with different stations and collection times. Benthic macrofauna, mainly polychaetes and amphipods, were recorded from the fifth day after the installation of the experiment. Annelids including Oligochaeta and Polychaeta were the most numerous group. Crustacea were represented by peracarids (Amphipoda and Tanaidacea) and decapods. Of Hexapoda, only juvenile forms and pupae were present. The most abundant polychaete species was Perinereis brevicirrata, followed by Capitella cf. capitata, Heteromastus filiformis and Neanthes succinea. In one-way analysis of variance (ANOVA) there were no statistical differences between the macrofauna of mangrove species, seasons, or collection times, except among collection times for R. mangle litter bags. Two-way ANOVA showed homogeneity for macrofauna abundance between the groups of collection times for both mangrove species. The richness was similar for R. mangle litter bags, and showed a significant difference for L. racemosa. Abundance and richness were also similar between the mangrove species. The colonization of detritus by benthic invertebrates followed a successional sequence during the decomposition process. This suggests that the density of these organisms and their foraging behaviour affected the decomposition rates of leaves of R. mangle and L. racemosa.

Leaf-litter decomposition of the mangrove speciesAvicennia schaueriana,Laguncularia racemosaandRhizophora mangle

“…Nordhaus et al (2011) suggested that plants with larger amounts of nitrogenous compounds were the preferred food for mangrove crabs. They feed on microorganisms, sediments and organic matter that settle on the leaf surface (Oliveira et al, 2012). Most annelid species in estuarine areas are surface deposit-feeders, with discrete motility and opportunistic behaviours (Magalhães & Barros, 2011;Oliveira et al, 2012).…”

“…The low N content and the thick cuticle of R. mangle may repel the crabs, but also these features may attract the annelids that were the predominant invertebrate group in this mangrove species. The different abundances of decapods and annelids on the three mangrove species and their respective decomposition rates may also suggest that annelids are less efficient shredders than decapods, although Camilleri (1992) and Oliveira et al (2012) noted the important role of polychaetes in processing leaves in tropical mangroves. They feed on microorganisms, sediments and organic matter that settle on the leaf surface (Oliveira et al, 2012).…”

“…The low N content and the thick cuticle of R. mangle may repel the crabs, but also these features may attract the annelids that were the predominant invertebrate group in this mangrove species. Most annelid species in estuarine areas are surface deposit-feeders, with discrete motility and opportunistic behaviours (Magalhães & Barros, 2011; Oliveira et al , 2012). They feed on microorganisms, sediments and organic matter that settle on the leaf surface (Oliveira et al , 2012).…”

“…Most annelid species in estuarine areas are surface deposit-feeders, with discrete motility and opportunistic behaviours (Magalhães & Barros, 2011; Oliveira et al , 2012). They feed on microorganisms, sediments and organic matter that settle on the leaf surface (Oliveira et al , 2012). The leaves of R. mangle , which showed the lowest decomposition rate, may be a more stable substrate than A. schaueriana and L. racemosa for the establishment of annelids and their food source.…”

“…The detritivores affect decomposition by shredding, ingesting and assimilating litter, which facilitates leaf decomposition and can increase microbial colonization (Imgraben & Dittmann, 2008; Alongi, 2009). Crustaceans, molluscs and annelids are the main macrofauna groups that process leaf litter into smaller particles (Alongi, 1998; Oliveira et al , 2012).…”