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

Abstract

This study evaluated the decomposition process of leaf litter from the main Brazilian mangrove species Avicennia schaueriana, Laguncularia racemosa and Rhizophora mangle. Senescent leaves were collected, dried and placed in nylon bags with different mesh sizes (fine: 2 × 2 mm and coarse: 8 × 8 mm). The bags were distributed over the sediment, and replicates of each species and mesh size were collected periodically over 4 months. In the laboratory, the dry weight of the samples was measured, and the decomposition coefficient (k) for each species and mesh size was obtained over time. All species showed a rapid decomposition rate at the beginning of the experiment, followed by a slower but steady rate of decomposition over time. The rate of leaf litter decomposition was highest in A. schaueriana, intermediate in L. racemosa and lowest in R. mangle. The difference was mainly linked to the activity and abundance of detritivores, together with the different litter quality of the species, which determined their palatability and probably influenced the decomposition process.

Trophic connectivity and basal food sources sustaining tropical aquatic consumers along a mangrove to ocean gradient

“…This process would explain why mangrove-derived nutrients in our study were assimilated by consumers inside the mangrove wetland, but not by consumers in the adjacent marine area, despite observations of mangrove leaves in adjacent sandy beaches. The mangrove-derived material found in the sandy beaches most likely could not be assimilated by local consumers due its more refractory characteristic (Rodelli et al 1984) and lower nutritional value (Lima et al 2014), similar to what has been observed in other coastal systems (Rodelli et al 1984, Hemminga et al 1994). …”

“…According to our mixing isotope models, L. racemosa was the only mangrove tree out of the three species occurring in this estuary that contributed significant amounts of nutrients to consumers. This species is comparatively dominant in the inner region of the estuary (Iaponira, 2009) and is characterized by a higher nutritional value than R. mangle (Lima et al 2014), which is dominant nearer the southern portion of the estuary. A proxy for the nutritional value is the C:N ratio because lower values indicate higher amounts of nitrogen than carbon and, consequently, a higher nutritional value to consumers (Ashton et al 1999).…”

“…Despite the fact that senescent mangrove leaves (mainly from R. mangle) were commonly found in the central portion of the estuary (tidal flat) and in the surf-zone of both open and reef-protected ocean sandy beaches, our isotope mixing results showed that mangrove detritus was not a significant food source for fishes and macrocrustaceans in these locations. This absence could be explained by the decomposition process of mangrove leaves, which occurs in two steps: a faster loss of soluble compounds followed by a slower decomposition of refractory material as lignin (Lima et al 2014). This process would explain why mangrove-derived nutrients in our study were assimilated by consumers inside the mangrove wetland, but not by consumers in the adjacent marine area, despite observations of mangrove leaves in adjacent sandy beaches.…”

Structure and floristic composition of mangroves in the Bahía de Cispatá, Colombian Caribbean

“…3). Las comparaciones de medias arrojaron diferencias estadísticamente significativas (Wilcoxon, p < 0.05) en la mayoría de variables físico-bióticas CUADRO 1 Valores promedio de las variables ambientales para tres manglares en la Bahía de Cispatá, Colombia (media ± desviación estándar) (Kristensen, Holmer, Banta, Jensen, & Hansen, 1995;Kathiresan & Bingham, 2001, Lima & Colpo, 2014. Adicionalmente, en bosques inundados, como los de borde de este trabajo, la descomposición de hojarasca es retardada por la reducción de oxígeno y el C queda almacenado en el suelo (Valdés-Velarde, 2010).…”

“…Esto justifica que los mayores valores de C total en el sedimento de los manglares de la bahía de Cispatá se encuentren en los de tipo cuenca. La tasa de descomposición de hojas de L. racemosa es más lenta que la de hojas de R. mangle, pero más rápida que la de A. germinans (Lima & Colpo, 2014). En el manglar de borde B, L. racemosa explica el mayor contenido de C respecto al de borde A. Valdés-Velarde (2010) registró mayor contribución al contenido de C en suelos cuando predominan tanto A. germinans como L. racemosa.…”