Mangrove Rehabilitation and Brachyuran Crab Biodiversity in Ranong, Thailand

Abstract

Mangroves rehabilitated after deforestation by commercial exploitation must be monitored to confirm that key ecosystem functions are being restored. Brachyuran crabs are conspicuous mangrove macrofauna and were selected as potential indicators of ecosystem recovery. A deforested former mangrove charcoal concession area in Ranong was rehabilitated by planting Rhizophora (1994), Bruguiera and Ceriops (1995) seedlings in single-species blocks. A second area, deforested and heavily degraded by tin mining, was rehabilitated with R. mucronata in 1985. Crabs at these sites were compared with those in a mixed-species conservation forest. Timed collections were made in 1999, 2008 and 2019 to compare crab diversity and relative abundance between sites and years. Thirty-three brachyuran crab species were recorded. Fiddler crabs (Austruca triangularis, Tubuca rosea) and the signal crab, Metaplax elegans, were most abundant, followed by sesarmid crabs (15 species). Species composition differed significantly between sites but not between the four planted tree species blocks. We propose Metaplax elegans as an indicator of ecological development in low-lying/newly formed sediments; fiddler crabs as equivalent indicators in young mangrove plantations/open forest habitats; and a diverse sesarmid community to indicate ecological functioning in older plantations/dense forests.

Biodiversidad de árboles de mangle en el manglar de Puerto Pizarro, Tumbes, Perú

“…El ecosistema del manglar recibe su nombre por los árboles de mangle que lo pueblan, éstos son vegetación adaptada a la anoxia, alta salinidad e inundación; los mangles a nivel mundial, comprenden 240 especies, 48 de las cuales se consideran mangles verdaderos y 192 asociados; dentro de las cuales se hallan entre 50 a 74 especies arbóreas; siendo los manglares de Asia los que tienen mayor cantidad de especies y los de América la menor cantidad (Bezerra et al, 2022;Mitra et al, 2021;Rahman et al, 2024;Segaran et al, 2023;Thattai et al, 2023). La mayor parte de los manglares se hallan en países en vías de desarrollo en los cuales muchos de ellos están en peligro crítico por la degradación de su hábitat, la deforestación y en especial por el cambio de uso del terreno, los que se han empleado para la agricultura y acuicultura (Ashton & Macintosh, 2024;Zhila et al, 2014). Ciertas investigaciones han mostrado que manglares expuestos al impacto antrópico pueden tener índices de biodiversidad distintos a los de manglares conservados (Zhila et al, 2014); por lo que para poder conocer mejor el estado de un manglar, una buena opción es evaluar su diversidad.…”