Assessing the impact of mangrove bark beetles (Coccotrypes rhizophorae) on red mangrove (Rhizophora mangle) propagule buoyancy and germination

Abstract

Throughout the coastal tropics, mangroves are a widely beneficial tree because they contribute to the maintenance of coastal areas by protecting shorelines against erosion, including wildlife and habitats within these intertidal areas. In the Galápagos, there are four native mangrove species, with Rhizophora mangle (red mangrove) being the most prominent. Rhizophora mangle can most commonly be found on the islands of Santa Cruz, Fernandina and Isabela. Although mangroves have survived in the Galápagos, the Coccotrypes rhizophorae beetle impacts propagule (mangrove seedling) state (i.e. horizontal, vertical and sunk) and survival. C. rhizophorae was first detected in 1985 and was found to infest R. mangle propagules by boring into and causing decay from the inside out, proving to be fatal for some propagules. Because of this observation, this study aims to determine the level of damage caused by C. rhizophorae onto R. mangle propagules, its impact on propagule buoyancy (~2 weeks), and initial growth (~3 weeks) periods. Currently, the direct impacts of C. rhizophorae on R. mangle remains unknown. Additionally, taking into account that R. mangle propagules rely on nutrients for growth, the impacts of nitrogen, phosphorus and potassium-rich fertilizer were assessed on both C. rhizophorae-infested and non-infested R. mangle propagules. This study found that C. rhizophorae infestations led to shorter flotation times in propagules. Additionally, it was found that fertilizer did not have any impact on propagule growth. Future research could implement smaller doses, possibly giving way to new findings on propagules exposed to controlled fertilizer treatments. This study aims to provide researchers and environmentalists with a better understanding on R. mangle survival and endurance against C. rhizophorae. By extension, this can allow environmental collaborators to discover new solutions to maintaining mangrove forests in the Galápagos, aiding in the protection of the archipelago’s unique biodiversity.