Soil nutrient content and water level variation drive mangrove forest aboveground biomass in the lagoonal ecosystem of Aldabra Atoll. (October 2022)

• Record Type: Journal Article
• Authors: Constance, Annabelle; Oehri, Jacqueline; Bunbury, Nancy; Wiesenberg, Guido L.B.; Pennekamp, Frank; A'Bear, Luke; Fleischer-Dogley, Frauke; Schaepman-Strub, Gabriela
• Is Part Of: Ecological indicators. Volume 143(2022)
• Publication Date: 2022-10
• Subjects: Blue carbon -- Coastal ecosystem -- Conservation -- Coralline -- Islands -- Structural equation model; Environmental monitoring -- Periodicals; Environmental management -- Periodicals; Environmental impact analysis -- Periodicals; Environmental risk assessment -- Periodicals; Sustainable development -- Periodicals; 333.71405
• DOI: 10.1016/j.ecolind.2022.109292
• Languages: English
• ISSNs: 1470-160X

Abstract

Graphical abstract: Highlights: In a protected area, we modelled effects of local drivers on mangrove functioning. The model input data came from a mangrove plot survey on tree, soil and water. The nutrient content of soil drives mangrove forest aboveground biomass. Changes in the water level contribute positively to the nutrient content of soils. Soil nutrients and water level variation are key indicators of mangrove functioning. Abstract: Lagoonal mangrove ecosystems are vital for carbon capture, protection of coastlines and conservation of biodiversity. Yet, they are decreasing globally at a higher rate than other mangrove ecosystems. In addition to human drivers, local environmental factors influence the functioning of lagoonal mangrove ecosystems, but their importance and combined effects are relatively unknown. Here, we investigate the drivers of mangrove functioning, approximated by mangrove aboveground biomass (AGB), in a protected lagoonal mangrove ecosystem on Aldabra Atoll, Seychelles. Based on a survey of the mangrove forest structure in 54 plots, we estimated that the mean mangrove forest AGB was 82 ± 13 Mg ha −1 . The total AGB of the mangrove area (1720 ha) was nearly 140, 600 Mg, equivalent to about 66, 100 Mg of carbon stored in the standing biomass on Aldabra. To assess the direct and indirect effects of soil nutrient content, water level variation and soil salinity on mangrove AGB, we used a structural equation model. Our structural equation model explained 82 % of the variation in mangrove AGB. The soil nutrient content (concentration of essential macronutrients in the soil column) had the greatest influence on mangrove AGB variation. Additionally, high variation in water level (change in water depth covering a location) increased mangrove AGB by increasing nutrient content levels. Our results highlight the important contribution of Aldabra's lagoonal ecosystem to Seychelles' carbon storage and the role of hydroperiod as a regulator controlling the availability of crucial nutrients needed for the functioning of mangroves within lagoonal systems. We suggest conservation managers worldwide focus on a holistic ecosystem-level perspective for successful mangrove conservation, including the protection and maintenance of nutrient cycling and hydrological processes.