Stable isotopes clearly track mangrove inputs and food web changes along a reforestation gradient
Document Type
Article
Publication Date
6-1-2021
Abstract
Despite worldwide efforts to restore degraded mangrove forests in the past decades, defining and tracking restoration success remains a major challenge. In this study, we used a multi-isotope approach to trace ecosystem responses to forest clearing and replanting in a tropical mangrove forest reserve at Matang, Malaysia. We measured delta H-2 or delta D deuterium, delta C-13 and delta N-15 (HCN isotopes) in common macroinvertebrate consumers (barnacles, prawns, gastropods, and crabs) across a 70-year chronosequence of mangroves. Functional food web recovery was indicated by a decrease in delta C-13 and delta N-15 and increase in delta D for gastropod and crab consumers in older forests. Timing of this shift in food web isotopic signals took place between 5 and 15 years post-clearing of mangroves. These changes in food web function paralleled changes in crab community composition, but also reflected changes in physicochemical conditions within the forest, such as increased tree cover and shading, which resulted in a shift of the food web base from microalgal-derived to mangrove-derived organic matter. Prawns and barnacles from tidal waters adjacent to the mangrove forests were estimated to derive 17 to 25% of their nutrition from mangroves, primarily from a microbial loop that was processing localised dissolved and particulate organic matter exported from mangrove marshes. The top-down mixing model approach using combined HCN isotope measurements clearly separated inputs from mangroves versus microalgae for the first time in estuarine food web studies, and tracked ecological mangrove ecosystem recovery. This combination of tracers is recommended for future studies of mangrove conservation and restoration.
Keywords
Carbon, Nitrogen, Hydrogen, Chronosequence, Crab, Gastropod, Malaysia, Microalgae, Microbial loop
Divisions
Science
Funders
IRU-MRUN Global Collaborative Research Programme grant [RU026-2015],Queensland Government through the Advance Queensland Program
Publication Title
Ecosystems
Volume
24
Issue
4
Publisher
Springer
Publisher Location
ONE NEW YORK PLAZA, SUITE 4600, NEW YORK, NY, UNITED STATES