Author Identifier
Leah Beltran: https://orcid.org/0000-0003-1246-1675
Date of Award
2025
Document Type
Thesis - ECU Access Only
Publisher
Edith Cowan University
Degree Name
Master of Science by Research
School
School of Science
First Supervisor
Glenn Hyndes
Second Supervisor
Richard Evans
Abstract
Mangroves are highly productive coastal ecosystems that provide valuable ecological functions and ecosystem services, including providing critical habitats and food sources for a wide range of organisms, particularly invertebrates. Despite their importance, research has primarily focused on mangroves in wet tropical regions, especially large riverine forests, leaving fringing mangroves in arid, macrotidal environments poorly understood. Furthermore, studies have generally concentrated on larger, more conspicuous epifauna, and infauna are underrepresented in the literature. This study aimed to investigate the ecological role of arid, fringing mangroves in the Dampier Archipelago by examining the processes driving faunal communities as well as nutrient transfer in food webs in an arid, fringing mangrove system.
Infauna were sampled from five different bays in the Dampier Archipelago across two seasons (wet summer and dry winter) and counted and identified to the lowest taxonomic level possible. Generalised additive models (GAMs) were produced to assess the influence of environmental parameters on the abundance, diversity, and structure of the infaunal communities. Season, as well as environmental variables considered for inclusion in the GAMs were the distance to nearest mangrove, area of mangrove, significant wave height in the bays, mean sediment grain size, and percentage of particulate organic matter (%POM). Mangroves had little direct influence on infaunal invertebrates. Instead, season, mean sediment grain size, and Percentage Particulate Organic Matter (%POM) were significant drivers of infaunal abundance, diversity, and community structure. Infaunal abundance and diversity were higher during the Dry season, with approximately three times more individuals recorded compared to the Wet season. Additionally, both abundance and diversity increased with increasing sediment grain size and increasing %POM to a threshold, suggesting the presence of optimal environmental conditions for infaunal communities. These findings demonstrate that infaunal communities in this arid, fringing mangrove system are shaped more by physical environmental conditions than by the presence of mangroves themselves.
Food web dynamics of the fringing mangroves were assessed using stable isotope analysis (SIA) and a Bayesian mixing model based on the δ13C and δ15N signatures of selected taxa from three feeding guilds: the herbivorous Mangrove whelk (Terebralia palustris), the omnivorous Hermit crab (Clibinarius longitarsus), and the filter feeding Rock oyster (Saccostrea cucullata). The stable isotope signatures of these consumers were analysed alongside those of primary producers to investigate trophic linkages. The SIA and mixing models suggested that mangrove nutrients were highly variable in the diets of epifauna, with median contributions ranging from ~70% for Mangrove whelks to ~5% in Rock oysters. The Hermit crabs exhibited the most varied diet of all three taxa, aligning with their opportunistic feeding strategies. However, mangrove nutrients still accounted for up 50% of Hermit crab diet. In comparison, macroalgae made the largest median contribution to the diet of Rock oysters (up to ~70%). While mangrove-derived nutrients play an important role in supporting the food web, these findings demonstrate that this mangrove system is also strongly influenced by in-welling from adjacent habitats. This emphasises the importance of both local and external nutrients sustaining food web dynamics in arid, macrotidal mangrove environments.
By highlighting the complex nature of these systems, this study contributes valuable baseline data on benthic invertebrates in the arid, tropical mangrove system, an underrepresented region and habitat type in the literature. Understanding the relative influence of physical drivers and basal nutrient sources is critical for the effective conservation and management of fringing mangrove ecosystems, particularly in arid, macrotidal regions facing increasing anthropogenic and climate pressures. The islands of the Dampier Archipelago are jointly managed between the Department of Biodiversity, Conservation and Attractions (DBCA) and the Murujuga Aboriginal Corporation (MAC) and a nomination has been put forward for the Murujuga Cultural Landscape (including the Dampier Archipelago) to be considered as a UNESCO World Heritage Listed site. This study provides an ecological framework to introduce evidence-based management practices that bring together the environmental and cultural needs of the region.
Access Note
Access to this thesis is embargoed until 18th December 2026
DOI
10.25958/736s-cm95
Recommended Citation
Beltran, L. (2025). The role of fringing mangroves in supporting macroinvertebrate fauna in an arid, macrotidal region of Australia. Edith Cowan University. https://doi.org/10.25958/736s-cm95