Mangrove-mudflat connectivity shapes benthic communities in a tropical intertidal system

Kasper J Meijer,El-Hacen M El-Hacen,Laura L Govers,Marc Lavaleye,Theunis Piersma,Han Olff

doi:10.1016/j.ecolind.2021.108030

Kasper J Meijer, El-Hacen M El-Hacen + Show 4 more

Open Access

https://doi.org/10.1016/j.ecolind.2021.108030

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Abstract

Understanding the connectivity among seascape habitats is an important emerging topic in marine ecology and coastal management. Mangroves are known to provide many ecosystem services such as coastal protection and carbon cycling, but their functional relationships with adjacent benthic intertidal communities are less clear. We examined how spatial adjacency to mangroves affects macrobenthic communities of intertidal mudflats in a tropical estuarine ecosystem. In the Bijagós Archipelago, Guinea-Bissau, benthic macrofauna assemblages were compared among sampling locations with different connectivities between intertidal mudflats and mangrove stands. We explored how a single mangrove connectivity index (MCI), combining mangrove tidal basin size and the distance to the mangrove edge, affected macrobenthic composition, and compared this effect to sediment properties. In addition, we used structural equation modelling (SEM) and ordination to determine how different environmental predictors directly and indirectly affected macrobenthic communities. MCI strongly affected macrobenthic composition and species abundance, and SEM revealed that this effect contained both a direct component and an indirect component through mudflat NDVI (normalized difference vegetation index, an indicator for microphytobenthos). Sediment properties (grain size, organic matter) affected macrobenthos independently from MCI, nevertheless sediment properties were also affected by MCI. We show the importance of accounting for the seascape structure of tidal basins when investigating the connectivity between mangroves and macrobenthic communities of intertidal mudflats. As benthic macrofauna is a key food source for endangered fish and waders in these systems, our findings provide strong arguments for the integrative conservation of intertidal mudflats and mangroves at the seascape scale.

Highlights

Nutrients and organic matter are transported from terrestrial to marine environments, and vice versa, in different forms via runoff, wind, tides, river flow, and through move ment of organisms (Moore et al, 2004; Nagelkerken, 2009; Olson et al, 2019)
The connectivity between terrestrial and marine ecosys tems is important for both the productivity and resilience of marine and estuarine habitats, as movement of animals and nutrients from other systems can help the recovery of disturbed habitats (Heck et al, 2008; Loreau et al, 2003; van de Koppel et al, 2015)
We examined the connectivity between mangroves and adjacent intertidal mudflats in the relatively pristine and little studied Bijagos Archipelago in Guinea-Bissau, West-Africa, a crucial destination for wintering migratory shorebirds in the East-Atlantic flyway (Lourenço et al, 2018; van Roomen et al, 2012; Zwarts, 1988)

Summary

Introduction

Nutrients and organic matter are transported from terrestrial to marine environments, and vice versa, in different (dissolved and par ticulate) forms via runoff, wind, tides, river flow, and through move ment of organisms (Moore et al, 2004; Nagelkerken, 2009; Olson et al, 2019). Fish play an especially important role here because do they transport large quantities of energy between systems, but their temporary foraging bouts between different habitats can maintain micro- and macroalgae-sensitive biogenic habitats, such as seagrass beds and coral reefs (Kohler et al, 2012; McMahon et al, 2012; Mumby and Hastings, 2007; Olds, Pitt, et al, 2012) Other motile organisms, such as birds, are known to move nutrients across habitat boundaries, which affects the productivity and residence of the recipient habitats (Anderson and Polis, 1999; Polis et al, 1997; Post et al, 1998). The spatio-temporal exchange of nutrients and energy, and the role of motile organisms in this system, should be included for a comprehensive un derstanding of the stability and resilience of coastal and estuarine habitats

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