Long-term changes in seagrass and benthos at Banc d’Arguin, Mauritania, the premier intertidal system along the East Atlantic Flyway

El-Hacen M El-Hacen,Mohamed A Sidi Cheikh,Tjeerd J Bouma,Han Olff,Theunis Piersma

doi:10.1016/j.gecco.2020.e01364

El-Hacen M El-Hacen, Mohamed A Sidi Cheikh + Show 3 more

Open Access

https://doi.org/10.1016/j.gecco.2020.e01364

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Abstract

The benthic communities of soft-sediment intertidal ecosystems trophically underpin the migration of birds and fish. Within the East Atlantic Flyway, along the coast of West-Africa, the intertidal mudflats of Banc d’Arguin, Mauritania, host over 2 million migratory waterbirds. Despite the protected status of the Banc d’Arguin, geographical remoteness and seemingly benign human exploitation, we show that large changes have taken place in the intertidal benthic macrofauna across an interval of 28 years. We compared the results of two comparable and spatially comprehensive large-scale benthic surveys in 1986 and 2014. Over this time, the benthos changed from a diverse community to one dominated by a few species of bivalve, with a loss of polychaete worms. The change was associated with a twofold increase in the seagrass cover. Our results suggest that the intertidal habitats of Banc d’Arguin have altered markedly over the last three decades and the estimated benthic secondary production has decreased by a factor of four. These shifts in community structure and production may have contributed to declines in some benthivorous migratory shorebirds.

Highlights

Due to human development and activities, over the last 100 years the world has lost 64e71% of its wetland habitats (Davidson, 2014)
We provide evidence of temporal change in the intertidal benthic macrofauna and seagrass cover of the Banc d’Arguin ecosystem
We found evidence for a major shift in benthic community composition of the Banc d’Arguin intertidal flats over the last decades, a shift from polychaete worms to bivalves

Summary

Introduction

Due to human development and activities, over the last 100 years the world has lost 64e71% of its wetland habitats (Davidson, 2014). Further wetland losses have led to further declines, especially in coastal-living shorebirds across the world (Conklin et al, 2014; van Roomen et al, 2015). The cause of these declines has been mostly attributed to habitat loss and modification (Kraan et al., E.-H.M. El-Hacen, M.A. Sidi Cheikh, T.J. Bouma et al.2009; Ma et al, 2014; Piersma et al, 2016; Zhang et al, 2018) directly affecting the survival of wintering waterbirds and the food ‘fuelling’ long distance migrations (e.g., Rakhimberdiev et al, 2018). The current global loss of natural habitat may be removing some of these key sites along the global flyways, and decreasing the quality of their habitats (Galbraith et al, 2005; Piersma, 2006, 2007)

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