Low macroinvertebrate biomass suggests limited food availability for shorebird communities in intertidal areas of the Bijagós archipelago (Guinea-Bissau)
Knowledge of the macrozoobenthic community and its interactions with predators is critical for understanding intertidal ecosystems but this information is still lacking for many tropical sites. We core-sampled three intertidal areas in the Bijagós archipelago, Guinea-Bissau, one of the largest intertidal wetlands in West Africa, to evaluate macroinvertebrate abundance and diversity, investigate ecological variables influencing macroinvertebrate distribution, and estimate food availability for several shorebird species. We found a low macroinvertebrate biomass, which mostly consisted of bivalves and polychaetes. The fiddler crab Afruca tangeri was also among the more abundant species. Both Shannon diversity and rarefied species richness indicate macrozoobenthic communities in the Bijagós have low diversity but there is large variation in species composition among sites. Sediment fine fraction, organic content and distance to the coast were correlated with the abundance of several macroinvertebrate taxa. Harvestable biomass for the shorebird species studied was very low, below the values described for intertidal sites in temperate areas and some other sites in the tropics. Although this fits with low shorebird densities in the Bijagós, it also suggests that wintering shorebird communities must depend on secondary production by macrobenthic invertebrates during the winter, in the same way as has been proposed for other tropical intertidal systems.
KeywordsHarvestable biomass Macrozoobenthos Mudflats Waders West Africa
We thank Alfredo da Silva, Aissa Regalla and Quintino Tchantchalam from Instituto da Biodiversidade e Áreas Protegidas (IBAP) for logistical support and permission to work in protected areas in Guinea-Bissau, and Santinho da Silva and other staff from IBAP, as well as Joãozinho Sá and Hamilton Monteiro (Gabinete de Planificação Costeira), for help in fieldwork and logistics. Paulo Catry provided advice on Bijagós during expedition’s preparation. Inês Catry provided invaluable help during field work in the Bijagós and Patricia Pedro helped analysing macroinvertebrate samples in the laboratory. This study was supported by Fundação para a Ciência e Tecnologia (FCT) through a postdoctoral grant to PML (SFRH/BPD/84237/2012) and project IF/00694/2015 granted to TC. Thanks are also due for the financial support to CESAM (UID/AMB/50017 - POCI-01-0145-FEDER-007638), to FCT/MCTES through national funds (PIDDAC), and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020.
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