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Spatio-temporal variability of Brachyura larval assemblages in mangroves of the Gulf of Guayaquil's inner estuary

Abstract:

Mangroves are the dominant coastal vegetation in tropical estuaries and host a large diversity of brachyuran crabs. Crab larvae have adapted to dynamic hydrological conditions in estuaries using several physiological and behavioral strategies. Changes in crab larval assemblages can be monitored in time in order to detect ecological changes occurring within estuaries. For this study, we sampled quarterly crab larval assemblages in two sub-estuaries (Salado and Churute) of the Gulf of Guayaquil (GG) during 2016–2017. The largest community dissimilarities occurred between sub-estuaries, with Salado having higher morphological diversity and larval densities than Churute. Temporal patterns were only evident within each sub-estuary, and in relation to total and individual morpho-species density values. Ocypodidae larvae were dominant across samples; with zoea I of the red mangrove crab (Ucides occidentalis) showing maximal density values during spring tides. Hydrological parameters (i.e., turbidity, conductivity, salinity and temperature) contributed to only 19% of the variability in biota, demonstrating that crab larvae are physiologically adapted to a wide range of water conditions. This study established an ecological baseline for future studies using crab larval assemblages in the assessment of ecological changes occurring in mangrove tidal creeks of the GG. However, longer time-series monitoring data and description of new species and stages of crab larvae are necessary to better assess potential future changes.