Sediment Geochemistry Influences Infaunal Invertebrate Community Composition and Population Abundances

Infaunal invertebrate communities are structured by various factors, including predation, resource availability, and environmental conditions. Given that these invertebrates live within sediment, it is not surprising that sediment properties play a critical role in many infaunal behaviours. When models explaining spatial and temporal variation in infaunal community composition are constructed using physical, biophysical, environmental, and sediment properties (salinity, detrital cover, elevation, particle size distribution, organic and water content, redox conditions, and penetrability), a considerable portion of the variation in the data is typically unaccounted for. This suggests that we do not fully understand all the variables that influence infaunal invertebrate communities. One suite of under-explored variables is the elemental composition/concentration of the sediments themselves. As such, we evaluated if sediment geochemistry improved model performance of the spatial variation in infaunal invertebrate communities on three intertidal mudflats in northern British Columbia, Canada. We observed that models including geochemistry data outperformed models that only included physical, biophysical, and environmental properties. Our results, therefore, suggest that some of the observed, and previously unaccounted for spatial variation in infaunal community composition may be a product of variation in sediment geochemistry. As such, sediment geochemistry should be accounted for when studying infaunal communities and assessing human impacts upon intertidal systems.