Biotic Interactions, Structure, and Long-term Changes in Marine Benthic Assemblages

Predicting spatial distribution of organisms still remains a challenge of ecology. Small-scale variation is high in most marine benthic communities. Our long-term observations on soft-sediment intertidal assemblages revealed high level of small-scale spatial variation, and most temporal variation was also associated with this scale. As biotic interactions often drive small-scale patterns, we focused on the communities with multiple foundation species where they are understudied. We assessed overgrowth and feeding interference between co-dominating foundation species, long-term recruitment variation in their populations, and their effect on on the rest of assemblage. Our observations and experiments indicated that large suspension-feeders develop a facilitation cascade in the White Sea shallow subtidal, boosting species diversity and driving patch dynamics on mixed sediments