Polychaete Engineers: Transport, Extinction, Juvenile Mortality At Range-Edge Sites

Diopatra biscayensis and Arenicola marina are important ecosystem engineers along the Atlantic coast of Europe. Diopatra creates biogenic habitats with significantly higher infaunal densities through dense patches of its large emergent tubes, while Arenicola creates a bed with emergent properties at ~30 m^-2 due to bioadvective forcing of porewater flux. As the Atlantic coast of Europe is warming, subtropical Diopatra is expanding its range, while the range of north temperate Arenicola is contracting. We examined population shifts at range edges in the context of climate change using high resolution (250 m grid scale) IFREMER ocean models to simulate 10 years of larval transport both forward and backwards in time. Larval transport limitation and spatial distribution of habitat islands, with episodic expansion and contractions due to inter-annual connectivity changes appear likely to doom range-edge populations of both species, at least at densities where their importance as ecosystem engineers is likely.