Thermal window of exercise performance of the ecosystem engineer <i>Lanice conchilega</i>

Ocean warming is reshaping marine ecosystems and shifting species distributions. Resilient habitat-forming species help stabilize conditions for other organisms, supporting community structure under change. The tube-worm Lanice conchilega is such a habitat-former, enhancing species richness in sandy environments. Its thermal performance range remains unknown, partly because standard methods are poorly suited for this species. We present a new experimental approach to assess thermal performance based on tube-building activity, an important trait for physical protection, feeding, and habitat engineering. Spring-collected individuals were exposed in the laboratory to an ecologically relevant temperature range. Tube-building activity matched spring field conditions with a thermal minimum, optimum, and maximum at 3.6, 12.4, and 21.4°C, respectively. Performance depended strongly on recent thermal history. Because thermal tolerance can shift through acclimation, seasonal performance curves are needed to determine whether cold winters or hot summers may constrain this ecosystem engineer with potential consequences for intertidal community structure.