Investigating down-shore migration effects on individual growth and reproduction of the ecosystem engineer Arenicola marina

Arenicola marina (Annelida Polychaeta) is a harvested ecosystem engineer inhabiting galleries within soft-sediment foreshores from the Mediterranean to the Arctic. It displays a typical distribution pattern on most foreshores, with the juveniles inhabiting the mediolittoral shore and migrating to the infralittoral shore while growing. In this study, we have characterized the shore migrations of a temperate population of A. marina and estimated its potential individual growth and reproduction under different migration scenarios using a Dynamic Energy Budget model. A sand temperature model was developed in order to predict the temperature experienced by lugworms according to the depth of their galleries and their bathymetric level. The food availability and the associated scaled functional response were estimated from in situ growth data and associated nitrogen content and chlorophyll-a concentration (Chla) data. The metabolic response of lugworms to temperature (temperature tolerance range, related Arrhenius temperatures) was assessed from literature data. The sand temperature model outputs did not explain alone spatial differences in individual growth and reproduction. However, an increase of food availability with bathymetry, with Chla as a proxy, well explained growth and reproduction. For now, the temperature hypothesis is discarded but other factors (desiccation or hypoxia) should be considered in future studies.