Dynamics of “trematode – edible cockle (Cerastoderma edule)” parasite – host systems in three coastal ecosystems along a North-Eastern Atlantic gradient

This study explores the dynamics of trematode infections in the edible cockle, Cerastoderma edule , across three diverse coastal ecosystems in the Northeast Atlantic: the Arcachon Bay in France, and the Merja Zerga and Oualidia lagoons in Morocco. Over a period of two years, the research focused on the infection patterns of four dominant trematode species: Himasthla quissetensis , H. interrupta , Curtuteria arguinae , and Gymnophallus minutus . The correlation between parasite abundance and three key parameters was evaluated: mean sea temperature, seasonal variations, and individual cockle biomass. The findings reveal distinct infection patterns for the four trematode parasites across the coastal ecosystems, with significant infection variations typically occurring between 17 and 22 °C. In nearly all cases, infection was correlated with the individual biomass of the host, i.e. its age. The results indicate clear seasonal infection patterns influenced by mean sea temperature, highlighting its critical but insufficient role in explaining infection patterns. The study suggests that temperature acts as an “on/off” factor in infection, with infection intensity depending on other habitat-specific factors. Additionally, it uncovers a nuanced interplay between various environmental parameters, demonstrating that no single factor can predict the parasitic dynamics in these marine organisms conclusively.