The role of Talitrus saltator in the decomposition of seaweed wrack on sandy beaches in northern Brittany: an experimental mesocosm approach
Résumé
This study reports an impact of a locally abundant detritivore amphipod species, Talitrus saltator (Amphipoda, Talitridae), on the decomposition of 5 representative seaweeds naturally deposited ashore, Fucus vesiculosus, F serratus, Enteromorpha sp., Ascophyllum nodosum, and Ulva sp., using an experimental mesocosm approach. The results show that the presence of T saltator has increased the rate of biomass loss of three of the seaweeds considered in our experiment, F vesiculosus, F serratus, and Enteromorpha sp., up to 50 %. Furthermore, we report a 4- to 15- fold overall increase of organic matter accumulated in the sand, as compared to controls, due to the presence and activity of the amphipods. We suggest that, in natural conditions, this organic matter derived from seaweeds may lead to a substantial enrichment of the pool of organic matter being washed back to the sea with the next high tides reaching the deposition level. Hence, T saltator may play a key role on exposed sandy beaches of Northern Brittany and the adjacent coastal ecosystems as an accelerator of nutrient recycling.