Organic matter distribution in burrows of the thalassinid crustacean Callichirus laurae, Gulf of Aqaba (Red Sea)

Analysis of sediments in and around the large and deep burrows made by the callianassid shrimp Callichirus laurae, Jordan Gulf of Aqaba (Red Sea), showed that organic carbon (OC), humic matter (HM), humic (HA) and fulvic acids (FA) are redistributed both quantitatively and qualitatively by sediment reworking activities: 1. OC and humic matter (HM) concentrations are ca. 30 times higher in the stomach content than in surface sand, proving a selective food uptake. 2. a 11 to 17 times increase in OC and HM is observed in the mucus-rich burrow wall when compared to ambient sediment. Among humic substances, FA seem preferentially absorbed by the shrimp, while HA are concentrated in the fecal pellets. The spatial distribution of organic matter in the form of a 3D network is discussed in relation with sampling procedures. Due to inadequate sampling gears, organic rich networks such as those of thalassinid shrimps are rarely considered in conventional sampling strategies, leading to an underestimation of the sediment organic content.