Distribution of trace elements in Callichirus laurae burrows and nearby sediments in the gulf of Aqaba, Jordan (Red Sea)

In nearshore waters of the Jordanian sector of the Gulf of Aqaba, the distributions of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, as well as Ca and Mg, were determined in the mucus-rich burrow lining made by the locally abundant Crustacea Callichirus laurae (Thalassinidea: Callianassideae), and compared with concentrations obtained in surface sediments surrounding the burrows. The highest concentrations of trace elements were observed in a sewage affected area. At uncontaminated stations, a marked increase from surface sand values was observed in the burrow lining. The correlations between the concentration of trace elements in this biogenic micro-environment and both the concentration of organic carbon and the mean granulometric diameter were highly significant.This study shows that the C. laurae burrow acts as a chemical reservoir that may reach several meters deep into the sediment. This special reservoir is created as an indirect consequence of the building of a mucus-rich, metal-reacting lining. It is demonstrated that the absolute quantity of trace elements incorporated in the lining is much higher (c. 85 to 250 times more, depending on the element) than in the dense and healthy Halophila stipulacea seagrass bed covering the surface.The environmental significance of large lined burrows for the distribution of trace elements is discussed.