Sediment properties and bacterial community in burrows of the ghost shrimp Pestarella tyrrhena (Decapoda: Thalassinidea)

Abstract

Chemical properties of burrow wall sediment from burrows of the thalassinidean shrimp Pestarella (=Callianassa) tyrrhena located at Vravrona Bay (Aegean Sea, Greece) were studied and found to be very different from the sediment surface and ambient anoxic sediment. P. tyrrhena burrow walls had significantly higher amounts of silt and clay, while total organic carbon (TOC) was up to 6 times higher than in surrounding sediment. Chlorophyll a (chl a) accounted for a small frac- tion of TOC and showed similar values in burrow walls and surface sediment, whereas the low chl a: chl a + phaeopigment ratio indicated the presence of more fresh material in the latter. Biopolymers (carbohydrates, proteins and lipids) were 4 to 11 times higher in burrow walls than in the surround- ing sediment, accounting for 47% of TOC. The low protein:carbohydrate ratio indicated that the high TOC in the burrow walls was caused by the presence of aged detritus of low nutritional quality, such as seagrass detritus. The distinct conditions along the burrow wall also affected the bacterial community and resulted in a 10-fold increase of bacterial abundance. Molecular fingerprints of the bacterial communities showed that the bacterial composition of the burrow wall was more similar to the ambient anoxic sediment and showed less seasonal change than the sediment surface. These results suggest that burrow walls have distinct properties and should not be considered merely as a simple extension of the sediment surface.