Physicochemical and Microbial Properties of Burrows of the Deposit-feeding Thalassinidean Ghost Shrimp Biffarius arenosus (Decapoda: Callianassidae)

Abstract

The physicochemical and microbial properties of the burrows of Biffarius arenosus, a ghost shrimp common in temperate south-eastern Australia, were investigated and shown to be more similar to the surface sediments than to the surrounding subsurface sediments. The burrow walls had a similar organic carbon content to that of the surrounding sediment, a result which was consistent with their lack of a discrete mucous lining. Burrow walls, however, were lined with compacted and smoothed sediment and were coloured a distinct light yellow/brown compared with the dark grey of the surrounding subsurface sediments. Moderately reducing redox conditions were found in both the burrow wall and surface sediment (means 213mV and 243mV, respectively), indicative of a burrow environment regularly flushed with overlying water by the resident shrimp. Microbial activity (measured as fluorescein diacetate hydrolysis) in the burrow walls was higher than in the surrounding sediments, but there were no significant differences across sediment types in bacterial abundances (epifluorescence microscopy total counts, using DAPI) or in microbial biomasses (total phospholipid contents). Biomarker analysis of the phospholipid fatty acid (PLFA) profiles indicated that bacteria dominated the benthic community (∼80% of total PLFAs), and showed the presence of both aerobic and anaerobic bacteria in all sediment samples.