Sedimentary OM is a mixture of plant and animal reactive detritus together with poorly reactive polymeric organic carbon. Microorganisms often use first the labile organic carbon in such away that poorly reactive C tends to accumulate into sediments. Our results showed that LOC was between 15.6 and 30.0% of total organic carbon at the saltmarsh, and between 12.1 and 46.5% at mudflat sediments. Also, reactive C pool showed values between 5.2 and 28.1% in the saltmarsh, and between 8.7 and 23.5% of total carbon in the mudflat, and these values are high when compared to the reported worldwide values. The results presented here
showed that bioturbation affected the quality, bioavailability and the spatial distribution of sedimentary OM in mudflats and saltmarshes. In contrast to what was found in other systems where bioturbated sediments had higher % LOC than non-bioturbated sediments, our results showed the highest LOC contents in non-bioturbated superficial sediment. The % LOC was mostly similar among bioturbated sediments types. This seems to be because the sediment reworking exerted by crabs transports and homogenizes the OM through the sediment column.
As in other saltmarsh crabs (e.g., Austrohelice crassa, Sesarma reticulatum,Uca spp.), N. granulata does not secrete mucus to lining burrow walls, which may constitute an important fraction of the LOC pool in many bioturbated sediments.