Effect of crab bioturbation on organicmatter processing in SouthWest Atlantic intertidal sediments

FANJUL, EUGENIA; ESCAPA, MAURICIO; MONTEMAYOR, DIANA I; ADDINO, MARIANA; ALVAREZ, M FERNANDA; GRELA,MARÍA A; IRIBARNE, OSCAR

JOURNAL OF SEA RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 95 p. 206 - 216

1385-1101

Organicmatter (OM) remineralization plays a key role in controlling the biogeochemistry ofmarine sediments. Through their burrowing activities, bioturbating macrofauna not only induces physical, chemical and biological modifications, which can affect microbial communities responsible for organic matter remineralization, but it could also directly affect the distribution and bioavailability of sedimentary organic matter. Through in situ ex- perimentsmanipulating crab and burrowdensity in intertidal soft-bottoms, we assessed if crab-bioturbation af- fects benthicmetabolism, andthe amount, distribution, andbioavailability of sedimentaryOM. Crab-bioturbation enhanced overallbenthicmetabolismand benthic flux of dissolvedOMtoward thewater columnat bothmudflat and saltmarsh zones. Moreover, our results revealed that bioturbation also changes the quality, bioavailability and distribution of sedimentaryOMinmudflats and saltmarshes. Overall, bioturbation enhanced the proportion of labile organic carbon of bioturbated sediments and homogenized the sediment column in terms of their pro- portion of labile organic carbon.However, crabs also generatedbiogenic structures (e.g.,mounds) that couldpro- mote spatial heterogeneity of high nutritional-value OM. Bioturbation-induced changes on benthic metabolism and onOMavailabilitywould result in a reduction of the storage capacity of carbon in our intertidal systems. Pre- viousworks indicated that crab-burrows trap detritus and OM-rich sediments. Our results suggest that detritus are efficiently remineralized at bioturbated sediment, and finally they are quickly exported to thewater column as CO2 and DOC. Thus, crabs are modifying theOMprocessing at intertidal soft bottoms, and theways inwhich carbon is exported to coastalwaters