Corinaldesi, Cinzia, Antonio Dell’Anno, and Roberto Danovaro
Limnol. Oceanogr., 52(4), 2007, 1710–1717
To provide new insights into the early diagenesis of extracellular deoxyribonucleic acid (DNA) and its relevance in trophodynamic processes, we collected sediment samples from a variety of coastal and deep-sea sites. Turnover times of extracellular DNA were approximately threefold shorter in coastal benthic systems than in deep-sea sediments (0.35 yr and 1.2 yr, respectively). This was due to the higher concentrations of bioavailable extracellular DNA in deep-sea over coastal sediments (19.8 ± 0.6 and 9.8 ± 2.6 mg DNA g-1, respectively), since deoxyribonuclease (DNase) activities did not show significant differences between sampling sites (135.8 ± 72.7 and 62.8 ± 19.0 ng DNA g-1 d-1, in coastal and deep-sea sediments, respectively). The coastal benthic systems were characterized by DNase activities per prokaryotic cell significantly lower than those of their deep-sea counterparts (0.12 ± 0.05 and 0.27 ± 0.06 fg DNA degraded cell-1 d-1, respectively), although carbon production per cell was not significantly different (6.9 ± 4.4 and 2.6 ± 0.9 fg C cell-1 d-1, respectively). These results suggest that DNase activity per cell may be more dependent on the amount of bioavailable substrate rather than on prokaryotic metabolism. Extracellular DNA may supply 20% and 47% of the daily prokaryote anabolic requirements for organic phosphorous in both coastal and deep-sea sediments, respectively. Overall, our data suggest that bioavailable extracellular DNA might represent an important nutrient source for benthic heterotrophic metabolism and open new perspectives for a better understanding of the factors that influence the functioning of benthic systems.