Heterogeneous distribution of prokaryotes and viruses at the microscale in a tidal sediment

Abstract

In this study we show for the first time the microscale (mm) 2- and 3-dimensional spatial distribution and abundance of prokaryotes, viruses, and oxygen in a tidal sediment. Prokaryotes and viruses were highly heterogeneously distributed with patches of elevated abundances surrounded by areas of ca. 3-fold lower abundance within distances of <2 mm. Abundances of prokaryotes and viruses ranged from 1.3 × 109 to 4.2 × 109 cells cm-3 and 4.1 × 109 to 13.1 × 109 viruses cm-3, respectively. The results showed oxygen concentration and uptake rates to be heterogeneously distributed at the same spatial scale, with the oxygen penetration depth varying from 1.5 to 5.8 mm and with an average (±SD) diffusive oxygen uptake of 18.9 ± 6.4 mmol m-2 d-1. Locally, prokaryotes, viruses, and oxygen were found to be positively, negatively, or not correlated, but overall no significant relationship was detected. The lack of consistent spatial correlation between viruses and prokaryotes was explained by a temporal experiment using organic carbon-enriched homogenized sediment samples. Enhancement in metabolic activity and the proliferation of prokaryotes and viruses were not completely phased. These results suggest that local nourishment is likely to be an important driver of a high small-scale heterogeneity in abundance and dynamics of benthic viruses and prokaryotes. This is expected to influence the rates and regulation of benthic virus-host interactions and thus microbial biogeochemical cycling. © Inter-Research 2013.