title: Activity and distribution of bacterial populations in Middle Atlantic Bight shelf sands.
abstract: Abstract Spatiotemporal variation and metabolic activity of the microbial community were studied in coarse-grained Middle Atlantic Bight shelf sediments in relation to pools of dissolved and particulate carbon. Algal cells were present 8->70 mum) fraction of the sediment held the major share (61-98%) of benthic bacteria. Bacterial and algal cell abundances, exoenzymatic activity, and [DOC] generally showed higher values in May/July 2001 than in August/December 2000. Carbohydrates and proteins were hydrolyzed at potential rates of 1-12 nmol cm(-3) h(-1) (beta-glucosidase) and 3-70 nmol cm(-3) h(-1) (aminopeptidase), respectively. Fluorescence in situ hybridization analyses of the benthic microbes assigned 45-56% of DAPI-stained cells to Eubacteria and less than 2% to Eukarya. The prokaryotic community was dominated by planctomycetes and members of the Cytophaga/Flavobacterium cluster. Near the sediment surface, iodonitrotetrazolium violet reducing cells, that are considered actively respiring, amounted to 15-29% of total bacteria. Despite a low organic content (particulate organic carbon <0.03%) and relatively low bacterial abundances (<10(9) cm(-3)), the Middle Atlantic Bight shelf sediments showed organic matter turnover rates that are comparable to those found in organic-rich finer-grained deposits. Our findings suggest a high biocatalytic filtration activity in these coarse permeable sediments.
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Rusch
authors.forename: Markus
authors.initials: M
authors.lastname: Huettel
authors.forename: Clare E
authors.initials: CE
authors.lastname: Reimers
authors.forename: Gary L
authors.initials: GL
authors.lastname: Taghon
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: Fuller