Microbial communities colonising nutrient-enriched marine sediment

Abstract

Sediment cores were set up to study microbial colonisation and interactions on marine sand grains under enrichment conditions. Cores were enriched with photosynthetic media in the light and dark (PL, PD) and heterotrophic media in the light and dark (HL, HD), and were incubated for 25 days. Sediment chlorophylls were then measured by acetone extraction, viable heterotrophic bacteria by plate counts, and numbers of cells mm-2 sand grain surface by s.e.m. Chlorophyll a occurred in all sediments but was highest in the PL sediment. Bacteriochlorophyll a was only observed in the HL sediment. Heterotrophic viable counts were high in the HL and H D sediments. Dense growth of diatoms and blue-green algae, and a marine fungal Thraustochytrid sp. occurred on PL grains. The blue-green alga Schizothrix was often associated with the diatom Amphora on PL grains. Many different bacteria grew on HL and H D grains and some unusual colony and cell morphologies were recorded (Caulobacter, Flexibacter, polymer strands). Characteristic flakey material sometimes occurred in hollows on grains. The results are discussed in relation to microbial communities in low energy sedimentary environments.

Biomodulation of Nitrogen Cycle in Suspended Sediment

“…B HET also showed a higher preference for NH over NO ; however, its growth was greatly suppressed by B PHOTO due to high K M for C 6 H 12 O 6 . Similar experimental observations were also found in Tufail () and Kirchman and Wheeler (). Although O 2 (aq) inhibition on B DNR was higher than B DEN , approximately 30% of total N was partitioned into DNR in R7 at high nutrient leaching rates (Figure g) because B DNR had lower K M for both NO and C 6 H 12 O 6 than B DEN .…”

Biological modifiers of marine benthic seascapes: Their role as ecosystem engineers

“…As with the meiofauna, they are most abundant in near shore sediments but are also present in the deep sea. Unlike the meiofauna, however, a large literature exists (ZoBell, 1946;Anderson, 1966, 1968;Rheinheimer, 1977;Tufail, 1985Tufail, , 1987Meadows et al, 1994a,b;Meadows and Meadows, 2004b;Hyun et al, 2009;Lubarsky et al, 2010;Bruckner et al, 2011;Raes et al, 2011). Almost without exception they produce extracellular dissolved material, alter geochemical process, and secrete extracellular polymeric materials.…”